diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index 8d01a9b17..d30eb909f 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -35,6 +35,11 @@ jobs:
         with:
           command: test
           args: --verbose ${{ env.CARGO_ARGS }}
+      - name: check compilation without threading
+        uses: actions-rs/cargo@v1
+        with:
+          command: check
+          args: ${{ env.CARGO_ARGS }} --no-default-features
 
   snippets_cpython:
     name: Run snippets and cpython tests
diff --git a/Cargo.lock b/Cargo.lock
index 385b861fa..fbb71e5d6 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -7,16 +7,22 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "fe438c63458706e03479442743baae6c88256498e6431708f6dfc520a26515d3"
 
 [[package]]
-name = "adler32"
-version = "1.0.4"
+name = "adler"
+version = "0.2.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5d2e7343e7fc9de883d1b0341e0b13970f764c14101234857d2ddafa1cb1cac2"
+checksum = "ee2a4ec343196209d6594e19543ae87a39f96d5534d7174822a3ad825dd6ed7e"
+
+[[package]]
+name = "adler32"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "567b077b825e468cc974f0020d4082ee6e03132512f207ef1a02fd5d00d1f32d"
 
 [[package]]
 name = "aho-corasick"
-version = "0.7.10"
+version = "0.7.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8716408b8bc624ed7f65d223ddb9ac2d044c0547b6fa4b0d554f3a9540496ada"
+checksum = "043164d8ba5c4c3035fec9bbee8647c0261d788f3474306f93bb65901cae0e86"
 dependencies = [
  "memchr",
 ]
@@ -47,8 +53,8 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "0609c78bd572f4edc74310dfb63a01f5609d53fa8b4dd7c4d98aef3b3e8d72d1"
 dependencies = [
  "proc-macro-hack",
- "quote 1.0.3",
- "syn 1.0.17",
+ "quote 1.0.7",
+ "syn 1.0.35",
 ]
 
 [[package]]
@@ -112,9 +118,9 @@ checksum = "b41b7ea54a0c9d92199de89e20e58d49f02f8e699814ef3fdf266f6f748d15c7"
 
 [[package]]
 name = "bincode"
-version = "1.2.1"
+version = "1.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5753e2a71534719bf3f4e57006c3a4f0d2c672a4b676eec84161f763eca87dbf"
+checksum = "f30d3a39baa26f9651f17b375061f3233dde33424a8b72b0dbe93a68a0bc896d"
 dependencies = [
  "byteorder 1.3.4",
  "serde",
@@ -122,18 +128,18 @@ dependencies = [
 
 [[package]]
 name = "bit-set"
-version = "0.5.1"
+version = "0.5.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e84c238982c4b1e1ee668d136c510c67a13465279c0cb367ea6baf6310620a80"
+checksum = "6e11e16035ea35e4e5997b393eacbf6f63983188f7a2ad25bfb13465f5ad59de"
 dependencies = [
  "bit-vec",
 ]
 
 [[package]]
 name = "bit-vec"
-version = "0.5.1"
+version = "0.6.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f59bbe95d4e52a6398ec21238d31577f2b28a9d86807f06ca59d191d8440d0bb"
+checksum = "5f0dc55f2d8a1a85650ac47858bb001b4c0dd73d79e3c455a842925e68d29cd3"
 
 [[package]]
 name = "bitflags"
@@ -187,9 +193,9 @@ dependencies = [
 
 [[package]]
 name = "bstr"
-version = "0.2.12"
+version = "0.2.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2889e6d50f394968c8bf4240dc3f2a7eb4680844d27308f798229ac9d4725f41"
+checksum = "31accafdb70df7871592c058eca3985b71104e15ac32f64706022c58867da931"
 dependencies = [
  "lazy_static 1.4.0",
  "memchr",
@@ -205,9 +211,9 @@ checksum = "39092a32794787acd8525ee150305ff051b0aa6cc2abaf193924f5ab05425f39"
 
 [[package]]
 name = "bumpalo"
-version = "3.2.1"
+version = "3.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "12ae9db68ad7fac5fe51304d20f016c911539251075a214f8e663babefa35187"
+checksum = "2e8c087f005730276d1096a652e92a8bacee2e2472bcc9715a74d2bec38b5820"
 
 [[package]]
 name = "byte-tools"
@@ -239,9 +245,9 @@ dependencies = [
 
 [[package]]
 name = "cc"
-version = "1.0.50"
+version = "1.0.58"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "95e28fa049fda1c330bcf9d723be7663a899c4679724b34c81e9f5a326aab8cd"
+checksum = "f9a06fb2e53271d7c279ec1efea6ab691c35a2ae67ec0d91d7acec0caf13b518"
 
 [[package]]
 name = "cfg-if"
@@ -251,9 +257,9 @@ checksum = "4785bdd1c96b2a846b2bd7cc02e86b6b3dbf14e7e53446c4f54c92a361040822"
 
 [[package]]
 name = "chrono"
-version = "0.4.11"
+version = "0.4.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "80094f509cf8b5ae86a4966a39b3ff66cd7e2a3e594accec3743ff3fabeab5b2"
+checksum = "c74d84029116787153e02106bf53e66828452a4b325cc8652b788b5967c0a0b6"
 dependencies = [
  "js-sys",
  "num-integer",
@@ -264,9 +270,9 @@ dependencies = [
 
 [[package]]
 name = "clap"
-version = "2.33.0"
+version = "2.33.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5067f5bb2d80ef5d68b4c87db81601f0b75bca627bc2ef76b141d7b846a3c6d9"
+checksum = "bdfa80d47f954d53a35a64987ca1422f495b8d6483c0fe9f7117b36c2a792129"
 dependencies = [
  "ansi_term",
  "atty",
@@ -379,9 +385,9 @@ version = "2.1.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "cb582b60359da160a9477ee80f15c8d784c477e69c217ef2cdd4169c24ea380f"
 dependencies = [
- "proc-macro2 1.0.10",
- "quote 1.0.3",
- "syn 1.0.17",
+ "proc-macro2 1.0.19",
+ "quote 1.0.7",
+ "syn 1.0.35",
 ]
 
 [[package]]
@@ -410,16 +416,6 @@ dependencies = [
  "winapi",
 ]
 
-[[package]]
-name = "dirs"
-version = "2.0.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1c4ef5a8b902d393339e2a2c7fe573af92ce7e0ee5a3ff827b4c9ad7e07e4fa1"
-dependencies = [
- "cfg-if",
- "dirs-sys",
-]
-
 [[package]]
 name = "dirs-next"
 version = "1.0.1"
@@ -430,18 +426,6 @@ dependencies = [
  "dirs-sys-next",
 ]
 
-[[package]]
-name = "dirs-sys"
-version = "0.3.4"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "afa0b23de8fd801745c471deffa6e12d248f962c9fd4b4c33787b055599bde7b"
-dependencies = [
- "cfg-if",
- "libc",
- "redox_users",
- "winapi",
-]
-
 [[package]]
 name = "dirs-sys-next"
 version = "0.1.0"
@@ -455,9 +439,9 @@ dependencies = [
 
 [[package]]
 name = "dns-lookup"
-version = "1.0.1"
+version = "1.0.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "13988670860b076248c74e1b54444efc4f1dec70c8bb25da4b7c0024396b72bf"
+checksum = "4cbea23c15f7e685a7ad01c994407f3849fa7c88556aaafe4054215b6df93f78"
 dependencies = [
  "libc",
  "socket2",
@@ -560,9 +544,9 @@ dependencies = [
 
 [[package]]
 name = "flate2"
-version = "1.0.14"
+version = "1.0.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2cfff41391129e0a856d6d822600b8d71179d46879e310417eb9c762eb178b42"
+checksum = "68c90b0fc46cf89d227cc78b40e494ff81287a92dd07631e5af0d06fe3cf885e"
 dependencies = [
  "cfg-if",
  "crc32fast",
@@ -573,9 +557,9 @@ dependencies = [
 
 [[package]]
 name = "fnv"
-version = "1.0.6"
+version = "1.0.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2fad85553e09a6f881f739c29f0b00b0f01357c743266d478b68951ce23285f3"
+checksum = "3f9eec918d3f24069decb9af1554cad7c880e2da24a9afd88aca000531ab82c1"
 
 [[package]]
 name = "foreign-types"
@@ -606,9 +590,9 @@ checksum = "1b980f2816d6ee8673b6517b52cb0e808a180efc92e5c19d02cdda79066703ef"
 
 [[package]]
 name = "generational-arena"
-version = "0.2.3"
+version = "0.2.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "921c3803adaeb9f9639de5149d9f0f9f4b79f00c423915b701db2e02ed80b9ce"
+checksum = "8e1d3b771574f62d0548cee0ad9057857e9fc25d7a3335f140c84f6acd0bf601"
 dependencies = [
  "cfg-if",
 ]
@@ -645,10 +629,19 @@ dependencies = [
 ]
 
 [[package]]
-name = "hermit-abi"
-version = "0.1.10"
+name = "hashbrown"
+version = "0.8.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "725cf19794cf90aa94e65050cb4191ff5d8fa87a498383774c47b332e3af952e"
+checksum = "34f595585f103464d8d2f6e9864682d74c1601fed5e07d62b1c9058dba8246fb"
+dependencies = [
+ "autocfg 1.0.0",
+]
+
+[[package]]
+name = "hermit-abi"
+version = "0.1.15"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "3deed196b6e7f9e44a2ae8d94225d80302d81208b1bb673fd21fe634645c85a9"
 dependencies = [
  "libc",
 ]
@@ -676,18 +669,24 @@ dependencies = [
 
 [[package]]
 name = "indexmap"
-version = "1.3.2"
+version = "1.5.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "076f042c5b7b98f31d205f1249267e12a6518c1481e9dae9764af19b707d2292"
+checksum = "5b88cd59ee5f71fea89a62248fc8f387d44400cefe05ef548466d61ced9029a7"
 dependencies = [
  "autocfg 1.0.0",
+ "hashbrown",
 ]
 
 [[package]]
 name = "instant"
-version = "0.1.4"
+version = "0.1.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7777a24a1ce5de49fcdde84ec46efa487c3af49d5b6e6e0a50367cc5c1096182"
+checksum = "5b141fdc7836c525d4d594027d318c84161ca17aaf8113ab1f81ab93ae897485"
+dependencies = [
+ "js-sys",
+ "wasm-bindgen",
+ "web-sys",
+]
 
 [[package]]
 name = "is-macro"
@@ -697,9 +696,9 @@ checksum = "04807f3dc9e3ea39af3f8469a5297267faf94859637afb836b33f47d9b2650ee"
 dependencies = [
  "Inflector",
  "pmutil",
- "proc-macro2 1.0.10",
- "quote 1.0.3",
- "syn 1.0.17",
+ "proc-macro2 1.0.19",
+ "quote 1.0.7",
+ "syn 1.0.35",
 ]
 
 [[package]]
@@ -713,15 +712,15 @@ dependencies = [
 
 [[package]]
 name = "itoa"
-version = "0.4.5"
+version = "0.4.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b8b7a7c0c47db5545ed3fef7468ee7bb5b74691498139e4b3f6a20685dc6dd8e"
+checksum = "dc6f3ad7b9d11a0c00842ff8de1b60ee58661048eb8049ed33c73594f359d7e6"
 
 [[package]]
 name = "js-sys"
-version = "0.3.37"
+version = "0.3.42"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6a27d435371a2fa5b6d2b028a74bbdb1234f308da363226a2854ca3ff8ba7055"
+checksum = "52732a3d3ad72c58ad2dc70624f9c17b46ecd0943b9a4f1ee37c4c18c5d983e2"
 dependencies = [
  "wasm-bindgen",
 ]
@@ -801,9 +800,9 @@ dependencies = [
 
 [[package]]
 name = "libc"
-version = "0.2.71"
+version = "0.2.73"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9457b06509d27052635f90d6466700c65095fdf75409b3fbdd903e988b886f49"
+checksum = "bd7d4bd64732af4bf3a67f367c27df8520ad7e230c5817b8ff485864d80242b9"
 
 [[package]]
 name = "libz-sys"
@@ -819,18 +818,18 @@ dependencies = [
 
 [[package]]
 name = "lock_api"
-version = "0.4.0"
+version = "0.4.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "de302ce1fe7482db13738fbaf2e21cfb06a986b89c0bf38d88abf16681aada4e"
+checksum = "28247cc5a5be2f05fbcd76dd0cf2c7d3b5400cb978a28042abcd4fa0b3f8261c"
 dependencies = [
  "scopeguard",
 ]
 
 [[package]]
 name = "log"
-version = "0.4.8"
+version = "0.4.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "14b6052be84e6b71ab17edffc2eeabf5c2c3ae1fdb464aae35ac50c67a44e1f7"
+checksum = "4fabed175da42fed1fa0746b0ea71f412aa9d35e76e95e59b192c64b9dc2bf8b"
 dependencies = [
  "cfg-if",
 ]
@@ -876,11 +875,11 @@ checksum = "3728d817d99e5ac407411fa471ff9800a778d88a24685968b36824eaf4bee400"
 
 [[package]]
 name = "miniz_oxide"
-version = "0.3.6"
+version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "aa679ff6578b1cddee93d7e82e263b94a575e0bfced07284eb0c037c1d2416a5"
+checksum = "be0f75932c1f6cfae3c04000e40114adf955636e19040f9c0a2c380702aa1c7f"
 dependencies = [
- "adler32",
+ "adler",
 ]
 
 [[package]]
@@ -985,9 +984,9 @@ dependencies = [
 
 [[package]]
 name = "num_cpus"
-version = "1.12.0"
+version = "1.13.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "46203554f085ff89c235cd12f7075f3233af9b11ed7c9e16dfe2560d03313ce6"
+checksum = "05499f3756671c15885fee9034446956fff3f243d6077b91e5767df161f766b3"
 dependencies = [
  "hermit-abi",
  "libc",
@@ -1010,16 +1009,16 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "ffa5a33ddddfee04c0283a7653987d634e880347e96b5b2ed64de07efb59db9d"
 dependencies = [
  "proc-macro-crate",
- "proc-macro2 1.0.10",
- "quote 1.0.3",
- "syn 1.0.17",
+ "proc-macro2 1.0.19",
+ "quote 1.0.7",
+ "syn 1.0.35",
 ]
 
 [[package]]
 name = "once_cell"
-version = "1.3.1"
+version = "1.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b1c601810575c99596d4afc46f78a678c80105117c379eb3650cf99b8a21ce5b"
+checksum = "0b631f7e854af39a1739f401cf34a8a013dfe09eac4fa4dba91e9768bd28168d"
 
 [[package]]
 name = "opaque-debug"
@@ -1029,9 +1028,9 @@ checksum = "2839e79665f131bdb5782e51f2c6c9599c133c6098982a54c794358bf432529c"
 
 [[package]]
 name = "openssl"
-version = "0.10.29"
+version = "0.10.30"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cee6d85f4cb4c4f59a6a85d5b68a233d280c82e29e822913b9c8b129fbf20bdd"
+checksum = "8d575eff3665419f9b83678ff2815858ad9d11567e082f5ac1814baba4e2bcb4"
 dependencies = [
  "bitflags",
  "cfg-if",
@@ -1049,18 +1048,18 @@ checksum = "77af24da69f9d9341038eba93a073b1fdaaa1b788221b00a69bce9e762cb32de"
 
 [[package]]
 name = "openssl-src"
-version = "111.8.1+1.1.1f"
+version = "111.10.2+1.1.1g"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f04f0299a91de598dde58d2e99101895498dcf3d58896a3297798f28b27c8b72"
+checksum = "a287fdb22e32b5b60624d4a5a7a02dbe82777f730ec0dbc42a0554326fef5a70"
 dependencies = [
  "cc",
 ]
 
 [[package]]
 name = "openssl-sys"
-version = "0.9.55"
+version = "0.9.58"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7717097d810a0f2e2323f9e5d11e71608355e24828410b55b9d4f18aa5f9a5d8"
+checksum = "a842db4709b604f0fe5d1170ae3565899be2ad3d9cbc72dedc789ac0511f78de"
 dependencies = [
  "autocfg 1.0.0",
  "cc",
@@ -1104,9 +1103,9 @@ dependencies = [
 
 [[package]]
 name = "paste"
-version = "0.1.10"
+version = "0.1.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ab4fb1930692d1b6a9cfabdde3d06ea0a7d186518e2f4d67660d8970e2fa647a"
+checksum = "45ca20c77d80be666aef2b45486da86238fabe33e38306bd3118fe4af33fa880"
 dependencies = [
  "paste-impl",
  "proc-macro-hack",
@@ -1114,14 +1113,11 @@ dependencies = [
 
 [[package]]
 name = "paste-impl"
-version = "0.1.10"
+version = "0.1.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "a62486e111e571b1e93b710b61e8f493c0013be39629b714cb166bdb06aa5a8a"
+checksum = "d95a7db200b97ef370c8e6de0088252f7e0dfff7d047a28528e47456c0fc98b6"
 dependencies = [
  "proc-macro-hack",
- "proc-macro2 1.0.10",
- "quote 1.0.3",
- "syn 1.0.17",
 ]
 
 [[package]]
@@ -1155,9 +1151,9 @@ dependencies = [
 
 [[package]]
 name = "pkg-config"
-version = "0.3.17"
+version = "0.3.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "05da548ad6865900e60eaba7f589cc0783590a92e940c26953ff81ddbab2d677"
+checksum = "d36492546b6af1463394d46f0c834346f31548646f6ba10849802c9c9a27ac33"
 
 [[package]]
 name = "pmutil"
@@ -1165,16 +1161,16 @@ version = "0.5.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3894e5d549cccbe44afecf72922f277f603cd4bb0219c8342631ef18fffbe004"
 dependencies = [
- "proc-macro2 1.0.10",
- "quote 1.0.3",
- "syn 1.0.17",
+ "proc-macro2 1.0.19",
+ "quote 1.0.7",
+ "syn 1.0.35",
 ]
 
 [[package]]
 name = "ppv-lite86"
-version = "0.2.6"
+version = "0.2.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "74490b50b9fbe561ac330df47c08f3f33073d2d00c150f719147d7c54522fa1b"
+checksum = "237a5ed80e274dbc66f86bd59c1e25edc039660be53194b5fe0a482e0f2612ea"
 
 [[package]]
 name = "precomputed-hash"
@@ -1184,18 +1180,18 @@ checksum = "925383efa346730478fb4838dbe9137d2a47675ad789c546d150a6e1dd4ab31c"
 
 [[package]]
 name = "proc-macro-crate"
-version = "0.1.4"
+version = "0.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e10d4b51f154c8a7fb96fd6dad097cb74b863943ec010ac94b9fd1be8861fe1e"
+checksum = "1d6ea3c4595b96363c13943497db34af4460fb474a95c43f4446ad341b8c9785"
 dependencies = [
  "toml",
 ]
 
 [[package]]
 name = "proc-macro-hack"
-version = "0.5.15"
+version = "0.5.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0d659fe7c6d27f25e9d80a1a094c223f5246f6a6596453e09d7229bf42750b63"
+checksum = "7e0456befd48169b9f13ef0f0ad46d492cf9d2dbb918bcf38e01eed4ce3ec5e4"
 
 [[package]]
 name = "proc-macro2"
@@ -1208,11 +1204,11 @@ dependencies = [
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.10"
+version = "1.0.19"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "df246d292ff63439fea9bc8c0a270bed0e390d5ebd4db4ba15aba81111b5abe3"
+checksum = "04f5f085b5d71e2188cb8271e5da0161ad52c3f227a661a3c135fdf28e258b12"
 dependencies = [
- "unicode-xid 0.2.0",
+ "unicode-xid 0.2.1",
 ]
 
 [[package]]
@@ -1242,11 +1238,11 @@ dependencies = [
 
 [[package]]
 name = "quote"
-version = "1.0.3"
+version = "1.0.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2bdc6c187c65bca4260c9011c9e3132efe4909da44726bad24cf7572ae338d7f"
+checksum = "aa563d17ecb180e500da1cfd2b028310ac758de548efdd203e18f283af693f37"
 dependencies = [
- "proc-macro2 1.0.10",
+ "proc-macro2 1.0.19",
 ]
 
 [[package]]
@@ -1407,9 +1403,9 @@ dependencies = [
 
 [[package]]
 name = "redox_syscall"
-version = "0.1.56"
+version = "0.1.57"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2439c63f3f6139d1b57529d16bc3b8bb855230c8efcc5d3a896c8bea7c3b1e84"
+checksum = "41cc0f7e4d5d4544e8861606a285bb08d3e70712ccc7d2b84d7c0ccfaf4b05ce"
 
 [[package]]
 name = "redox_users"
@@ -1424,9 +1420,9 @@ dependencies = [
 
 [[package]]
 name = "regex"
-version = "1.3.6"
+version = "1.3.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7f6946991529684867e47d86474e3a6d0c0ab9b82d5821e314b1ede31fa3a4b3"
+checksum = "9c3780fcf44b193bc4d09f36d2a3c87b251da4a046c87795a0d35f4f927ad8e6"
 dependencies = [
  "aho-corasick",
  "memchr",
@@ -1445,9 +1441,9 @@ dependencies = [
 
 [[package]]
 name = "regex-syntax"
-version = "0.6.17"
+version = "0.6.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "7fe5bd57d1d7414c6b5ed48563a2c855d995ff777729dcd91c369ec7fea395ae"
+checksum = "26412eb97c6b088a6997e05f69403a802a92d520de2f8e63c2b65f9e0f47c4e8"
 
 [[package]]
 name = "result-like"
@@ -1521,6 +1517,19 @@ dependencies = [
  "serde",
 ]
 
