source: python/trunk/Modules/_multiprocessing/semaphore.c

Last change on this file was 391, checked in by dmik, 11 years ago

python: Merge vendor 2.7.6 to trunk.
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Line 
1/*
2 * A type which wraps a semaphore
3 *
4 * semaphore.c
5 *
6 * Copyright (c) 2006-2008, R Oudkerk --- see COPYING.txt
7 */
8
9#include "multiprocessing.h"
10
11enum { RECURSIVE_MUTEX, SEMAPHORE };
12
13typedef struct {
14 PyObject_HEAD
15 SEM_HANDLE handle;
16 long last_tid;
17 int count;
18 int maxvalue;
19 int kind;
20} SemLockObject;
21
22#define ISMINE(o) (o->count > 0 && PyThread_get_thread_ident() == o->last_tid)
23
24
25#ifdef MS_WINDOWS
26
27/*
28 * Windows definitions
29 */
30
31#define SEM_FAILED NULL
32
33#define SEM_CLEAR_ERROR() SetLastError(0)
34#define SEM_GET_LAST_ERROR() GetLastError()
35#define SEM_CREATE(name, val, max) CreateSemaphore(NULL, val, max, NULL)
36#define SEM_CLOSE(sem) (CloseHandle(sem) ? 0 : -1)
37#define SEM_GETVALUE(sem, pval) _GetSemaphoreValue(sem, pval)
38#define SEM_UNLINK(name) 0
39
40static int
41_GetSemaphoreValue(HANDLE handle, long *value)
42{
43 long previous;
44
45 switch (WaitForSingleObject(handle, 0)) {
46 case WAIT_OBJECT_0:
47 if (!ReleaseSemaphore(handle, 1, &previous))
48 return MP_STANDARD_ERROR;
49 *value = previous + 1;
50 return 0;
51 case WAIT_TIMEOUT:
52 *value = 0;
53 return 0;
54 default:
55 return MP_STANDARD_ERROR;
56 }
57}
58
59static PyObject *
60semlock_acquire(SemLockObject *self, PyObject *args, PyObject *kwds)
61{
62 int blocking = 1;
63 double timeout;
64 PyObject *timeout_obj = Py_None;
65 DWORD res, full_msecs, msecs, start, ticks;
66
67 static char *kwlist[] = {"block", "timeout", NULL};
68
69 if (!PyArg_ParseTupleAndKeywords(args, kwds, "|iO", kwlist,
70 &blocking, &timeout_obj))
71 return NULL;
72
73 /* calculate timeout */
74 if (!blocking) {
75 full_msecs = 0;
76 } else if (timeout_obj == Py_None) {
77 full_msecs = INFINITE;
78 } else {
79 timeout = PyFloat_AsDouble(timeout_obj);
80 if (PyErr_Occurred())
81 return NULL;
82 timeout *= 1000.0; /* convert to millisecs */
83 if (timeout < 0.0) {
84 timeout = 0.0;
85 } else if (timeout >= 0.5 * INFINITE) { /* 25 days */
86 PyErr_SetString(PyExc_OverflowError,
87 "timeout is too large");
88 return NULL;
89 }
90 full_msecs = (DWORD)(timeout + 0.5);
91 }
92
93 /* check whether we already own the lock */
94 if (self->kind == RECURSIVE_MUTEX && ISMINE(self)) {
95 ++self->count;
96 Py_RETURN_TRUE;
97 }
98
99 /* check whether we can acquire without blocking */
100 if (WaitForSingleObject(self->handle, 0) == WAIT_OBJECT_0) {
101 self->last_tid = GetCurrentThreadId();
102 ++self->count;
103 Py_RETURN_TRUE;
104 }
105
106 msecs = full_msecs;
107 start = GetTickCount();
108
109 for ( ; ; ) {
110 HANDLE handles[2] = {self->handle, sigint_event};
111
112 /* do the wait */
113 Py_BEGIN_ALLOW_THREADS
114 ResetEvent(sigint_event);
115 res = WaitForMultipleObjects(2, handles, FALSE, msecs);
116 Py_END_ALLOW_THREADS
117
118 /* handle result */
119 if (res != WAIT_OBJECT_0 + 1)
120 break;
121
122 /* got SIGINT so give signal handler a chance to run */
123 Sleep(1);
124
125 /* if this is main thread let KeyboardInterrupt be raised */
126 if (PyErr_CheckSignals())
127 return NULL;
128
129 /* recalculate timeout */
