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gh-133171: Make the executor_list thread-safe #140038

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gh-133171: Make the executor_list thread-safe #140038

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e178e42
Add lock with operations on _PyExecutorObject list
aisk Oct 13, 2025
f3a9c74
Using FT_MUTEX_LOCK macro
aisk Oct 13, 2025
283f453
Merge remote-tracking branch 'upstream/main' into executor-list-lock
aisk Nov 9, 2025
6858161
Free the executors outside the lock in _Py_ClearExecutorDeletionList
aisk Nov 9, 2025
fa0dd0b
Fix a potential dead lock in add_to_pending_deletion_list
aisk Nov 9, 2025
bf48bb4
Using a _PyRecursiveMutex for executors lock
aisk Nov 9, 2025
6a5a1a9
Fix refcount
aisk Nov 9, 2025
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15 changes: 15 additions & 0 deletions Include/internal/pycore_interp_structs.h
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Original file line number Diff line number Diff line change
Expand Up @@ -9,6 +9,7 @@ extern "C" {

#include "pycore_ast_state.h" // struct ast_state
#include "pycore_llist.h" // struct llist_node
#include "pycore_lock.h" // _PyRecursiveMutex
#include "pycore_opcode_utils.h" // NUM_COMMON_CONSTANTS
#include "pycore_pymath.h" // _PY_SHORT_FLOAT_REPR
#include "pycore_structs.h" // PyHamtObject
Expand All @@ -29,6 +30,17 @@ extern "C" {
# define NUM_WEAKREF_LIST_LOCKS 127
#endif

// Executor list lock macros for thread-safe access to executor linked lists
#ifdef Py_GIL_DISABLED
#define EXECUTOR_LIST_LOCK(interp) \
_PyRecursiveMutex_Lock(&(interp)->executor_list_lock)
#define EXECUTOR_LIST_UNLOCK(interp) \
_PyRecursiveMutex_Unlock(&(interp)->executor_list_lock)
#else
#define EXECUTOR_LIST_LOCK(interp)
#define EXECUTOR_LIST_UNLOCK(interp)
#endif

typedef int (*_Py_pending_call_func)(void *);

struct _pending_call {
Expand Down Expand Up @@ -939,6 +951,9 @@ struct _is {
struct _PyExecutorObject *executor_deletion_list_head;
struct _PyExecutorObject *cold_executor;
int executor_deletion_list_remaining_capacity;
#ifdef Py_GIL_DISABLED
_PyRecursiveMutex executor_list_lock;
#endif
size_t executor_creation_counter;
_rare_events rare_events;
PyDict_WatchCallback builtins_dict_watcher;
Expand Down
52 changes: 50 additions & 2 deletions Python/optimizer.c
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Original file line number Diff line number Diff line change
Expand Up @@ -245,6 +245,16 @@ _Py_ClearExecutorDeletionList(PyInterpreterState *interp)
ts = PyThreadState_Next(ts);
HEAD_UNLOCK(runtime);
}

/* Create a list to collect executors that need to be freed.
* This avoids calling _PyExecutor_Free while holding the lock,
* which could trigger destructors and cause deadlock. */
PyObject *to_free = PyList_New(0);
if (to_free == NULL) {
goto error;
}

EXECUTOR_LIST_LOCK(interp);
_PyExecutorObject **prev_to_next_ptr = &interp->executor_deletion_list_head;
_PyExecutorObject *exec = *prev_to_next_ptr;
while (exec != NULL) {
Expand All @@ -255,24 +265,48 @@ _Py_ClearExecutorDeletionList(PyInterpreterState *interp)
}
else {
*prev_to_next_ptr = exec->vm_data.links.next;
_PyExecutor_Free(exec);
if (PyList_Append(to_free, (PyObject *)exec)) {
EXECUTOR_LIST_UNLOCK(interp);
goto error;
}
}
exec = *prev_to_next_ptr;
}
interp->executor_deletion_list_remaining_capacity = EXECUTOR_DELETE_LIST_MAX;
EXECUTOR_LIST_UNLOCK(interp);

for (Py_ssize_t i = 0; i < PyList_GET_SIZE(to_free); i++) {
_PyExecutorObject *exec = (_PyExecutorObject *)PyList_GET_ITEM(to_free, i);
PyList_SET_ITEM(to_free, i, NULL);
_PyExecutor_Free(exec);
}
Py_DECREF(to_free);
return;

error:
PyErr_Clear();
Py_XDECREF(to_free);
}

static void
add_to_pending_deletion_list(_PyExecutorObject *self)
{
PyInterpreterState *interp = PyInterpreterState_Get();
EXECUTOR_LIST_LOCK(interp);
self->vm_data.links.next = interp->executor_deletion_list_head;
interp->executor_deletion_list_head = self;
if (interp->executor_deletion_list_remaining_capacity > 0) {
interp->executor_deletion_list_remaining_capacity--;
EXECUTOR_LIST_UNLOCK(interp);
}
else {
/* Release the lock before calling _Py_ClearExecutorDeletionList
* to avoid deadlock, since it also tries to acquire the same lock */
EXECUTOR_LIST_UNLOCK(interp);
_Py_ClearExecutorDeletionList(interp);
EXECUTOR_LIST_LOCK(interp);
Comment on lines +303 to +307
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@Fidget-Spinner Fidget-Spinner Nov 9, 2025

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Do we still need this?

