source: python/trunk/Python/pystate.c@ 1538

Last change on this file since 1538 was 391, checked in by dmik, 12 years ago

python: Merge vendor 2.7.6 to trunk.
  • Property svn:eol-style set to native
File size: 19.2 KB
Line 
1
2/* Thread and interpreter state structures and their interfaces */
3
4#include "Python.h"
5
6/* --------------------------------------------------------------------------
7CAUTION
8
9Always use malloc() and free() directly in this file. A number of these
10functions are advertised as safe to call when the GIL isn't held, and in
11a debug build Python redirects (e.g.) PyMem_NEW (etc) to Python's debugging
12obmalloc functions. Those aren't thread-safe (they rely on the GIL to avoid
13the expense of doing their own locking).
14-------------------------------------------------------------------------- */
15
16#ifdef HAVE_DLOPEN
17#ifdef HAVE_DLFCN_H
18#include <dlfcn.h>
19#endif
20#ifndef RTLD_LAZY
21#define RTLD_LAZY 1
22#endif
23#endif
24
25#ifdef __cplusplus
26extern "C" {
27#endif
28
29#ifdef WITH_THREAD
30#include "pythread.h"
31static PyThread_type_lock head_mutex = NULL; /* Protects interp->tstate_head */
32#define HEAD_INIT() (void)(head_mutex || (head_mutex = PyThread_allocate_lock()))
33#define HEAD_LOCK() PyThread_acquire_lock(head_mutex, WAIT_LOCK)
34#define HEAD_UNLOCK() PyThread_release_lock(head_mutex)
35
36/* The single PyInterpreterState used by this process'
37 GILState implementation
38*/
39static PyInterpreterState *autoInterpreterState = NULL;
40static int autoTLSkey = 0;
41#else
42#define HEAD_INIT() /* Nothing */
43#define HEAD_LOCK() /* Nothing */
44#define HEAD_UNLOCK() /* Nothing */
45#endif
46
47static PyInterpreterState *interp_head = NULL;
48
49PyThreadState *_PyThreadState_Current = NULL;
50PyThreadFrameGetter _PyThreadState_GetFrame = NULL;
51
52#ifdef WITH_THREAD
53static void _PyGILState_NoteThreadState(PyThreadState* tstate);
54#endif
55
56
57PyInterpreterState *
58PyInterpreterState_New(void)
59{
60 PyInterpreterState *interp = (PyInterpreterState *)
61 malloc(sizeof(PyInterpreterState));
62
63 if (interp != NULL) {
64 HEAD_INIT();
65#ifdef WITH_THREAD
66 if (head_mutex == NULL)
67 Py_FatalError("Can't initialize threads for interpreter");
68#endif
69 interp->modules = NULL;
70 interp->modules_reloading = NULL;
71 interp->sysdict = NULL;
72 interp->builtins = NULL;
73 interp->tstate_head = NULL;
74 interp->codec_search_path = NULL;
75 interp->codec_search_cache = NULL;
76 interp->codec_error_registry = NULL;
77#ifdef HAVE_DLOPEN
78#ifdef RTLD_NOW
79 interp->dlopenflags = RTLD_NOW;
80#else
81 interp->dlopenflags = RTLD_LAZY;
82#endif
83#endif
84#ifdef WITH_TSC
85 interp->tscdump = 0;
86#endif
87
88 HEAD_LOCK();
89 interp->next = interp_head;
90 interp_head = interp;
91 HEAD_UNLOCK();
92 }
93
94 return interp;
95}
96
97
98void
99PyInterpreterState_Clear(PyInterpreterState *interp)
100{
101 PyThreadState *p;
102 HEAD_LOCK();
103 for (p = interp->tstate_head; p != NULL; p = p->next)
104 PyThreadState_Clear(p);
105 HEAD_UNLOCK();
106 Py_CLEAR(interp->codec_search_path);
107 Py_CLEAR(interp->codec_search_cache);
108 Py_CLEAR(interp->codec_error_registry);
109 Py_CLEAR(interp->modules);
110 Py_CLEAR(interp->modules_reloading);
111 Py_CLEAR(interp->sysdict);
112 Py_CLEAR(interp->builtins);
113}
114
115
116static void
117zapthreads(PyInterpreterState *interp)
118{
119 PyThreadState *p;
120 /* No need to lock the mutex here because this should only happen
121 when the threads are all really dead (XXX famous last words). */
122 while ((p = interp->tstate_head) != NULL) {
123 PyThreadState_Delete(p);
124 }
125}
126
127
128void
129PyInterpreterState_Delete(PyInterpreterState *interp)
130{
131 PyInterpreterState **p;
132 zapthreads(interp);
133 HEAD_LOCK();
