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/Python/thread_pthread.h

http://unladen-swallow.googlecode.com/
C++ Header | 533 lines | 372 code | 89 blank | 72 comment | 57 complexity | 0f6b61b34ddeef59b07a41d73ad97f2d MD5 | raw file
  1
  2/* Posix threads interface */
  3
  4#include <stdlib.h>
  5#include <string.h>
  6#if defined(__APPLE__) || defined(HAVE_PTHREAD_DESTRUCTOR)
  7#define destructor xxdestructor
  8#endif
  9#include <pthread.h>
 10#if defined(__APPLE__) || defined(HAVE_PTHREAD_DESTRUCTOR)
 11#undef destructor
 12#endif
 13#include <signal.h>
 14
 15/* The POSIX spec requires that use of pthread_attr_setstacksize
 16   be conditional on _POSIX_THREAD_ATTR_STACKSIZE being defined. */
 17#ifdef _POSIX_THREAD_ATTR_STACKSIZE
 18#ifndef THREAD_STACK_SIZE
 19#define	THREAD_STACK_SIZE	0	/* use default stack size */
 20#endif
 21/* for safety, ensure a viable minimum stacksize */
 22#define	THREAD_STACK_MIN	0x8000	/* 32kB */
 23#else  /* !_POSIX_THREAD_ATTR_STACKSIZE */
 24#ifdef THREAD_STACK_SIZE
 25#error "THREAD_STACK_SIZE defined but _POSIX_THREAD_ATTR_STACKSIZE undefined"
 26#endif
 27#endif
 28
 29/* The POSIX spec says that implementations supporting the sem_*
 30   family of functions must indicate this by defining
 31   _POSIX_SEMAPHORES. */   
 32#ifdef _POSIX_SEMAPHORES
 33/* On FreeBSD 4.x, _POSIX_SEMAPHORES is defined empty, so 
 34   we need to add 0 to make it work there as well. */
 35#if (_POSIX_SEMAPHORES+0) == -1
 36#define HAVE_BROKEN_POSIX_SEMAPHORES
 37#else
 38#include <semaphore.h>
 39#include <errno.h>
 40#endif
 41#endif
 42
 43/* Before FreeBSD 5.4, system scope threads was very limited resource
 44   in default setting.  So the process scope is preferred to get
 45   enough number of threads to work. */
 46#ifdef __FreeBSD__
 47#include <osreldate.h>
 48#if __FreeBSD_version >= 500000 && __FreeBSD_version < 504101
 49#undef PTHREAD_SYSTEM_SCHED_SUPPORTED
 50#endif
 51#endif
 52
 53#if !defined(pthread_attr_default)
 54#  define pthread_attr_default ((pthread_attr_t *)NULL)
 55#endif
 56#if !defined(pthread_mutexattr_default)
 57#  define pthread_mutexattr_default ((pthread_mutexattr_t *)NULL)
 58#endif
 59#if !defined(pthread_condattr_default)
 60#  define pthread_condattr_default ((pthread_condattr_t *)NULL)
 61#endif
 62
 63
 64/* Whether or not to use semaphores directly rather than emulating them with
 65 * mutexes and condition variables:
 66 */
 67#if defined(_POSIX_SEMAPHORES) && !defined(HAVE_BROKEN_POSIX_SEMAPHORES)
 68#  define USE_SEMAPHORES
 69#else
 70#  undef USE_SEMAPHORES
 71#endif
 72
 73
 74/* On platforms that don't use standard POSIX threads pthread_sigmask()
 75 * isn't present.  DEC threads uses sigprocmask() instead as do most
 76 * other UNIX International compliant systems that don't have the full
 77 * pthread implementation.
 78 */
 79#if defined(HAVE_PTHREAD_SIGMASK) && !defined(HAVE_BROKEN_PTHREAD_SIGMASK)
 80#  define SET_THREAD_SIGMASK pthread_sigmask
 81#else
 82#  define SET_THREAD_SIGMASK sigprocmask
 83#endif
 84
 85
 86/* A pthread mutex isn't sufficient to model the Python lock type
 87 * because, according to Draft 5 of the docs (P1003.4a/D5), both of the
 88 * following are undefined:
 89 *  -> a thread tries to lock a mutex it already has locked
 90 *  -> a thread tries to unlock a mutex locked by a different thread
 91 * pthread mutexes are designed for serializing threads over short pieces
 92 * of code anyway, so wouldn't be an appropriate implementation of
 93 * Python's locks regardless.
