pythongh-111924: Use PyMutex for runtime global locks.

This replaces some usages of PyThread_type_lock with PyMutex, which
does not require memory allocation to initialize.

Include/internal/pycore_atexit.h

@@ -1,5 +1,8 @@
 #ifndef Py_INTERNAL_ATEXIT_H
 #define Py_INTERNAL_ATEXIT_H
+
+#include "pycore_lock.h"        // PyMutex
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -15,7 +18,7 @@ extern "C" {
 typedef void (*atexit_callbackfunc)(void);
 
 struct _atexit_runtime_state {
-    PyThread_type_lock mutex;
+    PyMutex mutex;
 #define NEXITFUNCS 32
     atexit_callbackfunc callbacks[NEXITFUNCS];
     int ncallbacks;

Include/internal/pycore_ceval.h

@@ -41,8 +41,7 @@ PyAPI_FUNC(int) _PyEval_MakePendingCalls(PyThreadState *);
 #endif
 
 extern void _Py_FinishPendingCalls(PyThreadState *tstate);
-extern void _PyEval_InitState(PyInterpreterState *, PyThread_type_lock);
-extern void _PyEval_FiniState(struct _ceval_state *ceval);
+extern void _PyEval_InitState(PyInterpreterState *);
 extern void _PyEval_SignalReceived(PyInterpreterState *interp);
 
 // bitwise flags:

Include/internal/pycore_ceval_state.h

@@ -8,14 +8,15 @@ extern "C" {
 #  error "this header requires Py_BUILD_CORE define"
 #endif
 
+#include "pycore_lock.h"            // PyMutex
 #include "pycore_gil.h"             // struct _gil_runtime_state
 
 
 typedef int (*_Py_pending_call_func)(void *);
 
 struct _pending_calls {
     int busy;
-    PyThread_type_lock lock;
+    PyMutex mutex;
     /* Request for running pending calls. */
     int32_t calls_to_do;
 #define NPENDINGCALLS 32

Include/internal/pycore_crossinterp.h

@@ -8,6 +8,7 @@ extern "C" {
 #  error "this header requires Py_BUILD_CORE define"
 #endif
 
+#include "pycore_lock.h"            // PyMutex
 #include "pycore_pyerrors.h"
 
 
@@ -128,7 +129,7 @@ struct _xidregitem {
 struct _xidregistry {
     int global;  /* builtin types or heap types */
     int initialized;
-    PyThread_type_lock mutex;
+    PyMutex mutex;
     struct _xidregitem *head;
 };
 

Include/internal/pycore_import.h

@@ -9,6 +9,7 @@ extern "C" {
 #  error "this header requires Py_BUILD_CORE define"
 #endif
 
+#include "pycore_lock.h"          // PyMutex
 #include "pycore_hashtable.h"     // _Py_hashtable_t
 #include "pycore_time.h"          // _PyTime_t
 
@@ -47,7 +48,7 @@ struct _import_runtime_state {
     Py_ssize_t last_module_index;
     struct {
         /* A lock to guard the cache. */
-        PyThread_type_lock mutex;
+        PyMutex mutex;
         /* The actual cache of (filename, name, PyModuleDef) for modules.
            Only legacy (single-phase init) extension modules are added
            and only if they support multiple initialization (m_size >- 0)

Include/internal/pycore_lock.h

@@ -108,6 +108,16 @@ typedef enum _PyLockFlags {
 extern PyLockStatus
 _PyMutex_LockTimed(PyMutex *m, _PyTime_t timeout_ns, _PyLockFlags flags);
 
+// Lock a mutex with aditional options. See _PyLockFlags for details.
+static inline void
+PyMutex_LockFlags(PyMutex *m, _PyLockFlags flags)
+{
+    uint8_t expected = _Py_UNLOCKED;
+    if (!_Py_atomic_compare_exchange_uint8(&m->v, &expected, _Py_LOCKED)) {
+        _PyMutex_LockTimed(m, -1, flags);
+    }
+}
+
 // Unlock a mutex, returns 0 if the mutex is not locked (used for improved
 // error messages).
 extern int _PyMutex_TryUnlock(PyMutex *m);

