mirror of
https://github.com/python/cpython
synced 2024-07-21 10:15:53 +00:00
89c0ec9beb
thread's id can't get duplicated, because (of course!) the current thread is still running. The code should work either way, but reverting the gratuitous change should make backporting easier, and gets the bad reasoning out of 2.35's new comments.
508 lines
13 KiB
C
508 lines
13 KiB
C
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/* Thread and interpreter state structures and their interfaces */
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#include "Python.h"
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/* --------------------------------------------------------------------------
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CAUTION
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Always use malloc() and free() directly in this file. A number of these
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functions are advertised as safe to call when the GIL isn't held, and in
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a debug build Python redirects (e.g.) PyMem_NEW (etc) to Python's debugging
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obmalloc functions. Those aren't thread-safe (they rely on the GIL to avoid
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the expense of doing their own locking).
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-------------------------------------------------------------------------- */
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#ifdef HAVE_DLOPEN
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#ifdef HAVE_DLFCN_H
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#include <dlfcn.h>
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#endif
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#ifndef RTLD_LAZY
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#define RTLD_LAZY 1
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#endif
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#endif
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#define ZAP(x) { \
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PyObject *tmp = (PyObject *)(x); \
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(x) = NULL; \
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Py_XDECREF(tmp); \
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}
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#ifdef WITH_THREAD
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#include "pythread.h"
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static PyThread_type_lock head_mutex = NULL; /* Protects interp->tstate_head */
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#define HEAD_INIT() (void)(head_mutex || (head_mutex = PyThread_allocate_lock()))
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#define HEAD_LOCK() PyThread_acquire_lock(head_mutex, WAIT_LOCK)
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#define HEAD_UNLOCK() PyThread_release_lock(head_mutex)
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#else
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#define HEAD_INIT() /* Nothing */
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#define HEAD_LOCK() /* Nothing */
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#define HEAD_UNLOCK() /* Nothing */
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#endif
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static PyInterpreterState *interp_head = NULL;
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PyThreadState *_PyThreadState_Current = NULL;
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PyThreadFrameGetter _PyThreadState_GetFrame = NULL;
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PyInterpreterState *
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PyInterpreterState_New(void)
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{
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PyInterpreterState *interp = (PyInterpreterState *)
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malloc(sizeof(PyInterpreterState));
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if (interp != NULL) {
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HEAD_INIT();
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interp->modules = NULL;
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interp->sysdict = NULL;
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interp->builtins = NULL;
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interp->tstate_head = NULL;
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interp->codec_search_path = NULL;
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interp->codec_search_cache = NULL;
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interp->codec_error_registry = NULL;
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#ifdef HAVE_DLOPEN
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#ifdef RTLD_NOW
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interp->dlopenflags = RTLD_NOW;
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#else
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interp->dlopenflags = RTLD_LAZY;
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#endif
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#endif
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#ifdef WITH_TSC
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interp->tscdump = 0;
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#endif
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HEAD_LOCK();
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interp->next = interp_head;
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interp_head = interp;
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HEAD_UNLOCK();
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}
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return interp;
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}
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void
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PyInterpreterState_Clear(PyInterpreterState *interp)
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{
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PyThreadState *p;
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HEAD_LOCK();
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for (p = interp->tstate_head; p != NULL; p = p->next)
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PyThreadState_Clear(p);
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HEAD_UNLOCK();
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ZAP(interp->codec_search_path);
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ZAP(interp->codec_search_cache);
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ZAP(interp->codec_error_registry);
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ZAP(interp->modules);
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ZAP(interp->sysdict);
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ZAP(interp->builtins);
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}
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static void
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zapthreads(PyInterpreterState *interp)
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{
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PyThreadState *p;
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/* No need to lock the mutex here because this should only happen
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when the threads are all really dead (XXX famous last words). */
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while ((p = interp->tstate_head) != NULL) {
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PyThreadState_Delete(p);
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}
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}
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void
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PyInterpreterState_Delete(PyInterpreterState *interp)
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{
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PyInterpreterState **p;
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zapthreads(interp);
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HEAD_LOCK();
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for (p = &interp_head; ; p = &(*p)->next) {
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if (*p == NULL)
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Py_FatalError(
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"PyInterpreterState_Delete: invalid interp");
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if (*p == interp)
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break;
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}
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if (interp->tstate_head != NULL)
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Py_FatalError("PyInterpreterState_Delete: remaining threads");
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*p = interp->next;
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HEAD_UNLOCK();
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free(interp);
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}
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/* Default implementation for _PyThreadState_GetFrame */