+[[package]]
+name = "rustpython-common"
+version = "0.0.0"
+dependencies = [
+ "cfg-if",
+ "hexf-parse",
+ "lexical",
+ "num-bigint",
+ "num-traits",
+ "parking_lot",
+ "rand 0.7.3",
+]
+
 [[package]]
 name = "rustpython-compiler"
 version = "0.1.2"
@@ -1540,11 +1549,11 @@ version = "0.1.2"
 dependencies = [
  "maplit",
  "once_cell",
- "proc-macro2 1.0.10",
- "quote 1.0.3",
+ "proc-macro2 1.0.19",
+ "quote 1.0.7",
  "rustpython-bytecode",
  "rustpython-compiler",
- "syn 1.0.17",
+ "syn 1.0.35",
 ]
 
 [[package]]
@@ -1631,6 +1640,7 @@ dependencies = [
  "result-like",
  "rustc_version_runtime",
  "rustpython-bytecode",
+ "rustpython-common",
  "rustpython-compiler",
  "rustpython-derive",
  "rustpython-parser",
@@ -1676,6 +1686,7 @@ dependencies = [
  "futures",
  "generational-arena",
  "js-sys",
+ "parking_lot",
  "rustpython-compiler",
  "rustpython-parser",
  "rustpython-vm",
@@ -1688,16 +1699,17 @@ dependencies = [
 
 [[package]]
 name = "rustyline"
-version = "6.1.0"
+version = "6.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6155a1169c281a8b75ee943a83eef0e2bb63aff057688c2111be319e51fc9f63"
+checksum = "3358c21cbbc1a751892528db4e1de4b7a2b6a73f001e215aaba97d712cfa9777"
 dependencies = [
  "cfg-if",
- "dirs 2.0.1",
+ "dirs-next",
  "libc",
  "log",
  "memchr",
  "nix",
+ "scopeguard",
  "unicode-segmentation",
  "unicode-width",
  "utf8parse",
@@ -1706,15 +1718,15 @@ dependencies = [
 
 [[package]]
 name = "ryu"
-version = "1.0.3"
+version = "1.0.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "535622e6be132bccd223f4bb2b8ac8d53cda3c7a6394944d3b2b33fb974f9d76"
+checksum = "71d301d4193d031abdd79ff7e3dd721168a9572ef3fe51a1517aba235bd8f86e"
 
 [[package]]
 name = "schannel"
-version = "0.1.18"
+version = "0.1.19"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "039c25b130bd8c1321ee2d7de7fde2659fa9c2744e4bb29711cfc852ea53cd19"
+checksum = "8f05ba609c234e60bee0d547fe94a4c7e9da733d1c962cf6e59efa4cd9c8bc75"
 dependencies = [
  "lazy_static 1.4.0",
  "winapi",
@@ -1743,9 +1755,9 @@ checksum = "388a1df253eca08550bef6c72392cfe7c30914bf41df5269b68cbd6ff8f570a3"
 
 [[package]]
 name = "serde"
-version = "1.0.106"
+version = "1.0.114"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "36df6ac6412072f67cf767ebbde4133a5b2e88e76dc6187fa7104cd16f783399"
+checksum = "5317f7588f0a5078ee60ef675ef96735a1442132dc645eb1d12c018620ed8cd3"
 dependencies = [
  "serde_derive",
 ]
@@ -1764,20 +1776,20 @@ dependencies = [
 
 [[package]]
 name = "serde_derive"
-version = "1.0.106"
+version = "1.0.114"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9e549e3abf4fb8621bd1609f11dfc9f5e50320802273b12f3811a67e6716ea6c"
+checksum = "2a0be94b04690fbaed37cddffc5c134bf537c8e3329d53e982fe04c374978f8e"
 dependencies = [
- "proc-macro2 1.0.10",
- "quote 1.0.3",
- "syn 1.0.17",
+ "proc-macro2 1.0.19",
+ "quote 1.0.7",
+ "syn 1.0.35",
 ]
 
 [[package]]
 name = "serde_json"
-version = "1.0.51"
+version = "1.0.56"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "da07b57ee2623368351e9a0488bb0b261322a15a6e0ae53e243cbdc0f4208da9"
+checksum = "3433e879a558dde8b5e8feb2a04899cf34fdde1fafb894687e52105fc1162ac3"
 dependencies = [
  "itoa",
  "ryu",
@@ -1798,9 +1810,9 @@ dependencies = [
 
 [[package]]
 name = "sha2"
-version = "0.8.1"
+version = "0.8.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "27044adfd2e1f077f649f59deb9490d3941d674002f7d062870a60ebe9bd47a0"
+checksum = "a256f46ea78a0c0d9ff00077504903ac881a1dafdc20da66545699e7776b3e69"
 dependencies = [
  "block-buffer",
  "digest",
@@ -1835,9 +1847,9 @@ checksum = "aa0eec6425219a55511a35afac416a2eecc62f5fa1bec14f9b97de0caa7daebe"
 
 [[package]]
 name = "smallvec"
-version = "1.4.0"
+version = "1.4.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c7cb5678e1615754284ec264d9bb5b4c27d2018577fd90ac0ceb578591ed5ee4"
+checksum = "3757cb9d89161a2f24e1cf78efa0c1fcff485d18e3f55e0aa3480824ddaa0f3f"
 
 [[package]]
 name = "socket2"
@@ -1889,8 +1901,8 @@ checksum = "f0f45ed1b65bf9a4bf2f7b7dc59212d1926e9eaf00fa998988e420fd124467c6"
 dependencies = [
  "phf_generator",
  "phf_shared",
- "proc-macro2 1.0.10",
- "quote 1.0.3",
+ "proc-macro2 1.0.19",
+ "quote 1.0.7",
  "string_cache_shared",
 ]
 
@@ -1931,13 +1943,13 @@ dependencies = [
 
 [[package]]
 name = "syn"
-version = "1.0.17"
+version = "1.0.35"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "0df0eb663f387145cab623dea85b09c2c5b4b0aef44e945d928e682fce71bb03"
+checksum = "fb7f4c519df8c117855e19dd8cc851e89eb746fe7a73f0157e0d95fdec5369b0"
 dependencies = [
- "proc-macro2 1.0.10",
- "quote 1.0.3",
- "unicode-xid 0.2.0",
+ "proc-macro2 1.0.19",
+ "quote 1.0.7",
+ "unicode-xid 0.2.1",
 ]
 
 [[package]]
@@ -1947,7 +1959,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "edd106a334b7657c10b7c540a0106114feadeb4dc314513e97df481d5d966f42"
 dependencies = [
  "byteorder 1.3.4",
- "dirs 1.0.5",
+ "dirs",
  "winapi",
 ]
 
@@ -1999,6 +2011,12 @@ dependencies = [
  "winapi",
 ]
 
+[[package]]
+name = "tinyvec"
+version = "0.3.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "53953d2d3a5ad81d9f844a32f14ebb121f50b650cd59d0ee2a07cf13c617efed"
+
 [[package]]
 name = "toml"
 version = "0.5.6"
@@ -2010,9 +2028,9 @@ dependencies = [
 
 [[package]]
 name = "typenum"
-version = "1.11.2"
+version = "1.12.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6d2783fe2d6b8c1101136184eb41be8b1ad379e4657050b8aaff0c79ee7575f9"
+checksum = "373c8a200f9e67a0c95e62a4f52fbf80c23b4381c05a17845531982fa99e6b33"
 
 [[package]]
 name = "uname"
@@ -2147,11 +2165,11 @@ checksum = "623f59e6af2a98bdafeb93fa277ac8e1e40440973001ca15cf4ae1541cd16d56"
 
 [[package]]
 name = "unicode-normalization"
-version = "0.1.12"
+version = "0.1.13"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5479532badd04e128284890390c1e876ef7a993d0570b3597ae43dfa1d59afa4"
+checksum = "6fb19cf769fa8c6a80a162df694621ebeb4dafb606470b2b2fce0be40a98a977"
 dependencies = [
- "smallvec",
+ "tinyvec",
 ]
 
 [[package]]
@@ -2162,9 +2180,9 @@ checksum = "e83e153d1053cbb5a118eeff7fd5be06ed99153f00dbcd8ae310c5fb2b22edc0"
 
 [[package]]
 name = "unicode-width"
-version = "0.1.7"
+version = "0.1.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "caaa9d531767d1ff2150b9332433f32a24622147e5ebb1f26409d5da67afd479"
+checksum = "9337591893a19b88d8d87f2cec1e73fad5cdfd10e5a6f349f498ad6ea2ffb1e3"
 
 [[package]]
 name = "unicode-xid"
@@ -2174,9 +2192,9 @@ checksum = "fc72304796d0818e357ead4e000d19c9c174ab23dc11093ac919054d20a6a7fc"
 
 [[package]]
 name = "unicode-xid"
-version = "0.2.0"
+version = "0.2.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "826e7639553986605ec5979c7dd957c7895e93eabed50ab2ffa7f6128a75097c"
+checksum = "f7fe0bb3479651439c9112f72b6c505038574c9fbb575ed1bf3b797fa39dd564"
 
 [[package]]
 name = "unicode_names2"
@@ -2202,15 +2220,15 @@ dependencies = [
 
 [[package]]
 name = "vcpkg"
-version = "0.2.8"
+version = "0.2.10"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3fc439f2794e98976c88a2a2dafce96b930fe8010b0a256b3c2199a773933168"
+checksum = "6454029bf181f092ad1b853286f23e2c507d8e8194d01d92da4a55c274a5508c"
 
 [[package]]
 name = "vec_map"
-version = "0.8.1"
+version = "0.8.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "05c78687fb1a80548ae3250346c3db86a80a7cdd77bda190189f2d0a0987c81a"
+checksum = "f1bddf1187be692e79c5ffeab891132dfb0f236ed36a43c7ed39f1165ee20191"
 
 [[package]]
 name = "void"
@@ -2232,9 +2250,9 @@ checksum = "cccddf32554fecc6acb585f82a32a72e28b48f8c4c1883ddfeeeaa96f7d8e519"
 
 [[package]]
 name = "wasm-bindgen"
-version = "0.2.60"
+version = "0.2.65"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2cc57ce05287f8376e998cbddfb4c8cb43b84a7ec55cf4551d7c00eef317a47f"
+checksum = "f3edbcc9536ab7eababcc6d2374a0b7bfe13a2b6d562c5e07f370456b1a8f33d"
 dependencies = [
  "cfg-if",
  "wasm-bindgen-macro",
@@ -2242,16 +2260,16 @@ dependencies = [
 
 [[package]]
 name = "wasm-bindgen-backend"
-version = "0.2.60"
+version = "0.2.65"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d967d37bf6c16cca2973ca3af071d0a2523392e4a594548155d89a678f4237cd"
+checksum = "89ed2fb8c84bfad20ea66b26a3743f3e7ba8735a69fe7d95118c33ec8fc1244d"
 dependencies = [
  "bumpalo",
  "lazy_static 1.4.0",
  "log",
- "proc-macro2 1.0.10",
- "quote 1.0.3",
- "syn 1.0.17",
+ "proc-macro2 1.0.19",
+ "quote 1.0.7",
+ "syn 1.0.35",
  "wasm-bindgen-shared",
 ]
 
@@ -2270,38 +2288,38 @@ dependencies = [
 
 [[package]]
 name = "wasm-bindgen-macro"
-version = "0.2.60"
+version = "0.2.65"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8bd151b63e1ea881bb742cd20e1d6127cef28399558f3b5d415289bc41eee3a4"
+checksum = "eb071268b031a64d92fc6cf691715ca5a40950694d8f683c5bb43db7c730929e"
 dependencies = [
- "quote 1.0.3",
+ "quote 1.0.7",
  "wasm-bindgen-macro-support",
 ]
 
 [[package]]
 name = "wasm-bindgen-macro-support"
-version = "0.2.60"
+version = "0.2.65"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d68a5b36eef1be7868f668632863292e37739656a80fc4b9acec7b0bd35a4931"
+checksum = "cf592c807080719d1ff2f245a687cbadb3ed28b2077ed7084b47aba8b691f2c6"
 dependencies = [
- "proc-macro2 1.0.10",
- "quote 1.0.3",
- "syn 1.0.17",
+ "proc-macro2 1.0.19",
+ "quote 1.0.7",
+ "syn 1.0.35",
  "wasm-bindgen-backend",
  "wasm-bindgen-shared",
 ]
 
 [[package]]
 name = "wasm-bindgen-shared"
-version = "0.2.60"
+version = "0.2.65"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "daf76fe7d25ac79748a37538b7daeed1c7a6867c92d3245c12c6222e4a20d639"
+checksum = "72b6c0220ded549d63860c78c38f3bcc558d1ca3f4efa74942c536ddbbb55e87"
 
 [[package]]
 name = "web-sys"
-version = "0.3.37"
+version = "0.3.42"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "2d6f51648d8c56c366144378a33290049eafdd784071077f6fe37dae64c1c4cb"
+checksum = "8be2398f326b7ba09815d0b403095f34dd708579220d099caae89be0b32137b2"
 dependencies = [
  "js-sys",
  "wasm-bindgen",
@@ -2309,9 +2327,9 @@ dependencies = [
 
 [[package]]
 name = "winapi"
-version = "0.3.8"
+version = "0.3.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8093091eeb260906a183e6ae1abdba2ef5ef2257a21801128899c3fc699229c6"
+checksum = "5c839a674fcd7a98952e593242ea400abe93992746761e38641405d28b00f419"
 dependencies = [
  "winapi-i686-pc-windows-gnu",
  "winapi-x86_64-pc-windows-gnu",
@@ -2325,9 +2343,9 @@ checksum = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
 
 [[package]]
 name = "winapi-util"
-version = "0.1.4"
+version = "0.1.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fa515c5163a99cc82bab70fd3bfdd36d827be85de63737b40fcef2ce084a436e"
+checksum = "70ec6ce85bb158151cae5e5c87f95a8e97d2c0c4b001223f33a334e3ce5de178"
 dependencies = [
  "winapi",
 ]
diff --git a/Cargo.toml b/Cargo.toml
index 78a179ade..8491aea3f 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -8,15 +8,17 @@ repository = "https://github.com/RustPython/RustPython"
 license = "MIT"
 
 [workspace]
-members = [".", "derive", "vm", "wasm/lib", "parser", "compiler", "bytecode", "examples/freeze", "vm/pylib-crate"]
+members = [".", "derive", "vm", "wasm/lib", "parser", "compiler", "bytecode", "examples/freeze", "vm/pylib-crate", "common"]
 
 [[bench]]
 name = "bench"
 path = "./benchmarks/bench.rs"
 
 [features]
+default = ["threading"]
 flame-it = ["rustpython-vm/flame-it", "flame", "flamescope"]
 freeze-stdlib = ["rustpython-vm/freeze-stdlib"]
+threading = ["rustpython-vm/threading"]
 
 ssl = ["rustpython-vm/ssl"]
 
@@ -24,9 +26,9 @@ ssl = ["rustpython-vm/ssl"]
 log = "0.4"
 env_logger = "0.7"
 clap = "2.33"
-rustpython-compiler = {path = "compiler", version = "0.1.1"}
-rustpython-parser = {path = "parser", version = "0.1.1"}
-rustpython-vm = {path = "vm", version = "0.1.1"}
+rustpython-compiler = { path = "compiler", version = "0.1.1" }
+rustpython-parser = { path = "parser", version = "0.1.1" }
+rustpython-vm = { path = "vm", version = "0.1.1", default-features = false, features = ["compile-parse"] }
 dirs = { package = "dirs-next", version = "1.0" }
 num-traits = "0.2.8"
 cfg-if = "0.1"
diff --git a/Lib/importlib/_bootstrap_external.py b/Lib/importlib/_bootstrap_external.py
index f8ff5f4f2..a4e6a7176 100644
--- a/Lib/importlib/_bootstrap_external.py
+++ b/Lib/importlib/_bootstrap_external.py
@@ -1587,7 +1587,10 @@ def _setup(_bootstrap_module):
     setattr(self_module, '_pathseps_with_colon', {f':{s}' for s in path_separators})
 
     # Directly load the _thread module (needed during bootstrap).
-    thread_module = _bootstrap._builtin_from_name('_thread')
+    try:
+        thread_module = _bootstrap._builtin_from_name('_thread')
+    except ImportError:
+        thread_module = None
     setattr(self_module, '_thread', thread_module)
 