130 if (msecs != INFINITE) {
131 ticks = GetTickCount();
132 if ((DWORD)(ticks - start) >= full_msecs)
133 Py_RETURN_FALSE;
134 msecs = full_msecs - (ticks - start);
135 }
136 }
137
138 /* handle result */
139 switch (res) {
140 case WAIT_TIMEOUT:
141 Py_RETURN_FALSE;
142 case WAIT_OBJECT_0:
143 self->last_tid = GetCurrentThreadId();
144 ++self->count;
145 Py_RETURN_TRUE;
146 case WAIT_FAILED:
147 return PyErr_SetFromWindowsErr(0);
148 default:
149 PyErr_Format(PyExc_RuntimeError, "WaitForSingleObject() or "
150 "WaitForMultipleObjects() gave unrecognized "
151 "value %d", res);
152 return NULL;
153 }
154}
155
156static PyObject *
157semlock_release(SemLockObject *self, PyObject *args)
158{
159 if (self->kind == RECURSIVE_MUTEX) {
160 if (!ISMINE(self)) {
161 PyErr_SetString(PyExc_AssertionError, "attempt to "
162 "release recursive lock not owned "
163 "by thread");
164 return NULL;
165 }
166 if (self->count > 1) {
167 --self->count;
168 Py_RETURN_NONE;
169 }
170 assert(self->count == 1);
171 }
172
173 if (!ReleaseSemaphore(self->handle, 1, NULL)) {
174 if (GetLastError() == ERROR_TOO_MANY_POSTS) {
175 PyErr_SetString(PyExc_ValueError, "semaphore or lock "
176 "released too many times");
177 return NULL;
178 } else {
179 return PyErr_SetFromWindowsErr(0);
180 }
181 }
182
183 --self->count;
184 Py_RETURN_NONE;
185}
186
187#else /* !MS_WINDOWS */
188
189/*
190 * Unix definitions
191 */
192
193#define SEM_CLEAR_ERROR()
194#define SEM_GET_LAST_ERROR() 0
195#define SEM_CREATE(name, val, max) sem_open(name, O_CREAT | O_EXCL, 0600, val)
196#define SEM_CLOSE(sem) sem_close(sem)
197#define SEM_GETVALUE(sem, pval) sem_getvalue(sem, pval)
198#define SEM_UNLINK(name) sem_unlink(name)
199
200/* OS X 10.4 defines SEM_FAILED as -1 instead of (sem_t *)-1; this gives
201 compiler warnings, and (potentially) undefined behaviour. */
202#ifdef __APPLE__
203# undef SEM_FAILED
204# define SEM_FAILED ((sem_t *)-1)
205#endif
206
207#ifndef HAVE_SEM_UNLINK
208# define sem_unlink(name) 0
209#endif
210
211#ifndef HAVE_SEM_TIMEDWAIT
212# define sem_timedwait(sem,deadline) sem_timedwait_save(sem,deadline,_save)
213
214int
215sem_timedwait_save(sem_t *sem, struct timespec *deadline, PyThreadState *_save)
216{
217 int res;
218 unsigned long delay, difference;
219 struct timeval now, tvdeadline, tvdelay;
220
221 errno = 0;
222 tvdeadline.tv_sec = deadline->tv_sec;
223 tvdeadline.tv_usec = deadline->tv_nsec / 1000;
224
225 for (delay = 0 ; ; delay += 1000) {
226 /* poll */
227 if (sem_trywait(sem) == 0)
228 return 0;
229 else if (errno != EAGAIN)
230 return MP_STANDARD_ERROR;
231
232 /* get current time */
233 if (gettimeofday(&now, NULL) < 0)
234 return MP_STANDARD_ERROR;
235
236 /* check for timeout */
237 if (tvdeadline.tv_sec < now.tv_sec ||
238 (tvdeadline.tv_sec == now.tv_sec &&
239 tvdeadline.tv_usec <= now.tv_usec)) {
240 errno = ETIMEDOUT;
241 return MP_STANDARD_ERROR;
242 }
243
244 /* calculate how much time is left */
245 difference = (tvdeadline.tv_sec - now.tv_sec) * 1000000 +
246 (tvdeadline.tv_usec - now.tv_usec);
247
248 /* check delay not too long -- maximum is 20 msecs */
249 if (delay > 20000)
250 delay = 20000;
251 if (delay > difference)
252 delay = difference;
253
254 /* sleep */
255 tvdelay.tv_sec = delay / 1000000;
256 tvdelay.tv_usec = delay % 1000000;
