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gh-129185: Use PyMutex in tracemalloc #129246

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Jan 24, 2025
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gh-129185: Use PyMutex in tracemalloc #129246

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2 changes: 1 addition & 1 deletion Include/internal/pycore_tracemalloc.h
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Original file line number Diff line number Diff line change
Expand Up @@ -70,7 +70,7 @@ struct _tracemalloc_runtime_state {
PyMemAllocatorEx obj;
} allocators;

PyThread_type_lock tables_lock;
PyMutex tables_lock;
/* Size in bytes of currently traced memory.
Protected by TABLES_LOCK(). */
size_t traced_memory;
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17 changes: 3 additions & 14 deletions Python/tracemalloc.c
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Expand Up @@ -3,6 +3,7 @@
#include "pycore_gc.h" // PyGC_Head
#include "pycore_hashtable.h" // _Py_hashtable_t
#include "pycore_initconfig.h" // _PyStatus_NO_MEMORY()
#include "pycore_lock.h" // PyMutex_LockFlags()
#include "pycore_object.h" // _PyType_PreHeaderSize()
#include "pycore_pymem.h" // _Py_tracemalloc_config
#include "pycore_runtime.h" // _Py_ID()
Expand Down Expand Up @@ -37,8 +38,8 @@ static int _PyTraceMalloc_TraceRef(PyObject *op, PyRefTracerEvent event,
the GIL held from PyMem_RawFree(). It cannot acquire the lock because it
would introduce a deadlock in _PyThreadState_DeleteCurrent(). */
#define tables_lock _PyRuntime.tracemalloc.tables_lock
#define TABLES_LOCK() PyThread_acquire_lock(tables_lock, 1)
#define TABLES_UNLOCK() PyThread_release_lock(tables_lock)
#define TABLES_LOCK() PyMutex_LockFlags(&tables_lock, _Py_LOCK_DONT_DETACH)
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@vstinner vstinner Jan 23, 2025 •
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PyMutex_Lock(&tables_lock) cannot be used "free" allocator hooks which don't acquire the GIL.

Maybe PyMutex_Lock(&tables_lock) should be preferred in functions which hold the GIL?

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@ZeroIntensity ZeroIntensity Jan 23, 2025 •
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I don't think it matters. TABLES_LOCK() didn't detach the thread state before, no need to now. (In fact, some unpredictable things might happen if another thread takes the GIL and then uses tracemalloc.)

#define TABLES_UNLOCK() PyMutex_Unlock(&tables_lock)


#define DEFAULT_DOMAIN 0
Expand Down Expand Up @@ -741,13 +742,6 @@ _PyTraceMalloc_Init(void)
return _PyStatus_NO_MEMORY();
}

if (tables_lock == NULL) {
tables_lock = PyThread_allocate_lock();
if (tables_lock == NULL) {
return _PyStatus_NO_MEMORY();
}
}

tracemalloc_filenames = hashtable_new(hashtable_hash_pyobject,
hashtable_compare_unicode,
tracemalloc_clear_filename, NULL);
Expand Down Expand Up @@ -792,11 +786,6 @@ tracemalloc_deinit(void)
_Py_hashtable_destroy(tracemalloc_tracebacks);
_Py_hashtable_destroy(tracemalloc_filenames);

if (tables_lock != NULL) {
PyThread_free_lock(tables_lock);
tables_lock = NULL;
}

PyThread_tss_delete(&tracemalloc_reentrant_key);
}

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