interp->executor_deletion_list_head = self;
EXECUTOR_LIST_UNLOCK(interp);
}
}

Expand Down Expand Up @@ -1450,6 +1484,7 @@ static void
link_executor(_PyExecutorObject *executor)
{
PyInterpreterState *interp = _PyInterpreterState_GET();
EXECUTOR_LIST_LOCK(interp);
_PyExecutorLinkListNode *links = &executor->vm_data.links;
_PyExecutorObject *head = interp->executor_list_head;
if (head == NULL) {
Expand All @@ -1467,6 +1502,7 @@ link_executor(_PyExecutorObject *executor)
executor->vm_data.linked = true;
/* executor_list_head must be first in list */
assert(interp->executor_list_head->vm_data.links.previous == NULL);
EXECUTOR_LIST_UNLOCK(interp);
}

static void
Expand All @@ -1475,6 +1511,8 @@ unlink_executor(_PyExecutorObject *executor)
if (!executor->vm_data.linked) {
return;
}
PyInterpreterState *interp = PyInterpreterState_Get();
EXECUTOR_LIST_LOCK(interp);
_PyExecutorLinkListNode *links = &executor->vm_data.links;
assert(executor->vm_data.valid);
_PyExecutorObject *next = links->next;
Expand All @@ -1487,11 +1525,11 @@ unlink_executor(_PyExecutorObject *executor)
}
else {
// prev == NULL implies that executor is the list head
PyInterpreterState *interp = PyInterpreterState_Get();
assert(interp->executor_list_head == executor);
interp->executor_list_head = next;
}
executor->vm_data.linked = false;
EXECUTOR_LIST_UNLOCK(interp);
}

/* This must be called by optimizers before using the executor */
Expand Down Expand Up @@ -1616,16 +1654,19 @@ _Py_Executors_InvalidateDependency(PyInterpreterState *interp, void *obj, int is
}
/* Clearing an executor can deallocate others, so we need to make a list of
* executors to invalidate first */
EXECUTOR_LIST_LOCK(interp);
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@Fidget-Spinner Fidget-Spinner Nov 7, 2025

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This is fine. nice.!

for (_PyExecutorObject *exec = interp->executor_list_head; exec != NULL;) {
assert(exec->vm_data.valid);
_PyExecutorObject *next = exec->vm_data.links.next;
if (bloom_filter_may_contain(&exec->vm_data.bloom, &obj_filter) &&
PyList_Append(invalidate, (PyObject *)exec))
{
EXECUTOR_LIST_UNLOCK(interp);
goto error;
}
exec = next;
}
EXECUTOR_LIST_UNLOCK(interp);
for (Py_ssize_t i = 0; i < PyList_GET_SIZE(invalidate); i++) {
PyObject *exec = PyList_GET_ITEM(invalidate, i);
executor_clear(exec);
Expand All @@ -1646,6 +1687,7 @@ _Py_Executors_InvalidateDependency(PyInterpreterState *interp, void *obj, int is
void
_Py_Executors_InvalidateAll(PyInterpreterState *interp, int is_invalidation)
{
EXECUTOR_LIST_LOCK(interp);
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@Fidget-Spinner Fidget-Spinner Nov 7, 2025

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This should be a stop the world event.

while (interp->executor_list_head) {
_PyExecutorObject *executor = interp->executor_list_head;
assert(executor->vm_data.valid == 1 && executor->vm_data.linked == 1);
Expand All @@ -1660,6 +1702,7 @@ _Py_Executors_InvalidateAll(PyInterpreterState *interp, int is_invalidation)
OPT_STAT_INC(executors_invalidated);
}
}
EXECUTOR_LIST_UNLOCK(interp);
}

void
Expand All @@ -1674,11 +1717,13 @@ _Py_Executors_InvalidateCold(PyInterpreterState *interp)

/* Clearing an executor can deallocate others, so we need to make a list of
* executors to invalidate first */
EXECUTOR_LIST_LOCK(interp);
for (_PyExecutorObject *exec = interp->executor_list_head; exec != NULL;) {
assert(exec->vm_data.valid);
_PyExecutorObject *next = exec->vm_data.links.next;

if (!exec->vm_data.warm && PyList_Append(invalidate, (PyObject *)exec) < 0) {
EXECUTOR_LIST_UNLOCK(interp);
goto error;
}
else {
Expand All @@ -1687,6 +1732,7 @@ _Py_Executors_InvalidateCold(PyInterpreterState *interp)

exec = next;
}
EXECUTOR_LIST_UNLOCK(interp);
for (Py_ssize_t i = 0; i < PyList_GET_SIZE(invalidate); i++) {
PyObject *exec = PyList_GET_ITEM(invalidate, i);
executor_clear(exec);
Expand Down Expand Up @@ -1810,10 +1856,12 @@ _PyDumpExecutors(FILE *out)
fprintf(out, "digraph ideal {\n\n");
fprintf(out, " rankdir = \"LR\"\n\n");
PyInterpreterState *interp = PyInterpreterState_Get();
EXECUTOR_LIST_LOCK(interp);
for (_PyExecutorObject *exec = interp->executor_list_head; exec != NULL;) {
executor_to_gv(exec, out);
exec = exec->vm_data.links.next;
}
EXECUTOR_LIST_UNLOCK(interp);
fprintf(out, "}\n\n");
return 0;
}
Expand Down
3 changes: 3 additions & 0 deletions Python/pystate.c
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Original file line number Diff line number Diff line change
Expand Up @@ -575,6 +575,9 @@ init_interpreter(PyInterpreterState *interp,
interp->executor_list_head = NULL;
interp->executor_deletion_list_head = NULL;
interp->executor_deletion_list_remaining_capacity = 0;
#ifdef Py_GIL_DISABLED
interp->executor_list_lock = (_PyRecursiveMutex){0};
#endif
interp->executor_creation_counter = JIT_CLEANUP_THRESHOLD;
if (interp != &runtime->_main_interpreter) {
/* Fix the self-referential, statically initialized fields. */
Expand Down
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