 94 *
 95 * The pthread_lock struct implements a Python lock as a "locked?" bit
 96 * and a <condition, mutex> pair.  In general, if the bit can be acquired
 97 * instantly, it is, else the pair is used to block the thread until the
 98 * bit is cleared.     9 May 1994 tim@ksr.com
 99 */
100
101typedef struct {
102	char             locked; /* 0=unlocked, 1=locked */
103	/* a <cond, mutex> pair to handle an acquire of a locked lock */
104	pthread_cond_t   lock_released;
105	pthread_mutex_t  mut;
106} pthread_lock;
107
108#define CHECK_STATUS(name)  if (status != 0) { perror(name); error = 1; }
109
110/*
111 * Initialization.
112 */
113
114#ifdef _HAVE_BSDI
115static
116void _noop(void)
117{
118}
119
120static void
121PyThread__init_thread(void)
122{
123	/* DO AN INIT BY STARTING THE THREAD */
124	static int dummy = 0;
125	pthread_t thread1;
126	pthread_create(&thread1, NULL, (void *) _noop, &dummy);
127	pthread_join(thread1, NULL);
128}
129
130#else /* !_HAVE_BSDI */
131
132static void
133PyThread__init_thread(void)
134{
135#if defined(_AIX) && defined(__GNUC__)
136	pthread_init();
137#endif
138}
139
140#endif /* !_HAVE_BSDI */
141
142/*
143 * Thread support.
144 */
145
146
147long
148PyThread_start_new_thread(void (*func)(void *), void *arg)
149{
150	pthread_t th;
151	int status;
152#if defined(THREAD_STACK_SIZE) || defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
153	pthread_attr_t attrs;
154#endif
155#if defined(THREAD_STACK_SIZE)
156	size_t	tss;
157#endif
158
159	dprintf(("PyThread_start_new_thread called\n"));
160	if (!initialized)
161		PyThread_init_thread();
162
163#if defined(THREAD_STACK_SIZE) || defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
164	if (pthread_attr_init(&attrs) != 0)
165		return -1;
166#endif
167#if defined(THREAD_STACK_SIZE)
168	tss = (_pythread_stacksize != 0) ? _pythread_stacksize
169					 : THREAD_STACK_SIZE;
170	if (tss != 0) {
171		if (pthread_attr_setstacksize(&attrs, tss) != 0) {
172			pthread_attr_destroy(&attrs);
173			return -1;
174		}
175	}
176#endif
177#if defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
178        pthread_attr_setscope(&attrs, PTHREAD_SCOPE_SYSTEM);
179#endif
180
181	status = pthread_create(&th, 
182#if defined(THREAD_STACK_SIZE) || defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
183				 &attrs,
184#else
185				 (pthread_attr_t*)NULL,
186#endif
187				 (void* (*)(void *))func,
188				 (void *)arg
189				 );
190
191#if defined(THREAD_STACK_SIZE) || defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
192	pthread_attr_destroy(&attrs);
193#endif
194	if (status != 0)
195            return -1;
196
197        pthread_detach(th);
198
199#if SIZEOF_PTHREAD_T <= SIZEOF_LONG
200	return (long) th;
201#else
202	return (long) *(long *) &th;
203#endif
204}
205
206/* XXX This implementation is considered (to quote Tim Peters) "inherently
207   hosed" because:
208     - It does not guarantee the promise that a non-zero integer is returned.
209     - The cast to long is inherently unsafe.
210     - It is not clear that the 'volatile' (for AIX?) and ugly casting in the
211       latter return statement (for Alpha OSF/1) are any longer necessary.
