Source

cpython-withatomic / Python / pystate.c

The branch '2.5' does not exist.
  1
  2
  3
  4
  5
  6
  7
  8
  9
 10
 11
 12
 13
 14
 15
 16
 17
 18
 19
 20
 21
 22
 23
 24
 25
 26
 27
 28
 29
 30
 31
 32
 33
 34
 35
 36
 37
 38
 39
 40
 41
 42
 43
 44
 45
 46
 47
 48
 49
 50
 51
 52
 53
 54
 55
 56
 57
 58
 59
 60
 61
 62
 63
 64
 65
 66
 67
 68
 69
 70
 71
 72
 73
 74
 75
 76
 77
 78
 79
 80
 81
 82
 83
 84
 85
 86
 87
 88
 89
 90
 91
 92
 93
 94
 95
 96
 97
 98
 99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
/* Thread and interpreter state structures and their interfaces */

#include "Python.h"

/* --------------------------------------------------------------------------
CAUTION

Always use malloc() and free() directly in this file.  A number of these
functions are advertised as safe to call when the GIL isn't held, and in
a debug build Python redirects (e.g.) PyMem_NEW (etc) to Python's debugging
obmalloc functions.  Those aren't thread-safe (they rely on the GIL to avoid
the expense of doing their own locking).
-------------------------------------------------------------------------- */

#ifdef HAVE_DLOPEN
#ifdef HAVE_DLFCN_H
#include <dlfcn.h>
#endif
#ifndef RTLD_LAZY
#define RTLD_LAZY 1
#endif
#endif


#ifdef WITH_THREAD
#include "pythread.h"
static PyThread_type_lock head_mutex = NULL; /* Protects interp->tstate_head */
#define HEAD_INIT() (void)(head_mutex || (head_mutex = PyThread_allocate_lock()))
#define HEAD_LOCK() PyThread_acquire_lock(head_mutex, WAIT_LOCK)
#define HEAD_UNLOCK() PyThread_release_lock(head_mutex)

#ifdef __cplusplus
extern "C" {
#endif

/* The single PyInterpreterState used by this process'
   GILState implementation
*/
static PyInterpreterState *autoInterpreterState = NULL;
static int autoTLSkey = 0;
#else
#define HEAD_INIT() /* Nothing */
#define HEAD_LOCK() /* Nothing */
#define HEAD_UNLOCK() /* Nothing */
#endif

static PyInterpreterState *interp_head = NULL;

PyThreadState *_PyThreadState_Current = NULL;
PyThreadFrameGetter _PyThreadState_GetFrame = NULL;

#ifdef WITH_THREAD
static void _PyGILState_NoteThreadState(PyThreadState* tstate);
#endif


PyInterpreterState *
PyInterpreterState_New(void)
{
	PyInterpreterState *interp = (PyInterpreterState *)
				     malloc(sizeof(PyInterpreterState));

	if (interp != NULL) {
		HEAD_INIT();
#ifdef WITH_THREAD
		if (head_mutex == NULL)
			Py_FatalError("Can't initialize threads for interpreter");
#endif
		interp->modules = NULL;
		interp->modules_reloading = NULL;
		interp->sysdict = NULL;
		interp->builtins = NULL;
		interp->tstate_head = NULL;
		interp->codec_search_path = NULL;
		interp->codec_search_cache = NULL;
		interp->codec_error_registry = NULL;
#ifdef HAVE_DLOPEN
#ifdef RTLD_NOW
                interp->dlopenflags = RTLD_NOW;
#else
		interp->dlopenflags = RTLD_LAZY;
#endif
#endif
#ifdef WITH_TSC
		interp->tscdump = 0;
#endif

		HEAD_LOCK();
		interp->next = interp_head;
		interp_head = interp;
		HEAD_UNLOCK();
	}

	return interp;
}


void
PyInterpreterState_Clear(PyInterpreterState *interp)
{
	PyThreadState *p;
	HEAD_LOCK();
	for (p = interp->tstate_head; p != NULL; p = p->next)
		PyThreadState_Clear(p);
	HEAD_UNLOCK();
	Py_CLEAR(interp->codec_search_path);
	Py_CLEAR(interp->codec_search_cache);
	Py_CLEAR(interp->codec_error_registry);
	Py_CLEAR(interp->modules);
	Py_CLEAR(interp->modules_reloading);
	Py_CLEAR(interp->sysdict);
	Py_CLEAR(interp->builtins);
}