     # Directly load the _weakref module (needed during bootstrap).
diff --git a/common/Cargo.toml b/common/Cargo.toml
new file mode 100644
index 000000000..b8603397a
--- /dev/null
+++ b/common/Cargo.toml
@@ -0,0 +1,19 @@
+[package]
+name = "rustpython-common"
+version = "0.0.0"
+authors = ["RustPython Team"]
+edition = "2018"
+
+[features]
+threading = ["parking_lot"]
+
+[dependencies]
+parking_lot = { version = "0.11.0", optional = true }
+num-traits = "0.2"
+num-bigint = "0.3"
+lexical = "4"
+hexf-parse = "0.1.0"
+cfg-if = "0.1"
+
+[dev-dependencies]
+rand = "0.7.3"
diff --git a/common/src/cell.rs b/common/src/cell.rs
new file mode 100644
index 000000000..4c48326eb
--- /dev/null
+++ b/common/src/cell.rs
@@ -0,0 +1,132 @@
+#[cfg(feature = "threading")]
+use parking_lot::{Mutex, MutexGuard, RwLock, RwLockReadGuard, RwLockWriteGuard};
+#[cfg(not(feature = "threading"))]
+use std::cell::{Ref, RefCell, RefMut};
+use std::ops::{Deref, DerefMut};
+
+cfg_if::cfg_if! {
+    if #[cfg(feature = "threading")] {
+        type MutexInner<T> = Mutex<T>;
+        type MutexGuardInner<'a, T> = MutexGuard<'a, T>;
+        const fn new_mutex<T>(value: T) -> MutexInner<T> {
+            parking_lot::const_mutex(value)
+        }
+        fn lock_mutex<T: ?Sized>(m: &MutexInner<T>) -> MutexGuardInner<T> {
+            m.lock()
+        }
+    } else {
+        type MutexInner<T> = RefCell<T>;
+        type MutexGuardInner<'a, T> = RefMut<'a, T>;
+        const fn new_mutex<T>(value: T) -> MutexInner<T> {
+            RefCell::new(value)
+        }
+        fn lock_mutex<T: ?Sized>(m: &MutexInner<T>) -> MutexGuardInner<T> {
+            m.borrow_mut()
+        }
+    }
+}
+
+#[derive(Debug, Default)]
+#[repr(transparent)]
+pub struct PyMutex<T: ?Sized>(MutexInner<T>);
+
+impl<T> PyMutex<T> {
+    pub const fn new(value: T) -> Self {
+        Self(new_mutex(value))
+    }
+}
+
+impl<T: ?Sized> PyMutex<T> {
+    pub fn lock(&self) -> PyMutexGuard<T> {
+        PyMutexGuard(lock_mutex(&self.0))
+    }
+}
+
+#[derive(Debug)]
+#[repr(transparent)]
+pub struct PyMutexGuard<'a, T: ?Sized>(MutexGuardInner<'a, T>);
+impl<T: ?Sized> Deref for PyMutexGuard<'_, T> {
+    type Target = T;
+    fn deref(&self) -> &T {
+        self.0.deref()
+    }
+}
+impl<T: ?Sized> DerefMut for PyMutexGuard<'_, T> {
+    fn deref_mut(&mut self) -> &mut T {
+        self.0.deref_mut()
+    }
+}
+
+cfg_if::cfg_if! {
+    if #[cfg(feature = "threading")] {
+        type RwLockInner<T> = RwLock<T>;
+        type RwLockReadInner<'a, T> = RwLockReadGuard<'a, T>;
+        type RwLockWriteInner<'a, T> = RwLockWriteGuard<'a, T>;
+        const fn new_rwlock<T>(value: T) -> RwLockInner<T> {
+            parking_lot::const_rwlock(value)
+        }
+        fn read_rwlock<T: ?Sized>(m: &RwLockInner<T>) -> RwLockReadInner<T> {
+            m.read()
+        }
+        fn write_rwlock<T: ?Sized>(m: &RwLockInner<T>) -> RwLockWriteInner<T> {
+            m.write()
+        }
+    } else {
+        type RwLockInner<T> = RefCell<T>;
+        type RwLockReadInner<'a, T> = Ref<'a, T>;
+        type RwLockWriteInner<'a, T> = RefMut<'a, T>;
+        const fn new_rwlock<T>(value: T) -> RwLockInner<T> {
+            RefCell::new(value)
+        }
+        fn read_rwlock<T: ?Sized>(m: &RwLockInner<T>) -> RwLockReadInner<T> {
+            m.borrow()
+        }
+        fn write_rwlock<T: ?Sized>(m: &RwLockInner<T>) -> RwLockWriteInner<T> {
+            m.borrow_mut()
+        }
+    }
+}
+
+#[derive(Debug, Default)]
+#[repr(transparent)]
+pub struct PyRwLock<T: ?Sized>(RwLockInner<T>);
+
+impl<T> PyRwLock<T> {
+    pub const fn new(value: T) -> Self {
+        Self(new_rwlock(value))
+    }
+}
+
+impl<T: ?Sized> PyRwLock<T> {
+    pub fn read(&self) -> PyRwLockReadGuard<T> {
+        PyRwLockReadGuard(read_rwlock(&self.0))
+    }
+    pub fn write(&self) -> PyRwLockWriteGuard<T> {
+        PyRwLockWriteGuard(write_rwlock(&self.0))
+    }
+}
+
+#[derive(Debug)]
+#[repr(transparent)]
+pub struct PyRwLockReadGuard<'a, T: ?Sized>(RwLockReadInner<'a, T>);
+impl<T: ?Sized> Deref for PyRwLockReadGuard<'_, T> {
+    type Target = T;
+    fn deref(&self) -> &T {
+        self.0.deref()
+    }
+}
+
+#[derive(Debug)]
+#[repr(transparent)]
+pub struct PyRwLockWriteGuard<'a, T: ?Sized>(RwLockWriteInner<'a, T>);
+impl<T: ?Sized> Deref for PyRwLockWriteGuard<'_, T> {
+    type Target = T;
+    fn deref(&self) -> &T {
+        self.0.deref()
+    }
+}
+impl<T: ?Sized> DerefMut for PyRwLockWriteGuard<'_, T> {
+    fn deref_mut(&mut self) -> &mut T {
+        self.0.deref_mut()
+    }
+}
diff --git a/common/src/float_ops.rs b/common/src/float_ops.rs
new file mode 100644
index 000000000..34f2c4e6a
--- /dev/null
+++ b/common/src/float_ops.rs
@@ -0,0 +1,194 @@
+use num_bigint::{BigInt, ToBigInt};
+use num_traits::{Float, Signed, ToPrimitive, Zero};
+
+pub fn ufrexp(value: f64) -> (f64, i32) {
+    if 0.0 == value {
+        (0.0, 0i32)
+    } else {
+        let bits = value.to_bits();
+        let exponent: i32 = ((bits >> 52) & 0x7ff) as i32 - 1022;
+        let mantissa_bits = bits & (0x000f_ffff_ffff_ffff) | (1022 << 52);
+        (f64::from_bits(mantissa_bits), exponent)
+    }
+}
+
+pub fn eq_int(value: f64, other: &BigInt) -> bool {
+    if let (Some(self_int), Some(other_float)) = (value.to_bigint(), other.to_f64()) {
+        value == other_float && self_int == *other
+    } else {
+        false
+    }
+}
+
+pub fn lt_int(value: f64, other_int: &BigInt) -> bool {
+    match (value.to_bigint(), other_int.to_f64()) {
+        (Some(self_int), Some(other_float)) => value < other_float || self_int < *other_int,
+        // finite float, other_int too big for float,
+        // the result depends only on other_int’s sign
+        (Some(_), None) => other_int.is_positive(),
+        // infinite float must be bigger or lower than any int, depending on its sign
+        _ if value.is_infinite() => value.is_sign_negative(),
+        // NaN, always false
+        _ => false,
+    }
+}
+
+pub fn gt_int(value: f64, other_int: &BigInt) -> bool {
+    match (value.to_bigint(), other_int.to_f64()) {
+        (Some(self_int), Some(other_float)) => value > other_float || self_int > *other_int,
+        // finite float, other_int too big for float,
+        // the result depends only on other_int’s sign
+        (Some(_), None) => other_int.is_negative(),
+        // infinite float must be bigger or lower than any int, depending on its sign
+        _ if value.is_infinite() => value.is_sign_positive(),
+        // NaN, always false
+        _ => false,
+    }
+}
+
+pub fn parse_str(literal: &str) -> Option<f64> {
+    if literal.starts_with('_') || literal.ends_with('_') {
+        return None;
+    }
+
+    let mut buf = String::with_capacity(literal.len());
+    let mut last_tok: Option<char> = None;
+    for c in literal.chars() {
+        if !(c.is_ascii_alphanumeric() || c == '_' || c == '+' || c == '-' || c == '.') {
+            return None;
+        }
+
+        if !c.is_ascii_alphanumeric() {
+            if let Some(l) = last_tok {
+                if !l.is_ascii_alphanumeric() && !(c == '.' && (l == '-' || l == '+')) {
+                    return None;
+                }
+            }
+        }
+
+        if c != '_' {
+            buf.push(c);
+        }
+        last_tok = Some(c);
+    }
+
+    if let Ok(f) = lexical::parse(buf.as_str()) {
+        Some(f)
+    } else {
+        None
+    }
+}
+
+pub fn is_integer(v: f64) -> bool {
+    (v - v.round()).abs() < std::f64::EPSILON
+}
+
+pub fn to_string(value: f64) -> String {
+    let lit = format!("{:e}", value);
+    if let Some(position) = lit.find('e') {
+        let significand = &lit[..position];
+        let exponent = &lit[position + 1..];
+        let exponent = exponent.parse::<i32>().unwrap();
+        if exponent < 16 && exponent > -5 {
+            if is_integer(value) {
+                format!("{:.1?}", value)
+            } else {
+                value.to_string()
+            }
+        } else {
+            format!("{}e{:+#03}", significand, exponent)
+        }
+    } else {
+        value.to_string()
+    }
+}
+
+pub fn from_hex(s: &str) -> Option<f64> {
+    if let Ok(f) = hexf_parse::parse_hexf64(s, false) {
+        return Some(f);
+    }
+    match s.to_ascii_lowercase().as_str() {
+        "nan" => Some(f64::NAN),
+        "+nan" => Some(f64::NAN),
+        "-nan" => Some(f64::NAN),
+        "inf" => Some(f64::INFINITY),
+        "infinity" => Some(f64::INFINITY),
+        "+inf" => Some(f64::INFINITY),
+        "+infinity" => Some(f64::INFINITY),
+        "-inf" => Some(f64::NEG_INFINITY),
+        "-infinity" => Some(f64::NEG_INFINITY),
+        value => {
+            let mut hex = String::with_capacity(value.len());
+            let has_0x = value.contains("0x");
+            let has_p = value.contains('p');
+            let has_dot = value.contains('.');
+            let mut start = 0;
+
+            if !has_0x && value.starts_with('-') {
+                hex.push_str("-0x");
+                start += 1;
+            } else if !has_0x {
+                hex.push_str("0x");
+                if value.starts_with('+') {
+                    start += 1;
+                }
+            }
+
+            for (index, ch) in value.chars().enumerate() {
+                if ch == 'p' && has_dot {
+                    hex.push_str("p");
+                } else if ch == 'p' && !has_dot {
+                    hex.push_str(".p");
+                } else if index >= start {
+                    hex.push(ch);
+                }
+            }
+
+            if !has_p && has_dot {
+                hex.push_str("p0");
+            } else if !has_p && !has_dot {
+                hex.push_str(".p0")
+            }
+
+            hexf_parse::parse_hexf64(hex.as_str(), false).ok()
+        }
+    }
+}
+
+pub fn to_hex(value: f64) -> String {
+    let (mantissa, exponent, sign) = value.integer_decode();
+    let sign_fmt = if sign < 0 { "-" } else { "" };
+    match value {
+        value if value.is_zero() => format!("{}0x0.0p+0", sign_fmt),
+        value if value.is_infinite() => format!("{}inf", sign_fmt),
+        value if value.is_nan() => "nan".to_owned(),
+        _ => {
+            const BITS: i16 = 52;
+            const FRACT_MASK: u64 = 0xf_ffff_ffff_ffff;
+            format!(
+                "{}0x{:x}.{:013x}p{:+}",
+                sign_fmt,
+                mantissa >> BITS,
+                mantissa & FRACT_MASK,
+                exponent + BITS
+            )
+        }
+    }
+}
+
+#[test]
+fn test_to_hex() {
+    use rand::Rng;
+    for _ in 0..20000 {
+        let bytes = rand::thread_rng().gen::<[u64; 1]>();
+        let f = f64::from_bits(bytes[0]);
+        if !f.is_finite() {
+            continue;
+        }
+        let hex = to_hex(f);
+        // println!("{} -> {}", f, hex);
+        let roundtrip = hexf_parse::parse_hexf64(&hex, false).unwrap();
+        // println!("  -> {}", roundtrip);
+        assert!(f == roundtrip, "{} {} {}", f, hex, roundtrip);
+    }
+}
diff --git a/vm/src/pyhash.rs b/common/src/hash.rs
similarity index 59%
rename from vm/src/pyhash.rs
rename to common/src/hash.rs
index 598bde2a0..12b858e5b 100644
--- a/vm/src/pyhash.rs
+++ b/common/src/hash.rs
@@ -1,12 +1,8 @@
 use num_bigint::BigInt;
 use num_traits::ToPrimitive;
+use std::collections::hash_map::DefaultHasher;
 use std::hash::{Hash, Hasher};
 
-use crate::obj::objfloat;
-use crate::pyobject::PyObjectRef;
-use crate::pyobject::PyResult;
-use crate::vm::VirtualMachine;
-
 pub type PyHash = i64;
 pub type PyUHash = u64;
 
@@ -18,6 +14,12 @@ pub const MODULUS: PyUHash = (1 << BITS) - 1;
 pub const INF: PyHash = 314_159;
 pub const NAN: PyHash = 0;
 pub const IMAG: PyHash = MULTIPLIER;
+pub const ALGO: &str = "siphasher13";
+pub const HASH_BITS: usize = std::mem::size_of::<PyHash>() * 8;
+// internally DefaultHasher uses 2 u64s as the seed, but
+// that's not guaranteed to be consistent across Rust releases
+// TODO: use something like the siphasher crate as our hash algorithm
+pub const SEED_BITS: usize = std::mem::size_of::<PyHash>() * 2 * 8;
 
 // pub const CUTOFF: usize = 7;
 
@@ -35,7 +37,7 @@ pub fn hash_float(value: f64) -> PyHash {
         };
     }
 
-    let frexp = objfloat::ufrexp(value);
+    let frexp = super::float_ops::ufrexp(value);
 
     // process 28 bits at a time;  this should work well both for binary
     // and hexadecimal floating point.
@@ -67,30 +69,32 @@ pub fn hash_float(value: f64) -> PyHash {
 }
 
 pub fn hash_value<T: Hash>(data: &T) -> PyHash {
-    let mut hasher = std::collections::hash_map::DefaultHasher::new();
+    let mut hasher = DefaultHasher::new();
     data.hash(&mut hasher);
     hasher.finish() as PyHash
 }
 
-pub fn hash_iter<'a, I: std::iter::Iterator<Item = &'a PyObjectRef>>(
-    iter: I,
-    vm: &VirtualMachine,
-) -> PyResult<PyHash> {
-    let mut hasher = std::collections::hash_map::DefaultHasher::new();
+pub fn hash_iter<'a, T: 'a, I, F, E>(iter: I, hashf: F) -> Result<PyHash, E>
+where
+    I: IntoIterator<Item = &'a T>,
+    F: Fn(&'a T) -> Result<PyHash, E>,
+{
+    let mut hasher = DefaultHasher::new();
     for element in iter {
-        let item_hash = vm._hash(&element)?;
+        let item_hash = hashf(element)?;
         item_hash.hash(&mut hasher);
     }
     Ok(hasher.finish() as PyHash)
 }
 
-pub fn hash_iter_unordered<'a, I: std::iter::Iterator<Item = &'a PyObjectRef>>(
-    iter: I,
-    vm: &VirtualMachine,
-) -> PyResult<PyHash> {
+pub fn hash_iter_unordered<'a, T: 'a, I, F, E>(iter: I, hashf: F) -> Result<PyHash, E>
+where
+    I: IntoIterator<Item = &'a T>,
+    F: Fn(&'a T) -> Result<PyHash, E>,
+{
     let mut hash: PyHash = 0;
     for element in iter {
-        let item_hash = vm._hash(element)?;
+        let item_hash = hashf(element)?;
         // xor is commutative and hash should be independent of order
         hash ^= item_hash;
     }
@@ -103,31 +107,3 @@ pub fn hash_bigint(value: &BigInt) -> PyHash {
         None => (value % MODULUS).to_i64().unwrap(),
     }
 }
-
-#[pystruct_sequence(module = "sys", name = "hash_info")]
-#[derive(Debug)]
-pub(crate) struct PyHashInfo {
-    width: usize,
-    modulus: PyUHash,
-    inf: PyHash,
-    nan: PyHash,
-    imag: PyHash,
-    algorithm: &'static str,
-    hash_bits: usize,
-    seed_bits: usize,
-}
-impl PyHashInfo {
-    pub const INFO: Self = PyHashInfo {
-        width: BITS,
-        modulus: MODULUS,
-        inf: INF,
-        nan: NAN,
-        imag: IMAG,
-        algorithm: "siphash13",
-        hash_bits: std::mem::size_of::<PyHash>() * 8,
-        // internally hash_map::DefaultHasher uses 2 u64s as the seed, but
-        // that's not guaranteed to be consistent across Rust releases
-        // TODO: use something like the siphasher crate as our hash algorithm
-        seed_bits: std::mem::size_of::<PyHash>() * 2 * 8,
-    };
-}
diff --git a/common/src/lib.rs b/common/src/lib.rs
new file mode 100644
index 000000000..f6d704744
--- /dev/null
+++ b/common/src/lib.rs
@@ -0,0 +1,6 @@
+//! A crate to hold types and functions common to all rustpython components.
+
+pub mod cell;
+pub mod float_ops;
+pub mod hash;
+pub mod rc;
diff --git a/common/src/rc.rs b/common/src/rc.rs
new file mode 100644
index 000000000..8021b6112
--- /dev/null
+++ b/common/src/rc.rs
@@ -0,0 +1,14 @@
+#[cfg(not(feature = "threading"))]
+use std::rc::{Rc, Weak};
+#[cfg(feature = "threading")]
+use std::sync::{Arc, Weak};
+
+// type aliases instead of newtypes because you can't do `fn method(self: PyRc<Self>)` with a
+// newtype; requires the arbitrary_self_types unstable feature
+
+#[cfg(feature = "threading")]
+pub type PyRc<T> = Arc<T>;
+#[cfg(not(feature = "threading"))]
+pub type PyRc<T> = Rc<T>;
+
+pub type PyWeak<T> = Weak<T>;
diff --git a/parser/Cargo.toml b/parser/Cargo.toml
index 8d3aa4b09..da88a7586 100644
--- a/parser/Cargo.toml
+++ b/parser/Cargo.toml
@@ -12,8 +12,8 @@ edition = "2018"
 lalrpop="0.17"
 
 [dependencies]
-lalrpop-util="0.17"
-log="0.4.1"
+lalrpop-util = "0.17"
+log = "0.4.1"
 num-bigint = "0.3"
 num-traits = "0.2"
 unic-emoji-char = "0.9"
diff --git a/vm/Cargo.toml b/vm/Cargo.toml
index 66c08aa9b..9279eadae 100644
--- a/vm/Cargo.toml
+++ b/vm/Cargo.toml
@@ -9,10 +9,12 @@ edition = "2018"
 include = ["src/**/*.rs", "Cargo.toml", "build.rs", "Lib/**/*.py"]
 
 [features]
-default = ["rustpython-parser", "rustpython-compiler"]
+default = ["compile-parse", "threading"]
 vm-tracing-logging = []
 flame-it = ["flame", "flamer"]
 freeze-stdlib = ["rustpython-pylib"]
+threading = ["rustpython-common/threading"]
+compile-parse = ["rustpython-parser", "rustpython-compiler"]
 
 ssl = ["openssl", "openssl-sys", "openssl-probe"]
 
@@ -91,6 +93,7 @@ unic-ucd-ident     = "0.9"
 
 flame = { version = "0.2", optional = true }
 flamer = { version = "0.3", optional = true }
+rustpython-common = { path = "../common" }
 
 [target.'cfg(unix)'.dependencies]
 exitcode = "1.1.2"
diff --git a/vm/pylib-crate/Cargo.toml b/vm/pylib-crate/Cargo.toml
index b49379f27..21e41087e 100644
--- a/vm/pylib-crate/Cargo.toml
+++ b/vm/pylib-crate/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "rustpython-pylib"
 version = "0.1.0"
-authors = ["Noah <33094578+coolreader18@users.noreply.github.com>"]
+authors = ["RustPython Team"]
 edition = "2018"
 
 [dependencies]
diff --git a/vm/src/builtins.rs b/vm/src/builtins.rs
index c6a073ebe..896fa8b9d 100644
--- a/vm/src/builtins.rs
+++ b/vm/src/builtins.rs
@@ -27,7 +27,6 @@ mod decl {
     use crate::obj::objsequence;
     use crate::obj::objstr::{PyString, PyStringRef};
     use crate::obj::objtype::{self, PyClassRef};
-    use crate::pyhash;
     use crate::pyobject::{
         Either, IdProtocol, ItemProtocol, PyCallable, PyIterable, PyObjectRef, PyResult, PyValue,
         TryFromObject, TypeProtocol,
@@ -37,6 +36,7 @@ mod decl {
     #[cfg(feature = "rustpython-parser")]
     use crate::stdlib::ast;
     use crate::vm::VirtualMachine;
+    use rustpython_common::hash::PyHash;
 
     #[pyfunction]
     fn abs(x: PyObjectRef, vm: &VirtualMachine) -> PyResult {
@@ -329,7 +329,7 @@ mod decl {
     }
 
     #[pyfunction]
-    fn hash(obj: PyObjectRef, vm: &VirtualMachine) -> PyResult<pyhash::PyHash> {
+    fn hash(obj: PyObjectRef, vm: &VirtualMachine) -> PyResult<PyHash> {
         vm._hash(&obj)
     }
 
diff --git a/vm/src/dictdatatype.rs b/vm/src/dictdatatype.rs
index 7ff9cb7db..6116af321 100644
--- a/vm/src/dictdatatype.rs
+++ b/vm/src/dictdatatype.rs
@@ -1,9 +1,9 @@
+use crate::common::cell::{PyRwLock, PyRwLockReadGuard, PyRwLockWriteGuard};
 use crate::obj::objstr::{PyString, PyStringRef};
-use crate::pyhash;
 use crate::pyobject::{IdProtocol, IntoPyObject, PyObjectRef, PyResult};
 use crate::vm::VirtualMachine;
 use num_bigint::ToBigInt;
-use parking_lot::{RwLock, RwLockReadGuard, RwLockWriteGuard};
+use rustpython_common::hash;
 /// Ordered dictionary implementation.
 /// Inspired by: https://morepypy.blogspot.com/2015/01/faster-more-memory-efficient-and-more.html
 /// And: https://www.youtube.com/watch?v=p33CVV29OG8
@@ -13,14 +13,14 @@ use std::hash::{Hash, Hasher};
 use std::mem::size_of;
 
 /// hash value of an object returned by __hash__
-type HashValue = pyhash::PyHash;
+type HashValue = hash::PyHash;
 /// index calculated by resolving collision
-type HashIndex = pyhash::PyHash;
+type HashIndex = hash::PyHash;
 /// entry index mapped in indices
 type EntryIndex = usize;
 
 pub struct Dict<T = PyObjectRef> {
-    inner: RwLock<InnerDict<T>>,
+    inner: PyRwLock<InnerDict<T>>,
 }
 
 struct InnerDict<T> {
@@ -42,7 +42,7 @@ impl<T: Clone> Clone for InnerDict<T> {
 impl<T: Clone> Clone for Dict<T> {
     fn clone(&self) -> Self {
         Dict {
-            inner: RwLock::new(self.inner.read().clone()),
+            inner: PyRwLock::new(self.inner.read().clone()),
         }
     }
 }
@@ -50,7 +50,7 @@ impl<T: Clone> Clone for Dict<T> {
 impl<T> Default for Dict<T> {
     fn default() -> Self {
         Dict {
-            inner: RwLock::new(InnerDict {
+            inner: PyRwLock::new(InnerDict {
                 size: 0,
                 indices: HashMap::new(),
                 entries: Vec::new(),
@@ -82,11 +82,11 @@ pub struct DictSize {
 }
 
 impl<T: Clone> Dict<T> {
-    fn borrow_value(&self) -> RwLockReadGuard<'_, InnerDict<T>> {
+    fn borrow_value(&self) -> PyRwLockReadGuard<'_, InnerDict<T>> {
         self.inner.read()
     }
 
-    fn borrow_value_mut(&self) -> RwLockWriteGuard<'_, InnerDict<T>> {
+    fn borrow_value_mut(&self) -> PyRwLockWriteGuard<'_, InnerDict<T>> {
         self.inner.write()
     }
 
@@ -463,8 +463,8 @@ impl DictKey for &PyStringRef {
 impl DictKey for &str {
     fn do_hash(self, _vm: &VirtualMachine) -> PyResult<HashValue> {
         // follow a similar route as the hashing of PyStringRef
-        let raw_hash = pyhash::hash_value(&self.to_owned()).to_bigint().unwrap();
-        let raw_hash = pyhash::hash_bigint(&raw_hash);
+        let raw_hash = hash::hash_value(&self.to_owned()).to_bigint().unwrap();
+        let raw_hash = hash::hash_bigint(&raw_hash);
         let mut hasher = DefaultHasher::new();
         raw_hash.hash(&mut hasher);
         Ok(hasher.finish() as HashValue)
diff --git a/vm/src/exceptions.rs b/vm/src/exceptions.rs
index 5f4e6b4a9..7f5d4d242 100644
--- a/vm/src/exceptions.rs
+++ b/vm/src/exceptions.rs
@@ -1,3 +1,4 @@
+use crate::common::cell::PyRwLock;
 use crate::function::PyFuncArgs;
 use crate::obj::objnone::PyNone;
 use crate::obj::objstr::{PyString, PyStringRef};
@@ -14,7 +15,6 @@ use crate::types::create_type;
 use crate::VirtualMachine;
 
 use itertools::Itertools;
-use parking_lot::RwLock;
 use std::fmt;
 use std::fs::File;
 use std::io::{self, BufRead, BufReader, Write};
@@ -23,11 +23,11 @@ use crossbeam_utils::atomic::AtomicCell;
 