212*/
213long 
214PyThread_get_thread_ident(void)
215{
216	volatile pthread_t threadid;
217	if (!initialized)
218		PyThread_init_thread();
219	/* Jump through some hoops for Alpha OSF/1 */
220	threadid = pthread_self();
221#if SIZEOF_PTHREAD_T <= SIZEOF_LONG
222	return (long) threadid;
223#else
224	return (long) *(long *) &threadid;
225#endif
226}
227
228static void 
229do_PyThread_exit_thread(int no_cleanup)
230{
231	dprintf(("PyThread_exit_thread called\n"));
232	if (!initialized) {
233		if (no_cleanup)
234			_exit(0);
235		else
236			exit(0);
237	}
238}
239
240void 
241PyThread_exit_thread(void)
242{
243	do_PyThread_exit_thread(0);
244}
245
246void 
247PyThread__exit_thread(void)
248{
249	do_PyThread_exit_thread(1);
250}
251
252#ifndef NO_EXIT_PROG
253static void 
254do_PyThread_exit_prog(int status, int no_cleanup)
255{
256	dprintf(("PyThread_exit_prog(%d) called\n", status));
257	if (!initialized)
258		if (no_cleanup)
259			_exit(status);
260		else
261			exit(status);
262}
263
264void 
265PyThread_exit_prog(int status)
266{
267	do_PyThread_exit_prog(status, 0);
268}
269
270void 
271PyThread__exit_prog(int status)
272{
273	do_PyThread_exit_prog(status, 1);
274}
275#endif /* NO_EXIT_PROG */
276
277#ifdef USE_SEMAPHORES
278
279/*
280 * Lock support.
281 */
282
283PyThread_type_lock 
284PyThread_allocate_lock(void)
285{
286	sem_t *lock;
287	int status, error = 0;
288
289	dprintf(("PyThread_allocate_lock called\n"));
290	if (!initialized)
291		PyThread_init_thread();
292
293	lock = (sem_t *)malloc(sizeof(sem_t));
294
295	if (lock) {
296		status = sem_init(lock,0,1);
297		CHECK_STATUS("sem_init");
298
299		if (error) {
300			free((void *)lock);
301			lock = NULL;
302		}
303	}
304
305	dprintf(("PyThread_allocate_lock() -> %p\n", lock));
306	return (PyThread_type_lock)lock;
307}
308
309void 
310PyThread_free_lock(PyThread_type_lock lock)
311{
312	sem_t *thelock = (sem_t *)lock;
313	int status, error = 0;
314
315	dprintf(("PyThread_free_lock(%p) called\n", lock));
316
317	if (!thelock)
318		return;
319
320	status = sem_destroy(thelock);
321	CHECK_STATUS("sem_destroy");
322
323	free((void *)thelock);
324}
325
326/*
327 * As of February 2002, Cygwin thread implementations mistakenly report error
328 * codes in the return value of the sem_ calls (like the pthread_ functions).
329 * Correct implementations return -1 and put the code in errno. This supports
330 * either.
331 */
332static int
333fix_status(int status)
334{
335	return (status == -1) ? errno : status;
336}
337
338int 
339PyThread_acquire_lock(PyThread_type_lock lock, int waitflag)
340{
341	int success;
342	sem_t *thelock = (sem_t *)lock;
343	int status, error = 0;
344
345	dprintf(("PyThread_acquire_lock(%p, %d) called\n", lock, waitflag));
346
347	do {
348		if (waitflag)
349			status = fix_status(sem_wait(thelock));
350		else
351			status = fix_status(sem_trywait(thelock));
352	} while (status == EINTR); /* Retry if interrupted by a signal */
353
354	if (waitflag) {
355		CHECK_STATUS("sem_wait");
356	} else if (status != EAGAIN) {
357		CHECK_STATUS("sem_trywait");
358	}
359	
360	success = (status == 0) ? 1 : 0;
361
362	dprintf(("PyThread_acquire_lock(%p, %d) -> %d\n", lock, waitflag, success));
363	return success;
364}
365
366void 
367PyThread_release_lock(PyThread_type_lock lock)
368{
369	sem_t *thelock = (sem_t *)lock;
370	int status, error = 0;
371
372	dprintf(("PyThread_release_lock(%p) called\n", lock));
373
374	status = sem_post(thelock);
375	CHECK_STATUS("sem_post");
376}
377
378#else /* USE_SEMAPHORES */
379
380/*
381 * Lock support.