static void
zapthreads(PyInterpreterState *interp)
{
	PyThreadState *p;
	/* No need to lock the mutex here because this should only happen
	   when the threads are all really dead (XXX famous last words). */
	while ((p = interp->tstate_head) != NULL) {
		PyThreadState_Delete(p);
	}
}


void
PyInterpreterState_Delete(PyInterpreterState *interp)
{
	PyInterpreterState **p;
	zapthreads(interp);
	HEAD_LOCK();
	for (p = &interp_head; ; p = &(*p)->next) {
		if (*p == NULL)
			Py_FatalError(
				"PyInterpreterState_Delete: invalid interp");
		if (*p == interp)
			break;
	}
	if (interp->tstate_head != NULL)
		Py_FatalError("PyInterpreterState_Delete: remaining threads");
	*p = interp->next;
	HEAD_UNLOCK();
	free(interp);
}


/* Default implementation for _PyThreadState_GetFrame */
static struct _frame *
threadstate_getframe(PyThreadState *self)
{
	return self->frame;
}

PyThreadState *
PyThreadState_New(PyInterpreterState *interp)
{
	PyThreadState *tstate = (PyThreadState *)malloc(sizeof(PyThreadState));

	if (_PyThreadState_GetFrame == NULL)
		_PyThreadState_GetFrame = threadstate_getframe;

	if (tstate != NULL) {
		tstate->interp = interp;

		tstate->frame = NULL;
		tstate->recursion_depth = 0;
		tstate->tracing = 0;
		tstate->use_tracing = 0;
		tstate->tick_counter = 0;
		tstate->gilstate_counter = 0;
		tstate->async_exc = NULL;
#ifdef WITH_THREAD
		tstate->thread_id = PyThread_get_thread_ident();
#else
		tstate->thread_id = 0;
#endif

		tstate->dict = NULL;

		tstate->curexc_type = NULL;
		tstate->curexc_value = NULL;
		tstate->curexc_traceback = NULL;

		tstate->exc_type = NULL;
		tstate->exc_value = NULL;
		tstate->exc_traceback = NULL;

		tstate->c_profilefunc = NULL;
		tstate->c_tracefunc = NULL;
		tstate->c_profileobj = NULL;
		tstate->c_traceobj = NULL;

#ifdef WITH_THREAD
		_PyGILState_NoteThreadState(tstate);
#endif

		HEAD_LOCK();
		tstate->next = interp->tstate_head;
		interp->tstate_head = tstate;
		HEAD_UNLOCK();
	}

	return tstate;
}


void
PyThreadState_Clear(PyThreadState *tstate)
{
	if (Py_VerboseFlag && tstate->frame != NULL)
		fprintf(stderr,
		  "PyThreadState_Clear: warning: thread still has a frame\n");

	Py_CLEAR(tstate->frame);

	Py_CLEAR(tstate->dict);
	Py_CLEAR(tstate->async_exc);

	Py_CLEAR(tstate->curexc_type);
	Py_CLEAR(tstate->curexc_value);
	Py_CLEAR(tstate->curexc_traceback);

	Py_CLEAR(tstate->exc_type);
	Py_CLEAR(tstate->exc_value);
	Py_CLEAR(tstate->exc_traceback);

	tstate->c_profilefunc = NULL;
	tstate->c_tracefunc = NULL;
	Py_CLEAR(tstate->c_profileobj);
	Py_CLEAR(tstate->c_traceobj);
}


/* Common code for PyThreadState_Delete() and PyThreadState_DeleteCurrent() */
static void
tstate_delete_common(PyThreadState *tstate)
{
	PyInterpreterState *interp;
	PyThreadState **p;
	PyThreadState *prev_p = NULL;
	if (tstate == NULL)
		Py_FatalError("PyThreadState_Delete: NULL tstate");
	interp = tstate->interp;
	if (interp == NULL)
		Py_FatalError("PyThreadState_Delete: NULL interp");
	HEAD_LOCK();
	for (p = &interp->tstate_head; ; p = &(*p)->next) {
		if (*p == NULL)
			Py_FatalError(
				"PyThreadState_Delete: invalid tstate");
		if (*p == tstate)
			break;
		/* Sanity check.  These states should never happen but if
		 * they do we must abort.  Otherwise we'll end up spinning in
		 * in a tight loop with the lock held.  A similar check is done
		 * in thread.c find_key().  */
		if (*p == prev_p)
			Py_FatalError(
				"PyThreadState_Delete: small circular list(!)"
                                " and tstate not found.");
		prev_p = *p;
		if ((*p)->next == interp->tstate_head)
			Py_FatalError(
				"PyThreadState_Delete: circular list(!) and"
                                " tstate not found.");
	}
	*p = tstate->next;
	HEAD_UNLOCK();
	free(tstate);
}