Include/internal/pycore_pymem.h

@@ -1,5 +1,8 @@
 #ifndef Py_INTERNAL_PYMEM_H
 #define Py_INTERNAL_PYMEM_H
+
+#include "pycore_lock.h"            // PyMutex
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -30,7 +33,7 @@ typedef struct {
 } debug_alloc_api_t;
 
 struct _pymem_allocators {
-    PyThread_type_lock mutex;
+    PyMutex mutex;
     struct {
         PyMemAllocatorEx raw;
         PyMemAllocatorEx mem;

Include/internal/pycore_pystate.h

@@ -220,9 +220,9 @@ PyAPI_FUNC(int) _PyState_AddModule(
 extern int _PyOS_InterruptOccurred(PyThreadState *tstate);
 
 #define HEAD_LOCK(runtime) \
-    PyThread_acquire_lock((runtime)->interpreters.mutex, WAIT_LOCK)
+    PyMutex_LockFlags(&(runtime)->interpreters.mutex, _Py_LOCK_DONT_DETACH)
 #define HEAD_UNLOCK(runtime) \
-    PyThread_release_lock((runtime)->interpreters.mutex)
+    PyMutex_Unlock(&(runtime)->interpreters.mutex)
 
 // Get the configuration of the current interpreter.
 // The caller must hold the GIL.

Include/internal/pycore_runtime.h

@@ -174,7 +174,7 @@ typedef struct pyruntimestate {
     unsigned long _finalizing_id;
 
     struct pyinterpreters {
-        PyThread_type_lock mutex;
+        PyMutex mutex;
         /* The linked list of interpreters, newest first. */
         PyInterpreterState *head;
         /* The runtime's initial interpreter, which has a special role
@@ -236,7 +236,7 @@ typedef struct pyruntimestate {
     Py_OpenCodeHookFunction open_code_hook;
     void *open_code_userdata;
     struct {
-        PyThread_type_lock mutex;
+        PyMutex mutex;
         _Py_AuditHookEntry *head;
     } audit_hooks;
 

Include/internal/pycore_unicodeobject.h

@@ -8,6 +8,7 @@ extern "C" {
 #  error "this header requires Py_BUILD_CORE define"
 #endif
 
+#include "pycore_lock.h"          // PyMutex
 #include "pycore_fileutils.h"     // _Py_error_handler
 #include "pycore_identifier.h"    // _Py_Identifier
 #include "pycore_ucnhash.h"       // _PyUnicode_Name_CAPI
@@ -277,7 +278,7 @@ extern PyTypeObject _PyUnicodeASCIIIter_Type;
 /* --- Other API ---------------------------------------------------------- */
 
 struct _Py_unicode_runtime_ids {
-    PyThread_type_lock lock;
+    PyMutex mutex;
     // next_index value must be preserved when Py_Initialize()/Py_Finalize()
     // is called multiple times: see _PyUnicode_FromId() implementation.
     Py_ssize_t next_index;

Objects/obmalloc.c

@@ -329,13 +329,9 @@ int
 _PyMem_SetDefaultAllocator(PyMemAllocatorDomain domain,
                            PyMemAllocatorEx *old_alloc)
 {
-    if (ALLOCATORS_MUTEX == NULL) {
-        /* The runtime must be initializing. */
-        return set_default_allocator_unlocked(domain, pydebug, old_alloc);
-    }
-    PyThread_acquire_lock(ALLOCATORS_MUTEX, WAIT_LOCK);
+    PyMutex_Lock(&ALLOCATORS_MUTEX);
     int res = set_default_allocator_unlocked(domain, pydebug, old_alloc);
-    PyThread_release_lock(ALLOCATORS_MUTEX);
+    PyMutex_Unlock(&ALLOCATORS_MUTEX);
     return res;
 }
 
@@ -467,9 +463,9 @@ set_up_allocators_unlocked(PyMemAllocatorName allocator)
 int
 _PyMem_SetupAllocators(PyMemAllocatorName allocator)
 {
-    PyThread_acquire_lock(ALLOCATORS_MUTEX, WAIT_LOCK);
+    PyMutex_Lock(&ALLOCATORS_MUTEX);
     int res = set_up_allocators_unlocked(allocator);
-    PyThread_release_lock(ALLOCATORS_MUTEX);
+    PyMutex_Unlock(&ALLOCATORS_MUTEX);
     return res;
 }
 