382 */
383PyThread_type_lock 
384PyThread_allocate_lock(void)
385{
386	pthread_lock *lock;
387	int status, error = 0;
388
389	dprintf(("PyThread_allocate_lock called\n"));
390	if (!initialized)
391		PyThread_init_thread();
392
393	lock = (pthread_lock *) malloc(sizeof(pthread_lock));
394	if (lock) {
395		memset((void *)lock, '\0', sizeof(pthread_lock));
396		lock->locked = 0;
397
398		status = pthread_mutex_init(&lock->mut,
399					    pthread_mutexattr_default);
400		CHECK_STATUS("pthread_mutex_init");
401
402		status = pthread_cond_init(&lock->lock_released,
403					   pthread_condattr_default);
404		CHECK_STATUS("pthread_cond_init");
405
406		if (error) {
407			free((void *)lock);
408			lock = 0;
409		}
410	}
411
412	dprintf(("PyThread_allocate_lock() -> %p\n", lock));
413	return (PyThread_type_lock) lock;
414}
415
416void 
417PyThread_free_lock(PyThread_type_lock lock)
418{
419	pthread_lock *thelock = (pthread_lock *)lock;
420	int status, error = 0;
421
422	dprintf(("PyThread_free_lock(%p) called\n", lock));
423
424	status = pthread_mutex_destroy( &thelock->mut );
425	CHECK_STATUS("pthread_mutex_destroy");
426
427	status = pthread_cond_destroy( &thelock->lock_released );
428	CHECK_STATUS("pthread_cond_destroy");
429
430	free((void *)thelock);
431}
432
433int 
434PyThread_acquire_lock(PyThread_type_lock lock, int waitflag)
435{
436	int success;
437	pthread_lock *thelock = (pthread_lock *)lock;
438	int status, error = 0;
439
440	dprintf(("PyThread_acquire_lock(%p, %d) called\n", lock, waitflag));
441
442	status = pthread_mutex_lock( &thelock->mut );
443	CHECK_STATUS("pthread_mutex_lock[1]");
444	success = thelock->locked == 0;
445
446	if ( !success && waitflag ) {
447		/* continue trying until we get the lock */
448
449		/* mut must be locked by me -- part of the condition
450		 * protocol */
451		while ( thelock->locked ) {
452			status = pthread_cond_wait(&thelock->lock_released,
453						   &thelock->mut);
454			CHECK_STATUS("pthread_cond_wait");
455		}
456		success = 1;
457	}
458	if (success) thelock->locked = 1;
459	status = pthread_mutex_unlock( &thelock->mut );
460	CHECK_STATUS("pthread_mutex_unlock[1]");
461
462	if (error) success = 0;
463	dprintf(("PyThread_acquire_lock(%p, %d) -> %d\n", lock, waitflag, success));
464	return success;
465}
466
467void 
468PyThread_release_lock(PyThread_type_lock lock)
469{
470	pthread_lock *thelock = (pthread_lock *)lock;
471	int status, error = 0;
472
473	dprintf(("PyThread_release_lock(%p) called\n", lock));
474
475	status = pthread_mutex_lock( &thelock->mut );
476	CHECK_STATUS("pthread_mutex_lock[3]");
477
478	thelock->locked = 0;
479
480	status = pthread_mutex_unlock( &thelock->mut );
481	CHECK_STATUS("pthread_mutex_unlock[3]");
482
483	/* wake up someone (anyone, if any) waiting on the lock */
484	status = pthread_cond_signal( &thelock->lock_released );
485	CHECK_STATUS("pthread_cond_signal");
486}
487
488#endif /* USE_SEMAPHORES */
489
490/* set the thread stack size.
491 * Return 0 if size is valid, -1 if size is invalid,
492 * -2 if setting stack size is not supported.
493 */
494static int
495_pythread_pthread_set_stacksize(size_t size)
496{
497#if defined(THREAD_STACK_SIZE)
498	pthread_attr_t attrs;
499	size_t tss_min;
500	int rc = 0;
501#endif
502
503	/* set to default */
504	if (size == 0) {
505		_pythread_stacksize = 0;
506		return 0;
507	}
508
509#if defined(THREAD_STACK_SIZE)
510#if defined(PTHREAD_STACK_MIN)
511	tss_min = PTHREAD_STACK_MIN > THREAD_STACK_MIN ? PTHREAD_STACK_MIN
512						       : THREAD_STACK_MIN;
513#else
514	tss_min = THREAD_STACK_MIN;
515#endif
516	if (size >= tss_min) {
517		/* validate stack size by setting thread attribute */
518		if (pthread_attr_init(&attrs) == 0) {
519			rc = pthread_attr_setstacksize(&attrs, size);
520			pthread_attr_destroy(&attrs);
521			if (rc == 0) {
522				_pythread_stacksize = size;
523				return 0;
524			}
525		}
526	}
527	return -1;
528#else
529	return -2;
530#endif
531}
532
533#define THREAD_SET_STACKSIZE(x)	_pythread_pthread_set_stacksize(x)