https://github.com/python/cpython/commit/e69d068ad0bd6a25434ea476a647b635da4d82bb
commit: e69d068ad0bd6a25434ea476a647b635da4d82bb
branch: main
author: Sam Gross <[email protected]>
committer: colesbury <[email protected]>
date: 2024-06-04T09:42:13-04:00
summary:
gh-117657: Fix race involving GC and heap initialization (#119923)
The `_PyThreadState_Bind()` function is called before the first
`PyEval_AcquireThread()` so it's not synchronized with the stop the
world GC. We had a race where `gc_visit_heaps()` might visit a thread's
heap while it's being initialized.
Use a simple atomic int to avoid visiting heaps for threads that are not
yet fully initialized (i.e., before `tstate_mimalloc_bind()` is called).
The race was reproducible by running:
`python Lib/test/test_importlib/partial/pool_in_threads.py`.
files:
M Include/internal/pycore_mimalloc.h
M Python/gc_free_threading.c
M Python/pystate.c
M Tools/tsan/suppressions_free_threading.txt
diff --git a/Include/internal/pycore_mimalloc.h
b/Include/internal/pycore_mimalloc.h
index 100f78d53021ee..d10b01d5b49b19 100644
--- a/Include/internal/pycore_mimalloc.h
+++ b/Include/internal/pycore_mimalloc.h
@@ -52,6 +52,7 @@ struct _mimalloc_thread_state {
mi_heap_t *current_object_heap;
mi_heap_t heaps[_Py_MIMALLOC_HEAP_COUNT];
mi_tld_t tld;
+ int initialized;
struct llist_node page_list;
};
#endif
diff --git a/Python/gc_free_threading.c b/Python/gc_free_threading.c
index d005b79ff40dbf..f19362c9573812 100644
--- a/Python/gc_free_threading.c
+++ b/Python/gc_free_threading.c
@@ -252,6 +252,10 @@ gc_visit_heaps_lock_held(PyInterpreterState *interp,
mi_block_visit_fun *visitor
// visit each thread's heaps for GC objects
for (PyThreadState *p = interp->threads.head; p != NULL; p = p->next) {
struct _mimalloc_thread_state *m = &((_PyThreadStateImpl
*)p)->mimalloc;
+ if (!_Py_atomic_load_int(&m->initialized)) {
+ // The thread may not have called tstate_mimalloc_bind() yet.
+ continue;
+ }
arg->offset = offset_base;
if (!mi_heap_visit_blocks(&m->heaps[_Py_MIMALLOC_HEAP_GC], true,
diff --git a/Python/pystate.c b/Python/pystate.c
index d0293915db7689..e1a95907b57d20 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -3074,6 +3074,8 @@ tstate_mimalloc_bind(PyThreadState *tstate)
// _PyObject_GC_New() and similar functions temporarily override this to
// use one of the GC heaps.
mts->current_object_heap = &mts->heaps[_Py_MIMALLOC_HEAP_OBJECT];
+
+ _Py_atomic_store_int(&mts->initialized, 1);
#endif
}
diff --git a/Tools/tsan/suppressions_free_threading.txt
b/Tools/tsan/suppressions_free_threading.txt
index d5fcac61f0db04..8b64d1ff321858 100644
--- a/Tools/tsan/suppressions_free_threading.txt
+++ b/Tools/tsan/suppressions_free_threading.txt
@@ -25,7 +25,6 @@ race:free_threadstate
race_top:_add_to_weak_set
race_top:_in_weak_set
-race_top:_mi_heap_delayed_free_partial
race_top:_PyEval_EvalFrameDefault
race_top:_PyImport_AcquireLock
race_top:_PyImport_ReleaseLock
@@ -33,7 +32,6 @@ race_top:_PyType_HasFeature
race_top:assign_version_tag
race_top:insertdict
race_top:lookup_tp_dict
-race_top:mi_heap_visit_pages
race_top:PyMember_GetOne
race_top:PyMember_SetOne
race_top:new_reference
@@ -58,7 +56,6 @@ race_top:_Py_slot_tp_getattr_hook
race_top:add_threadstate
race_top:dump_traceback
race_top:fatal_error
-race_top:mi_page_decode_padding
race_top:_multiprocessing_SemLock_release_impl
race_top:_PyFrame_GetCode
race_top:_PyFrame_Initialize
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