 #[pyclass]
 pub struct PyBaseException {
-    traceback: RwLock<Option<PyTracebackRef>>,
-    cause: RwLock<Option<PyBaseExceptionRef>>,
-    context: RwLock<Option<PyBaseExceptionRef>>,
+    traceback: PyRwLock<Option<PyTracebackRef>>,
+    cause: PyRwLock<Option<PyBaseExceptionRef>>,
+    context: PyRwLock<Option<PyBaseExceptionRef>>,
     suppress_context: AtomicCell<bool>,
-    args: RwLock<PyTupleRef>,
+    args: PyRwLock<PyTupleRef>,
 }
 
 impl fmt::Debug for PyBaseException {
@@ -51,11 +51,11 @@ impl PyValue for PyBaseException {
 impl PyBaseException {
     pub(crate) fn new(args: Vec<PyObjectRef>, vm: &VirtualMachine) -> PyBaseException {
         PyBaseException {
-            traceback: RwLock::new(None),
-            cause: RwLock::new(None),
-            context: RwLock::new(None),
+            traceback: PyRwLock::new(None),
+            cause: PyRwLock::new(None),
+            context: PyRwLock::new(None),
             suppress_context: AtomicCell::new(false),
-            args: RwLock::new(PyTuple::from(args).into_ref(vm)),
+            args: PyRwLock::new(PyTuple::from(args).into_ref(vm)),
         }
     }
 
diff --git a/vm/src/frame.rs b/vm/src/frame.rs
index 35fef5315..02f036b62 100644
--- a/vm/src/frame.rs
+++ b/vm/src/frame.rs
@@ -3,10 +3,10 @@ use std::sync::atomic::{AtomicUsize, Ordering};
 
 use indexmap::IndexMap;
 use itertools::Itertools;
-use parking_lot::Mutex;
 
 use crate::builtins::builtin_isinstance;
 use crate::bytecode;
+use crate::common::cell::PyMutex;
 use crate::exceptions::{self, ExceptionCtor, PyBaseExceptionRef};
 use crate::function::PyFuncArgs;
 use crate::obj::objasyncgenerator::PyAsyncGenWrappedValue;
@@ -92,7 +92,7 @@ pub struct Frame {
     pub scope: Scope,
     /// index of last instruction ran
     pub lasti: AtomicUsize,
-    state: Mutex<FrameState>,
+    state: PyMutex<FrameState>,
 }
 
 impl PyValue for Frame {
@@ -163,7 +163,7 @@ impl Frame {
             code,
             scope,
             lasti: AtomicUsize::new(0),
-            state: Mutex::new(FrameState {
+            state: PyMutex::new(FrameState {
                 stack: Vec::new(),
                 blocks: Vec::new(),
             }),
diff --git a/vm/src/lib.rs b/vm/src/lib.rs
index e775ce25d..80724fd85 100644
--- a/vm/src/lib.rs
+++ b/vm/src/lib.rs
@@ -68,7 +68,6 @@ pub mod function;
 pub mod import;
 pub mod obj;
 pub mod py_serde;
-mod pyhash;
 pub mod pyobject;
 pub mod readline;
 pub mod scope;
@@ -84,6 +83,7 @@ mod vm;
 // pub use self::pyobject::Executor;
 pub use self::vm::{InitParameter, PySettings, VirtualMachine};
 pub use rustpython_bytecode::*;
+pub use rustpython_common as common;
 
 #[doc(hidden)]
 pub mod __exports {
diff --git a/vm/src/obj/objbytearray.rs b/vm/src/obj/objbytearray.rs
index da7a47551..1be33d24f 100644
--- a/vm/src/obj/objbytearray.rs
+++ b/vm/src/obj/objbytearray.rs
@@ -1,8 +1,8 @@
 //! Implementation of the python bytearray object.
+use crate::common::cell::{PyRwLock, PyRwLockReadGuard, PyRwLockWriteGuard};
 use bstr::ByteSlice;
 use crossbeam_utils::atomic::AtomicCell;
 use num_traits::cast::ToPrimitive;
-use parking_lot::{RwLock, RwLockReadGuard, RwLockWriteGuard};
 use std::mem::size_of;
 
 use super::objbyteinner::{
@@ -36,7 +36,7 @@ use crate::vm::VirtualMachine;
 #[pyclass(name = "bytearray")]
 #[derive(Debug)]
 pub struct PyByteArray {
-    inner: RwLock<PyByteInner>,
+    inner: PyRwLock<PyByteInner>,
 }
 
 pub type PyByteArrayRef = PyRef<PyByteArray>;
@@ -44,21 +44,21 @@ pub type PyByteArrayRef = PyRef<PyByteArray>;
 impl PyByteArray {
     pub fn new(data: Vec<u8>) -> Self {
         PyByteArray {
-            inner: RwLock::new(PyByteInner { elements: data }),
+            inner: PyRwLock::new(PyByteInner { elements: data }),
         }
     }
 
     fn from_inner(inner: PyByteInner) -> Self {
         PyByteArray {
-            inner: RwLock::new(inner),
+            inner: PyRwLock::new(inner),
         }
     }
 
-    pub fn borrow_value(&self) -> RwLockReadGuard<'_, PyByteInner> {
+    pub fn borrow_value(&self) -> PyRwLockReadGuard<'_, PyByteInner> {
         self.inner.read()
     }
 
-    pub fn borrow_value_mut(&self) -> RwLockWriteGuard<'_, PyByteInner> {
+    pub fn borrow_value_mut(&self) -> PyRwLockWriteGuard<'_, PyByteInner> {
         self.inner.write()
     }
 }
@@ -98,8 +98,8 @@ impl PyByteArray {
     }
 
     #[pymethod(name = "__repr__")]
-    fn repr(&self) -> PyResult<String> {
-        Ok(format!("bytearray(b'{}')", self.borrow_value().repr()?))
+    fn repr(&self) -> String {
+        format!("bytearray(b'{}')", self.borrow_value().repr())
     }
 
     #[pymethod(name = "__len__")]
diff --git a/vm/src/obj/objbyteinner.rs b/vm/src/obj/objbyteinner.rs
index b4ef38139..4e5428d29 100644
--- a/vm/src/obj/objbyteinner.rs
+++ b/vm/src/obj/objbyteinner.rs
@@ -14,11 +14,11 @@ use super::objslice::PySliceRef;
 use super::objstr::{self, PyString, PyStringRef};
 use super::pystr::{self, PyCommonString, PyCommonStringContainer, PyCommonStringWrapper};
 use crate::function::{OptionalArg, OptionalOption};
-use crate::pyhash;
 use crate::pyobject::{
     Either, PyComparisonValue, PyIterable, PyObjectRef, PyResult, TryFromObject, TypeProtocol,
 };
 use crate::vm::VirtualMachine;
+use rustpython_common::hash;
 
 #[derive(Debug, Default, Clone)]
 pub struct PyByteInner {
@@ -253,7 +253,7 @@ impl ByteInnerSplitlinesOptions {
 
 #[allow(clippy::len_without_is_empty)]
 impl PyByteInner {
-    pub fn repr(&self) -> PyResult<String> {
+    pub fn repr(&self) -> String {
         let mut res = String::with_capacity(self.elements.len());
         for i in self.elements.iter() {
             match i {
@@ -266,7 +266,7 @@ impl PyByteInner {
                 _ => res.push_str(&format!("\\x{:x}", i)),
             }
         }
-        Ok(res)
+        res
     }
 
     pub fn len(&self) -> usize {
@@ -303,8 +303,8 @@ impl PyByteInner {
         self.cmp(other, |a, b| a < b, vm)
     }
 
-    pub fn hash(&self) -> pyhash::PyHash {
-        pyhash::hash_value(&self.elements)
+    pub fn hash(&self) -> hash::PyHash {
+        hash::hash_value(&self.elements)
     }
 
     pub fn add(&self, other: PyByteInner) -> Vec<u8> {
diff --git a/vm/src/obj/objbytes.rs b/vm/src/obj/objbytes.rs
index ffeea4c05..529ae1674 100644
--- a/vm/src/obj/objbytes.rs
+++ b/vm/src/obj/objbytes.rs
@@ -14,7 +14,6 @@ use super::objstr::{PyString, PyStringRef};
 use super::objtype::PyClassRef;
 use super::pystr::{self, PyCommonString};
 use crate::function::{OptionalArg, OptionalOption};
-use crate::pyhash;
 use crate::pyobject::{
     Either, IntoPyObject,
     PyArithmaticValue::{self, *},
@@ -22,6 +21,7 @@ use crate::pyobject::{
     TryFromObject, TypeProtocol,
 };
 use crate::vm::VirtualMachine;
+use rustpython_common::hash::PyHash;
 
 /// "bytes(iterable_of_ints) -> bytes\n\
 /// bytes(string, encoding[, errors]) -> bytes\n\
@@ -102,8 +102,8 @@ impl PyBytes {
     }
 
     #[pymethod(name = "__repr__")]
-    fn repr(&self, vm: &VirtualMachine) -> PyResult {
-        Ok(vm.new_str(format!("b'{}'", self.inner.repr()?)))
+    pub(crate) fn repr(&self) -> String {
+        format!("b'{}'", self.inner.repr())
     }
 
     #[pymethod(name = "__len__")]
@@ -133,7 +133,7 @@ impl PyBytes {
     }
 
     #[pymethod(name = "__hash__")]
-    fn hash(&self) -> pyhash::PyHash {
+    fn hash(&self) -> PyHash {
         self.inner.hash()
     }
 
diff --git a/vm/src/obj/objcomplex.rs b/vm/src/obj/objcomplex.rs
index 4b7f04de0..367db543b 100644
--- a/vm/src/obj/objcomplex.rs
+++ b/vm/src/obj/objcomplex.rs
@@ -8,11 +8,11 @@ use super::objint::{self, PyInt};
 use super::objstr::PyString;
 use super::objtype::PyClassRef;
 use crate::function::OptionalArg;
-use crate::pyhash;
 use crate::pyobject::{
     IntoPyObject, PyClassImpl, PyContext, PyObjectRef, PyRef, PyResult, PyValue, TypeProtocol,
 };
 use crate::vm::VirtualMachine;
+use rustpython_common::hash;
 
 /// Create a complex number from a real part and an optional imaginary part.
 ///
@@ -267,10 +267,10 @@ impl PyComplex {
     }
 
     #[pymethod(name = "__hash__")]
-    fn hash(&self) -> pyhash::PyHash {
-        let re_hash = pyhash::hash_float(self.value.re);
-        let im_hash = pyhash::hash_float(self.value.im);
-        let ret = Wrapping(re_hash) + Wrapping(im_hash) * Wrapping(pyhash::IMAG);
+    fn hash(&self) -> hash::PyHash {
+        let re_hash = hash::hash_float(self.value.re);
+        let im_hash = hash::hash_float(self.value.im);
+        let ret = Wrapping(re_hash) + Wrapping(im_hash) * Wrapping(hash::IMAG);
         ret.0
     }
 
diff --git a/vm/src/obj/objcoroinner.rs b/vm/src/obj/objcoroinner.rs
index 61a43357d..11d4515ab 100644
--- a/vm/src/obj/objcoroinner.rs
+++ b/vm/src/obj/objcoroinner.rs
@@ -4,8 +4,8 @@ use crate::frame::{ExecutionResult, FrameRef};
 use crate::pyobject::{PyObjectRef, PyResult};
 use crate::vm::VirtualMachine;
 
+use crate::common::cell::PyRwLock;
 use crossbeam_utils::atomic::AtomicCell;
-use parking_lot::RwLock;
 
 #[derive(Debug, PartialEq, Clone, Copy)]
 pub enum Variant {
@@ -37,7 +37,7 @@ pub struct Coro {
     frame: FrameRef,
     pub closed: AtomicCell<bool>,
     running: AtomicCell<bool>,
-    exceptions: RwLock<Vec<PyBaseExceptionRef>>,
+    exceptions: PyRwLock<Vec<PyBaseExceptionRef>>,
     started: AtomicCell<bool>,
     variant: Variant,
 }
@@ -48,7 +48,7 @@ impl Coro {
             frame,
             closed: AtomicCell::new(false),
             running: AtomicCell::new(false),
-            exceptions: RwLock::new(vec![]),
+            exceptions: PyRwLock::new(vec![]),
             started: AtomicCell::new(false),
             variant,
         }
diff --git a/vm/src/obj/objenumerate.rs b/vm/src/obj/objenumerate.rs
index 4adbfda78..e36e35ec7 100644
--- a/vm/src/obj/objenumerate.rs
+++ b/vm/src/obj/objenumerate.rs
@@ -1,4 +1,4 @@
-use parking_lot::RwLock;
+use crate::common::cell::PyRwLock;
 use std::ops::AddAssign;
 
 use num_bigint::BigInt;
@@ -14,7 +14,7 @@ use crate::vm::VirtualMachine;
 #[pyclass]
 #[derive(Debug)]
 pub struct PyEnumerate {
-    counter: RwLock<BigInt>,
+    counter: PyRwLock<BigInt>,
     iterator: PyObjectRef,
 }
 type PyEnumerateRef = PyRef<PyEnumerate>;
@@ -41,7 +41,7 @@ impl PyEnumerate {
 
         let iterator = objiter::get_iter(vm, &iterable)?;
         PyEnumerate {
-            counter: RwLock::new(counter),
+            counter: PyRwLock::new(counter),
             iterator,
         }
         .into_ref_with_type(vm, cls)
diff --git a/vm/src/obj/objfloat.rs b/vm/src/obj/objfloat.rs
index 8b30ade4d..dab3fe265 100644
--- a/vm/src/obj/objfloat.rs
+++ b/vm/src/obj/objfloat.rs
@@ -1,20 +1,19 @@
 use num_bigint::{BigInt, ToBigInt};
 use num_rational::Ratio;
-use num_traits::{float::Float, pow, sign::Signed, ToPrimitive, Zero};
+use num_traits::{pow, ToPrimitive, Zero};
 
 use super::objbytes::PyBytes;
 use super::objint::{self, PyInt, PyIntRef};
 use super::objstr::{PyString, PyStringRef};
 use super::objtype::PyClassRef;
-use crate::exceptions::PyBaseExceptionRef;
 use crate::format::FormatSpec;
 use crate::function::{OptionalArg, OptionalOption};
-use crate::pyhash;
 use crate::pyobject::{
     IntoPyObject, PyArithmaticValue::*, PyClassImpl, PyComparisonValue, PyContext, PyObjectRef,
     PyRef, PyResult, PyValue, TryFromObject, TypeProtocol,
 };
 use crate::vm::VirtualMachine;
+use rustpython_common::{float_ops, hash};
 
 /// Convert a string or number to a floating point number, if possible.
 #[pyclass(name = "float")]
@@ -135,32 +134,6 @@ fn inner_divmod(v1: f64, v2: f64, vm: &VirtualMachine) -> PyResult<(f64, f64)> {
     }
 }
 
-fn inner_lt_int(value: f64, other_int: &BigInt) -> bool {
-    match (value.to_bigint(), other_int.to_f64()) {
-        (Some(self_int), Some(other_float)) => value < other_float || self_int < *other_int,
-        // finite float, other_int too big for float,
-        // the result depends only on other_int’s sign
-        (Some(_), None) => other_int.is_positive(),
-        // infinite float must be bigger or lower than any int, depending on its sign
-        _ if value.is_infinite() => value.is_sign_negative(),
-        // NaN, always false
-        _ => false,
-    }
-}
-
-fn inner_gt_int(value: f64, other_int: &BigInt) -> bool {
-    match (value.to_bigint(), other_int.to_f64()) {
-        (Some(self_int), Some(other_float)) => value > other_float || self_int > *other_int,
-        // finite float, other_int too big for float,
-        // the result depends only on other_int’s sign
-        (Some(_), None) => other_int.is_negative(),
-        // infinite float must be bigger or lower than any int, depending on its sign
-        _ if value.is_infinite() => value.is_sign_positive(),
-        // NaN, always false
-        _ => false,
-    }
-}
-
 pub fn float_pow(v1: f64, v2: f64, vm: &VirtualMachine) -> PyResult<f64> {
     if v1.is_zero() {
         let msg = format!("{} cannot be raised to a negative power", v1);
@@ -170,14 +143,6 @@ pub fn float_pow(v1: f64, v2: f64, vm: &VirtualMachine) -> PyResult<f64> {
     }
 }
 
-fn int_eq(value: f64, other: &BigInt) -> bool {
-    if let (Some(self_int), Some(other_float)) = (value.to_bigint(), other.to_f64()) {
-        value == other_float && self_int == *other
-    } else {
-        false
-    }
-}
-
 #[pyimpl(flags(BASETYPE))]
 #[allow(clippy::trivially_copy_pass_by_ref)]
 impl PyFloat {
@@ -227,7 +192,7 @@ impl PyFloat {
 
     #[pymethod(name = "__eq__")]
     fn eq(&self, other: PyObjectRef, vm: &VirtualMachine) -> PyComparisonValue {
-        self.cmp(other, |a, b| a == b, int_eq, vm)
+        self.cmp(other, |a, b| a == b, float_ops::eq_int, vm)
     }
 
     #[pymethod(name = "__ne__")]
@@ -237,7 +202,7 @@ impl PyFloat {
 
     #[pymethod(name = "__lt__")]
     fn lt(&self, other: PyObjectRef, vm: &VirtualMachine) -> PyComparisonValue {
-        self.cmp(other, |a, b| a < b, inner_lt_int, vm)
+        self.cmp(other, |a, b| a < b, float_ops::lt_int, vm)
     }
 
     #[pymethod(name = "__le__")]
@@ -249,7 +214,7 @@ impl PyFloat {
                 if let (Some(a_int), Some(b_float)) = (a.to_bigint(), b.to_f64()) {
                     a <= b_float && a_int <= *b
                 } else {
-                    inner_lt_int(a, b)
+                    float_ops::lt_int(a, b)
                 }
             },
             vm,
@@ -258,7 +223,7 @@ impl PyFloat {
 
     #[pymethod(name = "__gt__")]
     fn gt(&self, other: PyObjectRef, vm: &VirtualMachine) -> PyComparisonValue {
-        self.cmp(other, |a, b| a > b, inner_gt_int, vm)
+        self.cmp(other, |a, b| a > b, float_ops::gt_int, vm)
     }
 
     #[pymethod(name = "__ge__")]
@@ -270,7 +235,7 @@ impl PyFloat {
                 if let (Some(a_int), Some(b_float)) = (a.to_bigint(), b.to_f64()) {
                     a >= b_float && a_int >= *b
                 } else {
-                    inner_gt_int(a, b)
+                    float_ops::gt_int(a, b)
                 }
             },
             vm,
@@ -386,23 +351,7 @@ impl PyFloat {
 
     #[pymethod(name = "__repr__")]
     fn repr(&self) -> String {
-        let value = format!("{:e}", self.value);
-        if let Some(position) = value.find('e') {
-            let significand = &value[..position];
-            let exponent = &value[position + 1..];
-            let exponent = exponent.parse::<i32>().unwrap();
-            if exponent < 16 && exponent > -5 {
-                if self.is_integer() {
-                    format!("{:.1?}", self.value)
-                } else {
-                    self.value.to_string()
-                }
-            } else {
-                format!("{}e{:+#03}", significand, exponent)
-            }
-        } else {
-            self.value.to_string()
-        }
+        float_ops::to_string(self.value)
     }
 
     #[pymethod(name = "__truediv__")]
@@ -499,8 +448,8 @@ impl PyFloat {
     }
 
     #[pymethod(name = "__hash__")]
-    fn hash(&self) -> pyhash::PyHash {
-        pyhash::hash_float(self.value)
+    fn hash(&self) -> hash::PyHash {
+        hash::hash_float(self.value)
     }
 
     #[pyproperty]
@@ -520,8 +469,7 @@ impl PyFloat {
 
     #[pymethod(name = "is_integer")]
     fn is_integer(&self) -> bool {
-        let v = self.value;
-        (v - v.round()).abs() < std::f64::EPSILON
+        float_ops::is_integer(self.value)
     }
 
     #[pymethod(name = "as_integer_ratio")]
@@ -544,116 +492,33 @@ impl PyFloat {
 
     #[pymethod]
     fn fromhex(repr: PyStringRef, vm: &VirtualMachine) -> PyResult<f64> {
-        hexf_parse::parse_hexf64(repr.as_str().trim(), false).or_else(|_| {
-            match repr.as_str().to_lowercase().trim() {
-                "nan" => Ok(std::f64::NAN),
-                "+nan" => Ok(std::f64::NAN),
-                "-nan" => Ok(std::f64::NAN),
-                "inf" => Ok(std::f64::INFINITY),
-                "infinity" => Ok(std::f64::INFINITY),
-                "+inf" => Ok(std::f64::INFINITY),
-                "+infinity" => Ok(std::f64::INFINITY),
-                "-inf" => Ok(std::f64::NEG_INFINITY),
-                "-infinity" => Ok(std::f64::NEG_INFINITY),
-                value => {
-                    let mut hex = String::new();
-                    let has_0x = value.contains("0x");
-                    let has_p = value.contains('p');
-                    let has_dot = value.contains('.');
-                    let mut start = 0;
-
-                    if !has_0x && value.starts_with('-') {
-                        hex.push_str("-0x");
-                        start += 1;
-                    } else if !has_0x {
-                        hex.push_str("0x");
-                        if value.starts_with('+') {
-                            start += 1;
-                        }
-                    }
-
-                    for (index, ch) in value.chars().enumerate() {
-                        if ch == 'p' && has_dot {
-                            hex.push_str("p");
-                        } else if ch == 'p' && !has_dot {
-                            hex.push_str(".p");
-                        } else if index >= start {
-                            hex.push(ch);
-                        }
-                    }
-
-                    if !has_p && has_dot {
-                        hex.push_str("p0");
-                    } else if !has_p && !has_dot {
-                        hex.push_str(".p0")
-                    }
-
-                    hexf_parse::parse_hexf64(hex.as_str(), false).map_err(|_| {
-                        vm.new_value_error("invalid hexadecimal floating-point string".to_owned())
-                    })
-                }
-            }
+        float_ops::from_hex(repr.as_str().trim()).ok_or_else(|| {
+            vm.new_value_error("invalid hexadecimal floating-point string".to_owned())
         })
     }
 
     #[pymethod]
     fn hex(&self) -> String {
-        to_hex(self.value)
+        float_ops::to_hex(self.value)
     }
 }
 
