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gh-137514: Add a free-threading wrapper for mutexes #137515

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Merged
merged 7 commits into from
Aug 7, 2025
+44 −88
Merged

gh-137514: Add a free-threading wrapper for mutexes #137515

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8390e48
Add a common interface for FT-only locks
ZeroIntensity Aug 5, 2025
1eec109
Fix missing pyatomic includes.
ZeroIntensity Aug 7, 2025
ffdd0c6
Stray newline change.
ZeroIntensity Aug 7, 2025
fb77bb3
Keep formatting consistent.
ZeroIntensity Aug 7, 2025
ef59495
Apparently that wasn't a stray newline change.
ZeroIntensity Aug 7, 2025
513d011
Remove redundant code.
ZeroIntensity Aug 7, 2025
c725383
Simple readability/redundancy quirk.
ZeroIntensity Aug 7, 2025
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4 changes: 4 additions & 0 deletions Include/internal/pycore_pyatomic_ft_wrappers.h
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Original file line number Diff line number Diff line change
Expand Up @@ -111,6 +111,8 @@ extern "C" {
_Py_atomic_load_ullong_relaxed(&value)
#define FT_ATOMIC_ADD_SSIZE(value, new_value) \
(void)_Py_atomic_add_ssize(&value, new_value)
#define FT_MUTEX_LOCK(lock) PyMutex_Lock(lock)
#define FT_MUTEX_UNLOCK(lock) PyMutex_Unlock(lock)

#else
#define FT_ATOMIC_LOAD_PTR(value) value
Expand Down Expand Up @@ -159,6 +161,8 @@ extern "C" {
#define FT_ATOMIC_LOAD_ULLONG_RELAXED(value) value
#define FT_ATOMIC_STORE_ULLONG_RELAXED(value, new_value) value = new_value
#define FT_ATOMIC_ADD_SSIZE(value, new_value) (void)(value += new_value)
#define FT_MUTEX_LOCK(lock) do {} while (0)
#define FT_MUTEX_UNLOCK(lock) do {} while (0)

#endif

Expand Down
15 changes: 5 additions & 10 deletions Modules/_ctypes/malloc_closure.c
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Expand Up @@ -30,11 +30,6 @@

#ifdef Py_GIL_DISABLED
static PyMutex malloc_closure_lock;
# define MALLOC_CLOSURE_LOCK() PyMutex_Lock(&malloc_closure_lock)
# define MALLOC_CLOSURE_UNLOCK() PyMutex_Unlock(&malloc_closure_lock)
#else
# define MALLOC_CLOSURE_LOCK() ((void)0)
# define MALLOC_CLOSURE_UNLOCK() ((void)0)
#endif

typedef union _tagITEM {
Expand Down Expand Up @@ -120,11 +115,11 @@ void Py_ffi_closure_free(void *p)
}
#endif
#endif
MALLOC_CLOSURE_LOCK();
FT_MUTEX_LOCK(&malloc_closure_lock);
ITEM *item = (ITEM *)p;
item->next = free_list;
free_list = item;
MALLOC_CLOSURE_UNLOCK();
FT_MUTEX_UNLOCK(&malloc_closure_lock);
}

/* return one item from the free list, allocating more if needed */
Expand All @@ -143,13 +138,13 @@ void *Py_ffi_closure_alloc(size_t size, void** codeloc)
}
#endif
#endif
MALLOC_CLOSURE_LOCK();
FT_MUTEX_LOCK(&malloc_closure_lock);
ITEM *item;
if (!free_list) {
more_core();
}
if (!free_list) {
MALLOC_CLOSURE_UNLOCK();
FT_MUTEX_UNLOCK(&malloc_closure_lock);
return NULL;
}
item = free_list;
Expand All @@ -160,6 +155,6 @@ void *Py_ffi_closure_alloc(size_t size, void** codeloc)
#else
*codeloc = (void *)item;
#endif
MALLOC_CLOSURE_UNLOCK();
FT_MUTEX_UNLOCK(&malloc_closure_lock);
return (void *)item;
}
18 changes: 5 additions & 13 deletions Objects/codeobject.c
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Expand Up @@ -550,16 +550,12 @@ init_code(PyCodeObject *co, struct _PyCodeConstructor *con)
co->co_framesize = nlocalsplus + con->stacksize + FRAME_SPECIALS_SIZE;
co->co_ncellvars = ncellvars;
co->co_nfreevars = nfreevars;
#ifdef Py_GIL_DISABLED
PyMutex_Lock(&interp->func_state.mutex);
#endif
FT_MUTEX_LOCK(&interp->func_state.mutex);
co->co_version = interp->func_state.next_version;
if (interp->func_state.next_version != 0) {
interp->func_state.next_version++;
}
#ifdef Py_GIL_DISABLED
PyMutex_Unlock(&interp->func_state.mutex);
#endif
FT_MUTEX_UNLOCK(&interp->func_state.mutex);
co->_co_monitoring = NULL;
co->_co_instrumentation_version = 0;
/* not set */
Expand Down Expand Up @@ -689,7 +685,7 @@ intern_code_constants(struct _PyCodeConstructor *con)
#ifdef Py_GIL_DISABLED
PyInterpreterState *interp = _PyInterpreterState_GET();
struct _py_code_state *state = &interp->code_state;
PyMutex_Lock(&state->mutex);
FT_MUTEX_LOCK(&state->mutex);
#endif
if (intern_strings(con->names) < 0) {
goto error;
Expand All @@ -700,15 +696,11 @@ intern_code_constants(struct _PyCodeConstructor *con)
if (intern_strings(con->localsplusnames) < 0) {
goto error;
}
#ifdef Py_GIL_DISABLED
PyMutex_Unlock(&state->mutex);
#endif
FT_MUTEX_UNLOCK(&state->mutex);
return 0;

