mirrors/cpython
1
0
Fork 0
mirror of https://github.com/python/cpython.git synced 2025-10-10 00:43:41 +00:00
Code Issues Projects Releases Packages Wiki Activity Actions 18

gh-115035: Mark ThreadHandles as non-joinable earlier after forking (#115042)

Browse source 
This marks dead ThreadHandles as non-joinable earlier in
`PyOS_AfterFork_Child()` before we execute any Python code. The handles
are stored in a global linked list in `_PyRuntimeState` because `fork()`
affects the entire process.
This commit is contained in:
Sam Gross 2024-02-06 14:45:04 -05:00 • committed by GitHub
parent 71239d50b5
commit b6228b521b
No known key found for this signature in database
GPG key ID: B5690EEEBB952194
7 changed files with 50 additions and 41 deletions
Download patch file Download diff file Expand all files Collapse all files

53
Modules/_threadmodule.c
View file

@ -44,6 +44,7 @@ get_thread_state(PyObject *module)
typedef struct {
PyObject_HEAD
struct llist_node node; // linked list node (see _pythread_runtime_state)
PyThread_ident_t ident;
PyThread_handle_t handle;
char joinable;
@ -59,6 +60,11 @@ new_thread_handle(thread_module_state* state)
self->ident = 0;
self->handle = 0;
self->joinable = 0;
HEAD_LOCK(&_PyRuntime);
llist_insert_tail(&_PyRuntime.threads.handles, &self->node);
HEAD_UNLOCK(&_PyRuntime);
return self;
}
@ -66,6 +72,14 @@ static void
ThreadHandle_dealloc(ThreadHandleObject *self)
{
PyObject *tp = (PyObject *) Py_TYPE(self);
// Remove ourself from the global list of handles
HEAD_LOCK(&_PyRuntime);
if (self->node.next != NULL) {
llist_remove(&self->node);
}
HEAD_UNLOCK(&_PyRuntime);
if (self->joinable) {
int ret = PyThread_detach_thread(self->handle);
if (ret) {
@ -77,6 +91,28 @@ ThreadHandle_dealloc(ThreadHandleObject *self)
Py_DECREF(tp);
}
void
_PyThread_AfterFork(struct _pythread_runtime_state *state)
{
// gh-115035: We mark ThreadHandles as not joinable early in the child's
// after-fork handler. We do this before calling any Python code to ensure
// that it happens before any ThreadHandles are deallocated, such as by a
// GC cycle.
PyThread_ident_t current = PyThread_get_thread_ident_ex();
struct llist_node *node;
llist_for_each_safe(node, &state->handles) {
ThreadHandleObject *hobj = llist_data(node, ThreadHandleObject, node);
if (hobj->ident == current) {
continue;
}
// Disallow calls to detach() and join() as they could crash.
hobj->joinable = 0;
llist_remove(node);
}
}
static PyObject *
ThreadHandle_repr(ThreadHandleObject *self)
{
@ -91,21 +127,6 @@ ThreadHandle_get_ident(ThreadHandleObject *self, void *ignored)
}
static PyObject *
ThreadHandle_after_fork_alive(ThreadHandleObject *self, void* ignored)
{
PyThread_update_thread_after_fork(&self->ident, &self->handle);
Py_RETURN_NONE;
}
static PyObject *
ThreadHandle_after_fork_dead(ThreadHandleObject *self, void* ignored)
{
// Disallow calls to detach() and join() as they could crash.
self->joinable = 0;
Py_RETURN_NONE;
}
static PyObject *
ThreadHandle_detach(ThreadHandleObject *self, void* ignored)
{
@ -157,8 +178,6 @@ static PyGetSetDef ThreadHandle_getsetlist[] = {
static PyMethodDef ThreadHandle_methods[] =
{
{"after_fork_alive", (PyCFunction)ThreadHandle_after_fork_alive, METH_NOARGS},
{"after_fork_dead", (PyCFunction)ThreadHandle_after_fork_dead, METH_NOARGS},
{"detach", (PyCFunction)ThreadHandle_detach, METH_NOARGS},
{"join", (PyCFunction)ThreadHandle_join, METH_NOARGS},
{0, 0}