-fn str_to_float(vm: &VirtualMachine, literal: &str) -> PyResult<f64> {
-    if literal.starts_with('_') || literal.ends_with('_') {
-        return Err(invalid_convert(vm, literal));
-    }
-
-    let mut buf = String::with_capacity(literal.len());
-    let mut last_tok: Option<char> = None;
-    for c in literal.chars() {
-        if !(c.is_ascii_alphanumeric() || c == '_' || c == '+' || c == '-' || c == '.') {
-            return Err(invalid_convert(vm, literal));
-        }
-
-        if !c.is_ascii_alphanumeric() {
-            if let Some(l) = last_tok {
-                if !l.is_ascii_alphanumeric() && !(c == '.' && (l == '-' || l == '+')) {
-                    return Err(invalid_convert(vm, literal));
-                }
-            }
-        }
-
-        if c != '_' {
-            buf.push(c);
-        }
-        last_tok = Some(c);
-    }
-
-    if let Ok(f) = lexical::parse(buf.as_str()) {
-        Ok(f)
-    } else {
-        Err(invalid_convert(vm, literal))
-    }
-}
-
-fn invalid_convert(vm: &VirtualMachine, literal: &str) -> PyBaseExceptionRef {
-    vm.new_value_error(format!("could not convert string to float: '{}'", literal))
-}
-
 fn to_float(vm: &VirtualMachine, obj: &PyObjectRef) -> PyResult<f64> {
     let value = if let Some(float) = obj.payload_if_subclass::<PyFloat>(vm) {
         float.value
     } else if let Some(int) = obj.payload_if_subclass::<PyInt>(vm) {
         objint::try_float(int.as_bigint(), vm)?
     } else if let Some(s) = obj.payload_if_subclass::<PyString>(vm) {
-        str_to_float(vm, s.as_str().trim())?
+        float_ops::parse_str(s.as_str().trim()).ok_or_else(|| {
+            vm.new_value_error(format!("could not convert string to float: '{}'", s))
+        })?
     } else if let Some(bytes) = obj.payload_if_subclass::<PyBytes>(vm) {
-        match lexical::parse(bytes.get_value()) {
-            Ok(f) => f,
-            Err(_) => {
-                let arg_repr = vm.to_pystr(obj)?;
-                return Err(invalid_convert(vm, arg_repr.as_str()));
-            }
-        }
+        lexical::parse(bytes.get_value()).map_err(|_| {
+            vm.new_value_error(format!(
+                "could not convert string to float: '{}'",
+                bytes.repr()
+            ))
+        })?
     } else {
         let method = vm.get_method_or_type_error(obj.clone(), "__float__", || {
             format!(
@@ -667,55 +532,6 @@ fn to_float(vm: &VirtualMachine, obj: &PyObjectRef) -> PyResult<f64> {
     Ok(value)
 }
 
-fn to_hex(value: f64) -> String {
-    let (mantissa, exponent, sign) = value.integer_decode();
-    let sign_fmt = if sign < 0 { "-" } else { "" };
-    match value {
-        value if value.is_zero() => format!("{}0x0.0p+0", sign_fmt),
-        value if value.is_infinite() => format!("{}inf", sign_fmt),
-        value if value.is_nan() => "nan".to_owned(),
-        _ => {
-            const BITS: i16 = 52;
-            const FRACT_MASK: u64 = 0xf_ffff_ffff_ffff;
-            format!(
-                "{}0x{:x}.{:013x}p{:+}",
-                sign_fmt,
-                mantissa >> BITS,
-                mantissa & FRACT_MASK,
-                exponent + BITS
-            )
-        }
-    }
-}
-
-#[test]
-fn test_to_hex() {
-    use rand::Rng;
-    for _ in 0..20000 {
-        let bytes = rand::thread_rng().gen::<[u64; 1]>();
-        let f = f64::from_bits(bytes[0]);
-        if !f.is_finite() {
-            continue;
-        }
-        let hex = to_hex(f);
-        // println!("{} -> {}", f, hex);
-        let roundtrip = hexf_parse::parse_hexf64(&hex, false).unwrap();
-        // println!("  -> {}", roundtrip);
-        assert!(f == roundtrip, "{} {} {}", f, hex, roundtrip);
-    }
-}
-
-pub fn ufrexp(value: f64) -> (f64, i32) {
-    if 0.0 == value {
-        (0.0, 0i32)
-    } else {
-        let bits = value.to_bits();
-        let exponent: i32 = ((bits >> 52) & 0x7ff) as i32 - 1022;
-        let mantissa_bits = bits & (0x000f_ffff_ffff_ffff) | (1022 << 52);
-        (f64::from_bits(mantissa_bits), exponent)
-    }
-}
-
 pub type PyFloatRef = PyRef<PyFloat>;
 
 // Retrieve inner float value:
diff --git a/vm/src/obj/objint.rs b/vm/src/obj/objint.rs
index 780b7ebd2..e011f23c0 100644
--- a/vm/src/obj/objint.rs
+++ b/vm/src/obj/objint.rs
@@ -15,13 +15,13 @@ use super::objstr::{PyString, PyStringRef};
 use super::objtype::{self, PyClassRef};
 use crate::format::FormatSpec;
 use crate::function::{OptionalArg, PyFuncArgs};
-use crate::pyhash;
 use crate::pyobject::{
     IdProtocol, IntoPyObject, PyArithmaticValue, PyClassImpl, PyComparisonValue, PyContext,
     PyObjectRef, PyRef, PyResult, PyValue, TryFromObject, TypeProtocol,
 };
 use crate::stdlib::array::PyArray;
 use crate::vm::VirtualMachine;
+use rustpython_common::hash;
 
 /// int(x=0) -> integer
 /// int(x, base=10) -> integer
@@ -419,8 +419,8 @@ impl PyInt {
     }
 
     #[pymethod(name = "__hash__")]
-    pub fn hash(&self) -> pyhash::PyHash {
-        pyhash::hash_bigint(&self.value)
+    pub fn hash(&self) -> hash::PyHash {
+        hash::hash_bigint(&self.value)
     }
 
     #[pymethod(name = "__abs__")]
diff --git a/vm/src/obj/objlist.rs b/vm/src/obj/objlist.rs
index 70139ab45..6c48f3b6c 100644
--- a/vm/src/obj/objlist.rs
+++ b/vm/src/obj/objlist.rs
@@ -2,10 +2,10 @@ use std::fmt;
 use std::mem::size_of;
 use std::ops::{DerefMut, Range};
 
+use crate::common::cell::{PyRwLock, PyRwLockReadGuard, PyRwLockWriteGuard};
 use crossbeam_utils::atomic::AtomicCell;
 use num_bigint::{BigInt, ToBigInt};
 use num_traits::{One, Signed, ToPrimitive, Zero};
-use parking_lot::{RwLock, RwLockReadGuard, RwLockWriteGuard};
 
 use super::objbool;
 use super::objbyteinner;
@@ -29,7 +29,7 @@ use crate::vm::{ReprGuard, VirtualMachine};
 #[pyclass]
 #[derive(Default)]
 pub struct PyList {
-    elements: RwLock<Vec<PyObjectRef>>,
+    elements: PyRwLock<Vec<PyObjectRef>>,
 }
 
 impl fmt::Debug for PyList {
@@ -42,7 +42,7 @@ impl fmt::Debug for PyList {
 impl From<Vec<PyObjectRef>> for PyList {
     fn from(elements: Vec<PyObjectRef>) -> Self {
         PyList {
-            elements: RwLock::new(elements),
+            elements: PyRwLock::new(elements),
         }
     }
 }
@@ -54,11 +54,11 @@ impl PyValue for PyList {
 }
 
 impl PyList {
-    pub fn borrow_elements(&self) -> RwLockReadGuard<'_, Vec<PyObjectRef>> {
+    pub fn borrow_elements(&self) -> PyRwLockReadGuard<'_, Vec<PyObjectRef>> {
         self.elements.read()
     }
 
-    pub fn borrow_elements_mut(&self) -> RwLockWriteGuard<'_, Vec<PyObjectRef>> {
+    pub fn borrow_elements_mut(&self) -> PyRwLockWriteGuard<'_, Vec<PyObjectRef>> {
         self.elements.write()
     }
 
@@ -315,7 +315,7 @@ impl PyList {
     }
 
     fn _set_slice(
-        mut elements: RwLockWriteGuard<'_, Vec<PyObjectRef>>,
+        mut elements: PyRwLockWriteGuard<'_, Vec<PyObjectRef>>,
         range: Range<usize>,
         items: Vec<PyObjectRef>,
         vm: &VirtualMachine,
@@ -327,7 +327,7 @@ impl PyList {
     }
 
     fn _set_stepped_slice(
-        elements: RwLockWriteGuard<'_, Vec<PyObjectRef>>,
+        elements: PyRwLockWriteGuard<'_, Vec<PyObjectRef>>,
         range: Range<usize>,
         step: usize,
         items: Vec<PyObjectRef>,
@@ -365,7 +365,7 @@ impl PyList {
     }
 
     fn _set_stepped_slice_reverse(
-        elements: RwLockWriteGuard<'_, Vec<PyObjectRef>>,
+        elements: PyRwLockWriteGuard<'_, Vec<PyObjectRef>>,
         range: Range<usize>,
         step: usize,
         items: Vec<PyObjectRef>,
@@ -403,7 +403,7 @@ impl PyList {
     }
 
     fn _replace_indexes<I>(
-        mut elements: RwLockWriteGuard<'_, Vec<PyObjectRef>>,
+        mut elements: PyRwLockWriteGuard<'_, Vec<PyObjectRef>>,
         indexes: I,
         items: &[PyObjectRef],
     ) where
@@ -673,12 +673,12 @@ impl PyList {
         }
     }
 
-    fn _del_slice(mut elements: RwLockWriteGuard<'_, Vec<PyObjectRef>>, range: Range<usize>) {
+    fn _del_slice(mut elements: PyRwLockWriteGuard<'_, Vec<PyObjectRef>>, range: Range<usize>) {
         elements.drain(range);
     }
 
     fn _del_stepped_slice(
-        mut elements: RwLockWriteGuard<'_, Vec<PyObjectRef>>,
+        mut elements: PyRwLockWriteGuard<'_, Vec<PyObjectRef>>,
         range: Range<usize>,
         step: usize,
     ) {
@@ -702,7 +702,7 @@ impl PyList {
     }
 
     fn _del_stepped_slice_reverse(
-        mut elements: RwLockWriteGuard<'_, Vec<PyObjectRef>>,
+        mut elements: PyRwLockWriteGuard<'_, Vec<PyObjectRef>>,
         range: Range<usize>,
         step: usize,
     ) {
diff --git a/vm/src/obj/objobject.rs b/vm/src/obj/objobject.rs
index c64fa6883..4c1149681 100644
--- a/vm/src/obj/objobject.rs
+++ b/vm/src/obj/objobject.rs
@@ -5,7 +5,6 @@ use super::objstr::PyStringRef;
 use super::objtype::PyClassRef;
 use crate::function::{OptionalArg, PyFuncArgs};
 use crate::obj::objtype::PyClass;
-use crate::pyhash;
 use crate::pyobject::{
     IdProtocol, ItemProtocol, PyArithmaticValue::*, PyAttributes, PyClassImpl, PyComparisonValue,
     PyContext, PyObject, PyObjectRef, PyResult, PyValue, TryFromObject, TypeProtocol,
@@ -85,8 +84,8 @@ impl PyBaseObject {
     }
 
     #[pymethod(magic)]
-    fn hash(zelf: PyObjectRef) -> pyhash::PyHash {
-        zelf.get_id() as pyhash::PyHash
+    fn hash(zelf: PyObjectRef) -> rustpython_common::hash::PyHash {
+        zelf.get_id() as _
     }
 
     #[pymethod(magic)]
diff --git a/vm/src/obj/objproperty.rs b/vm/src/obj/objproperty.rs
index 909ca4321..737f7e8cf 100644
--- a/vm/src/obj/objproperty.rs
+++ b/vm/src/obj/objproperty.rs
@@ -1,7 +1,7 @@
 /*! Python `property` descriptor class.
 
 */
-use parking_lot::RwLock;
+use crate::common::cell::PyRwLock;
 
 use super::objtype::PyClassRef;
 use crate::function::OptionalArg;
@@ -49,7 +49,7 @@ pub struct PyProperty {
     getter: Option<PyObjectRef>,
     setter: Option<PyObjectRef>,
     deleter: Option<PyObjectRef>,
-    doc: RwLock<Option<PyObjectRef>>,
+    doc: PyRwLock<Option<PyObjectRef>>,
 }
 
 impl PyValue for PyProperty {
@@ -98,7 +98,7 @@ impl PyProperty {
             getter: args.fget,
             setter: args.fset,
             deleter: args.fdel,
-            doc: RwLock::new(args.doc),
+            doc: PyRwLock::new(args.doc),
         }
         .into_ref_with_type(vm, cls)
     }
@@ -160,7 +160,7 @@ impl PyProperty {
             getter: getter.or_else(|| zelf.getter.clone()),
             setter: zelf.setter.clone(),
             deleter: zelf.deleter.clone(),
-            doc: RwLock::new(None),
+            doc: PyRwLock::new(None),
         }
         .into_ref_with_type(vm, TypeProtocol::class(&zelf))
     }
@@ -175,7 +175,7 @@ impl PyProperty {
             getter: zelf.getter.clone(),
             setter: setter.or_else(|| zelf.setter.clone()),
             deleter: zelf.deleter.clone(),
-            doc: RwLock::new(None),
+            doc: PyRwLock::new(None),
         }
         .into_ref_with_type(vm, TypeProtocol::class(&zelf))
     }
@@ -190,7 +190,7 @@ impl PyProperty {
             getter: zelf.getter.clone(),
             setter: zelf.setter.clone(),
             deleter: deleter.or_else(|| zelf.deleter.clone()),
-            doc: RwLock::new(None),
+            doc: PyRwLock::new(None),
         }
         .into_ref_with_type(vm, TypeProtocol::class(&zelf))
     }
diff --git a/vm/src/obj/objrange.rs b/vm/src/obj/objrange.rs
index ef93ee230..ac8668f9c 100644
--- a/vm/src/obj/objrange.rs
+++ b/vm/src/obj/objrange.rs
@@ -10,11 +10,12 @@ use super::objtuple::PyTuple;
 use super::objtype::PyClassRef;
 
 use crate::function::{OptionalArg, PyFuncArgs};
-use crate::pyhash;
 use crate::pyobject::{
-    PyClassImpl, PyContext, PyObjectRef, PyRef, PyResult, PyValue, TryFromObject, TypeProtocol,
+    self, PyClassImpl, PyContext, PyObjectRef, PyRef, PyResult, PyValue, TryFromObject,
+    TypeProtocol,
 };
 use crate::vm::VirtualMachine;
+use rustpython_common::hash::PyHash;
 
 /// range(stop) -> range object
 /// range(start, stop[, step]) -> range object
@@ -363,7 +364,7 @@ impl PyRange {
     }
 
     #[pymethod(name = "__hash__")]
-    fn hash(zelf: PyRef<Self>, vm: &VirtualMachine) -> PyResult<pyhash::PyHash> {
+    fn hash(zelf: PyRef<Self>, vm: &VirtualMachine) -> PyResult<PyHash> {
         let length = zelf.length();
         let elements = if length.is_zero() {
             vec![vm.ctx.new_int(length), vm.get_none(), vm.get_none()]
@@ -380,7 +381,7 @@ impl PyRange {
                 zelf.step().into_object(),
             ]
         };
-        pyhash::hash_iter(elements.iter(), vm)
+        pyobject::hash_iter(&elements, vm)
     }
 
     #[pyslot]
diff --git a/vm/src/obj/objset.rs b/vm/src/obj/objset.rs
index 7577933e6..019f00b9a 100644
--- a/vm/src/obj/objset.rs
+++ b/vm/src/obj/objset.rs
@@ -7,12 +7,12 @@ use super::objlist::PyListIterator;
 use super::objtype::{self, PyClassRef};
 use crate::dictdatatype;
 use crate::function::{Args, OptionalArg};
-use crate::pyhash;
 use crate::pyobject::{
-    PyClassImpl, PyContext, PyIterable, PyObjectRef, PyRef, PyResult, PyValue, TryFromObject,
+    self, PyClassImpl, PyContext, PyIterable, PyObjectRef, PyRef, PyResult, PyValue, TryFromObject,
     TypeProtocol,
 };
 use crate::vm::{ReprGuard, VirtualMachine};
+use rustpython_common::hash::PyHash;
 
 pub type SetContentType = dictdatatype::Dict<()>;
 
@@ -329,8 +329,8 @@ impl PySetInner {
         Ok(())
     }
 
-    fn hash(&self, vm: &VirtualMachine) -> PyResult<pyhash::PyHash> {
-        pyhash::hash_iter_unordered(self.content.keys().iter(), vm)
+    fn hash(&self, vm: &VirtualMachine) -> PyResult<PyHash> {
+        pyobject::hash_iter_unordered(self.content.keys().iter(), vm)
     }
 }
 
@@ -787,7 +787,7 @@ impl PyFrozenSet {
     }
 
     #[pymethod(name = "__hash__")]
-    fn hash(&self, vm: &VirtualMachine) -> PyResult<pyhash::PyHash> {
+    fn hash(&self, vm: &VirtualMachine) -> PyResult<PyHash> {
         self.inner.hash(vm)
     }
 }
diff --git a/vm/src/obj/objstr.rs b/vm/src/obj/objstr.rs
index 02acf5d04..dd905416c 100644
--- a/vm/src/obj/objstr.rs
+++ b/vm/src/obj/objstr.rs
@@ -24,12 +24,12 @@ use super::pystr::{
 };
 use crate::format::{FormatParseError, FormatSpec, FormatString, FromTemplate};
 use crate::function::{OptionalArg, OptionalOption, PyFuncArgs};
-use crate::pyhash;
 use crate::pyobject::{
     IdProtocol, IntoPyObject, ItemProtocol, PyClassImpl, PyContext, PyIterable, PyObjectRef, PyRef,
     PyResult, PyValue, TryFromObject, TryIntoRef, TypeProtocol,
 };
 use crate::vm::VirtualMachine;
+use rustpython_common::hash;
 
 /// str(object='') -> str
 /// str(bytes_or_buffer[, encoding[, errors]]) -> str
@@ -45,7 +45,7 @@ use crate::vm::VirtualMachine;
 #[derive(Debug)]
 pub struct PyString {
     value: String,
-    hash: AtomicCell<Option<pyhash::PyHash>>,
+    hash: AtomicCell<Option<hash::PyHash>>,
     len: AtomicCell<Option<usize>>,
 }
 
@@ -280,9 +280,9 @@ impl PyString {
     }
 
     #[pymethod(name = "__hash__")]
-    pub(crate) fn hash(&self) -> pyhash::PyHash {
+    pub(crate) fn hash(&self) -> hash::PyHash {
         self.hash.load().unwrap_or_else(|| {
-            let hash = pyhash::hash_value(&self.value);
+            let hash = hash::hash_value(&self.value);
             self.hash.store(Some(hash));
             hash
         })
diff --git a/vm/src/obj/objtuple.rs b/vm/src/obj/objtuple.rs
index 43570b386..92e591f46 100644
--- a/vm/src/obj/objtuple.rs
+++ b/vm/src/obj/objtuple.rs
@@ -5,14 +5,14 @@ use super::objiter;
 use super::objsequence::get_item;
 use super::objtype::PyClassRef;
 use crate::function::OptionalArg;
-use crate::pyhash;
 use crate::pyobject::{
-    IntoPyObject,
+    self, IntoPyObject,
     PyArithmaticValue::{self, *},
     PyClassImpl, PyComparisonValue, PyContext, PyObjectRef, PyRef, PyResult, PyValue,
 };
 use crate::sequence::{self, SimpleSeq};
 use crate::vm::{ReprGuard, VirtualMachine};
+use rustpython_common::hash::PyHash;
 
 /// tuple() -> empty tuple
 /// tuple(iterable) -> tuple initialized from iterable's items
@@ -156,8 +156,8 @@ impl PyTuple {
     }
 
     #[pymethod(name = "__hash__")]
-    fn hash(&self, vm: &VirtualMachine) -> PyResult<pyhash::PyHash> {
-        pyhash::hash_iter(self.elements.iter(), vm)
+    fn hash(&self, vm: &VirtualMachine) -> PyResult<PyHash> {
+        pyobject::hash_iter(self.elements.iter(), vm)
     }
 
     #[pymethod(name = "__iter__")]
diff --git a/vm/src/obj/objtype.rs b/vm/src/obj/objtype.rs
index 1dff7f790..236c76216 100644
--- a/vm/src/obj/objtype.rs
+++ b/vm/src/obj/objtype.rs
@@ -1,4 +1,4 @@
-use parking_lot::RwLock;
+use crate::common::cell::PyRwLock;
 use std::collections::{HashMap, HashSet};
 use std::fmt;
 
@@ -29,9 +29,9 @@ pub struct PyClass {
     pub name: String,
     pub bases: Vec<PyClassRef>,
     pub mro: Vec<PyClassRef>,
-    pub subclasses: RwLock<Vec<PyWeak>>,
-    pub attributes: RwLock<PyAttributes>,
-    pub slots: RwLock<PyClassSlots>,
+    pub subclasses: PyRwLock<Vec<PyWeak>>,
+    pub attributes: PyRwLock<PyAttributes>,
+    pub slots: PyRwLock<PyClassSlots>,
 }
 
 impl fmt::Display for PyClass {
@@ -595,12 +595,12 @@ pub fn new(
             name: String::from(name),
             bases,
             mro,
-            subclasses: RwLock::default(),
-            attributes: RwLock::new(dict),
-            slots: RwLock::default(),
+            subclasses: PyRwLock::default(),
+            attributes: PyRwLock::new(dict),
+            slots: PyRwLock::default(),
         },
         dict: None,
-        typ: RwLock::new(typ.into_typed_pyobj()),
+        typ: PyRwLock::new(typ.into_typed_pyobj()),
     }
     .into_ref();
 
diff --git a/vm/src/obj/objweakref.rs b/vm/src/obj/objweakref.rs
index d50fc378a..f67233eb8 100644
--- a/vm/src/obj/objweakref.rs
+++ b/vm/src/obj/objweakref.rs
@@ -6,10 +6,10 @@ use crate::pyobject::{
 };
 use crate::slots::SlotCall;
 use crate::vm::VirtualMachine;
+use rustpython_common::hash::PyHash;
+use rustpython_common::rc::{PyRc, PyWeak as Weak};
 
-use crate::pyhash::PyHash;
 use crossbeam_utils::atomic::AtomicCell;
-use std::sync::{Arc, Weak};
 
 #[pyclass]
 #[derive(Debug)]
@@ -21,7 +21,7 @@ pub struct PyWeak {
 impl PyWeak {
     pub fn downgrade(obj: &PyObjectRef) -> PyWeak {
         PyWeak {
-            referent: Arc::downgrade(obj),
+            referent: PyRc::downgrade(obj),
             hash: AtomicCell::new(None),
         }
     }
diff --git a/vm/src/pyobject.rs b/vm/src/pyobject.rs
index cfd2df03e..639fd85d8 100644
--- a/vm/src/pyobject.rs
+++ b/vm/src/pyobject.rs
@@ -3,7 +3,6 @@ use std::collections::HashMap;
 use std::fmt;
 use std::marker::PhantomData;
 use std::ops::Deref;
-use std::sync::Arc;
 
 use indexmap::IndexMap;
 use num_bigint::BigInt;
@@ -40,7 +39,8 @@ use crate::scope::Scope;
 use crate::slots::PyTpFlags;
 use crate::types::{create_type, initialize_types, TypeZoo};
 use crate::vm::VirtualMachine;
-use parking_lot::{RwLock, RwLockReadGuard};
+use rustpython_common::cell::{PyRwLock, PyRwLockReadGuard};
+use rustpython_common::rc::PyRc;
 
 /* Python objects and references.
 