error:
#ifdef Py_GIL_DISABLED
PyMutex_Unlock(&state->mutex);
#endif
FT_MUTEX_UNLOCK(&state->mutex);
return -1;
}

Expand Down
20 changes: 7 additions & 13 deletions Objects/unicodeobject.c
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Expand Up @@ -114,14 +114,6 @@ NOTE: In the interpreter's initialization phase, some globals are currently
# define _PyUnicode_CHECK(op) PyUnicode_Check(op)
#endif

#ifdef Py_GIL_DISABLED
# define LOCK_INTERNED(interp) PyMutex_Lock(&_Py_INTERP_CACHED_OBJECT(interp, interned_mutex))
# define UNLOCK_INTERNED(interp) PyMutex_Unlock(&_Py_INTERP_CACHED_OBJECT(interp, interned_mutex))
#else
# define LOCK_INTERNED(interp)
# define UNLOCK_INTERNED(interp)
#endif

static inline char* _PyUnicode_UTF8(PyObject *op)
{
return FT_ATOMIC_LOAD_PTR_ACQUIRE(_PyCompactUnicodeObject_CAST(op)->utf8);
Expand Down Expand Up @@ -15992,14 +15984,16 @@ intern_common(PyInterpreterState *interp, PyObject *s /* stolen */,
/* Do a setdefault on the per-interpreter cache. */
PyObject *interned = get_interned_dict(interp);
assert(interned != NULL);

LOCK_INTERNED(interp);
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I believe it is worth to keep the old interface here. And implement LOCK_INTERNED via FT_MUTEX_LOCK.

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Why?

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It is shorter, easier to read and less error-prone on my sight.

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Hm, instead of adding another locking macro, how about an INTERN_MUTEX macro that acts as a shorthand for &_Py_INTERP_CACHED_OBJECT(interp, interned_mutex).

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Looks like a good idea!

#ifdef Py_GIL_DISABLED
# define INTERN_MUTEX &_Py_INTERP_CACHED_OBJECT(interp, interned_mutex)
#endif
FT_MUTEX_LOCK(INTERN_MUTEX);
PyObject *t;
{
int res = PyDict_SetDefaultRef(interned, s, s, &t);
if (res < 0) {
PyErr_Clear();
UNLOCK_INTERNED(interp);
FT_MUTEX_UNLOCK(INTERN_MUTEX);
return s;
}
else if (res == 1) {
Expand All @@ -16009,7 +16003,7 @@ intern_common(PyInterpreterState *interp, PyObject *s /* stolen */,
PyUnicode_CHECK_INTERNED(t) == SSTATE_INTERNED_MORTAL) {
immortalize_interned(t);
}
UNLOCK_INTERNED(interp);
FT_MUTEX_UNLOCK(INTERN_MUTEX);
return t;
}
else {
Expand Down Expand Up @@ -16042,7 +16036,7 @@ intern_common(PyInterpreterState *interp, PyObject *s /* stolen */,
immortalize_interned(s);
}

UNLOCK_INTERNED(interp);
FT_MUTEX_UNLOCK(INTERN_MUTEX);
return s;
}

Expand Down
25 changes: 9 additions & 16 deletions Parser/pegen.c
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Expand Up @@ -5,6 +5,7 @@
#include "pycore_pyerrors.h" // PyExc_IncompleteInputError
#include "pycore_runtime.h" // _PyRuntime
#include "pycore_unicodeobject.h" // _PyUnicode_InternImmortal
#include "pycore_pyatomic_ft_wrappers.h"
#include <errcode.h>