257 if (select(0, NULL, NULL, NULL, &tvdelay) < 0)
258 return MP_STANDARD_ERROR;
259
260 /* check for signals */
261 Py_BLOCK_THREADS
262 res = PyErr_CheckSignals();
263 Py_UNBLOCK_THREADS
264
265 if (res) {
266 errno = EINTR;
267 return MP_EXCEPTION_HAS_BEEN_SET;
268 }
269 }
270}
271
272#endif /* !HAVE_SEM_TIMEDWAIT */
273
274static PyObject *
275semlock_acquire(SemLockObject *self, PyObject *args, PyObject *kwds)
276{
277 int blocking = 1, res;
278 double timeout;
279 PyObject *timeout_obj = Py_None;
280 struct timespec deadline = {0};
281 struct timeval now;
282 long sec, nsec;
283
284 static char *kwlist[] = {"block", "timeout", NULL};
285
286 if (!PyArg_ParseTupleAndKeywords(args, kwds, "|iO", kwlist,
287 &blocking, &timeout_obj))
288 return NULL;
289
290 if (self->kind == RECURSIVE_MUTEX && ISMINE(self)) {
291 ++self->count;
292 Py_RETURN_TRUE;
293 }
294
295 if (timeout_obj != Py_None) {
296 timeout = PyFloat_AsDouble(timeout_obj);
297 if (PyErr_Occurred())
298 return NULL;
299 if (timeout < 0.0)
300 timeout = 0.0;
301
302 if (gettimeofday(&now, NULL) < 0) {
303 PyErr_SetFromErrno(PyExc_OSError);
304 return NULL;
305 }
306 sec = (long) timeout;
307 nsec = (long) (1e9 * (timeout - sec) + 0.5);
308 deadline.tv_sec = now.tv_sec + sec;
309 deadline.tv_nsec = now.tv_usec * 1000 + nsec;
310 deadline.tv_sec += (deadline.tv_nsec / 1000000000);
311 deadline.tv_nsec %= 1000000000;
312 }
313
314 do {
315 Py_BEGIN_ALLOW_THREADS
316 if (blocking && timeout_obj == Py_None)
317 res = sem_wait(self->handle);
318 else if (!blocking)
319 res = sem_trywait(self->handle);
320 else
321 res = sem_timedwait(self->handle, &deadline);
322 Py_END_ALLOW_THREADS
323 if (res == MP_EXCEPTION_HAS_BEEN_SET)
324 break;
325 } while (res < 0 && errno == EINTR && !PyErr_CheckSignals());
326
327 if (res < 0) {
328 if (errno == EAGAIN || errno == ETIMEDOUT)
329 Py_RETURN_FALSE;
330 else if (errno == EINTR)
331 return NULL;
332 else
333 return PyErr_SetFromErrno(PyExc_OSError);
334 }
335
336 ++self->count;
337 self->last_tid = PyThread_get_thread_ident();
338
339 Py_RETURN_TRUE;
340}
341
342static PyObject *
343semlock_release(SemLockObject *self, PyObject *args)
344{
345 if (self->kind == RECURSIVE_MUTEX) {
346 if (!ISMINE(self)) {
347 PyErr_SetString(PyExc_AssertionError, "attempt to "
348 "release recursive lock not owned "
349 "by thread");
350 return NULL;
351 }
352 if (self->count > 1) {
353 --self->count;
354 Py_RETURN_NONE;
355 }
356 assert(self->count == 1);
357 } else {
358#ifdef HAVE_BROKEN_SEM_GETVALUE
359 /* We will only check properly the maxvalue == 1 case */
360 if (self->maxvalue == 1) {
361 /* make sure that already locked */
362 if (sem_trywait(self->handle) < 0) {
363 if (errno != EAGAIN) {
364 PyErr_SetFromErrno(PyExc_OSError);
365 return NULL;
366 }
367 /* it is already locked as expected */
368 } else {
369 /* it was not locked so undo wait and raise */
370 if (sem_post(self->handle) < 0) {
371 PyErr_SetFromErrno(PyExc_OSError);
372 return NULL;
373 }
374 PyErr_SetString(PyExc_ValueError, "semaphore "
375 "or lock released too many "
376 "times");
377 return NULL;
378 }
379 }
380#else
381 int sval;
382
383 /* This check is not an absolute guarantee that the semaphore
384 does not rise above maxvalue. */
385 if (sem_getvalue(self->handle, &sval) < 0) {