void
PyThreadState_Delete(PyThreadState *tstate)
{
	if (tstate == _PyThreadState_Current)
		Py_FatalError("PyThreadState_Delete: tstate is still current");
	tstate_delete_common(tstate);
#ifdef WITH_THREAD
	if (autoTLSkey && PyThread_get_key_value(autoTLSkey) == tstate)
		PyThread_delete_key_value(autoTLSkey);
#endif /* WITH_THREAD */
}


#ifdef WITH_THREAD
void
PyThreadState_DeleteCurrent()
{
	PyThreadState *tstate = _PyThreadState_Current;
	if (tstate == NULL)
		Py_FatalError(
			"PyThreadState_DeleteCurrent: no current tstate");
	_PyThreadState_Current = NULL;
	tstate_delete_common(tstate);
	if (autoTLSkey && PyThread_get_key_value(autoTLSkey) == tstate)
		PyThread_delete_key_value(autoTLSkey);
	PyEval_ReleaseLock();
}
#endif /* WITH_THREAD */


PyThreadState *
PyThreadState_Get(void)
{
	if (_PyThreadState_Current == NULL)
		Py_FatalError("PyThreadState_Get: no current thread");

	return _PyThreadState_Current;
}


PyThreadState *
PyThreadState_Swap(PyThreadState *newts)
{
	PyThreadState *oldts = _PyThreadState_Current;

	_PyThreadState_Current = newts;
	/* It should not be possible for more than one thread state
	   to be used for a thread.  Check this the best we can in debug
	   builds.
	*/
#if defined(Py_DEBUG) && defined(WITH_THREAD)
	if (newts) {
		/* This can be called from PyEval_RestoreThread(). Similar
		   to it, we need to ensure errno doesn't change.
		*/
		int err = errno;
		PyThreadState *check = PyGILState_GetThisThreadState();
		if (check && check->interp == newts->interp && check != newts)
			Py_FatalError("Invalid thread state for this thread");
		errno = err;
	}
#endif
	return oldts;
}

/* An extension mechanism to store arbitrary additional per-thread state.
   PyThreadState_GetDict() returns a dictionary that can be used to hold such
   state; the caller should pick a unique key and store its state there.  If
   PyThreadState_GetDict() returns NULL, an exception has *not* been raised
   and the caller should assume no per-thread state is available. */

PyObject *
PyThreadState_GetDict(void)
{
	if (_PyThreadState_Current == NULL)
		return NULL;

	if (_PyThreadState_Current->dict == NULL) {
		PyObject *d;
		_PyThreadState_Current->dict = d = PyDict_New();
		if (d == NULL)
			PyErr_Clear();
	}
	return _PyThreadState_Current->dict;
}


/* Asynchronously raise an exception in a thread.
   Requested by Just van Rossum and Alex Martelli.
   To prevent naive misuse, you must write your own extension
   to call this, or use ctypes.  Must be called with the GIL held.
   Returns the number of tstates modified (normally 1, but 0 if `id` didn't
   match any known thread id).  Can be called with exc=NULL to clear an
   existing async exception.  This raises no exceptions. */

int
PyThreadState_SetAsyncExc(long id, PyObject *exc) {
	PyThreadState *tstate = PyThreadState_GET();
	PyInterpreterState *interp = tstate->interp;
	PyThreadState *p;