@@ -554,9 +550,9 @@ get_current_allocator_name_unlocked(void)
 const char*
 _PyMem_GetCurrentAllocatorName(void)
 {
-    PyThread_acquire_lock(ALLOCATORS_MUTEX, WAIT_LOCK);
+    PyMutex_Lock(&ALLOCATORS_MUTEX);
     const char *name = get_current_allocator_name_unlocked();
-    PyThread_release_lock(ALLOCATORS_MUTEX);
+    PyMutex_Unlock(&ALLOCATORS_MUTEX);
     return name;
 }
 
@@ -653,14 +649,9 @@ set_up_debug_hooks_unlocked(void)
 void
 PyMem_SetupDebugHooks(void)
 {
-    if (ALLOCATORS_MUTEX == NULL) {
-        /* The runtime must not be completely initialized yet. */
-        set_up_debug_hooks_unlocked();
-        return;
-    }
-    PyThread_acquire_lock(ALLOCATORS_MUTEX, WAIT_LOCK);
+    PyMutex_Lock(&ALLOCATORS_MUTEX);
     set_up_debug_hooks_unlocked();
-    PyThread_release_lock(ALLOCATORS_MUTEX);
+    PyMutex_Unlock(&ALLOCATORS_MUTEX);
 }
 
 static void
@@ -696,53 +687,33 @@ set_allocator_unlocked(PyMemAllocatorDomain domain, PyMemAllocatorEx *allocator)
 void
 PyMem_GetAllocator(PyMemAllocatorDomain domain, PyMemAllocatorEx *allocator)
 {
-    if (ALLOCATORS_MUTEX == NULL) {
-        /* The runtime must not be completely initialized yet. */
-        get_allocator_unlocked(domain, allocator);
-        return;
-    }
-    PyThread_acquire_lock(ALLOCATORS_MUTEX, WAIT_LOCK);
+    PyMutex_Lock(&ALLOCATORS_MUTEX);
     get_allocator_unlocked(domain, allocator);
-    PyThread_release_lock(ALLOCATORS_MUTEX);
+    PyMutex_Unlock(&ALLOCATORS_MUTEX);
 }
 
 void
 PyMem_SetAllocator(PyMemAllocatorDomain domain, PyMemAllocatorEx *allocator)
 {
-    if (ALLOCATORS_MUTEX == NULL) {
-        /* The runtime must not be completely initialized yet. */
-        set_allocator_unlocked(domain, allocator);
-        return;
-    }
-    PyThread_acquire_lock(ALLOCATORS_MUTEX, WAIT_LOCK);
+    PyMutex_Lock(&ALLOCATORS_MUTEX);
     set_allocator_unlocked(domain, allocator);
-    PyThread_release_lock(ALLOCATORS_MUTEX);
+    PyMutex_Unlock(&ALLOCATORS_MUTEX);
 }
 
 void
 PyObject_GetArenaAllocator(PyObjectArenaAllocator *allocator)
 {
-    if (ALLOCATORS_MUTEX == NULL) {
-        /* The runtime must not be completely initialized yet. */
-        *allocator = _PyObject_Arena;
-        return;
-    }
-    PyThread_acquire_lock(ALLOCATORS_MUTEX, WAIT_LOCK);
+    PyMutex_Lock(&ALLOCATORS_MUTEX);
     *allocator = _PyObject_Arena;
-    PyThread_release_lock(ALLOCATORS_MUTEX);
+    PyMutex_Unlock(&ALLOCATORS_MUTEX);
 }
 
 void
 PyObject_SetArenaAllocator(PyObjectArenaAllocator *allocator)
 {
-    if (ALLOCATORS_MUTEX == NULL) {
-        /* The runtime must not be completely initialized yet. */
-        _PyObject_Arena = *allocator;
-        return;
-    }
-    PyThread_acquire_lock(ALLOCATORS_MUTEX, WAIT_LOCK);
+    PyMutex_Lock(&ALLOCATORS_MUTEX);
     _PyObject_Arena = *allocator;
-    PyThread_release_lock(ALLOCATORS_MUTEX);
+    PyMutex_Unlock(&ALLOCATORS_MUTEX);
 }
 
 

Objects/unicodeobject.c

@@ -1904,7 +1904,7 @@ _PyUnicode_FromId(_Py_Identifier *id)
     if (index < 0) {
         struct _Py_unicode_runtime_ids *rt_ids = &interp->runtime->unicode_state.ids;
 