134 for (p = &interp_head; ; p = &(*p)->next) {
135 if (*p == NULL)
136 Py_FatalError(
137 "PyInterpreterState_Delete: invalid interp");
138 if (*p == interp)
139 break;
140 }
141 if (interp->tstate_head != NULL)
142 Py_FatalError("PyInterpreterState_Delete: remaining threads");
143 *p = interp->next;
144 HEAD_UNLOCK();
145 free(interp);
146}
147
148
149/* Default implementation for _PyThreadState_GetFrame */
150static struct _frame *
151threadstate_getframe(PyThreadState *self)
152{
153 return self->frame;
154}
155
156static PyThreadState *
157new_threadstate(PyInterpreterState *interp, int init)
158{
159 PyThreadState *tstate = (PyThreadState *)malloc(sizeof(PyThreadState));
160
161 if (_PyThreadState_GetFrame == NULL)
162 _PyThreadState_GetFrame = threadstate_getframe;
163
164 if (tstate != NULL) {
165 tstate->interp = interp;
166
167 tstate->frame = NULL;
168 tstate->recursion_depth = 0;
169 tstate->tracing = 0;
170 tstate->use_tracing = 0;
171 tstate->tick_counter = 0;
172 tstate->gilstate_counter = 0;
173 tstate->async_exc = NULL;
174#ifdef WITH_THREAD
175 tstate->thread_id = PyThread_get_thread_ident();
176#else
177 tstate->thread_id = 0;
178#endif
179
180 tstate->dict = NULL;
181
182 tstate->curexc_type = NULL;
183 tstate->curexc_value = NULL;
184 tstate->curexc_traceback = NULL;
185
186 tstate->exc_type = NULL;
187 tstate->exc_value = NULL;
188 tstate->exc_traceback = NULL;
189
190 tstate->c_profilefunc = NULL;
191 tstate->c_tracefunc = NULL;
192 tstate->c_profileobj = NULL;
193 tstate->c_traceobj = NULL;
194
195 tstate->trash_delete_nesting = 0;
196 tstate->trash_delete_later = NULL;
197
198 if (init)
199 _PyThreadState_Init(tstate);
200
201 HEAD_LOCK();
202 tstate->next = interp->tstate_head;
203 interp->tstate_head = tstate;
204 HEAD_UNLOCK();
205 }
206
207 return tstate;
208}
209
210PyThreadState *
211PyThreadState_New(PyInterpreterState *interp)
212{
213 return new_threadstate(interp, 1);
214}
215
216PyThreadState *
217_PyThreadState_Prealloc(PyInterpreterState *interp)
218{
219 return new_threadstate(interp, 0);
220}
221
222void
223_PyThreadState_Init(PyThreadState *tstate)
224{
225#ifdef WITH_THREAD
226 _PyGILState_NoteThreadState(tstate);
227#endif
228}
229
230void
231PyThreadState_Clear(PyThreadState *tstate)
232{
233 if (Py_VerboseFlag && tstate->frame != NULL)
234 fprintf(stderr,
235 "PyThreadState_Clear: warning: thread still has a frame\n");
236
237 Py_CLEAR(tstate->frame);
238
239 Py_CLEAR(tstate->dict);
240 Py_CLEAR(tstate->async_exc);
241
242 Py_CLEAR(tstate->curexc_type);
243 Py_CLEAR(tstate->curexc_value);
244 Py_CLEAR(tstate->curexc_traceback);
245
246 Py_CLEAR(tstate->exc_type);
247 Py_CLEAR(tstate->exc_value);
248 Py_CLEAR(tstate->exc_traceback);
249
250 tstate->c_profilefunc = NULL;
251 tstate->c_tracefunc = NULL;
252 Py_CLEAR(tstate->c_profileobj);
253 Py_CLEAR(tstate->c_traceobj);
254}
255
256
257/* Common code for PyThreadState_Delete() and PyThreadState_DeleteCurrent() */
258static void
259tstate_delete_common(PyThreadState *tstate)
260{
261 PyInterpreterState *interp;
262 PyThreadState **p;
263 PyThreadState *prev_p = NULL;
264 if (tstate == NULL)
265 Py_FatalError("PyThreadState_Delete: NULL tstate");
266 interp = tstate->interp;
267 if (interp == NULL)
268 Py_FatalError("PyThreadState_Delete: NULL interp");
269 HEAD_LOCK();
270 for (p = &interp->tstate_head; ; p = &(*p)->next) {
271 if (*p == NULL)
272 Py_FatalError(
273 "PyThreadState_Delete: invalid tstate");
274 if (*p == tstate)
275 break;
276 /* Sanity check. These states should never happen but if
277 * they do we must abort. Otherwise we'll end up spinning in
278 * in a tight loop with the lock held. A similar check is done
279 * in thread.c find_key(). */
280 if (*p == prev_p)
281 Py_FatalError(
282 "PyThreadState_Delete: small circular list(!)"