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static struct _frame *
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threadstate_getframe(PyThreadState *self)
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{
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return self->frame;
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}
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PyThreadState *
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PyThreadState_New(PyInterpreterState *interp)
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{
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PyThreadState *tstate = (PyThreadState *)malloc(sizeof(PyThreadState));
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if (_PyThreadState_GetFrame == NULL)
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_PyThreadState_GetFrame = threadstate_getframe;
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if (tstate != NULL) {
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tstate->interp = interp;
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tstate->frame = NULL;
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tstate->recursion_depth = 0;
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tstate->tracing = 0;
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tstate->use_tracing = 0;
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tstate->tick_counter = 0;
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tstate->gilstate_counter = 0;
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tstate->async_exc = NULL;
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#ifdef WITH_THREAD
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tstate->thread_id = PyThread_get_thread_ident();
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#else
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tstate->thread_id = 0;
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#endif
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tstate->dict = NULL;
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tstate->curexc_type = NULL;
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tstate->curexc_value = NULL;
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tstate->curexc_traceback = NULL;
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tstate->exc_type = NULL;
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tstate->exc_value = NULL;
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tstate->exc_traceback = NULL;
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tstate->c_profilefunc = NULL;
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tstate->c_tracefunc = NULL;
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tstate->c_profileobj = NULL;
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tstate->c_traceobj = NULL;
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HEAD_LOCK();
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tstate->next = interp->tstate_head;
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interp->tstate_head = tstate;
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HEAD_UNLOCK();
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}
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return tstate;
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}
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void
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PyThreadState_Clear(PyThreadState *tstate)
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{
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if (Py_VerboseFlag && tstate->frame != NULL)
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fprintf(stderr,
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"PyThreadState_Clear: warning: thread still has a frame\n");
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ZAP(tstate->frame);
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ZAP(tstate->dict);
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ZAP(tstate->async_exc);
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ZAP(tstate->curexc_type);
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ZAP(tstate->curexc_value);
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ZAP(tstate->curexc_traceback);
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ZAP(tstate->exc_type);
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ZAP(tstate->exc_value);
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ZAP(tstate->exc_traceback);
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tstate->c_profilefunc = NULL;
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tstate->c_tracefunc = NULL;
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ZAP(tstate->c_profileobj);
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ZAP(tstate->c_traceobj);
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}
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/* Common code for PyThreadState_Delete() and PyThreadState_DeleteCurrent() */
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static void
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tstate_delete_common(PyThreadState *tstate)
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{
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PyInterpreterState *interp;
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PyThreadState **p;
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if (tstate == NULL)
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Py_FatalError("PyThreadState_Delete: NULL tstate");
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interp = tstate->interp;
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if (interp == NULL)
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Py_FatalError("PyThreadState_Delete: NULL interp");
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HEAD_LOCK();
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for (p = &interp->tstate_head; ; p = &(*p)->next) {
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if (*p == NULL)
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Py_FatalError(
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"PyThreadState_Delete: invalid tstate");
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if (*p == tstate)
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break;
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}
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*p = tstate->next;
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HEAD_UNLOCK();
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free(tstate);
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}
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void
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PyThreadState_Delete(PyThreadState *tstate)
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{
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if (tstate == _PyThreadState_Current)
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Py_FatalError("PyThreadState_Delete: tstate is still current");
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tstate_delete_common(tstate);
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}
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#ifdef WITH_THREAD
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void
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PyThreadState_DeleteCurrent()
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{
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PyThreadState *tstate = _PyThreadState_Current;
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if (tstate == NULL)
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Py_FatalError(
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"PyThreadState_DeleteCurrent: no current tstate");
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_PyThreadState_Current = NULL;
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tstate_delete_common(tstate);
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PyEval_ReleaseLock();
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}
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#endif /* WITH_THREAD */
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PyThreadState *
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PyThreadState_Get(void)
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{
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if (_PyThreadState_Current == NULL)
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Py_FatalError("PyThreadState_Get: no current thread");
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return _PyThreadState_Current;
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}
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PyThreadState *
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PyThreadState_Swap(PyThreadState *new)
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{
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PyThreadState *old = _PyThreadState_Current;
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_PyThreadState_Current = new;
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/* It should not be possible for more than one thread state
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to be used for a thread. Check this the best we can in debug
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builds.
