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GH-96071: fix deadlock in PyGILState_Ensure (GH-96124) (#96129)

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Alternative of GH-96107
(cherry picked from commit e0d54a4a79)

Co-authored-by: Kumar Aditya <59607654+kumaraditya303@users.noreply.github.com>

Co-authored-by: Kumar Aditya <59607654+kumaraditya303@users.noreply.github.com>
This commit is contained in:
Miss Islington (bot) 2022-08-19 14:11:31 -07:00 • committed by GitHub
parent fcf04217ab
commit 1fa9644c23
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2 changed files with 17 additions and 11 deletions
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27
Python/pystate.c
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@ -795,7 +795,15 @@ new_threadstate(PyInterpreterState *interp)
{
PyThreadState *tstate;
_PyRuntimeState *runtime = interp->runtime;
// We don't need to allocate a thread state for the main interpreter
// (the common case), but doing it later for the other case revealed a
// reentrancy problem (deadlock). So for now we always allocate before
// taking the interpreters lock. See GH-96071.
PyThreadState *new_tstate = alloc_threadstate();
int used_newtstate;
if (new_tstate == NULL) {
return NULL;
}
/* We serialize concurrent creation to protect global state. */
HEAD_LOCK(runtime);
@ -807,18 +815,15 @@ new_threadstate(PyInterpreterState *interp)
if (old_head == NULL) {
// It's the interpreter's initial thread state.
assert(id == 1);
used_newtstate = 0;
tstate = &interp->_initial_thread;
}
else {
// Every valid interpreter must have at least one thread.
assert(id > 1);
assert(old_head->prev == NULL);
tstate = alloc_threadstate();
if (tstate == NULL) {
goto error;
}
used_newtstate = 1;
tstate = new_tstate;
// Set to _PyThreadState_INIT.
memcpy(tstate,
&initial._main_interpreter._initial_thread,
@ -829,11 +834,11 @@ new_threadstate(PyInterpreterState *interp)
init_threadstate(tstate, interp, id, old_head);
HEAD_UNLOCK(runtime);
if (!used_newtstate) {
// Must be called with lock unlocked to avoid re-entrancy deadlock.
PyMem_RawFree(new_tstate);
}
return tstate;
error:
HEAD_UNLOCK(runtime);
return NULL;
}
PyThreadState *