Prevent array.tofile re-entrant deadlock and add regression snippet (#6559)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: youknowone <69878+youknowone@users.noreply.github.com>

crates/stdlib/src/array.rs

@@ -938,8 +938,10 @@ mod array {
             /* XXX Make the block size settable */
             const BLOCKSIZE: usize = 64 * 1024;
 
-            let bytes = self.read();
-            let bytes = bytes.get_bytes();
+            let bytes = {
+                let bytes = self.read();
+                bytes.get_bytes().to_vec()
+            };
 
             for b in bytes.chunks(BLOCKSIZE) {
                 let b = PyBytes::from(b.to_vec()).into_ref(&vm.ctx);

extra_tests/snippets/stdlib_array.py

@@ -126,3 +126,20 @@ assert str(i.__class__.__name__) == "arrayiterator"
 a = array("B", [0])
 assert a.__contains__(0)
 assert not a.__contains__(1)
+
+
+class _ReenteringWriter:
+    def __init__(self, arr):
+        self.arr = arr
+        self.reentered = False
+
+    def write(self, chunk):
+        if not self.reentered:
+            self.reentered = True
+            self.arr.append(0)
+        return len(chunk)
+
+
+arr = array("b", range(128))
+arr.tofile(_ReenteringWriter(arr))
+assert len(arr) == 129