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Yusuke EndohandClaude Opus 5.5
053f8da910
Under the M:N thread scheduler, a Ruby thread in a non-main Ractor may be
resumed on a different native thread after it blocks. The C compiler
assumes that the native thread never changes within a function, so it may
compute the address of ruby_current_ec once (`__tls_get_addr` in
libruby.so) and reuse it after the switch. The address then refers to the
TLS of the previous native thread, which leads to a SEGV or to using
another thread's ec.
8.times.map do
Ractor.new do
50.times do
",,".split(/(,)/) { sleep 0.001 }
end
:ok
end
end.map(&:value)
#=> [BUG] Segmentation fault at 0x0000000000000030 (with Clang 21)
arm64 and ppc64le already use the out-of-line rb_current_ec()
(RB_THREAD_CURRENT_EC_NOINLINE), which prevents the compiler from caching
the address. Use it on all platforms, and remove the macro.
[Bug #22453]
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
27 lines
1.0 KiB
C
27 lines
1.0 KiB
C
#ifndef RUBY_THREAD_NONE_H
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#define RUBY_THREAD_NONE_H
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#define RB_NATIVETHREAD_LOCK_INIT (void)(0)
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#define RB_NATIVETHREAD_COND_INIT (void)(0)
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// no-thread impl doesn't use TLS but define this to avoid using tls key
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// based implementation in vm.c
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#define RB_THREAD_LOCAL_SPECIFIER
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// This model brings its own scheduler stubs (thread_none.c) instead of the
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// common one; thread.c keys off this.
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#define RB_THREAD_SCHED_NONE 1
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// The scheduler's types are shared with the threaded platforms: the code that
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// reads them (vm_sync.c, ractor.c, thread.c) is compiled for every thread
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// model, so it needs the real fields even here, where nothing ever runs
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// concurrently and they all stay zero. thread_none.c only ever passes the
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// structs around, never looks inside them.
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#include "thread_sched.h"
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RUBY_EXTERN struct rb_execution_context_struct *ruby_current_ec;
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NOINLINE(struct rb_execution_context_struct *rb_current_ec_noinline(void)); // for assertions
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struct rb_execution_context_struct *rb_current_ec(void);
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#endif /* RUBY_THREAD_NONE_H */
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