283 " and tstate not found.");
284 prev_p = *p;
285 if ((*p)->next == interp->tstate_head)
286 Py_FatalError(
287 "PyThreadState_Delete: circular list(!) and"
288 " tstate not found.");
289 }
290 *p = tstate->next;
291 HEAD_UNLOCK();
292 free(tstate);
293}
294
295
296void
297PyThreadState_Delete(PyThreadState *tstate)
298{
299 if (tstate == _PyThreadState_Current)
300 Py_FatalError("PyThreadState_Delete: tstate is still current");
301 tstate_delete_common(tstate);
302#ifdef WITH_THREAD
303 if (autoInterpreterState && PyThread_get_key_value(autoTLSkey) == tstate)
304 PyThread_delete_key_value(autoTLSkey);
305#endif /* WITH_THREAD */
306}
307
308
309#ifdef WITH_THREAD
310void
311PyThreadState_DeleteCurrent()
312{
313 PyThreadState *tstate = _PyThreadState_Current;
314 if (tstate == NULL)
315 Py_FatalError(
316 "PyThreadState_DeleteCurrent: no current tstate");
317 _PyThreadState_Current = NULL;
318 tstate_delete_common(tstate);
319 if (autoInterpreterState && PyThread_get_key_value(autoTLSkey) == tstate)
320 PyThread_delete_key_value(autoTLSkey);
321 PyEval_ReleaseLock();
322}
323#endif /* WITH_THREAD */
324
325
326PyThreadState *
327PyThreadState_Get(void)
328{
329 if (_PyThreadState_Current == NULL)
330 Py_FatalError("PyThreadState_Get: no current thread");
331
332 return _PyThreadState_Current;
333}
334
335
336PyThreadState *
337PyThreadState_Swap(PyThreadState *newts)
338{
339 PyThreadState *oldts = _PyThreadState_Current;
340
341 _PyThreadState_Current = newts;
342 /* It should not be possible for more than one thread state
343 to be used for a thread. Check this the best we can in debug
344 builds.
345 */
346#if defined(Py_DEBUG) && defined(WITH_THREAD)
347 if (newts) {
348 /* This can be called from PyEval_RestoreThread(). Similar
349 to it, we need to ensure errno doesn't change.
350 */
351 int err = errno;
352 PyThreadState *check = PyGILState_GetThisThreadState();
353 if (check && check->interp == newts->interp && check != newts)
354 Py_FatalError("Invalid thread state for this thread");
355 errno = err;
356 }
357#endif
358 return oldts;
359}
360
361/* An extension mechanism to store arbitrary additional per-thread state.
362 PyThreadState_GetDict() returns a dictionary that can be used to hold such
363 state; the caller should pick a unique key and store its state there. If
364 PyThreadState_GetDict() returns NULL, an exception has *not* been raised
365 and the caller should assume no per-thread state is available. */
366
367PyObject *
368PyThreadState_GetDict(void)
369{
370 if (_PyThreadState_Current == NULL)
371 return NULL;
372
373 if (_PyThreadState_Current->dict == NULL) {
374 PyObject *d;
375 _PyThreadState_Current->dict = d = PyDict_New();
376 if (d == NULL)
377 PyErr_Clear();
378 }
379 return _PyThreadState_Current->dict;
380}
381
382
383/* Asynchronously raise an exception in a thread.
384 Requested by Just van Rossum and Alex Martelli.
385 To prevent naive misuse, you must write your own extension
386 to call this, or use ctypes. Must be called with the GIL held.
387 Returns the number of tstates modified (normally 1, but 0 if `id` didn't
388 match any known thread id). Can be called with exc=NULL to clear an
389 existing async exception. This raises no exceptions. */
390
391int
392PyThreadState_SetAsyncExc(long id, PyObject *exc) {
393 PyThreadState *tstate = PyThreadState_GET();
394 PyInterpreterState *interp = tstate->interp;
395 PyThreadState *p;
396
397 /* Although the GIL is held, a few C API functions can be called
398 * without the GIL held, and in particular some that create and
399 * destroy thread and interpreter states. Those can mutate the
400 * list of thread states we're traversing, so to prevent that we lock
401 * head_mutex for the duration.