	/* Although the GIL is held, a few C API functions can be called
	 * without the GIL held, and in particular some that create and
	 * destroy thread and interpreter states.  Those can mutate the
	 * list of thread states we're traversing, so to prevent that we lock
	 * head_mutex for the duration.
	 */
	HEAD_LOCK();
	for (p = interp->tstate_head; p != NULL; p = p->next) {
		if (p->thread_id == id) {
			/* Tricky:  we need to decref the current value
			 * (if any) in p->async_exc, but that can in turn
			 * allow arbitrary Python code to run, including
			 * perhaps calls to this function.  To prevent
			 * deadlock, we need to release head_mutex before
			 * the decref.
			 */
			PyObject *old_exc = p->async_exc;
			Py_XINCREF(exc);
			p->async_exc = exc;
			HEAD_UNLOCK();
			Py_XDECREF(old_exc);
			return 1;
		}
	}
	HEAD_UNLOCK();
	return 0;
}


/* Routines for advanced debuggers, requested by David Beazley.
   Don't use unless you know what you are doing! */

PyInterpreterState *
PyInterpreterState_Head(void)
{
	return interp_head;
}

PyInterpreterState *
PyInterpreterState_Next(PyInterpreterState *interp) {
	return interp->next;
}

PyThreadState *
PyInterpreterState_ThreadHead(PyInterpreterState *interp) {
	return interp->tstate_head;
}

PyThreadState *
PyThreadState_Next(PyThreadState *tstate) {
	return tstate->next;
}

/* The implementation of sys._current_frames().  This is intended to be
   called with the GIL held, as it will be when called via
   sys._current_frames().  It's possible it would work fine even without
   the GIL held, but haven't thought enough about that.
*/
PyObject *
_PyThread_CurrentFrames(void)
{
	PyObject *result;
	PyInterpreterState *i;

	result = PyDict_New();
	if (result == NULL)
		return NULL;

	/* for i in all interpreters:
	 *     for t in all of i's thread states:
	 *          if t's frame isn't NULL, map t's id to its frame
	 * Because these lists can mutute even when the GIL is held, we
	 * need to grab head_mutex for the duration.
	 */
	HEAD_LOCK();
	for (i = interp_head; i != NULL; i = i->next) {
		PyThreadState *t;
		for (t = i->tstate_head; t != NULL; t = t->next) {
			PyObject *id;
			int stat;
			struct _frame *frame = t->frame;
			if (frame == NULL)
				continue;
			id = PyInt_FromLong(t->thread_id);
			if (id == NULL)
				goto Fail;
			stat = PyDict_SetItem(result, id, (PyObject *)frame);
			Py_DECREF(id);
			if (stat < 0)
				goto Fail;
		}
	}
	HEAD_UNLOCK();
	return result;

 Fail:
 	HEAD_UNLOCK();
 	Py_DECREF(result);
 	return NULL;
}

/* Python "auto thread state" API. */
#ifdef WITH_THREAD

/* Keep this as a static, as it is not reliable!  It can only
   ever be compared to the state for the *current* thread.
   * If not equal, then it doesn't matter that the actual
     value may change immediately after comparison, as it can't
     possibly change to the current thread's state.
   * If equal, then the current thread holds the lock, so the value can't
     change until we yield the lock.
*/
static int
PyThreadState_IsCurrent(PyThreadState *tstate)
{
	/* Must be the tstate for this thread */
	assert(PyGILState_GetThisThreadState()==tstate);
	/* On Windows at least, simple reads and writes to 32 bit values
	   are atomic.
	*/
	return tstate == _PyThreadState_Current;
}

/* Internal initialization/finalization functions called by
   Py_Initialize/Py_Finalize
*/
void
_PyGILState_Init(PyInterpreterState *i, PyThreadState *t)
{
	assert(i && t); /* must init with valid states */
	autoTLSkey = PyThread_create_key();
	autoInterpreterState = i;
	assert(PyThread_get_key_value(autoTLSkey) == NULL);
	assert(t->gilstate_counter == 0);

	_PyGILState_NoteThreadState(t);
}

void
_PyGILState_Fini(void)
{
	PyThread_delete_key(autoTLSkey);
	autoTLSkey = 0;
	autoInterpreterState = NULL;
}

/* When a thread state is created for a thread by some mechanism other than
   PyGILState_Ensure, it's important that the GILState machinery knows about
   it so it doesn't try to create another thread state for the thread (this is
   a better fix for SF bug #1010677 than the first one attempted).
*/
static void
_PyGILState_NoteThreadState(PyThreadState* tstate)
{
	/* If autoTLSkey is 0, this must be the very first threadstate created
	   in Py_Initialize().  Don't do anything for now (we'll be back here
	   when _PyGILState_Init is called). */
	if (!autoTLSkey)
		return;

	/* Stick the thread state for this thread in thread local storage.

