https://github.com/python/cpython/commit/347acded845d07b70232cade8d576b6f0aaeb473
commit: 347acded845d07b70232cade8d576b6f0aaeb473
branch: main
author: Sam Gross <[email protected]>
committer: DinoV <[email protected]>
date: 2024-02-21T10:00:08-08:00
summary:
gh-115491: Keep some fields valid across allocations in obmalloc
(free-threading) (#115745)
files:
M Objects/object.c
M Objects/obmalloc.c
diff --git a/Objects/object.c b/Objects/object.c
index 23eab8288a41e8..df14fe0c6fbfec 100644
--- a/Objects/object.c
+++ b/Objects/object.c
@@ -299,13 +299,13 @@ _Py_DecRef(PyObject *o)
#ifdef Py_GIL_DISABLED
# ifdef Py_REF_DEBUG
-static inline int
-is_shared_refcnt_dead(Py_ssize_t shared)
+static int
+is_dead(PyObject *o)
{
# if SIZEOF_SIZE_T == 8
- return shared == (Py_ssize_t)0xDDDDDDDDDDDDDDDD;
+ return (uintptr_t)o->ob_type == 0xDDDDDDDDDDDDDDDD;
# else
- return shared == (Py_ssize_t)0xDDDDDDDD;
+ return (uintptr_t)o->ob_type == 0xDDDDDDDD;
# endif
}
# endif
@@ -335,8 +335,8 @@ _Py_DecRefSharedDebug(PyObject *o, const char *filename,
int lineno)
}
#ifdef Py_REF_DEBUG
- if ((_Py_REF_IS_MERGED(new_shared) && new_shared < 0) ||
- is_shared_refcnt_dead(shared))
+ if ((new_shared < 0 && _Py_REF_IS_MERGED(new_shared)) ||
+ (should_queue && is_dead(o)))
{
_Py_NegativeRefcount(filename, lineno, o);
}
diff --git a/Objects/obmalloc.c b/Objects/obmalloc.c
index 9bf4eeb9c822a5..43427d4449eb1a 100644
--- a/Objects/obmalloc.c
+++ b/Objects/obmalloc.c
@@ -2459,6 +2459,24 @@ write_size_t(void *p, size_t n)
}
}
+static void
+fill_mem_debug(debug_alloc_api_t *api, void *data, int c, size_t nbytes)
+{
+#ifdef Py_GIL_DISABLED
+ if (api->api_id == 'o') {
+ // Don't overwrite the first few bytes of a PyObject allocation in the
+ // free-threaded build
+ _PyThreadStateImpl *tstate = (_PyThreadStateImpl
*)_PyThreadState_GET();
+ size_t debug_offset =
tstate->mimalloc.current_object_heap->debug_offset;
+ if (debug_offset < nbytes) {
+ memset((char *)data + debug_offset, c, nbytes - debug_offset);
+ }
+ return;
+ }
+#endif
+ memset(data, c, nbytes);
+}
+
/* Let S = sizeof(size_t). The debug malloc asks for 4 * S extra bytes and
fills them with useful stuff, here calling the underlying malloc's result p:
@@ -2535,7 +2553,7 @@ _PyMem_DebugRawAlloc(int use_calloc, void *ctx, size_t
nbytes)
memset(p + SST + 1, PYMEM_FORBIDDENBYTE, SST-1);
if (nbytes > 0 && !use_calloc) {
- memset(data, PYMEM_CLEANBYTE, nbytes);
+ fill_mem_debug(api, data, PYMEM_CLEANBYTE, nbytes);
}
/* at tail, write pad (SST bytes) and serialno (SST bytes) */
@@ -2583,8 +2601,9 @@ _PyMem_DebugRawFree(void *ctx, void *p)
_PyMem_DebugCheckAddress(__func__, api->api_id, p);
nbytes = read_size_t(q);
- nbytes += PYMEM_DEBUG_EXTRA_BYTES;
- memset(q, PYMEM_DEADBYTE, nbytes);
+ nbytes += PYMEM_DEBUG_EXTRA_BYTES - 2*SST;
+ memset(q, PYMEM_DEADBYTE, 2*SST);
+ fill_mem_debug(api, p, PYMEM_DEADBYTE, nbytes);
api->alloc.free(api->alloc.ctx, q);
}
@@ -2604,7 +2623,6 @@ _PyMem_DebugRawRealloc(void *ctx, void *p, size_t nbytes)
size_t total; /* 2 * SST + nbytes + 2 * SST */
size_t original_nbytes;
#define ERASED_SIZE 64
- uint8_t save[2*ERASED_SIZE]; /* A copy of erased bytes. */
_PyMem_DebugCheckAddress(__func__, api->api_id, p);
@@ -2621,9 +2639,11 @@ _PyMem_DebugRawRealloc(void *ctx, void *p, size_t nbytes)
#ifdef PYMEM_DEBUG_SERIALNO
size_t block_serialno = read_size_t(tail + SST);
#endif
+#ifndef Py_GIL_DISABLED
/* Mark the header, the trailer, ERASED_SIZE bytes at the begin and
ERASED_SIZE bytes at the end as dead and save the copy of erased bytes.
*/
+ uint8_t save[2*ERASED_SIZE]; /* A copy of erased bytes. */
if (original_nbytes <= sizeof(save)) {
memcpy(save, data, original_nbytes);
memset(data - 2 * SST, PYMEM_DEADBYTE,
@@ -2636,6 +2656,7 @@ _PyMem_DebugRawRealloc(void *ctx, void *p, size_t nbytes)
memset(tail - ERASED_SIZE, PYMEM_DEADBYTE,
ERASED_SIZE + PYMEM_DEBUG_EXTRA_BYTES - 2 * SST);
}
+#endif
/* Resize and add decorations. */
r = (uint8_t *)api->alloc.realloc(api->alloc.ctx, head, total);
@@ -2663,6 +2684,7 @@ _PyMem_DebugRawRealloc(void *ctx, void *p, size_t nbytes)
write_size_t(tail + SST, block_serialno);
#endif
+#ifndef Py_GIL_DISABLED
/* Restore saved bytes. */
if (original_nbytes <= sizeof(save)) {
memcpy(data, save, Py_MIN(nbytes, original_nbytes));
@@ -2675,6 +2697,7 @@ _PyMem_DebugRawRealloc(void *ctx, void *p, size_t nbytes)
Py_MIN(nbytes - i, ERASED_SIZE));
}
}
+#endif
if (r == NULL) {
return NULL;
_______________________________________________
Python-checkins mailing list -- [email protected]
To unsubscribe send an email to [email protected]
https://mail.python.org/mailman3/lists/python-checkins.python.org/
Member address: [email protected]