402 */
403 HEAD_LOCK();
404 for (p = interp->tstate_head; p != NULL; p = p->next) {
405 if (p->thread_id == id) {
406 /* Tricky: we need to decref the current value
407 * (if any) in p->async_exc, but that can in turn
408 * allow arbitrary Python code to run, including
409 * perhaps calls to this function. To prevent
410 * deadlock, we need to release head_mutex before
411 * the decref.
412 */
413 PyObject *old_exc = p->async_exc;
414 Py_XINCREF(exc);
415 p->async_exc = exc;
416 HEAD_UNLOCK();
417 Py_XDECREF(old_exc);
418 return 1;
419 }
420 }
421 HEAD_UNLOCK();
422 return 0;
423}
424
425
426/* Routines for advanced debuggers, requested by David Beazley.
427 Don't use unless you know what you are doing! */
428
429PyInterpreterState *
430PyInterpreterState_Head(void)
431{
432 return interp_head;
433}
434
435PyInterpreterState *
436PyInterpreterState_Next(PyInterpreterState *interp) {
437 return interp->next;
438}
439
440PyThreadState *
441PyInterpreterState_ThreadHead(PyInterpreterState *interp) {
442 return interp->tstate_head;
443}
444
445PyThreadState *
446PyThreadState_Next(PyThreadState *tstate) {
447 return tstate->next;
448}
449
450/* The implementation of sys._current_frames(). This is intended to be
451 called with the GIL held, as it will be when called via
452 sys._current_frames(). It's possible it would work fine even without
453 the GIL held, but haven't thought enough about that.
454*/
455PyObject *
456_PyThread_CurrentFrames(void)
457{
458 PyObject *result;
459 PyInterpreterState *i;
460
461 result = PyDict_New();
462 if (result == NULL)
463 return NULL;
464
465 /* for i in all interpreters:
466 * for t in all of i's thread states:
467 * if t's frame isn't NULL, map t's id to its frame
468 * Because these lists can mutate even when the GIL is held, we
469 * need to grab head_mutex for the duration.
470 */
471 HEAD_LOCK();
472 for (i = interp_head; i != NULL; i = i->next) {
473 PyThreadState *t;
474 for (t = i->tstate_head; t != NULL; t = t->next) {
475 PyObject *id;
476 int stat;
477 struct _frame *frame = t->frame;
478 if (frame == NULL)
479 continue;
480 id = PyInt_FromLong(t->thread_id);
481 if (id == NULL)
482 goto Fail;
483 stat = PyDict_SetItem(result, id, (PyObject *)frame);
484 Py_DECREF(id);
485 if (stat < 0)
486 goto Fail;
487 }
488 }
489 HEAD_UNLOCK();
490 return result;
491
492 Fail:
493 HEAD_UNLOCK();
494 Py_DECREF(result);
495 return NULL;
496}
497
498/* Python "auto thread state" API. */
499#ifdef WITH_THREAD
500
501/* Keep this as a static, as it is not reliable! It can only
502 ever be compared to the state for the *current* thread.
503 * If not equal, then it doesn't matter that the actual
504 value may change immediately after comparison, as it can't
505 possibly change to the current thread's state.
506 * If equal, then the current thread holds the lock, so the value can't
507 change until we yield the lock.
508*/
509static int
510PyThreadState_IsCurrent(PyThreadState *tstate)
511{
512 /* Must be the tstate for this thread */
513 assert(PyGILState_GetThisThreadState()==tstate);
514 /* On Windows at least, simple reads and writes to 32 bit values
515 are atomic.
516 */
517 return tstate == _PyThreadState_Current;
518}
519
520/* Internal initialization/finalization functions called by
521 Py_Initialize/Py_Finalize
522*/
523void
524_PyGILState_Init(PyInterpreterState *i, PyThreadState *t)
525{
526 assert(i && t); /* must init with valid states */
527 autoTLSkey = PyThread_create_key();
528 autoInterpreterState = i;
529 assert(PyThread_get_key_value(autoTLSkey) == NULL);
530 assert(t->gilstate_counter == 0);
531
532 _PyGILState_NoteThreadState(t);
533}
534
535void
536_PyGILState_Fini(void)
537{
538 PyThread_delete_key(autoTLSkey);
539 autoInterpreterState = NULL;
540}
541
542/* When a thread state is created for a thread by some mechanism other than
543 PyGILState_Ensure, it's important that the GILState machinery knows about
544 it so it doesn't try to create another thread state for the thread (this is
545 a better fix for SF bug #1010677 than the first one attempted).
