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gh-157415: Fix data race in pthread wrapper #157430

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gh-157415: Fix data race in pthread wrapper #157430

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250cf48
gh-157415: Fix data race in pthread wrapper
vstinner Sep 13, 2026
b422bba
Reenable @nomemtest on TSAN
vstinner Sep 16, 2026
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6 changes: 1 addition & 5 deletions Lib/test/support/__init__.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1373,11 +1373,7 @@ def internal(*args, **kwargs):
import_module('_testcapi')
return test(*args, **kwargs)

use_tsan = check_sanitizer(thread=True)
reason ='not working with thread sanitizer (gh-157415)'
skip_if_tsan = unittest.skipIf(use_tsan, reason)

return cpython_only(skip_if_tsan(internal))
return cpython_only(internal)

def bigaddrspacetest(f):
"""Decorator for tests that fill the address space."""
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8 changes: 5 additions & 3 deletions Python/thread_pthread.h
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Original file line number Diff line number Diff line change
Expand Up @@ -231,7 +231,7 @@ pythread_wrapper(void *arg)
pythread_callback *callback = arg;
void (*func)(void *) = callback->func;
void *func_arg = callback->arg;
PyMem_RawFree(arg);
free(callback);

func(func_arg);
return NULL;
Expand Down Expand Up @@ -271,7 +271,9 @@ do_start_joinable_thread(void (*func)(void *), void *arg, pthread_t* out_id)
pthread_attr_setscope(&attrs, PTHREAD_SCOPE_SYSTEM);
#endif

pythread_callback *callback = PyMem_RawMalloc(sizeof(pythread_callback));
// Use free() instead of PyMem_RawFree() in pythread_wrapper() to avoid a
// data race if another thread calls PyMem_SetAllocator() in parallel.
pythread_callback *callback = malloc(sizeof(pythread_callback));

if (callback == NULL) {
return -1;
Expand All @@ -293,7 +295,7 @@ do_start_joinable_thread(void (*func)(void *), void *arg, pthread_t* out_id)
#endif

if (status != 0) {
PyMem_RawFree(callback);
free(callback);
return -1;
}
*out_id = th;
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