@@ -61,7 +61,7 @@ Basically reference counting, but then done by rust.
 /// this reference counting is accounted for by this type. Use the `.clone()`
 /// method to create a new reference and increment the amount of references
 /// to the python object by 1.
-pub type PyObjectRef = Arc<PyObject<dyn PyObjectPayload>>;
+pub type PyObjectRef = PyRc<PyObject<dyn PyObjectPayload>>;
 
 /// Use this type for functions which return a python object or an exception.
 /// Both the python object and the python exception are `PyObjectRef` types
@@ -586,8 +586,8 @@ impl PyContext {
 
     pub fn new_base_object(&self, class: PyClassRef, dict: Option<PyDictRef>) -> PyObjectRef {
         PyObject {
-            typ: RwLock::new(class.into_typed_pyobj()),
-            dict: dict.map(|d| RwLock::new(d.into_typed_pyobj())),
+            typ: PyRwLock::new(class.into_typed_pyobj()),
+            dict: dict.map(|d| PyRwLock::new(d.into_typed_pyobj())),
             payload: objobject::PyBaseObject,
         }
         .into_ref()
@@ -643,8 +643,8 @@ pub struct PyObject<T>
 where
     T: ?Sized + PyObjectPayload,
 {
-    pub(crate) typ: RwLock<Arc<PyObject<PyClass>>>, // __class__ member
-    pub(crate) dict: Option<RwLock<Arc<PyObject<PyDict>>>>, // __dict__ member
+    pub(crate) typ: PyRwLock<PyRc<PyObject<PyClass>>>, // __class__ member
+    pub(crate) dict: Option<PyRwLock<PyRc<PyObject<PyDict>>>>, // __dict__ member
     pub payload: T,
 }
 
@@ -653,7 +653,7 @@ impl PyObject<dyn PyObjectPayload> {
     ///
     /// If the downcast fails, the original ref is returned in as `Err` so
     /// another downcast can be attempted without unnecessary cloning.
-    pub fn downcast<T: PyObjectPayload>(self: Arc<Self>) -> Result<PyRef<T>, PyObjectRef> {
+    pub fn downcast<T: PyObjectPayload>(self: PyRc<Self>) -> Result<PyRef<T>, PyObjectRef> {
         if self.payload_is::<T>() {
             Ok(PyRef {
                 obj: self,
@@ -664,15 +664,15 @@ impl PyObject<dyn PyObjectPayload> {
         }
     }
 
-    /// Downcast this PyObjectRef to an `Arc<PyObject<T>>`. The [`downcast`](#method.downcast) method
+    /// Downcast this PyObjectRef to an `PyRc<PyObject<T>>`. The [`downcast`](#method.downcast) method
     /// is generally preferred, as the `PyRef<T>` it returns implements `Deref<Target=T>`, and
     /// therefore can be used similarly to an `&T`.
     pub fn downcast_generic<T: PyObjectPayload>(
-        self: Arc<Self>,
-    ) -> Result<Arc<PyObject<T>>, PyObjectRef> {
+        self: PyRc<Self>,
+    ) -> Result<PyRc<PyObject<T>>, PyObjectRef> {
         if self.payload_is::<T>() {
-            let ptr = Arc::into_raw(self) as *const PyObject<T>;
-            let ret = unsafe { Arc::from_raw(ptr) };
+            let ptr = PyRc::into_raw(self) as *const PyObject<T>;
+            let ret = unsafe { PyRc::from_raw(ptr) };
             Ok(ret)
         } else {
             Err(self)
@@ -738,7 +738,7 @@ impl<T: PyValue> PyRef<T> {
         self.obj
     }
 
-    pub fn into_typed_pyobj(self) -> Arc<PyObject<T>> {
+    pub fn into_typed_pyobj(self) -> PyRc<PyObject<T>> {
         self.into_object().downcast_generic().unwrap()
     }
 }
@@ -850,7 +850,7 @@ impl<T: ?Sized + PyObjectPayload> IdProtocol for PyObject<T> {
     }
 }
 
-impl<T: ?Sized + IdProtocol> IdProtocol for Arc<T> {
+impl<T: ?Sized + IdProtocol> IdProtocol for PyRc<T> {
     fn get_id(&self) -> usize {
         (**self).get_id()
     }
@@ -877,7 +877,7 @@ impl<T: IdProtocol> IdProtocol for &'_ T {
 /// A borrow of a reference to a Python object. This avoids having clone the `PyRef<T>`/
 /// `PyObjectRef`, which isn't that cheap as that increments the atomic reference counter.
 pub struct PyLease<'a, T: PyObjectPayload> {
-    inner: RwLockReadGuard<'a, Arc<PyObject<T>>>,
+    inner: PyRwLockReadGuard<'a, PyRc<PyObject<T>>>,
 }
 
 impl<'a, T: PyObjectPayload + PyValue> PyLease<'a, T> {
@@ -1212,8 +1212,8 @@ where
     #[allow(clippy::new_ret_no_self)]
     pub fn new(payload: T, typ: PyClassRef, dict: Option<PyDictRef>) -> PyObjectRef {
         PyObject {
-            typ: RwLock::new(typ.into_typed_pyobj()),
-            dict: dict.map(|d| RwLock::new(d.into_typed_pyobj())),
+            typ: PyRwLock::new(typ.into_typed_pyobj()),
+            dict: dict.map(|d| PyRwLock::new(d.into_typed_pyobj())),
             payload,
         }
         .into_ref()
@@ -1221,10 +1221,10 @@ where
 
     // Move this object into a reference object, transferring ownership.
     pub fn into_ref(self) -> PyObjectRef {
-        Arc::new(self)
+        PyRc::new(self)
     }
 
-    pub fn into_pyref(self: Arc<Self>) -> PyRef<T>
+    pub fn into_pyref(self: PyRc<Self>) -> PyRef<T>
     where
         T: PyValue,
     {
@@ -1276,7 +1276,17 @@ impl PyObject<dyn PyObjectPayload> {
     }
 }
 
-pub trait PyValue: fmt::Debug + Send + Sync + Sized + 'static {
+cfg_if::cfg_if! {
+    if #[cfg(feature = "threading")] {
+        pub trait PyThreadingConstraint: Send + Sync {}
+        impl<T: Send + Sync> PyThreadingConstraint for T {}
+    } else {
+        pub trait PyThreadingConstraint {}
+        impl<T> PyThreadingConstraint for T {}
+    }
+}
+
+pub trait PyValue: fmt::Debug + PyThreadingConstraint + Sized + 'static {
     const HAVE_DICT: bool = false;
 
     fn class(vm: &VirtualMachine) -> PyClassRef;
@@ -1306,7 +1316,7 @@ pub trait PyValue: fmt::Debug + Send + Sync + Sized + 'static {
     }
 }
 
-pub trait PyObjectPayload: Any + fmt::Debug + Send + Sync + 'static {
+pub trait PyObjectPayload: Any + fmt::Debug + PyThreadingConstraint + 'static {
     fn as_any(&self) -> &dyn Any;
 }
 
@@ -1452,6 +1462,20 @@ impl<T: TryFromObject> TryFromObject for PySequence<T> {
     }
 }
 
+pub fn hash_iter<'a, I: IntoIterator<Item = &'a PyObjectRef>>(
+    iter: I,
+    vm: &VirtualMachine,
+) -> PyResult<rustpython_common::hash::PyHash> {
+    rustpython_common::hash::hash_iter(iter, |obj| vm._hash(obj))
+}
+
+pub fn hash_iter_unordered<'a, I: IntoIterator<Item = &'a PyObjectRef>>(
+    iter: I,
+    vm: &VirtualMachine,
+) -> PyResult<rustpython_common::hash::PyHash> {
+    rustpython_common::hash::hash_iter_unordered(iter, |obj| vm._hash(obj))
+}
+
 #[cfg(test)]
 mod tests {
     use super::*;
diff --git a/vm/src/stdlib/array.rs b/vm/src/stdlib/array.rs
index 0f6dde5f2..87c2afaa2 100644
--- a/vm/src/stdlib/array.rs
+++ b/vm/src/stdlib/array.rs
@@ -10,7 +10,7 @@ use crate::pyobject::{
 };
 use crate::VirtualMachine;
 
-use parking_lot::{RwLock, RwLockReadGuard, RwLockWriteGuard};
+use crate::common::cell::{PyRwLock, PyRwLockReadGuard, PyRwLockWriteGuard};
 use std::fmt;
 
 use crossbeam_utils::atomic::AtomicCell;
@@ -239,7 +239,7 @@ def_array_enum!(
 #[pyclass(name = "array")]
 #[derive(Debug)]
 pub struct PyArray {
-    array: RwLock<ArrayContentType>,
+    array: PyRwLock<ArrayContentType>,
 }
 
 pub type PyArrayRef = PyRef<PyArray>;
@@ -252,11 +252,11 @@ impl PyValue for PyArray {
 
 #[pyimpl(flags(BASETYPE))]
 impl PyArray {
-    fn borrow_value(&self) -> RwLockReadGuard<'_, ArrayContentType> {
+    fn borrow_value(&self) -> PyRwLockReadGuard<'_, ArrayContentType> {
         self.array.read()
     }
 
-    fn borrow_value_mut(&self) -> RwLockWriteGuard<'_, ArrayContentType> {
+    fn borrow_value_mut(&self) -> PyRwLockWriteGuard<'_, ArrayContentType> {
         self.array.write()
     }
 
@@ -278,7 +278,7 @@ impl PyArray {
         let array =
             ArrayContentType::from_char(spec).map_err(|err| vm.new_value_error(err.to_string()))?;
         let zelf = PyArray {
-            array: RwLock::new(array),
+            array: PyRwLock::new(array),
         };
         if let OptionalArg::Present(init) = init {
             zelf.extend(init, vm)?;
diff --git a/vm/src/stdlib/collections.rs b/vm/src/stdlib/collections.rs
index a959970b8..eabc0fce1 100644
--- a/vm/src/stdlib/collections.rs
+++ b/vm/src/stdlib/collections.rs
@@ -2,6 +2,7 @@ pub(crate) use _collections::make_module;
 
 #[pymodule]
 mod _collections {
+    use crate::common::cell::{PyRwLock, PyRwLockReadGuard, PyRwLockWriteGuard};
     use crate::function::OptionalArg;
     use crate::obj::{objiter, objtype::PyClassRef};
     use crate::pyobject::{
@@ -12,7 +13,6 @@ mod _collections {
     use crate::vm::ReprGuard;
     use crate::VirtualMachine;
     use itertools::Itertools;
-    use parking_lot::{RwLock, RwLockReadGuard, RwLockWriteGuard};
     use std::collections::VecDeque;
 
     use crossbeam_utils::atomic::AtomicCell;
@@ -20,7 +20,7 @@ mod _collections {
     #[pyclass(name = "deque")]
     #[derive(Debug)]
     struct PyDeque {
-        deque: RwLock<VecDeque<PyObjectRef>>,
+        deque: PyRwLock<VecDeque<PyObjectRef>>,
         maxlen: AtomicCell<Option<usize>>,
     }
     type PyDequeRef = PyRef<PyDeque>;
@@ -38,16 +38,16 @@ mod _collections {
     }
 
     impl PyDeque {
-        fn borrow_deque(&self) -> RwLockReadGuard<'_, VecDeque<PyObjectRef>> {
+        fn borrow_deque(&self) -> PyRwLockReadGuard<'_, VecDeque<PyObjectRef>> {
             self.deque.read()
         }
 
-        fn borrow_deque_mut(&self) -> RwLockWriteGuard<'_, VecDeque<PyObjectRef>> {
+        fn borrow_deque_mut(&self) -> PyRwLockWriteGuard<'_, VecDeque<PyObjectRef>> {
             self.deque.write()
         }
     }
 
-    struct SimpleSeqDeque<'a>(RwLockReadGuard<'a, VecDeque<PyObjectRef>>);
+    struct SimpleSeqDeque<'a>(PyRwLockReadGuard<'a, VecDeque<PyObjectRef>>);
 
     impl sequence::SimpleSeq for SimpleSeqDeque<'_> {
         fn len(&self) -> usize {
@@ -59,8 +59,8 @@ mod _collections {
         }
     }
 
-    impl<'a> From<RwLockReadGuard<'a, VecDeque<PyObjectRef>>> for SimpleSeqDeque<'a> {
-        fn from(from: RwLockReadGuard<'a, VecDeque<PyObjectRef>>) -> Self {
+    impl<'a> From<PyRwLockReadGuard<'a, VecDeque<PyObjectRef>>> for SimpleSeqDeque<'a> {
+        fn from(from: PyRwLockReadGuard<'a, VecDeque<PyObjectRef>>) -> Self {
             Self { 0: from }
         }
     }
@@ -75,7 +75,7 @@ mod _collections {
             vm: &VirtualMachine,
         ) -> PyResult<PyRef<Self>> {
             let py_deque = PyDeque {
-                deque: RwLock::default(),
+                deque: PyRwLock::default(),
                 maxlen: AtomicCell::new(maxlen),
             };
             if let OptionalArg::Present(iter) = iter {
@@ -110,7 +110,7 @@ mod _collections {
         #[pymethod]
         fn copy(&self) -> Self {
             PyDeque {
-                deque: RwLock::new(self.borrow_deque().clone()),
+                deque: PyRwLock::new(self.borrow_deque().clone()),
                 maxlen: AtomicCell::new(self.maxlen.load()),
             }
         }
@@ -383,7 +383,7 @@ mod _collections {
             };
             let deque = mul.skip(skipped).cloned().collect();
             PyDeque {
-                deque: RwLock::new(deque),
+                deque: PyRwLock::new(deque),
                 maxlen: AtomicCell::new(self.maxlen.load()),
             }
         }
diff --git a/vm/src/stdlib/csv.rs b/vm/src/stdlib/csv.rs
index bef432b00..452650c75 100644
--- a/vm/src/stdlib/csv.rs
+++ b/vm/src/stdlib/csv.rs
@@ -1,11 +1,10 @@
-use parking_lot::RwLock;
 use std::fmt::{self, Debug, Formatter};
 
 use csv as rust_csv;
 use itertools::join;
 
+use crate::common::cell::PyRwLock;
 use crate::function::PyFuncArgs;
-
 use crate::obj::objiter;
 use crate::obj::objstr::{self, PyString};
 use crate::obj::objtype::PyClassRef;
@@ -126,7 +125,7 @@ impl ReadState {
 
 #[pyclass(name = "Reader")]
 struct Reader {
-    state: RwLock<ReadState>,
+    state: PyRwLock<ReadState>,
 }
 
 impl Debug for Reader {
@@ -143,7 +142,7 @@ impl PyValue for Reader {
 
 impl Reader {
     fn new(iter: PyIterable<PyObjectRef>, config: ReaderOption) -> Self {
-        let state = RwLock::new(ReadState::new(iter, config));
+        let state = PyRwLock::new(ReadState::new(iter, config));
         Reader { state }
     }
 }
diff --git a/vm/src/stdlib/hashlib.rs b/vm/src/stdlib/hashlib.rs
index 43f8442dc..262755279 100644
--- a/vm/src/stdlib/hashlib.rs
+++ b/vm/src/stdlib/hashlib.rs
@@ -1,10 +1,10 @@
+use crate::common::cell::{PyRwLock, PyRwLockReadGuard, PyRwLockWriteGuard};
 use crate::function::{OptionalArg, PyFuncArgs};
 use crate::obj::objbytes::{PyBytes, PyBytesRef};
 use crate::obj::objstr::PyStringRef;
 use crate::obj::objtype::PyClassRef;
 use crate::pyobject::{PyClassImpl, PyObjectRef, PyResult, PyValue};
 use crate::vm::VirtualMachine;
-use parking_lot::{RwLock, RwLockReadGuard, RwLockWriteGuard};
 use std::fmt;
 
 use blake2::{Blake2b, Blake2s};
@@ -17,7 +17,7 @@ use sha3::{Sha3_224, Sha3_256, Sha3_384, Sha3_512}; // TODO: , Shake128, Shake25
 #[pyclass(name = "hasher")]
 struct PyHasher {
     name: String,
-    buffer: RwLock<HashWrapper>,
+    buffer: PyRwLock<HashWrapper>,
 }
 
 impl fmt::Debug for PyHasher {
@@ -37,15 +37,15 @@ impl PyHasher {
     fn new(name: &str, d: HashWrapper) -> Self {
         PyHasher {
             name: name.to_owned(),
-            buffer: RwLock::new(d),
+            buffer: PyRwLock::new(d),
         }
     }
 
-    fn borrow_value(&self) -> RwLockReadGuard<'_, HashWrapper> {
+    fn borrow_value(&self) -> PyRwLockReadGuard<'_, HashWrapper> {
         self.buffer.read()
     }
 
-    fn borrow_value_mut(&self) -> RwLockWriteGuard<'_, HashWrapper> {
+    fn borrow_value_mut(&self) -> PyRwLockWriteGuard<'_, HashWrapper> {
         self.buffer.write()
     }
 
diff --git a/vm/src/stdlib/io.rs b/vm/src/stdlib/io.rs
index 26daec8d0..743e9955f 100644
--- a/vm/src/stdlib/io.rs
+++ b/vm/src/stdlib/io.rs
@@ -1,13 +1,13 @@
 /*
  * I/O core tools.
  */
-use parking_lot::{RwLock, RwLockWriteGuard};
 use std::fs;
 use std::io::{self, prelude::*, Cursor, SeekFrom};
 
 use crossbeam_utils::atomic::AtomicCell;
 use num_traits::ToPrimitive;
 
+use crate::common::cell::{PyRwLock, PyRwLockWriteGuard};
 use crate::exceptions::PyBaseExceptionRef;
 use crate::function::{Args, KwArgs, OptionalArg, OptionalOption, PyFuncArgs};
 use crate::obj::objbool;
@@ -121,7 +121,7 @@ impl BufferedIO {
 
 #[derive(Debug)]
 struct PyStringIO {
-    buffer: RwLock<BufferedIO>,
+    buffer: PyRwLock<BufferedIO>,
     closed: AtomicCell<bool>,
 }
 
@@ -134,7 +134,7 @@ impl PyValue for PyStringIO {
 }
 
 impl PyStringIORef {
-    fn buffer(&self, vm: &VirtualMachine) -> PyResult<RwLockWriteGuard<'_, BufferedIO>> {
+    fn buffer(&self, vm: &VirtualMachine) -> PyResult<PyRwLockWriteGuard<'_, BufferedIO>> {
         if !self.closed.load() {
             Ok(self.buffer.write())
         } else {
@@ -236,7 +236,7 @@ fn string_io_new(
     let input = flatten.map_or_else(Vec::new, |v| objstr::borrow_value(&v).as_bytes().to_vec());
 
     PyStringIO {
-        buffer: RwLock::new(BufferedIO::new(Cursor::new(input))),
+        buffer: PyRwLock::new(BufferedIO::new(Cursor::new(input))),
         closed: AtomicCell::new(false),
     }
     .into_ref_with_type(vm, cls)
@@ -244,7 +244,7 @@ fn string_io_new(
 
 #[derive(Debug)]
 struct PyBytesIO {
-    buffer: RwLock<BufferedIO>,
+    buffer: PyRwLock<BufferedIO>,
     closed: AtomicCell<bool>,
 }
 
@@ -257,7 +257,7 @@ impl PyValue for PyBytesIO {
 }
 
 impl PyBytesIORef {
-    fn buffer(&self, vm: &VirtualMachine) -> PyResult<RwLockWriteGuard<'_, BufferedIO>> {
+    fn buffer(&self, vm: &VirtualMachine) -> PyResult<PyRwLockWriteGuard<'_, BufferedIO>> {
         if !self.closed.load() {
             Ok(self.buffer.write())
         } else {
@@ -341,7 +341,7 @@ fn bytes_io_new(
     };
 
