mirrors/cpython
1
0
Fork 0
mirror of https://github.com/python/cpython.git synced 2025-08-22 09:45:06 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 13

gh-111924: Fix data races when swapping allocators (gh-130287)

Browse source 
CPython current temporarily changes `PYMEM_DOMAIN_RAW` to the default
allocator during initialization and shutdown. The motivation is to
ensure that core runtime structures are allocated and freed using the
same allocator. However, modifying the current allocator changes global
state and is not thread-safe even with the GIL. Other threads may be
allocating or freeing objects use PYMEM_DOMAIN_RAW; they are not
required to hold the GIL to call PyMem_RawMalloc/PyMem_RawFree.

This adds new internal-only functions like `_PyMem_DefaultRawMalloc`
that aren't affected by calls to `PyMem_SetAllocator()`, so they're
appropriate for Python runtime initialization and finalization. Use
these calls in places where we previously swapped to the default raw
allocator.
This commit is contained in:
Sam Gross 2025-02-20 11:31:15 -05:00 • committed by GitHub
parent 568db400ff
commit ca22147547
No known key found for this signature in database
GPG key ID: B5690EEEBB952194
9 changed files with 155 additions and 154 deletions
Download patch file Download diff file Expand all files Collapse all files

43
Python/import.c
View file

@ -13,7 +13,7 @@
#include "pycore_pyerrors.h" // _PyErr_SetString()
#include "pycore_pyhash.h" // _Py_KeyedHash()
#include "pycore_pylifecycle.h"
#include "pycore_pymem.h" // _PyMem_SetDefaultAllocator()
#include "pycore_pymem.h" // _PyMem_DefaultRawFree()
#include "pycore_pystate.h" // _PyInterpreterState_GET()
#include "pycore_sysmodule.h" // _PySys_ClearAttrString()
#include "pycore_time.h" // _PyTime_AsMicroseconds()
@ -2387,14 +2387,11 @@ PyImport_ExtendInittab(struct _inittab *newtab)
/* Force default raw memory allocator to get a known allocator to be able
to release the memory in _PyImport_Fini2() */
PyMemAllocatorEx old_alloc;
_PyMem_SetDefaultAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
/* Allocate new memory for the combined table */
p = NULL;
if (i + n <= SIZE_MAX / sizeof(struct _inittab) - 1) {
size_t size = sizeof(struct _inittab) * (i + n + 1);
p = PyMem_RawRealloc(inittab_copy, size);
p = _PyMem_DefaultRawRealloc(inittab_copy, size);
}
if (p == NULL) {
res = -1;
@ -2408,9 +2405,7 @@ PyImport_ExtendInittab(struct _inittab *newtab)
}
memcpy(p + i, newtab, (n + 1) * sizeof(struct _inittab));
PyImport_Inittab = inittab_copy = p;
done:
PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
return res;
}
@ -2445,7 +2440,7 @@ init_builtin_modules_table(void)
size++;
/* Make the copy. */
struct _inittab *copied = PyMem_RawMalloc(size * sizeof(struct _inittab));
struct _inittab *copied = _PyMem_DefaultRawMalloc(size * sizeof(struct _inittab));
if (copied == NULL) {
return -1;
}
@ -2459,7 +2454,7 @@ fini_builtin_modules_table(void)
{
struct _inittab *inittab = INITTAB;
INITTAB = NULL;
PyMem_RawFree(inittab);
_PyMem_DefaultRawFree(inittab);
}
PyObject *
@ -3977,22 +3972,10 @@ _PyImport_Init(void)
if (INITTAB != NULL) {
return _PyStatus_ERR("global import state already initialized");
}
PyStatus status = _PyStatus_OK();
/* Force default raw memory allocator to get a known allocator to be able
to release the memory in _PyImport_Fini() */
PyMemAllocatorEx old_alloc;
_PyMem_SetDefaultAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
if (init_builtin_modules_table() != 0) {
status = PyStatus_NoMemory();
goto done;
return PyStatus_NoMemory();
}
done:
PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
return status;
return _PyStatus_OK();
}
void
@ -4003,31 +3986,19 @@ _PyImport_Fini(void)
// ever dlclose() the module files?
_extensions_cache_clear_all();
/* Use the same memory allocator as _PyImport_Init(). */
PyMemAllocatorEx old_alloc;
_PyMem_SetDefaultAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
/* Free memory allocated by _PyImport_Init() */
fini_builtin_modules_table();
PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
}
void
_PyImport_Fini2(void)
{
/* Use the same memory allocator than PyImport_ExtendInittab(). */
PyMemAllocatorEx old_alloc;
_PyMem_SetDefaultAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
// Reset PyImport_Inittab
PyImport_Inittab = _PyImport_Inittab;
/* Free memory allocated by PyImport_ExtendInittab() */
PyMem_RawFree(inittab_copy);
_PyMem_DefaultRawFree(inittab_copy);
inittab_copy = NULL;
PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
}