#include "lexer/lexer.h"
Expand Down Expand Up @@ -299,22 +300,14 @@ _PyPegen_fill_token(Parser *p)
#define NSTATISTICS _PYPEGEN_NSTATISTICS
#define memo_statistics _PyRuntime.parser.memo_statistics

#ifdef Py_GIL_DISABLED
#define MUTEX_LOCK() PyMutex_Lock(&_PyRuntime.parser.mutex)
#define MUTEX_UNLOCK() PyMutex_Unlock(&_PyRuntime.parser.mutex)
#else
#define MUTEX_LOCK()
#define MUTEX_UNLOCK()
#endif

void
_PyPegen_clear_memo_statistics(void)
{
MUTEX_LOCK();
FT_MUTEX_LOCK(&_PyRuntime.parser.mutex);
for (int i = 0; i < NSTATISTICS; i++) {
memo_statistics[i] = 0;
}
MUTEX_UNLOCK();
FT_MUTEX_UNLOCK(&_PyRuntime.parser.mutex);
}

PyObject *
Expand All @@ -325,22 +318,22 @@ _PyPegen_get_memo_statistics(void)
return NULL;
}

MUTEX_LOCK();
FT_MUTEX_LOCK(&_PyRuntime.parser.mutex);
for (int i = 0; i < NSTATISTICS; i++) {
PyObject *value = PyLong_FromLong(memo_statistics[i]);
if (value == NULL) {
MUTEX_UNLOCK();
FT_MUTEX_UNLOCK(&_PyRuntime.parser.mutex);
Py_DECREF(ret);
return NULL;
}
// PyList_SetItem borrows a reference to value.
if (PyList_SetItem(ret, i, value) < 0) {
MUTEX_UNLOCK();
FT_MUTEX_UNLOCK(&_PyRuntime.parser.mutex);
Py_DECREF(ret);
return NULL;
}
}
MUTEX_UNLOCK();
FT_MUTEX_UNLOCK(&_PyRuntime.parser.mutex);
return ret;
}
#endif
Expand All @@ -366,9 +359,9 @@ _PyPegen_is_memoized(Parser *p, int type, void *pres)
if (count <= 0) {
count = 1;
}
MUTEX_LOCK();
FT_MUTEX_LOCK(&_PyRuntime.parser.mutex);
memo_statistics[type] += count;
MUTEX_UNLOCK();
FT_MUTEX_UNLOCK(&_PyRuntime.parser.mutex);
}
#endif
p->mark = m->mark;
Expand Down
8 changes: 2 additions & 6 deletions Python/ceval_gil.c
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Expand Up @@ -907,13 +907,9 @@ unsignal_pending_calls(PyThreadState *tstate, PyInterpreterState *interp)
static void
clear_pending_handling_thread(struct _pending_calls *pending)
{
#ifdef Py_GIL_DISABLED
PyMutex_Lock(&pending->mutex);
pending->handling_thread = NULL;
PyMutex_Unlock(&pending->mutex);
#else
FT_MUTEX_LOCK(&pending->mutex);
pending->handling_thread = NULL;
#endif
FT_MUTEX_UNLOCK(&pending->mutex);
}

static int
Expand Down
19 changes: 6 additions & 13 deletions Python/codecs.c
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Expand Up @@ -16,7 +16,7 @@ Copyright (c) Corporation for National Research Initiatives.
#include "pycore_runtime.h" // _Py_ID()
#include "pycore_ucnhash.h" // _PyUnicode_Name_CAPI
#include "pycore_unicodeobject.h" // _PyUnicode_InternMortal()

#include "pycore_pyatomic_ft_wrappers.h"

static const char *codecs_builtin_error_handlers[] = {
"strict", "ignore", "replace",
Expand All @@ -40,13 +40,10 @@ int PyCodec_Register(PyObject *search_function)
PyErr_SetString(PyExc_TypeError, "argument must be callable");
goto onError;
}
#ifdef Py_GIL_DISABLED
PyMutex_Lock(&interp->codecs.search_path_mutex);
#endif
FT_MUTEX_LOCK(&interp->codecs.search_path_mutex);
int ret = PyList_Append(interp->codecs.search_path, search_function);
#ifdef Py_GIL_DISABLED
PyMutex_Unlock(&interp->codecs.search_path_mutex);
#endif
FT_MUTEX_UNLOCK(&interp->codecs.search_path_mutex);

return ret;

