bpo-20891: Fix PyGILState_Ensure() (#4650) (#4657)
When PyGILState_Ensure() is called in a non-Python thread before
PyEval_InitThreads(), only call PyEval_InitThreads() after calling
PyThreadState_New() to fix a crash.
(cherry picked from commit b4d1e1f7c1af6ae33f0e371576c8bcafedb099db)
diff --git a/Python/pystate.c b/Python/pystate.c
index eb992c1..f33f182 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -588,6 +588,8 @@
{
int current;
PyThreadState *tcur;
+ int need_init_threads = 0;
+
/* Note that we do not auto-init Python here - apart from
potential races with 2 threads auto-initializing, pep-311
spells out other issues. Embedders are expected to have
@@ -596,6 +598,8 @@
assert(autoInterpreterState); /* Py_Initialize() hasn't been called! */
tcur = (PyThreadState *)PyThread_get_key_value(autoTLSkey);
if (tcur == NULL) {
+ need_init_threads = 1;
+
/* Create a new thread state for this thread */
tcur = PyThreadState_New(autoInterpreterState);
if (tcur == NULL)
@@ -605,16 +609,28 @@
tcur->gilstate_counter = 0;
current = 0; /* new thread state is never current */
}
- else
+ else {
current = PyThreadState_IsCurrent(tcur);
- if (current == 0)
+ }
+
+ if (current == 0) {
PyEval_RestoreThread(tcur);
+ }
+
/* Update our counter in the thread-state - no need for locks:
- tcur will remain valid as we hold the GIL.
- the counter is safe as we are the only thread "allowed"
to modify this value
*/
++tcur->gilstate_counter;
+
+ if (need_init_threads) {
+ /* At startup, Python has no concrete GIL. If PyGILState_Ensure() is
+ called from a new thread for the first time, we need the create the
+ GIL. */
+ PyEval_InitThreads();
+ }
+
return current ? PyGILState_LOCKED : PyGILState_UNLOCKED;
}