386 return PyErr_SetFromErrno(PyExc_OSError);
387 } else if (sval >= self->maxvalue) {
388 PyErr_SetString(PyExc_ValueError, "semaphore or lock "
389 "released too many times");
390 return NULL;
391 }
392#endif
393 }
394
395 if (sem_post(self->handle) < 0)
396 return PyErr_SetFromErrno(PyExc_OSError);
397
398 --self->count;
399 Py_RETURN_NONE;
400}
401
402#endif /* !MS_WINDOWS */
403
404/*
405 * All platforms
406 */
407
408static PyObject *
409newsemlockobject(PyTypeObject *type, SEM_HANDLE handle, int kind, int maxvalue)
410{
411 SemLockObject *self;
412
413 self = PyObject_New(SemLockObject, type);
414 if (!self)
415 return NULL;
416 self->handle = handle;
417 self->kind = kind;
418 self->count = 0;
419 self->last_tid = 0;
420 self->maxvalue = maxvalue;
421 return (PyObject*)self;
422}
423
424static PyObject *
425semlock_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
426{
427 char buffer[256];
428 SEM_HANDLE handle = SEM_FAILED;
429 int kind, maxvalue, value;
430 PyObject *result;
431 static char *kwlist[] = {"kind", "value", "maxvalue", NULL};
432 static int counter = 0;
433
434 if (!PyArg_ParseTupleAndKeywords(args, kwds, "iii", kwlist,
435 &kind, &value, &maxvalue))
436 return NULL;
437
438 if (kind != RECURSIVE_MUTEX && kind != SEMAPHORE) {
439 PyErr_SetString(PyExc_ValueError, "unrecognized kind");
440 return NULL;
441 }
442
443 PyOS_snprintf(buffer, sizeof(buffer), "/mp%ld-%d", (long)getpid(), counter++);
444
445 SEM_CLEAR_ERROR();
446 handle = SEM_CREATE(buffer, value, maxvalue);
447 /* On Windows we should fail if GetLastError()==ERROR_ALREADY_EXISTS */
448 if (handle == SEM_FAILED || SEM_GET_LAST_ERROR() != 0)
449 goto failure;
450
451 if (SEM_UNLINK(buffer) < 0)
452 goto failure;
453
454 result = newsemlockobject(type, handle, kind, maxvalue);
455 if (!result)
456 goto failure;
457
458 return result;
459
460 failure:
461 if (handle != SEM_FAILED)
462 SEM_CLOSE(handle);
463 mp_SetError(NULL, MP_STANDARD_ERROR);
464 return NULL;
465}
466
467static PyObject *
468semlock_rebuild(PyTypeObject *type, PyObject *args)
469{
470 SEM_HANDLE handle;
471 int kind, maxvalue;
472
473 if (!PyArg_ParseTuple(args, F_SEM_HANDLE "ii",
474 &handle, &kind, &maxvalue))
475 return NULL;
476
477 return newsemlockobject(type, handle, kind, maxvalue);
478}
479
480static void
481semlock_dealloc(SemLockObject* self)
482{
483 if (self->handle != SEM_FAILED)
484 SEM_CLOSE(self->handle);
485 PyObject_Del(self);
486}
487
488static PyObject *
489semlock_count(SemLockObject *self)
490{
491 return PyInt_FromLong((long)self->count);
492}
493
494static PyObject *
495semlock_ismine(SemLockObject *self)
496{
497 /* only makes sense for a lock */
498 return PyBool_FromLong(ISMINE(self));
499}
500
501static PyObject *
502semlock_getvalue(SemLockObject *self)
503{
504#ifdef HAVE_BROKEN_SEM_GETVALUE
505 PyErr_SetNone(PyExc_NotImplementedError);
506 return NULL;
507#else
508 int sval;
509 if (SEM_GETVALUE(self->handle, &sval) < 0)
510 return mp_SetError(NULL, MP_STANDARD_ERROR);
511 /* some posix implementations use negative numbers to indicate
512 the number of waiting threads */
513 if (sval < 0)
514 sval = 0;
515 return PyInt_FromLong((long)sval);
516#endif
517}
518
519static PyObject *
520semlock_iszero(SemLockObject *self)
521{
