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

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Alternative of #96107
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Kumar Aditya 2022-08-20 01:13:00 +05:30 • committed by GitHub
parent 822955c166
commit e0d54a4a79
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2 changed files with 17 additions and 11 deletions
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Misc/NEWS.d/next/Core and Builtins/2022-08-19-06-51-17.gh-issue-96071.mVgPAo.rst Normal file
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@ -0,0 +1 @@
Fix a deadlock in :c:func:`PyGILState_Ensure` when allocating new thread state. Patch by Kumar Aditya.

27
Python/pystate.c
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@ -810,7 +810,15 @@ new_threadstate(PyInterpreterState *interp)
{ {
PyThreadState *tstate; PyThreadState *tstate;
_PyRuntimeState *runtime = interp->runtime; _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. */ /* We serialize concurrent creation to protect global state. */
HEAD_LOCK(runtime); HEAD_LOCK(runtime);
@ -822,18 +830,15 @@ new_threadstate(PyInterpreterState *interp)
if (old_head == NULL) { if (old_head == NULL) {
// It's the interpreter's initial thread state. // It's the interpreter's initial thread state.
assert(id == 1); assert(id == 1);
used_newtstate = 0;
tstate = &interp->_initial_thread; tstate = &interp->_initial_thread;
} }
else { else {
// Every valid interpreter must have at least one thread. // Every valid interpreter must have at least one thread.
assert(id > 1); assert(id > 1);
assert(old_head->prev == NULL); assert(old_head->prev == NULL);
used_newtstate = 1;
tstate = alloc_threadstate(); tstate = new_tstate;
if (tstate == NULL) {
goto error;
}
// Set to _PyThreadState_INIT. // Set to _PyThreadState_INIT.
memcpy(tstate, memcpy(tstate,
&initial._main_interpreter._initial_thread, &initial._main_interpreter._initial_thread,
@ -844,11 +849,11 @@ new_threadstate(PyInterpreterState *interp)
init_threadstate(tstate, interp, id, old_head); init_threadstate(tstate, interp, id, old_head);
HEAD_UNLOCK(runtime); HEAD_UNLOCK(runtime);
if (!used_newtstate) {
// Must be called with lock unlocked to avoid re-entrancy deadlock.
PyMem_RawFree(new_tstate);
}
return tstate; return tstate;
error:
HEAD_UNLOCK(runtime);
return NULL;
} }
PyThreadState * PyThreadState *