onError:
Expand All @@ -66,19 +63,15 @@ PyCodec_Unregister(PyObject *search_function)
PyObject *codec_search_path = interp->codecs.search_path;
assert(PyList_CheckExact(codec_search_path));
for (Py_ssize_t i = 0; i < PyList_GET_SIZE(codec_search_path); i++) {
#ifdef Py_GIL_DISABLED
PyMutex_Lock(&interp->codecs.search_path_mutex);
#endif
FT_MUTEX_LOCK(&interp->codecs.search_path_mutex);
PyObject *item = PyList_GetItemRef(codec_search_path, i);
int ret = 1;
if (item == search_function) {
// We hold a reference to the item, so its destructor can't run
// while we hold search_path_mutex.
ret = PyList_SetSlice(codec_search_path, i, i+1, NULL);
}
#ifdef Py_GIL_DISABLED
PyMutex_Unlock(&interp->codecs.search_path_mutex);
#endif
FT_MUTEX_UNLOCK(&interp->codecs.search_path_mutex);
Py_DECREF(item);
if (ret != 1) {
assert(interp->codecs.search_cache != NULL);
Expand Down
15 changes: 4 additions & 11 deletions Python/legacy_tracing.c
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Expand Up @@ -20,13 +20,6 @@ typedef struct _PyLegacyEventHandler {

#define _PyLegacyEventHandler_CAST(op) ((_PyLegacyEventHandler *)(op))

#ifdef Py_GIL_DISABLED
#define LOCK_SETUP() PyMutex_Lock(&_PyRuntime.ceval.sys_trace_profile_mutex);
#define UNLOCK_SETUP() PyMutex_Unlock(&_PyRuntime.ceval.sys_trace_profile_mutex);
#else
#define LOCK_SETUP()
#define UNLOCK_SETUP()
#endif
/* The Py_tracefunc function expects the following arguments:
* obj: the trace object (PyObject *)
* frame: the current frame (PyFrameObject *)
Expand Down Expand Up @@ -509,9 +502,9 @@ _PyEval_SetProfile(PyThreadState *tstate, Py_tracefunc func, PyObject *arg)

// needs to be decref'd outside of the lock
PyObject *old_profileobj;
LOCK_SETUP();
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Same here. I think it is better to keep the old one.

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I think this one is fine. We already used sys_trace_profile_mutex inline in pystate.c.

FT_MUTEX_LOCK(&_PyRuntime.ceval.sys_trace_profile_mutex);
Py_ssize_t profiling_threads = setup_profile(tstate, func, arg, &old_profileobj);
UNLOCK_SETUP();
FT_MUTEX_UNLOCK(&_PyRuntime.ceval.sys_trace_profile_mutex);
Py_XDECREF(old_profileobj);

uint32_t events = 0;
Expand Down Expand Up @@ -605,10 +598,10 @@ _PyEval_SetTrace(PyThreadState *tstate, Py_tracefunc func, PyObject *arg)
}
// needs to be decref'd outside of the lock
PyObject *old_traceobj;
LOCK_SETUP();
FT_MUTEX_LOCK(&_PyRuntime.ceval.sys_trace_profile_mutex);
assert(tstate->interp->sys_tracing_threads >= 0);
Py_ssize_t tracing_threads = setup_tracing(tstate, func, arg, &old_traceobj);
UNLOCK_SETUP();
FT_MUTEX_UNLOCK(&_PyRuntime.ceval.sys_trace_profile_mutex);
Py_XDECREF(old_traceobj);
if (tracing_threads < 0) {
return -1;
Expand Down
8 changes: 2 additions & 6 deletions Python/pystate.c
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Expand Up @@ -1689,9 +1689,7 @@ PyThreadState_Clear(PyThreadState *tstate)
"PyThreadState_Clear: warning: thread still has a generator\n");
}

#ifdef Py_GIL_DISABLED
PyMutex_Lock(&_PyRuntime.ceval.sys_trace_profile_mutex);
#endif
FT_MUTEX_LOCK(&_PyRuntime.ceval.sys_trace_profile_mutex);

if (tstate->c_profilefunc != NULL) {
tstate->interp->sys_profiling_threads--;
Expand All @@ -1702,9 +1700,7 @@ PyThreadState_Clear(PyThreadState *tstate)
tstate->c_tracefunc = NULL;
}

#ifdef Py_GIL_DISABLED
PyMutex_Unlock(&_PyRuntime.ceval.sys_trace_profile_mutex);
#endif
FT_MUTEX_UNLOCK(&_PyRuntime.ceval.sys_trace_profile_mutex);

Py_CLEAR(tstate->c_profileobj);
Py_CLEAR(tstate->c_traceobj);
Expand Down
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