522#ifdef HAVE_BROKEN_SEM_GETVALUE
523 if (sem_trywait(self->handle) < 0) {
524 if (errno == EAGAIN)
525 Py_RETURN_TRUE;
526 return mp_SetError(NULL, MP_STANDARD_ERROR);
527 } else {
528 if (sem_post(self->handle) < 0)
529 return mp_SetError(NULL, MP_STANDARD_ERROR);
530 Py_RETURN_FALSE;
531 }
532#else
533 int sval;
534 if (SEM_GETVALUE(self->handle, &sval) < 0)
535 return mp_SetError(NULL, MP_STANDARD_ERROR);
536 return PyBool_FromLong((long)sval == 0);
537#endif
538}
539
540static PyObject *
541semlock_afterfork(SemLockObject *self)
542{
543 self->count = 0;
544 Py_RETURN_NONE;
545}
546
547/*
548 * Semaphore methods
549 */
550
551static PyMethodDef semlock_methods[] = {
552 {"acquire", (PyCFunction)semlock_acquire, METH_VARARGS | METH_KEYWORDS,
553 "acquire the semaphore/lock"},
554 {"release", (PyCFunction)semlock_release, METH_NOARGS,
555 "release the semaphore/lock"},
556 {"__enter__", (PyCFunction)semlock_acquire, METH_VARARGS | METH_KEYWORDS,
557 "enter the semaphore/lock"},
558 {"__exit__", (PyCFunction)semlock_release, METH_VARARGS,
559 "exit the semaphore/lock"},
560 {"_count", (PyCFunction)semlock_count, METH_NOARGS,
561 "num of `acquire()`s minus num of `release()`s for this process"},
562 {"_is_mine", (PyCFunction)semlock_ismine, METH_NOARGS,
563 "whether the lock is owned by this thread"},
564 {"_get_value", (PyCFunction)semlock_getvalue, METH_NOARGS,
565 "get the value of the semaphore"},
566 {"_is_zero", (PyCFunction)semlock_iszero, METH_NOARGS,
567 "returns whether semaphore has value zero"},
568 {"_rebuild", (PyCFunction)semlock_rebuild, METH_VARARGS | METH_CLASS,
569 ""},
570 {"_after_fork", (PyCFunction)semlock_afterfork, METH_NOARGS,
571 "rezero the net acquisition count after fork()"},
572 {NULL}
573};
574
575/*
576 * Member table
577 */
578
579static PyMemberDef semlock_members[] = {
580 {"handle", T_SEM_HANDLE, offsetof(SemLockObject, handle), READONLY,
581 ""},
582 {"kind", T_INT, offsetof(SemLockObject, kind), READONLY,
583 ""},
584 {"maxvalue", T_INT, offsetof(SemLockObject, maxvalue), READONLY,
585 ""},
586 {NULL}
587};
588
589/*
590 * Semaphore type
591 */
592
593PyTypeObject SemLockType = {
594 PyVarObject_HEAD_INIT(NULL, 0)
595 /* tp_name */ "_multiprocessing.SemLock",
596 /* tp_basicsize */ sizeof(SemLockObject),
597 /* tp_itemsize */ 0,
598 /* tp_dealloc */ (destructor)semlock_dealloc,
599 /* tp_print */ 0,
600 /* tp_getattr */ 0,
601 /* tp_setattr */ 0,
602 /* tp_compare */ 0,
603 /* tp_repr */ 0,
604 /* tp_as_number */ 0,
605 /* tp_as_sequence */ 0,
606 /* tp_as_mapping */ 0,
607 /* tp_hash */ 0,
608 /* tp_call */ 0,
609 /* tp_str */ 0,
610 /* tp_getattro */ 0,
611 /* tp_setattro */ 0,
612 /* tp_as_buffer */ 0,
613 /* tp_flags */ Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
614 /* tp_doc */ "Semaphore/Mutex type",
615 /* tp_traverse */ 0,
616 /* tp_clear */ 0,
617 /* tp_richcompare */ 0,
618 /* tp_weaklistoffset */ 0,
619 /* tp_iter */ 0,
620 /* tp_iternext */ 0,
621 /* tp_methods */ semlock_methods,
622 /* tp_members */ semlock_members,
623 /* tp_getset */ 0,
624 /* tp_base */ 0,
625 /* tp_dict */ 0,
626 /* tp_descr_get */ 0,
627 /* tp_descr_set */ 0,
628 /* tp_dictoffset */ 0,
629 /* tp_init */ 0,
630 /* tp_alloc */ 0,
631 /* tp_new */ semlock_new,
632};
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