     PyBytesIO {
-        buffer: RwLock::new(BufferedIO::new(Cursor::new(raw_bytes))),
+        buffer: PyRwLock::new(BufferedIO::new(Cursor::new(raw_bytes))),
         closed: AtomicCell::new(false),
     }
     .into_ref_with_type(vm, cls)
diff --git a/vm/src/stdlib/itertools.rs b/vm/src/stdlib/itertools.rs
index b5ff02074..eb9752f5d 100644
--- a/vm/src/stdlib/itertools.rs
+++ b/vm/src/stdlib/itertools.rs
@@ -5,10 +5,9 @@ mod decl {
     use crossbeam_utils::atomic::AtomicCell;
     use num_bigint::BigInt;
     use num_traits::{One, Signed, ToPrimitive, Zero};
-    use parking_lot::{RwLock, RwLockWriteGuard};
     use std::iter;
-    use std::sync::Arc;
 
+    use crate::common::cell::{PyRwLock, PyRwLockWriteGuard};
     use crate::function::{Args, OptionalArg, OptionalOption, PyFuncArgs};
     use crate::obj::objbool;
     use crate::obj::objint::{self, PyInt, PyIntRef};
@@ -19,13 +18,14 @@ mod decl {
         IdProtocol, PyCallable, PyClassImpl, PyObjectRef, PyRef, PyResult, PyValue, TypeProtocol,
     };
     use crate::vm::VirtualMachine;
+    use rustpython_common::rc::PyRc;
 
     #[pyclass(name = "chain")]
     #[derive(Debug)]
     struct PyItertoolsChain {
         iterables: Vec<PyObjectRef>,
         cur_idx: AtomicCell<usize>,
-        cached_iter: RwLock<Option<PyObjectRef>>,
+        cached_iter: PyRwLock<Option<PyObjectRef>>,
     }
 
     impl PyValue for PyItertoolsChain {
@@ -41,7 +41,7 @@ mod decl {
             PyItertoolsChain {
                 iterables: args.args,
                 cur_idx: AtomicCell::new(0),
-                cached_iter: RwLock::new(None),
+                cached_iter: PyRwLock::new(None),
             }
             .into_ref_with_type(vm, cls)
         }
@@ -99,7 +99,7 @@ mod decl {
             PyItertoolsChain {
                 iterables,
                 cur_idx: AtomicCell::new(0),
-                cached_iter: RwLock::new(None),
+                cached_iter: PyRwLock::new(None),
             }
             .into_ref_with_type(vm, cls)
         }
@@ -159,7 +159,7 @@ mod decl {
     #[pyclass(name = "count")]
     #[derive(Debug)]
     struct PyItertoolsCount {
-        cur: RwLock<BigInt>,
+        cur: PyRwLock<BigInt>,
         step: BigInt,
     }
 
@@ -188,7 +188,7 @@ mod decl {
             };
 
             PyItertoolsCount {
-                cur: RwLock::new(start),
+                cur: PyRwLock::new(start),
                 step,
             }
             .into_ref_with_type(vm, cls)
@@ -212,7 +212,7 @@ mod decl {
     #[derive(Debug)]
     struct PyItertoolsCycle {
         iter: PyObjectRef,
-        saved: RwLock<Vec<PyObjectRef>>,
+        saved: PyRwLock<Vec<PyObjectRef>>,
         index: AtomicCell<usize>,
     }
 
@@ -234,7 +234,7 @@ mod decl {
 
             PyItertoolsCycle {
                 iter: iter.clone(),
-                saved: RwLock::new(Vec::new()),
+                saved: PyRwLock::new(Vec::new()),
                 index: AtomicCell::new(0),
             }
             .into_ref_with_type(vm, cls)
@@ -273,7 +273,7 @@ mod decl {
     #[derive(Debug)]
     struct PyItertoolsRepeat {
         object: PyObjectRef,
-        times: Option<RwLock<BigInt>>,
+        times: Option<PyRwLock<BigInt>>,
     }
 
     impl PyValue for PyItertoolsRepeat {
@@ -292,7 +292,7 @@ mod decl {
             vm: &VirtualMachine,
         ) -> PyResult<PyRef<Self>> {
             let times = match times.into_option() {
-                Some(int) => Some(RwLock::new(int.as_bigint().clone())),
+                Some(int) => Some(PyRwLock::new(int.as_bigint().clone())),
                 None => None,
             };
 
@@ -675,7 +675,7 @@ mod decl {
     struct PyItertoolsAccumulate {
         iterable: PyObjectRef,
         binop: PyObjectRef,
-        acc_value: RwLock<Option<PyObjectRef>>,
+        acc_value: PyRwLock<Option<PyObjectRef>>,
     }
 
     impl PyValue for PyItertoolsAccumulate {
@@ -698,7 +698,7 @@ mod decl {
             PyItertoolsAccumulate {
                 iterable: iter,
                 binop: binop.unwrap_or_else(|| vm.get_none()),
-                acc_value: RwLock::new(None),
+                acc_value: PyRwLock::new(None),
             }
             .into_ref_with_type(vm, cls)
         }
@@ -734,14 +734,14 @@ mod decl {
     #[derive(Debug)]
     struct PyItertoolsTeeData {
         iterable: PyObjectRef,
-        values: RwLock<Vec<PyObjectRef>>,
+        values: PyRwLock<Vec<PyObjectRef>>,
     }
 
     impl PyItertoolsTeeData {
-        fn new(iterable: PyObjectRef, vm: &VirtualMachine) -> PyResult<Arc<PyItertoolsTeeData>> {
-            Ok(Arc::new(PyItertoolsTeeData {
+        fn new(iterable: PyObjectRef, vm: &VirtualMachine) -> PyResult<PyRc<PyItertoolsTeeData>> {
+            Ok(PyRc::new(PyItertoolsTeeData {
                 iterable: get_iter(vm, &iterable)?,
-                values: RwLock::new(vec![]),
+                values: PyRwLock::new(vec![]),
             }))
         }
 
@@ -757,7 +757,7 @@ mod decl {
     #[pyclass(name = "tee")]
     #[derive(Debug)]
     struct PyItertoolsTee {
-        tee_data: Arc<PyItertoolsTeeData>,
+        tee_data: PyRc<PyItertoolsTeeData>,
         index: AtomicCell<usize>,
     }
 
@@ -812,7 +812,7 @@ mod decl {
         #[pymethod(name = "__copy__")]
         fn copy(&self, vm: &VirtualMachine) -> PyResult {
             Ok(PyItertoolsTee {
-                tee_data: Arc::clone(&self.tee_data),
+                tee_data: PyRc::clone(&self.tee_data),
                 index: AtomicCell::new(self.index.load()),
             }
             .into_ref_with_type(vm, Self::class(vm))?
@@ -836,7 +836,7 @@ mod decl {
     #[derive(Debug)]
     struct PyItertoolsProduct {
         pools: Vec<Vec<PyObjectRef>>,
-        idxs: RwLock<Vec<usize>>,
+        idxs: PyRwLock<Vec<usize>>,
         cur: AtomicCell<usize>,
         stop: AtomicCell<bool>,
     }
@@ -883,7 +883,7 @@ mod decl {
 
             PyItertoolsProduct {
                 pools,
-                idxs: RwLock::new(vec![0; l]),
+                idxs: PyRwLock::new(vec![0; l]),
                 cur: AtomicCell::new(l - 1),
                 stop: AtomicCell::new(false),
             }
@@ -920,7 +920,7 @@ mod decl {
             Ok(res.into_ref(vm).into_object())
         }
 
-        fn update_idxs(&self, mut idxs: RwLockWriteGuard<'_, Vec<usize>>) {
+        fn update_idxs(&self, mut idxs: PyRwLockWriteGuard<'_, Vec<usize>>) {
             let cur = self.cur.load();
             let lst_idx = &self.pools[cur].len() - 1;
 
@@ -948,7 +948,7 @@ mod decl {
     #[derive(Debug)]
     struct PyItertoolsCombinations {
         pool: Vec<PyObjectRef>,
-        indices: RwLock<Vec<usize>>,
+        indices: PyRwLock<Vec<usize>>,
         r: AtomicCell<usize>,
         exhausted: AtomicCell<bool>,
     }
@@ -981,7 +981,7 @@ mod decl {
 
             PyItertoolsCombinations {
                 pool,
-                indices: RwLock::new((0..r).collect()),
+                indices: PyRwLock::new((0..r).collect()),
                 r: AtomicCell::new(r),
                 exhausted: AtomicCell::new(r > n),
             }
@@ -1047,7 +1047,7 @@ mod decl {
     #[derive(Debug)]
     struct PyItertoolsCombinationsWithReplacement {
         pool: Vec<PyObjectRef>,
-        indices: RwLock<Vec<usize>>,
+        indices: PyRwLock<Vec<usize>>,
         r: AtomicCell<usize>,
         exhausted: AtomicCell<bool>,
     }
@@ -1080,7 +1080,7 @@ mod decl {
 
             PyItertoolsCombinationsWithReplacement {
                 pool,
-                indices: RwLock::new(vec![0; r]),
+                indices: PyRwLock::new(vec![0; r]),
                 r: AtomicCell::new(r),
                 exhausted: AtomicCell::new(n == 0 && r > 0),
             }
@@ -1140,12 +1140,12 @@ mod decl {
     #[pyclass(name = "permutations")]
     #[derive(Debug)]
     struct PyItertoolsPermutations {
-        pool: Vec<PyObjectRef>,             // Collected input iterable
-        indices: RwLock<Vec<usize>>,        // One index per element in pool
-        cycles: RwLock<Vec<usize>>,         // One rollover counter per element in the result
-        result: RwLock<Option<Vec<usize>>>, // Indexes of the most recently returned result
-        r: AtomicCell<usize>,               // Size of result tuple
-        exhausted: AtomicCell<bool>,        // Set when the iterator is exhausted
+        pool: Vec<PyObjectRef>,               // Collected input iterable
+        indices: PyRwLock<Vec<usize>>,        // One index per element in pool
+        cycles: PyRwLock<Vec<usize>>,         // One rollover counter per element in the result
+        result: PyRwLock<Option<Vec<usize>>>, // Indexes of the most recently returned result
+        r: AtomicCell<usize>,                 // Size of result tuple
+        exhausted: AtomicCell<bool>,          // Set when the iterator is exhausted
     }
 
     impl PyValue for PyItertoolsPermutations {
@@ -1186,9 +1186,9 @@ mod decl {
 
             PyItertoolsPermutations {
                 pool,
-                indices: RwLock::new((0..n).collect()),
-                cycles: RwLock::new((0..r).map(|i| n - i).collect()),
-                result: RwLock::new(None),
+                indices: PyRwLock::new((0..n).collect()),
+                cycles: PyRwLock::new((0..r).map(|i| n - i).collect()),
+                result: PyRwLock::new(None),
                 r: AtomicCell::new(r),
                 exhausted: AtomicCell::new(r > n),
             }
diff --git a/vm/src/stdlib/math.rs b/vm/src/stdlib/math.rs
index b0b957e02..4bda69436 100644
--- a/vm/src/stdlib/math.rs
+++ b/vm/src/stdlib/math.rs
@@ -15,6 +15,7 @@ use crate::obj::objint::{self, PyInt, PyIntRef};
 use crate::obj::objtype;
 use crate::pyobject::{Either, PyObjectRef, PyResult, TypeProtocol};
 use crate::vm::VirtualMachine;
+use rustpython_common::float_ops;
 
 #[cfg(not(target_arch = "wasm32"))]
 use libc::c_double;
@@ -253,7 +254,7 @@ fn math_floor(value: PyObjectRef, vm: &VirtualMachine) -> PyResult {
 fn math_frexp(value: IntoPyFloat) -> (f64, i32) {
     let value = value.to_f64();
     if value.is_finite() {
-        let (m, e) = objfloat::ufrexp(value);
+        let (m, e) = float_ops::ufrexp(value);
         (m * value.signum(), e)
     } else {
         (value, 0)
diff --git a/vm/src/stdlib/mod.rs b/vm/src/stdlib/mod.rs
index 71ff0d8be..880c1f9f2 100644
--- a/vm/src/stdlib/mod.rs
+++ b/vm/src/stdlib/mod.rs
@@ -32,6 +32,7 @@ mod string;
 mod symtable;
 mod sysconfigdata;
 #[cfg(not(target_arch = "wasm32"))]
+#[cfg(feature = "threading")]
 mod thread;
 mod time_module;
 #[cfg(feature = "rustpython-parser")]
@@ -131,6 +132,7 @@ pub fn get_module_inits() -> HashMap<String, StdlibInitFunc> {
         modules.insert("select".to_owned(), Box::new(select::make_module));
         #[cfg(feature = "ssl")]
         modules.insert("_ssl".to_owned(), Box::new(ssl::make_module));
+        #[cfg(feature = "threading")]
         modules.insert("_thread".to_owned(), Box::new(thread::make_module));
         #[cfg(not(target_os = "redox"))]
         modules.insert("zlib".to_owned(), Box::new(zlib::make_module));
diff --git a/vm/src/stdlib/os.rs b/vm/src/stdlib/os.rs
index a372ecc75..746e98d48 100644
--- a/vm/src/stdlib/os.rs
+++ b/vm/src/stdlib/os.rs
@@ -1,4 +1,3 @@
-use parking_lot::RwLock;
 use std::ffi;
 use std::fs::File;
 use std::fs::OpenOptions;
@@ -26,6 +25,7 @@ use std::os::unix::io::RawFd;
 use std::os::windows::io::RawHandle;
 
 use super::errno::errors;
+use crate::common::cell::PyRwLock;
 use crate::exceptions::PyBaseExceptionRef;
 use crate::function::{IntoPyNativeFunc, OptionalArg, PyFuncArgs};
 use crate::obj::objbyteinner::PyBytesLike;
@@ -726,7 +726,7 @@ impl DirEntryRef {
 #[pyclass]
 #[derive(Debug)]
 struct ScandirIterator {
-    entries: RwLock<fs::ReadDir>,
+    entries: PyRwLock<fs::ReadDir>,
     exhausted: AtomicCell<bool>,
     mode: OutputMode,
 }
@@ -791,7 +791,7 @@ fn os_scandir(path: OptionalArg<PyPathLike>, vm: &VirtualMachine) -> PyResult {
 
     match fs::read_dir(path.path) {
         Ok(iter) => Ok(ScandirIterator {
-            entries: RwLock::new(iter),
+            entries: PyRwLock::new(iter),
             exhausted: AtomicCell::new(false),
             mode: path.mode,
         }
diff --git a/vm/src/stdlib/random.rs b/vm/src/stdlib/random.rs
index bbff45667..1cdab8ec3 100644
--- a/vm/src/stdlib/random.rs
+++ b/vm/src/stdlib/random.rs
@@ -4,6 +4,7 @@ pub(crate) use _random::make_module;
 
 #[pymodule]
 mod _random {
+    use crate::common::cell::PyMutex;
     use crate::function::OptionalOption;
     use crate::obj::objint::PyIntRef;
     use crate::obj::objtype::PyClassRef;
@@ -13,8 +14,6 @@ mod _random {
     use num_traits::Signed;
     use rand::{rngs::StdRng, RngCore, SeedableRng};
 
-    use parking_lot::Mutex;
-
     #[derive(Debug)]
     enum PyRng {
         Std(Box<StdRng>),
@@ -57,7 +56,7 @@ mod _random {
     #[pyclass(name = "Random")]
     #[derive(Debug)]
     struct PyRandom {
-        rng: Mutex<PyRng>,
+        rng: PyMutex<PyRng>,
     }
 
     impl PyValue for PyRandom {
@@ -71,7 +70,7 @@ mod _random {
         #[pyslot(new)]
         fn new(cls: PyClassRef, vm: &VirtualMachine) -> PyResult<PyRef<Self>> {
             PyRandom {
-                rng: Mutex::default(),
+                rng: PyMutex::default(),
             }
             .into_ref_with_type(vm, cls)
         }
diff --git a/vm/src/stdlib/socket.rs b/vm/src/stdlib/socket.rs
index 25f7ab9da..ad423d083 100644
--- a/vm/src/stdlib/socket.rs
+++ b/vm/src/stdlib/socket.rs
@@ -1,4 +1,4 @@
-use parking_lot::{RwLock, RwLockReadGuard, RwLockWriteGuard};
+use crate::common::cell::{PyRwLock, PyRwLockReadGuard, PyRwLockWriteGuard};
 use std::io::{self, prelude::*};
 use std::net::{Ipv4Addr, Shutdown, SocketAddr, ToSocketAddrs};
 use std::time::Duration;
@@ -62,7 +62,7 @@ pub struct PySocket {
     kind: AtomicCell<i32>,
     family: AtomicCell<i32>,
     proto: AtomicCell<i32>,
-    sock: RwLock<Socket>,
+    sock: PyRwLock<Socket>,
 }
 
 impl PyValue for PySocket {
@@ -75,11 +75,11 @@ pub type PySocketRef = PyRef<PySocket>;
 
 #[pyimpl(flags(BASETYPE))]
 impl PySocket {
-    fn sock(&self) -> RwLockReadGuard<'_, Socket> {
+    fn sock(&self) -> PyRwLockReadGuard<'_, Socket> {
         self.sock.read()
     }
 
-    fn sock_mut(&self) -> RwLockWriteGuard<'_, Socket> {
+    fn sock_mut(&self) -> PyRwLockWriteGuard<'_, Socket> {
         self.sock.write()
     }
 
@@ -89,7 +89,7 @@ impl PySocket {
             kind: AtomicCell::default(),
             family: AtomicCell::default(),
             proto: AtomicCell::default(),
-            sock: RwLock::new(invalid_sock()),
+            sock: PyRwLock::new(invalid_sock()),
         }
         .into_ref_with_type(vm, cls)
     }
diff --git a/vm/src/stdlib/ssl.rs b/vm/src/stdlib/ssl.rs
index 9601e3764..3386df8ce 100644
--- a/vm/src/stdlib/ssl.rs
+++ b/vm/src/stdlib/ssl.rs
@@ -11,7 +11,7 @@ use crate::pyobject::{
 use crate::types::create_type;
 use crate::VirtualMachine;
 
-use parking_lot::{RwLock, RwLockWriteGuard};
+use crate::common::cell::{PyRwLock, PyRwLockWriteGuard};
 use std::convert::TryFrom;
 use std::ffi::{CStr, CString};
 use std::fmt;
@@ -230,7 +230,7 @@ fn ssl_rand_pseudo_bytes(n: i32, vm: &VirtualMachine) -> PyResult<(Vec<u8>, bool
 
 #[pyclass(name = "_SSLContext")]
 struct PySslContext {
-    ctx: RwLock<SslContextBuilder>,
+    ctx: PyRwLock<SslContextBuilder>,
     check_hostname: bool,
 }
 
@@ -248,7 +248,7 @@ impl PyValue for PySslContext {
 
 #[pyimpl(flags(BASETYPE))]
 impl PySslContext {
-    fn builder(&self) -> RwLockWriteGuard<'_, SslContextBuilder> {
+    fn builder(&self) -> PyRwLockWriteGuard<'_, SslContextBuilder> {
         self.ctx.write()
     }
     fn exec_ctx<F, R>(&self, func: F) -> R
@@ -308,7 +308,7 @@ impl PySslContext {
             .map_err(|e| convert_openssl_error(vm, e))?;
 
         PySslContext {
-            ctx: RwLock::new(builder),
+            ctx: PyRwLock::new(builder),
             check_hostname,
         }
         .into_ref_with_type(vm, cls)
@@ -471,10 +471,10 @@ impl PySslContext {
 
         Ok(PySslSocket {
             ctx: zelf,
-            stream: RwLock::new(Some(stream)),
+            stream: PyRwLock::new(Some(stream)),
             socket_type,
             server_hostname: args.server_hostname,
-            owner: RwLock::new(args.owner.as_ref().map(PyWeak::downgrade)),
+            owner: PyRwLock::new(args.owner.as_ref().map(PyWeak::downgrade)),
         })
     }
 }
@@ -507,10 +507,10 @@ struct LoadVerifyLocationsArgs {
 #[pyclass(name = "_SSLSocket")]
 struct PySslSocket {
     ctx: PyRef<PySslContext>,
-    stream: RwLock<Option<ssl::SslStreamBuilder<PySocketRef>>>,
+    stream: PyRwLock<Option<ssl::SslStreamBuilder<PySocketRef>>>,
     socket_type: SslServerOrClient,
     server_hostname: Option<PyStringRef>,
-    owner: RwLock<Option<PyWeak>>,
+    owner: PyRwLock<Option<PyWeak>>,
 }
 
 impl fmt::Debug for PySslSocket {
diff --git a/vm/src/stdlib/weakref.rs b/vm/src/stdlib/weakref.rs
index 35e440af9..6f59eeb6b 100644
--- a/vm/src/stdlib/weakref.rs
+++ b/vm/src/stdlib/weakref.rs
@@ -7,10 +7,10 @@
 
 use crate::pyobject::PyObjectRef;
 use crate::vm::VirtualMachine;
-use std::sync::Arc;
+use rustpython_common::rc::PyRc;
 
 fn weakref_getweakrefcount(obj: PyObjectRef) -> usize {
-    Arc::weak_count(&obj)
+    PyRc::weak_count(&obj)
 }
 
 fn weakref_getweakrefs(_obj: PyObjectRef, vm: &VirtualMachine) -> PyObjectRef {
diff --git a/vm/src/stdlib/winreg.rs b/vm/src/stdlib/winreg.rs
index c5a70a7c0..550b99d05 100644
--- a/vm/src/stdlib/winreg.rs
+++ b/vm/src/stdlib/winreg.rs
@@ -1,5 +1,5 @@
 #![allow(non_snake_case)]
-use parking_lot::{RwLock, RwLockReadGuard, RwLockWriteGuard};
+use crate::common::cell::{PyRwLock, PyRwLockReadGuard, PyRwLockWriteGuard};
 use std::convert::TryInto;
 use std::io;
 