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*/
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#if defined(Py_DEBUG) && defined(WITH_THREAD)
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if (new) {
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PyThreadState *check = PyGILState_GetThisThreadState();
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if (check && check != new)
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Py_FatalError("Invalid thread state for this thread");
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}
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#endif
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return old;
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}
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/* An extension mechanism to store arbitrary additional per-thread state.
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PyThreadState_GetDict() returns a dictionary that can be used to hold such
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state; the caller should pick a unique key and store its state there. If
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PyThreadState_GetDict() returns NULL, an exception has *not* been raised
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and the caller should assume no per-thread state is available. */
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PyObject *
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PyThreadState_GetDict(void)
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{
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if (_PyThreadState_Current == NULL)
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return NULL;
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if (_PyThreadState_Current->dict == NULL) {
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PyObject *d;
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_PyThreadState_Current->dict = d = PyDict_New();
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if (d == NULL)
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PyErr_Clear();
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}
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return _PyThreadState_Current->dict;
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}
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/* Asynchronously raise an exception in a thread.
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Requested by Just van Rossum and Alex Martelli.
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To prevent naive misuse, you must write your own exception
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to call this. Must be called with the GIL held.
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Returns the number of tstates modified; if it returns a number
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greater than one, you're in trouble, and you should call it again
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with exc=NULL to revert the effect. This raises no exceptions. */
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int
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PyThreadState_SetAsyncExc(long id, PyObject *exc) {
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PyThreadState *tstate = PyThreadState_GET();
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PyInterpreterState *interp = tstate->interp;
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PyThreadState *p;
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int count = 0;
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for (p = interp->tstate_head; p != NULL; p = p->next) {
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if (p->thread_id != id)
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continue;
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ZAP(p->async_exc);
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Py_XINCREF(exc);
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p->async_exc = exc;
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count += 1;
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}
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return count;
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}
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/* Routines for advanced debuggers, requested by David Beazley.
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Don't use unless you know what you are doing! */
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PyInterpreterState *
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PyInterpreterState_Head(void)
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{
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return interp_head;
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}
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PyInterpreterState *
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PyInterpreterState_Next(PyInterpreterState *interp) {
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return interp->next;
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}
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PyThreadState *
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PyInterpreterState_ThreadHead(PyInterpreterState *interp) {
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return interp->tstate_head;
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}
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PyThreadState *
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PyThreadState_Next(PyThreadState *tstate) {
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return tstate->next;
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}
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/* Python "auto thread state" API. */
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#ifdef WITH_THREAD
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/* Keep this as a static, as it is not reliable! It can only
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ever be compared to the state for the *current* thread.
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* If not equal, then it doesn't matter that the actual
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value may change immediately after comparison, as it can't
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possibly change to the current thread's state.
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* If equal, then the current thread holds the lock, so the value can't
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change until we yield the lock.
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*/
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static int
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PyThreadState_IsCurrent(PyThreadState *tstate)
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{
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/* Must be the tstate for this thread */
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assert(PyGILState_GetThisThreadState()==tstate);
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/* On Windows at least, simple reads and writes to 32 bit values
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are atomic.