-        PyThread_acquire_lock(rt_ids->lock, WAIT_LOCK);
+        PyMutex_Lock(&rt_ids->mutex);
         // Check again to detect concurrent access. Another thread can have
         // initialized the index while this thread waited for the lock.
         index = _Py_atomic_load_ssize(&id->index);
@@ -1914,7 +1914,7 @@ _PyUnicode_FromId(_Py_Identifier *id)
             rt_ids->next_index++;
             _Py_atomic_store_ssize(&id->index, index);
         }
-        PyThread_release_lock(rt_ids->lock);
+        PyMutex_Unlock(&rt_ids->mutex);
     }
     assert(index >= 0);
 

Python/ceval_gil.c

@@ -589,9 +589,7 @@ _PyEval_ReInitThreads(PyThreadState *tstate)
     take_gil(tstate);
 
     struct _pending_calls *pending = &tstate->interp->ceval.pending;
-    if (_PyThread_at_fork_reinit(&pending->lock) < 0) {
-        return _PyStatus_ERR("Can't reinitialize pending calls lock");
-    }
+    pending->mutex = (PyMutex){0};
 
     /* Destroy all threads except the current one */
     _PyThreadState_DeleteExcept(tstate);
@@ -720,13 +718,10 @@ _PyEval_AddPendingCall(PyInterpreterState *interp,
         assert(_Py_IsMainInterpreter(interp));
         pending = &_PyRuntime.ceval.pending_mainthread;
     }
-    /* Ensure that _PyEval_InitState() was called
-       and that _PyEval_FiniState() is not called yet. */
-    assert(pending->lock != NULL);
 
-    PyThread_acquire_lock(pending->lock, WAIT_LOCK);
+    PyMutex_Lock(&pending->mutex);
     int result = _push_pending_call(pending, func, arg, flags);
-    PyThread_release_lock(pending->lock);
+    PyMutex_Unlock(&pending->mutex);
 
     /* signal main loop */
     SIGNAL_PENDING_CALLS(interp);
@@ -768,9 +763,9 @@ _make_pending_calls(struct _pending_calls *pending)
         int flags = 0;
 
         /* pop one item off the queue while holding the lock */
-        PyThread_acquire_lock(pending->lock, WAIT_LOCK);
+        PyMutex_Lock(&pending->mutex);
         _pop_pending_call(pending, &func, &arg, &flags);
-        PyThread_release_lock(pending->lock);
+        PyMutex_Unlock(&pending->mutex);
 
         /* having released the lock, perform the callback */
         if (func == NULL) {
@@ -795,7 +790,7 @@ make_pending_calls(PyInterpreterState *interp)
 
     /* Only one thread (per interpreter) may run the pending calls
        at once.  In the same way, we don't do recursive pending calls. */
-    PyThread_acquire_lock(pending->lock, WAIT_LOCK);
+    PyMutex_Lock(&pending->mutex);
     if (pending->busy) {
         /* A pending call was added after another thread was already
            handling the pending calls (and had already "unsignaled").
@@ -807,11 +802,11 @@ make_pending_calls(PyInterpreterState *interp)
            care of any remaining pending calls.  Until then, though,
            all the interpreter's threads will be tripping the eval
            breaker every time it's checked. */
-        PyThread_release_lock(pending->lock);
+        PyMutex_Unlock(&pending->mutex);
         return 0;
     }
     pending->busy = 1;
-    PyThread_release_lock(pending->lock);
+    PyMutex_Unlock(&pending->mutex);
 
     /* unsignal before starting to call callbacks, so that any callback
        added in-between re-signals */
@@ -892,23 +887,9 @@ Py_MakePendingCalls(void)
 }
 
 void
-_PyEval_InitState(PyInterpreterState *interp, PyThread_type_lock pending_lock)
+_PyEval_InitState(PyInterpreterState *interp)
 {
     _gil_initialize(&interp->_gil);
-
-    struct _pending_calls *pending = &interp->ceval.pending;
-    assert(pending->lock == NULL);
-    pending->lock = pending_lock;
-}
-
-void
-_PyEval_FiniState(struct _ceval_state *ceval)
-{
-    struct _pending_calls *pending = &ceval->pending;
-    if (pending->lock != NULL) {
-        PyThread_free_lock(pending->lock);
-        pending->lock = NULL;
-    }
 }