@@ -16,7 +16,7 @@ use winreg::{enums::RegType, RegKey, RegValue};
 #[pyclass]
 #[derive(Debug)]
 struct PyHKEY {
-    key: RwLock<RegKey>,
+    key: PyRwLock<RegKey>,
 }
 type PyHKEYRef = PyRef<PyHKEY>;
 
@@ -33,15 +33,15 @@ impl PyValue for PyHKEY {
 impl PyHKEY {
     fn new(key: RegKey) -> Self {
         Self {
-            key: RwLock::new(key),
+            key: PyRwLock::new(key),
         }
     }
 
-    fn key(&self) -> RwLockReadGuard<'_, RegKey> {
+    fn key(&self) -> PyRwLockReadGuard<'_, RegKey> {
         self.key.read()
     }
 
-    fn key_mut(&self) -> RwLockWriteGuard<'_, RegKey> {
+    fn key_mut(&self) -> PyRwLockWriteGuard<'_, RegKey> {
         self.key.write()
     }
 
diff --git a/vm/src/stdlib/zlib.rs b/vm/src/stdlib/zlib.rs
index b7ee1bdce..43feb1cc5 100644
--- a/vm/src/stdlib/zlib.rs
+++ b/vm/src/stdlib/zlib.rs
@@ -1,3 +1,4 @@
+use crate::common::cell::PyMutex;
 use crate::exceptions::PyBaseExceptionRef;
 use crate::function::OptionalArg;
 use crate::obj::objbyteinner::PyBytesLike;
@@ -15,7 +16,6 @@ use flate2::{
 };
 use libz_sys as libz;
 
-use parking_lot::Mutex;
 use std::io::Write;
 
 // copied from zlibmodule.c (commit 530f506ac91338)
@@ -159,19 +159,19 @@ fn zlib_decompressobj(
         dict.with_ref(|d| decompress.set_dictionary(d).unwrap());
     }
     PyDecompress {
-        decompress: Mutex::new(decompress),
+        decompress: PyMutex::new(decompress),
         eof: AtomicCell::new(false),
-        unused_data: Mutex::new(PyBytes::new(vec![]).into_ref(vm)),
-        unconsumed_tail: Mutex::new(PyBytes::new(vec![]).into_ref(vm)),
+        unused_data: PyMutex::new(PyBytes::new(vec![]).into_ref(vm)),
+        unconsumed_tail: PyMutex::new(PyBytes::new(vec![]).into_ref(vm)),
     }
 }
 #[pyclass(name = "Decompress")]
 #[derive(Debug)]
 struct PyDecompress {
-    decompress: Mutex<Decompress>,
+    decompress: PyMutex<Decompress>,
     eof: AtomicCell<bool>,
-    unused_data: Mutex<PyBytesRef>,
-    unconsumed_tail: Mutex<PyBytesRef>,
+    unused_data: PyMutex<PyBytesRef>,
+    unconsumed_tail: PyMutex<PyBytesRef>,
 }
 impl PyValue for PyDecompress {
     fn class(vm: &VirtualMachine) -> PyClassRef {
@@ -359,7 +359,7 @@ fn zlib_compressobj(
     };
     let compress = Compress::new_with_window_bits(Compression::new(level), header, wbits);
     Ok(PyCompress {
-        inner: Mutex::new(CompressInner {
+        inner: PyMutex::new(CompressInner {
             compress,
             unconsumed: Vec::new(),
         }),
@@ -375,7 +375,7 @@ struct CompressInner {
 #[pyclass]
 #[derive(Debug)]
 struct PyCompress {
-    inner: Mutex<CompressInner>,
+    inner: PyMutex<CompressInner>,
 }
 
 impl PyValue for PyCompress {
diff --git a/vm/src/sysmodule.rs b/vm/src/sysmodule.rs
index ec3018e9e..8e8facb6f 100644
--- a/vm/src/sysmodule.rs
+++ b/vm/src/sysmodule.rs
@@ -1,16 +1,16 @@
-use std::sync::Arc;
 use std::{env, mem};
 
 use crate::builtins;
 use crate::frame::FrameRef;
 use crate::function::{Args, OptionalArg, PyFuncArgs};
 use crate::obj::objstr::PyStringRef;
-use crate::pyhash::PyHashInfo;
 use crate::pyobject::{
     IntoPyObject, ItemProtocol, PyClassImpl, PyContext, PyObjectRef, PyResult, TypeProtocol,
 };
 use crate::version;
 use crate::vm::{PySettings, VirtualMachine};
+use rustpython_common::hash::{PyHash, PyUHash};
+use rustpython_common::rc::PyRc;
 
 /*
  * The magic sys module.
@@ -110,7 +110,7 @@ impl SysFlags {
 }
 
 fn sys_getrefcount(obj: PyObjectRef) -> usize {
-    Arc::strong_count(&obj)
+    PyRc::strong_count(&obj)
 }
 
 fn sys_getsizeof(obj: PyObjectRef) -> usize {
@@ -257,6 +257,34 @@ pub fn sysconfigdata_name() -> String {
     format!("_sysconfigdata_{}_{}_{}", ABIFLAGS, PLATFORM, MULTIARCH)
 }
 
+#[pystruct_sequence(module = "sys", name = "hash_info")]
+#[derive(Debug)]
+struct PyHashInfo {
+    width: usize,
+    modulus: PyUHash,
+    inf: PyHash,
+    nan: PyHash,
+    imag: PyHash,
+    algorithm: &'static str,
+    hash_bits: usize,
+    seed_bits: usize,
+}
+impl PyHashInfo {
+    pub const INFO: Self = {
+        use rustpython_common::hash::*;
+        PyHashInfo {
+            width: BITS,
+            modulus: MODULUS,
+            inf: INF,
+            nan: NAN,
+            imag: IMAG,
+            algorithm: ALGO,
+            hash_bits: HASH_BITS,
+            seed_bits: SEED_BITS,
+        }
+    };
+}
+
 pub fn make_module(vm: &VirtualMachine, module: PyObjectRef, builtins: PyObjectRef) {
     let ctx = &vm.ctx;
 
diff --git a/vm/src/types.rs b/vm/src/types.rs
index a59ccb844..54435411b 100644
--- a/vm/src/types.rs
+++ b/vm/src/types.rs
@@ -40,10 +40,9 @@ use crate::obj::objweakproxy;
 use crate::obj::objweakref;
 use crate::obj::objzip;
 use crate::pyobject::{PyAttributes, PyContext, PyObject};
-use parking_lot::RwLock;
+use rustpython_common::{cell::PyRwLock, rc::PyRc};
 use std::mem::MaybeUninit;
 use std::ptr;
-use std::sync::Arc;
 
 /// Holder of references to builtin types.
 #[derive(Debug)]
@@ -275,14 +274,16 @@ macro_rules! partially_init {
     ) => {{
         // check all the fields are there but *don't* actually run it
         if false {
-            #[allow(invalid_value)]
+            #[allow(invalid_value, dead_code, unreachable_code)]
             let _ = {$ty {
                 $($init_field: $init_value,)*
-                $($uninit_field: ::std::mem::MaybeUninit::uninit().assume_init(),)*
+                $($uninit_field: unreachable!(),)*
             }};
         }
         let mut m = ::std::mem::MaybeUninit::<$ty>::uninit();
-        $(::std::ptr::write(&mut (*m.as_mut_ptr()).$init_field, $init_value);)*
+        unsafe {
+            $(::std::ptr::write(&mut (*m.as_mut_ptr()).$init_field, $init_value);)*
+        }
         m
     }};
 }
@@ -292,61 +293,64 @@ fn init_type_hierarchy() -> (PyClassRef, PyClassRef) {
     // and both `type` and `object are instances of `type`.
     // to produce this circular dependency, we need an unsafe block.
     // (and yes, this will never get dropped. TODO?)
-    let (type_type, object_type) = unsafe {
+    let (type_type, object_type) = {
         type PyClassObj = PyObject<PyClass>;
-        type UninitRef<T> = RwLock<Arc<MaybeUninit<T>>>;
+        type UninitRef<T> = PyRwLock<PyRc<MaybeUninit<T>>>;
 
-        let type_type: Arc<MaybeUninit<PyClassObj>> = Arc::new(partially_init!(
+        let type_type: PyRc<MaybeUninit<PyClassObj>> = PyRc::new(partially_init!(
             PyObject::<PyClass> {
                 dict: None,
                 payload: PyClass {
                     name: String::from("type"),
                     bases: vec![],
                     mro: vec![],
-                    subclasses: RwLock::default(),
-                    attributes: RwLock::new(PyAttributes::new()),
-                    slots: RwLock::default(),
+                    subclasses: PyRwLock::default(),
+                    attributes: PyRwLock::new(PyAttributes::new()),
+                    slots: PyRwLock::default(),
                 },
             },
             Uninit { typ }
         ));
-        let object_type: Arc<MaybeUninit<PyClassObj>> = Arc::new(partially_init!(
+        let object_type: PyRc<MaybeUninit<PyClassObj>> = PyRc::new(partially_init!(
             PyObject::<PyClass> {
                 dict: None,
                 payload: PyClass {
                     name: String::from("object"),
                     bases: vec![],
                     mro: vec![],
-                    subclasses: RwLock::default(),
-                    attributes: RwLock::new(PyAttributes::new()),
-                    slots: RwLock::default(),
+                    subclasses: PyRwLock::default(),
+                    attributes: PyRwLock::new(PyAttributes::new()),
+                    slots: PyRwLock::default(),
                 },
             },
             Uninit { typ },
         ));
 
         let object_type_ptr =
-            Arc::into_raw(object_type) as *mut MaybeUninit<PyClassObj> as *mut PyClassObj;
+            PyRc::into_raw(object_type) as *mut MaybeUninit<PyClassObj> as *mut PyClassObj;
         let type_type_ptr =
-            Arc::into_raw(type_type.clone()) as *mut MaybeUninit<PyClassObj> as *mut PyClassObj;
+            PyRc::into_raw(type_type.clone()) as *mut MaybeUninit<PyClassObj> as *mut PyClassObj;
 
-        ptr::write(
-            &mut (*object_type_ptr).typ as *mut RwLock<Arc<PyClassObj>>
-                as *mut UninitRef<PyClassObj>,
-            RwLock::new(type_type.clone()),
-        );
-        ptr::write(
-            &mut (*type_type_ptr).typ as *mut RwLock<Arc<PyClassObj>> as *mut UninitRef<PyClassObj>,
-            RwLock::new(type_type),
-        );
+        unsafe {
+            ptr::write(
+                &mut (*object_type_ptr).typ as *mut PyRwLock<PyRc<PyClassObj>>
+                    as *mut UninitRef<PyClassObj>,
+                PyRwLock::new(type_type.clone()),
+            );
+            ptr::write(
+                &mut (*type_type_ptr).typ as *mut PyRwLock<PyRc<PyClassObj>>
+                    as *mut UninitRef<PyClassObj>,
+                PyRwLock::new(type_type),
+            );
 
-        let type_type = PyClassRef::from_obj_unchecked(Arc::from_raw(type_type_ptr));
-        let object_type = PyClassRef::from_obj_unchecked(Arc::from_raw(object_type_ptr));
+            let type_type = PyClassRef::from_obj_unchecked(PyRc::from_raw(type_type_ptr));
+            let object_type = PyClassRef::from_obj_unchecked(PyRc::from_raw(object_type_ptr));
 
-        (*type_type_ptr).payload.mro = vec![object_type.clone()];
-        (*type_type_ptr).payload.bases = vec![object_type.clone()];
+            (*type_type_ptr).payload.mro = vec![object_type.clone()];
+            (*type_type_ptr).payload.bases = vec![object_type.clone()];
 
-        (type_type, object_type)
+            (type_type, object_type)
+        }
     };
 
     object_type
diff --git a/vm/src/vm.rs b/vm/src/vm.rs
index c629d8f23..c58486dcc 100644
--- a/vm/src/vm.rs
+++ b/vm/src/vm.rs
@@ -7,7 +7,6 @@
 use std::cell::{Cell, Ref, RefCell};
 use std::collections::hash_map::HashMap;
 use std::collections::hash_set::HashSet;
-use std::sync::Arc;
 use std::{env, fmt};
 
 use arr_macro::arr;
@@ -40,7 +39,6 @@ use crate::obj::objobject;
 use crate::obj::objstr::{PyString, PyStringRef};
 use crate::obj::objtuple::PyTuple;
 use crate::obj::objtype::{self, PyClassRef};
-use crate::pyhash;
 use crate::pyobject::{
     IdProtocol, ItemProtocol, PyContext, PyObject, PyObjectRef, PyResult, PyValue, TryFromObject,
     TryIntoRef, TypeProtocol,
@@ -48,6 +46,7 @@ use crate::pyobject::{
 use crate::scope::Scope;
 use crate::stdlib;
 use crate::sysmodule;
+use rustpython_common::rc::PyRc;
 
 // use objects::objects;
 
@@ -58,7 +57,7 @@ use crate::sysmodule;
 pub struct VirtualMachine {
     pub builtins: PyObjectRef,
     pub sys_module: PyObjectRef,
-    pub ctx: Arc<PyContext>,
+    pub ctx: PyRc<PyContext>,
     pub frames: RefCell<Vec<FrameRef>>,
     pub wasm_id: Option<String>,
     pub exceptions: RefCell<Vec<PyBaseExceptionRef>>,
@@ -68,7 +67,7 @@ pub struct VirtualMachine {
     pub use_tracing: Cell<bool>,
     pub recursion_limit: Cell<usize>,
     pub signal_handlers: Option<Box<RefCell<[PyObjectRef; NSIG]>>>,
-    pub state: Arc<PyGlobalState>,
+    pub state: PyRc<PyGlobalState>,
     pub initialized: bool,
 }
 
@@ -194,7 +193,7 @@ impl VirtualMachine {
         let mut vm = VirtualMachine {
             builtins: builtins.clone(),
             sys_module: sysmod.clone(),
-            ctx: Arc::new(ctx),
+            ctx: PyRc::new(ctx),
             frames: RefCell::new(vec![]),
             wasm_id: None,
             exceptions: RefCell::new(vec![]),
@@ -204,7 +203,7 @@ impl VirtualMachine {
             use_tracing: Cell::new(false),
             recursion_limit: Cell::new(if cfg!(debug_assertions) { 256 } else { 512 }),
             signal_handlers: Some(Box::new(signal_handlers)),
-            state: Arc::new(PyGlobalState {
+            state: PyRc::new(PyGlobalState {
                 settings,
                 stdlib_inits,
                 frozen,
@@ -288,6 +287,7 @@ impl VirtualMachine {
         }
     }
 
+    #[cfg(feature = "threading")]
     pub(crate) fn new_thread(&self) -> VirtualMachine {
         VirtualMachine {
             builtins: self.builtins.clone(),
@@ -753,7 +753,7 @@ impl VirtualMachine {
     pub fn isinstance(&self, obj: &PyObjectRef, cls: &PyClassRef) -> PyResult<bool> {
         // cpython first does an exact check on the type, although documentation doesn't state that
         // https://github.com/python/cpython/blob/a24107b04c1277e3c1105f98aff5bfa3a98b33a0/Objects/abstract.c#L2408
-        if Arc::ptr_eq(&obj.class().into_object(), cls.as_object()) {
+        if PyRc::ptr_eq(&obj.class().into_object(), cls.as_object()) {
             Ok(true)
         } else {
             let ret = self.call_method(cls.as_object(), "__instancecheck__", vec![obj.clone()])?;
@@ -1406,7 +1406,7 @@ impl VirtualMachine {
         })
     }
 
-    pub fn _hash(&self, obj: &PyObjectRef) -> PyResult<pyhash::PyHash> {
+    pub fn _hash(&self, obj: &PyObjectRef) -> PyResult<rustpython_common::hash::PyHash> {
         let hash_obj = self.call_method(obj, "__hash__", vec![])?;
         if let Some(hash_value) = hash_obj.payload_if_subclass::<PyInt>(self) {
             Ok(hash_value.hash())
diff --git a/wasm/lib/Cargo.lock b/wasm/lib/Cargo.lock
deleted file mode 100644
index 9bad7eeba..000000000
--- a/wasm/lib/Cargo.lock
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diff --git a/wasm/lib/Cargo.toml b/wasm/lib/Cargo.toml
index e9be7798d..9f74c5a98 100644
--- a/wasm/lib/Cargo.toml
+++ b/wasm/lib/Cargo.toml
@@ -17,7 +17,8 @@ freeze-stdlib = ["rustpython-vm/freeze-stdlib"]
 [dependencies]
 rustpython-compiler = { path = "../../compiler" }
 rustpython-parser = { path = "../../parser" }
-rustpython-vm = { path = "../../vm" }
+# no threading feature for rustpython-vm -- doesn't much matter anyway, but it might be more optimized
+rustpython-vm = { path = "../../vm", default-features = false, features = ["compile-parse"]  }
 cfg-if = "0.1.2"
 wasm-bindgen = "0.2"
 wasm-bindgen-futures = "0.3"
@@ -26,6 +27,8 @@ serde = "1.0"
 js-sys = "0.3"
 futures = "0.1"
 generational-arena = "0.2"
+# make parking_lot use wasm-bingden for instant
+parking_lot = { version = "0.11", features = ["wasm-bindgen"] }
 
 [dependencies.web-sys]
 version = "0.3"
diff --git a/wasm/lib/src/browser_module.rs b/wasm/lib/src/browser_module.rs
index a58d3f11b..d3b14fa20 100644
--- a/wasm/lib/src/browser_module.rs
+++ b/wasm/lib/src/browser_module.rs
@@ -1,10 +1,10 @@
 use futures::Future;
 use js_sys::Promise;
-use std::sync::Arc;
 use wasm_bindgen::prelude::*;
 use wasm_bindgen::JsCast;
 use wasm_bindgen_futures::{future_to_promise, JsFuture};
 
+use rustpython_vm::common::rc::PyRc;
 use rustpython_vm::function::{OptionalArg, PyFuncArgs};
 use rustpython_vm::import::import_file;
 use rustpython_vm::obj::{objdict::PyDictRef, objstr::PyStringRef, objtype::PyClassRef};
@@ -377,7 +377,7 @@ pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
 }
 
 pub fn setup_browser_module(vm: &mut VirtualMachine) {
-    let state = Arc::get_mut(&mut vm.state).unwrap();
+    let state = PyRc::get_mut(&mut vm.state).unwrap();
     state
         .stdlib_inits
         .insert("_browser".to_owned(), Box::new(make_module));
diff --git a/wasm/lib/src/js_module.rs b/wasm/lib/src/js_module.rs
index 9e39e7296..d84a8cadd 100644
--- a/wasm/lib/src/js_module.rs
+++ b/wasm/lib/src/js_module.rs
@@ -1,11 +1,11 @@
 use js_sys::{Array, Object, Reflect};
+use rustpython_vm::common::rc::PyRc;
 use rustpython_vm::exceptions::PyBaseExceptionRef;
 use rustpython_vm::function::Args;
 use rustpython_vm::obj::{objfloat::PyFloatRef, objstr::PyStringRef, objtype::PyClassRef};
 use rustpython_vm::pyobject::{PyClassImpl, PyObjectRef, PyRef, PyResult, PyValue, TryFromObject};
 use rustpython_vm::types::create_type;
 use rustpython_vm::VirtualMachine;
-use std::sync::Arc;
 use wasm_bindgen::{prelude::*, JsCast};
 
 #[wasm_bindgen(inline_js = "
@@ -259,7 +259,7 @@ pub fn make_module(vm: &VirtualMachine) -> PyObjectRef {
 }
 
 pub fn setup_js_module(vm: &mut VirtualMachine) {
-    let state = Arc::get_mut(&mut vm.state).unwrap();
+    let state = PyRc::get_mut(&mut vm.state).unwrap();
     state
         .stdlib_inits
         .insert("_js".to_owned(), Box::new(make_module));
diff --git a/wasm/lib/src/vm_class.rs b/wasm/lib/src/vm_class.rs
index afc6bb1a8..7e20a2bff 100644
--- a/wasm/lib/src/vm_class.rs
+++ b/wasm/lib/src/vm_class.rs
@@ -1,12 +1,12 @@
 use std::cell::RefCell;
 use std::collections::HashMap;
 use std::rc::{Rc, Weak};
-use std::sync::Arc;
 
 use js_sys::{Object, TypeError};
 use wasm_bindgen::prelude::*;
 
 use rustpython_compiler::compile;
+use rustpython_vm::common::rc::{PyRc, PyWeak};
 use rustpython_vm::pyobject::{ItemProtocol, PyObject, PyObjectPayload, PyObjectRef, PyValue};
 use rustpython_vm::scope::{NameProtocol, Scope};
 use rustpython_vm::{InitParameter, PySettings, VirtualMachine};
@@ -39,7 +39,7 @@ impl StoredVirtualMachine {
 
         js_module::setup_js_module(&mut vm);
         if inject_browser_module {
-            Arc::get_mut(&mut vm.state).unwrap().stdlib_inits.insert(
+            PyRc::get_mut(&mut vm.state).unwrap().stdlib_inits.insert(
                 "_window".to_owned(),
                 Box::new(|vm| {
                     py_module!(vm, "_window", {
@@ -177,9 +177,9 @@ impl WASMVirtualMachine {
     pub(crate) fn push_held_rc(
         &self,
         obj: PyObjectRef,
-    ) -> Result<std::sync::Weak<PyObject<dyn PyObjectPayload>>, JsValue> {
+    ) -> Result<PyWeak<PyObject<dyn PyObjectPayload>>, JsValue> {
         self.with(|stored_vm| {
-            let weak = std::sync::Arc::downgrade(&obj);
+            let weak = PyRc::downgrade(&obj);
             stored_vm.held_objects.borrow_mut().push(obj);
             weak
         })