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*/
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return tstate == _PyThreadState_Current;
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}
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/* The single PyInterpreterState used by this process'
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GILState implementation
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*/
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static PyInterpreterState *autoInterpreterState = NULL;
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static int autoTLSkey = 0;
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/* Internal initialization/finalization functions called by
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Py_Initialize/Py_Finalize
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*/
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void
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_PyGILState_Init(PyInterpreterState *i, PyThreadState *t)
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{
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assert(i && t); /* must init with valid states */
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autoTLSkey = PyThread_create_key();
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autoInterpreterState = i;
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/* Now stash the thread state for this thread in TLS */
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assert(PyThread_get_key_value(autoTLSkey) == NULL);
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if (PyThread_set_key_value(autoTLSkey, (void *)t) < 0)
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Py_FatalError("Couldn't create autoTLSkey mapping");
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assert(t->gilstate_counter == 0); /* must be a new thread state */
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t->gilstate_counter = 1;
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}
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void
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_PyGILState_Fini(void)
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{
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PyThread_delete_key(autoTLSkey);
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autoTLSkey = 0;
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autoInterpreterState = NULL;;
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}
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/* The public functions */
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PyThreadState *
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PyGILState_GetThisThreadState(void)
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{
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if (autoInterpreterState == NULL || autoTLSkey == 0)
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return NULL;
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return (PyThreadState *)PyThread_get_key_value(autoTLSkey);
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}
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PyGILState_STATE
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PyGILState_Ensure(void)
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{
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int current;
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PyThreadState *tcur;
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/* Note that we do not auto-init Python here - apart from
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potential races with 2 threads auto-initializing, pep-311
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spells out other issues. Embedders are expected to have
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called Py_Initialize() and usually PyEval_InitThreads().
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*/
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assert(autoInterpreterState); /* Py_Initialize() hasn't been called! */
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tcur = PyThread_get_key_value(autoTLSkey);
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if (tcur == NULL) {
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/* Create a new thread state for this thread */
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tcur = PyThreadState_New(autoInterpreterState);
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if (tcur == NULL)
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Py_FatalError("Couldn't create thread-state for new thread");
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if (PyThread_set_key_value(autoTLSkey, (void *)tcur) < 0)
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Py_FatalError("Couldn't create autoTLSkey mapping");
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current = 0; /* new thread state is never current */
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}
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else
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current = PyThreadState_IsCurrent(tcur);
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if (current == 0)
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PyEval_RestoreThread(tcur);
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/* Update our counter in the thread-state - no need for locks:
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- tcur will remain valid as we hold the GIL.
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- the counter is safe as we are the only thread "allowed"
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to modify this value
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*/
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++tcur->gilstate_counter;
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return current ? PyGILState_LOCKED : PyGILState_UNLOCKED;
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}
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void
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PyGILState_Release(PyGILState_STATE oldstate)
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{
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PyThreadState *tcur = PyThread_get_key_value(autoTLSkey);
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if (tcur == NULL)
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Py_FatalError("auto-releasing thread-state, "
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"but no thread-state for this thread");
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/* We must hold the GIL and have our thread state current */
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/* XXX - remove the check - the assert should be fine,
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but while this is very new (April 2003), the extra check
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by release-only users can't hurt.
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*/
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if (! PyThreadState_IsCurrent(tcur))
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Py_FatalError("This thread state must be current when releasing");
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assert(PyThreadState_IsCurrent(tcur));
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--tcur->gilstate_counter;
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assert(tcur->gilstate_counter >= 0); /* illegal counter value */
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/* If we are about to destroy this thread-state, we must
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clear it while the lock is held, as destructors may run
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*/
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if (tcur->gilstate_counter == 0) {
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/* can't have been locked when we created it */
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assert(oldstate == PyGILState_UNLOCKED);
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PyThreadState_Clear(tcur);
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}
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/* Release the lock if necessary */
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if (oldstate == PyGILState_UNLOCKED)
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PyEval_ReleaseThread(tcur);
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/* Now complete destruction of the thread if necessary */
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if (tcur->gilstate_counter == 0) {
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/* Delete this thread from our TLS */
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PyThread_delete_key_value(autoTLSkey);
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/* Delete the thread-state */
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PyThreadState_Delete(tcur);
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}
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}
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#endif /* WITH_THREAD */
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