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[3.13] gh-117657: Fix TSAN race involving import lock (GH-118523) (#120169)

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This adds a `_PyRecursiveMutex` type based on `PyMutex` and uses that
for the import lock. This fixes some data races in the free-threaded
build and generally simplifies the import lock code.
(cherry picked from commit e21057b999)

Co-authored-by: Sam Gross <colesbury@gmail.com>
This commit is contained in:
Miss Islington (bot) 2024-06-06 20:03:01 +02:00 • committed by GitHub
parent 015ddfeca5
commit 517733ce3c
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GPG key ID: B5690EEEBB952194
7 changed files with 90 additions and 105 deletions
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42
Python/lock.c
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@ -366,6 +366,48 @@ _PyOnceFlag_CallOnceSlow(_PyOnceFlag *flag, _Py_once_fn_t *fn, void *arg)
}
}
static int
recursive_mutex_is_owned_by(_PyRecursiveMutex *m, PyThread_ident_t tid)
{
return _Py_atomic_load_ullong_relaxed(&m->thread) == tid;
}
int
_PyRecursiveMutex_IsLockedByCurrentThread(_PyRecursiveMutex *m)
{
return recursive_mutex_is_owned_by(m, PyThread_get_thread_ident_ex());
}
void
_PyRecursiveMutex_Lock(_PyRecursiveMutex *m)
{
PyThread_ident_t thread = PyThread_get_thread_ident_ex();
if (recursive_mutex_is_owned_by(m, thread)) {
m->level++;
return;
}
PyMutex_Lock(&m->mutex);
_Py_atomic_store_ullong_relaxed(&m->thread, thread);
assert(m->level == 0);
}
void
_PyRecursiveMutex_Unlock(_PyRecursiveMutex *m)
{
PyThread_ident_t thread = PyThread_get_thread_ident_ex();
if (!recursive_mutex_is_owned_by(m, thread)) {
Py_FatalError("unlocking a recursive mutex that is not owned by the"
" current thread");
}
if (m->level > 0) {
m->level--;
return;
}
assert(m->level == 0);
_Py_atomic_store_ullong_relaxed(&m->thread, 0);
PyMutex_Unlock(&m->mutex);
}
#define _Py_WRITE_LOCKED 1
#define _PyRWMutex_READER_SHIFT 2
#define _Py_RWMUTEX_MAX_READERS (UINTPTR_MAX >> _PyRWMutex_READER_SHIFT)