diff options
Diffstat (limited to 'Objects/obmalloc.c')
| -rw-r--r-- | Objects/obmalloc.c | 28 |
1 files changed, 22 insertions, 6 deletions
diff --git a/Objects/obmalloc.c b/Objects/obmalloc.c index 7c3b00b..af12f41 100644 --- a/Objects/obmalloc.c +++ b/Objects/obmalloc.c @@ -667,11 +667,19 @@ that this test determines whether an arbitrary address is controlled by obmalloc in a small constant time, independent of the number of arenas obmalloc controls. Since this test is needed at every entry point, it's extremely desirable that it be this fast. + +Since Py_ADDRESS_IN_RANGE may be reading from memory which was not allocated +by Python, it is important that (POOL)->arenaindex is read only once, as +another thread may be concurrently modifying the value without holding the +GIL. To accomplish this, the arenaindex_temp variable is used to store +(POOL)->arenaindex for the duration of the Py_ADDRESS_IN_RANGE macro's +execution. The caller of the macro is responsible for declaring this +variable. */ #define Py_ADDRESS_IN_RANGE(P, POOL) \ - ((POOL)->arenaindex < maxarenas && \ - (uptr)(P) - arenas[(POOL)->arenaindex].address < (uptr)ARENA_SIZE && \ - arenas[(POOL)->arenaindex].address != 0) + ((arenaindex_temp = (POOL)->arenaindex) < maxarenas && \ + (uptr)(P) - arenas[arenaindex_temp].address < (uptr)ARENA_SIZE && \ + arenas[arenaindex_temp].address != 0) /* This is only useful when running memory debuggers such as @@ -923,6 +931,9 @@ PyObject_Free(void *p) block *lastfree; poolp next, prev; uint size; +#ifndef Py_USING_MEMORY_DEBUGGER + uint arenaindex_temp; +#endif if (p == NULL) /* free(NULL) has no effect */ return; @@ -1137,6 +1148,9 @@ PyObject_Realloc(void *p, size_t nbytes) void *bp; poolp pool; size_t size; +#ifndef Py_USING_MEMORY_DEBUGGER + uint arenaindex_temp; +#endif if (p == NULL) return PyObject_Malloc(nbytes); @@ -1758,8 +1772,10 @@ _PyObject_DebugMallocStats(void) int Py_ADDRESS_IN_RANGE(void *P, poolp pool) { - return pool->arenaindex < maxarenas && - (uptr)P - arenas[pool->arenaindex].address < (uptr)ARENA_SIZE && - arenas[pool->arenaindex].address != 0; + uint arenaindex_temp = pool->arenaindex; + + return arenaindex_temp < maxarenas && + (uptr)P - arenas[arenaindex_temp].address < (uptr)ARENA_SIZE && + arenas[arenaindex_temp].address != 0; } #endif |