diff --git a/Misc/NEWS.d/next/C API/2017-11-30-18-13-45.bpo-20891.wBnMdF.rst b/Misc/NEWS.d/next/C API/2017-11-30-18-13-45.bpo-20891.wBnMdF.rst new file mode 100644 index 00000000000000..e89cf1292afa8a --- /dev/null +++ b/Misc/NEWS.d/next/C API/2017-11-30-18-13-45.bpo-20891.wBnMdF.rst @@ -0,0 +1,3 @@ +Fix PyGILState_Ensure(). 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. diff --git a/Python/pystate.c b/Python/pystate.c index eb992c17801de0..f33f18202360f5 100644 --- a/Python/pystate.c +++ b/Python/pystate.c @@ -588,6 +588,8 @@ PyGILState_Ensure(void) { 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 @@ PyGILState_Ensure(void) 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 @@ PyGILState_Ensure(void) 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; }