	   The only situation where you can legitimately have more than one
	   thread state for an OS level thread is when there are multiple
	   interpreters, when:

	       a) You shouldn't really be using the PyGILState_ APIs anyway,
	          and:

	       b) The slightly odd way PyThread_set_key_value works (see
	          comments by its implementation) means that the first thread
	          state created for that given OS level thread will "win",
	          which seems reasonable behaviour.
	*/
	if (PyThread_set_key_value(autoTLSkey, (void *)tstate) < 0)
		Py_FatalError("Couldn't create autoTLSkey mapping");

	/* PyGILState_Release must not try to delete this thread state. */
	tstate->gilstate_counter = 1;
}

/* The public functions */
PyThreadState *
PyGILState_GetThisThreadState(void)
{
	if (autoInterpreterState == NULL || autoTLSkey == 0)
		return NULL;
	return (PyThreadState *)PyThread_get_key_value(autoTLSkey);
}

PyGILState_STATE
PyGILState_Ensure(void)
{
	int current;
	PyThreadState *tcur;
	/* 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
	   called Py_Initialize() and usually PyEval_InitThreads().
	*/
	assert(autoInterpreterState); /* Py_Initialize() hasn't been called! */
	tcur = (PyThreadState *)PyThread_get_key_value(autoTLSkey);
	if (tcur == NULL) {
		/* Create a new thread state for this thread */
		tcur = PyThreadState_New(autoInterpreterState);
		if (tcur == NULL)
			Py_FatalError("Couldn't create thread-state for new thread");
		/* This is our thread state!  We'll need to delete it in the
		   matching call to PyGILState_Release(). */
		tcur->gilstate_counter = 0;
		current = 0; /* new thread state is never current */
	}
	else
		current = PyThreadState_IsCurrent(tcur);
	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;
	return current ? PyGILState_LOCKED : PyGILState_UNLOCKED;
}

void
PyGILState_Release(PyGILState_STATE oldstate)
{
	PyThreadState *tcur = (PyThreadState *)PyThread_get_key_value(
                                                                autoTLSkey);
	if (tcur == NULL)
		Py_FatalError("auto-releasing thread-state, "
		              "but no thread-state for this thread");
	/* We must hold the GIL and have our thread state current */
	/* XXX - remove the check - the assert should be fine,
	   but while this is very new (April 2003), the extra check
	   by release-only users can't hurt.
	*/
	if (! PyThreadState_IsCurrent(tcur))
		Py_FatalError("This thread state must be current when releasing");
	assert(PyThreadState_IsCurrent(tcur));
	--tcur->gilstate_counter;
	assert(tcur->gilstate_counter >= 0); /* illegal counter value */

	/* If we're going to destroy this thread-state, we must
	 * clear it while the GIL is held, as destructors may run.
	 */
	if (tcur->gilstate_counter == 0) {
		/* can't have been locked when we created it */
		assert(oldstate == PyGILState_UNLOCKED);
		PyThreadState_Clear(tcur);
		/* Delete the thread-state.  Note this releases the GIL too!
		 * It's vital that the GIL be held here, to avoid shutdown
		 * races; see bugs 225673 and 1061968 (that nasty bug has a
		 * habit of coming back).
		 */
		PyThreadState_DeleteCurrent();
	}
	/* Release the lock if necessary */
	else if (oldstate == PyGILState_UNLOCKED)
		PyEval_SaveThread();
}

#ifdef __cplusplus
}
#endif

#endif /* WITH_THREAD */
Tip: Filter by directory path e.g. /media app.js to search for public/media/app.js.
Tip: Use camelCasing e.g. ProjME to search for ProjectModifiedEvent.java.
Tip: Filter by extension type e.g. /repo .js to search for all .js files in the /repo directory.
Tip: Separate your search with spaces e.g. /ssh pom.xml to search for src/ssh/pom.xml.
Tip: Use ↑ and ↓ arrow keys to navigate and return to view the file.
Tip: You can also navigate files with Ctrl+j (next) and Ctrl+k (previous) and view the file with Ctrl+o.
Tip: You can also navigate files with Alt+j (next) and Alt+k (previous) and view the file with Alt+o.