546*/
547static void
548_PyGILState_NoteThreadState(PyThreadState* tstate)
549{
550 /* If autoTLSkey isn't initialized, this must be the very first
551 threadstate created in Py_Initialize(). Don't do anything for now
552 (we'll be back here when _PyGILState_Init is called). */
553 if (!autoInterpreterState)
554 return;
555
556 /* Stick the thread state for this thread in thread local storage.
557
558 The only situation where you can legitimately have more than one
559 thread state for an OS level thread is when there are multiple
560 interpreters, when:
561
562 a) You shouldn't really be using the PyGILState_ APIs anyway,
563 and:
564
565 b) The slightly odd way PyThread_set_key_value works (see
566 comments by its implementation) means that the first thread
567 state created for that given OS level thread will "win",
568 which seems reasonable behaviour.
569 */
570 if (PyThread_set_key_value(autoTLSkey, (void *)tstate) < 0)
571 Py_FatalError("Couldn't create autoTLSkey mapping");
572
573 /* PyGILState_Release must not try to delete this thread state. */
574 tstate->gilstate_counter = 1;
575}
576
577/* The public functions */
578PyThreadState *
579PyGILState_GetThisThreadState(void)
580{
581 if (autoInterpreterState == NULL)
582 return NULL;
583 return (PyThreadState *)PyThread_get_key_value(autoTLSkey);
584}
585
586PyGILState_STATE
587PyGILState_Ensure(void)
588{
589 int current;
590 PyThreadState *tcur;
591 /* Note that we do not auto-init Python here - apart from
592 potential races with 2 threads auto-initializing, pep-311
593 spells out other issues. Embedders are expected to have
594 called Py_Initialize() and usually PyEval_InitThreads().
595 */
596 assert(autoInterpreterState); /* Py_Initialize() hasn't been called! */
597 tcur = (PyThreadState *)PyThread_get_key_value(autoTLSkey);
598 if (tcur == NULL) {
599 /* Create a new thread state for this thread */
600 tcur = PyThreadState_New(autoInterpreterState);
601 if (tcur == NULL)
602 Py_FatalError("Couldn't create thread-state for new thread");
603 /* This is our thread state! We'll need to delete it in the
604 matching call to PyGILState_Release(). */
605 tcur->gilstate_counter = 0;
606 current = 0; /* new thread state is never current */
607 }
608 else
609 current = PyThreadState_IsCurrent(tcur);
610 if (current == 0)
611 PyEval_RestoreThread(tcur);
612 /* Update our counter in the thread-state - no need for locks:
613 - tcur will remain valid as we hold the GIL.
614 - the counter is safe as we are the only thread "allowed"
615 to modify this value
616 */
617 ++tcur->gilstate_counter;
618 return current ? PyGILState_LOCKED : PyGILState_UNLOCKED;
619}
620
621void
622PyGILState_Release(PyGILState_STATE oldstate)
623{
624 PyThreadState *tcur = (PyThreadState *)PyThread_get_key_value(
625 autoTLSkey);
626 if (tcur == NULL)
627 Py_FatalError("auto-releasing thread-state, "
628 "but no thread-state for this thread");
629 /* We must hold the GIL and have our thread state current */
630 /* XXX - remove the check - the assert should be fine,
631 but while this is very new (April 2003), the extra check
632 by release-only users can't hurt.
633 */
634 if (! PyThreadState_IsCurrent(tcur))
635 Py_FatalError("This thread state must be current when releasing");
636 assert(PyThreadState_IsCurrent(tcur));
637 --tcur->gilstate_counter;
638 assert(tcur->gilstate_counter >= 0); /* illegal counter value */
639
640 /* If we're going to destroy this thread-state, we must
641 * clear it while the GIL is held, as destructors may run.
642 */
643 if (tcur->gilstate_counter == 0) {
644 /* can't have been locked when we created it */
645 assert(oldstate == PyGILState_UNLOCKED);
646 PyThreadState_Clear(tcur);
647 /* Delete the thread-state. Note this releases the GIL too!
648 * It's vital that the GIL be held here, to avoid shutdown
649 * races; see bugs 225673 and 1061968 (that nasty bug has a
650 * habit of coming back).
651 */
652 PyThreadState_DeleteCurrent();
653 }
654 /* Release the lock if necessary */
655 else if (oldstate == PyGILState_UNLOCKED)
656 PyEval_SaveThread();
657}
658
659#endif /* WITH_THREAD */
660
661#ifdef __cplusplus
662}
663#endif
664
665
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