summaryrefslogtreecommitdiffstats
path: root/Python/pystate.c
blob: 5793612b51a0596082cb702700e326bbe1da22f2 (plain)
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

/* Thread and interpreter state structures and their interfaces */

#include "Python.h"

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


#define ZAP(x) { \
	PyObject *tmp = (PyObject *)(x); \
	(x) = NULL; \
	Py_XDECREF(tmp); \
}


#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)
#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;


PyInterpreterState *
PyInterpreterState_New(void)
{
	PyInterpreterState *interp = PyMem_NEW(PyInterpreterState, 1);

	if (interp != NULL) {
		HEAD_INIT();
		interp->modules = 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

		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();
	ZAP(interp->codec_search_path);
	ZAP(interp->codec_search_cache);
	ZAP(interp->codec_error_registry);
	ZAP(interp->modules);
	ZAP(interp->sysdict);
	ZAP(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();
	PyMem_DEL(interp);
}


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

PyThreadState *
PyThreadState_New(PyInterpreterState *interp)
{
	PyThreadState *tstate = PyMem_NEW(PyThreadState, 1);
	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;

		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");

	ZAP(tstate->frame);

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

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

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

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


/* Common code for PyThreadState_Delete() and PyThreadState_DeleteCurrent() */
static void
tstate_delete_common(PyThreadState *tstate)
{
	PyInterpreterState *interp;
	PyThreadState **p;
	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;
	}
	*p = tstate->next;
	HEAD_UNLOCK();
	PyMem_DEL(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
void
PyThreadState_DeleteCurrent()
{
	PyThreadState *tstate = _PyThreadState_Current;
	if (tstate == NULL)
		Py_FatalError(
			"PyThreadState_DeleteCurrent: no current tstate");
	_PyThreadState_Current = NULL;
	tstate_delete_common(tstate);
	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 *new)
{
	PyThreadState *old = _PyThreadState_Current;

	_PyThreadState_Current = new;
	/* 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 (new) {
		PyThreadState *check = PyGILState_GetThisThreadState();
		if (check && check != new)
			Py_FatalError("Invalid thread state for this thread");
	}
#endif
	return old;
}

/* 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 exception
   to call this.  Must be called with the GIL held.
   Returns the number of tstates modified; if it returns a number
   greater than one, you're in trouble, and you should call it again
   with exc=NULL to revert the effect.  This raises no exceptions. */

int
PyThreadState_SetAsyncExc(long id, PyObject *exc) {
	PyThreadState *tstate = PyThreadState_Get();
	PyInterpreterState *interp = tstate->interp;
	PyThreadState *p;
	int count = 0;
	for (p = interp->tstate_head; p != NULL; p = p->next) {
		if (p->thread_id != id)
			continue;
		ZAP(p->async_exc);
		Py_XINCREF(exc);
		p->async_exc = exc;
		count += 1;
	}
	return count;
}


/* 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;
}


/* 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;
}

/* The single PyInterpreterState used by this process'
   GILState implementation
*/
static PyInterpreterState *autoInterpreterState = NULL;
static int autoTLSkey = 0;

/* Internal initialization/finalization functions called by 
   Py_Initialize/Py_Finalize 
*/
void _PyGILState_Init(PyInterpreterState *i, PyThreadState *t)
{
	assert(i && t); /* must init with a valid states */
	autoTLSkey = PyThread_create_key();
	autoInterpreterState = i;
	/* Now stash the thread state for this thread in TLS */
	PyThread_set_key_value(autoTLSkey, (void *)t);
	assert(t->gilstate_counter==0); /* must be a new thread state */
	t->gilstate_counter = 1;
}

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

/* 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 = 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");
		PyThread_set_key_value(autoTLSkey, (void *)tcur);
		current = 0; /* new thread state is never current */
	} else
		current = PyThreadState_IsCurrent(tcur);
	if (!current)
		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 = 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 -= 1;
	assert (tcur->gilstate_counter >= 0); /* illegal counter value */

	/* If we are about to destroy this thread-state, we must 
	   clear it while the lock 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);
	}

	/* Release the lock if necessary */
	if (oldstate==PyGILState_UNLOCKED)
		PyEval_ReleaseThread(tcur);

	/* Now complete destruction of the thread if necessary */
	if (tcur->gilstate_counter==0) {
		/* Delete this thread from our TLS */
		PyThread_delete_key_value(autoTLSkey);
		/* Delete the thread-state */
		PyThreadState_Delete(tcur);
	}
}
#endif /* WITH_THREAD */