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
22 #if (defined(__APPLE__) || defined(__FreeBSD__)) && defined(THREAD_STACK_SIZE) && THREAD_STACK_SIZE == 0
23 /* The default stack size for new threads on OSX is small enough that
24 * we'll get hard crashes instead of 'maximum recursion depth exceeded'
25 * exceptions.
26 *
27 * The default stack size below is the minimal stack size where a
28 * simple recursive function doesn't cause a hard crash.
29 */
30 #undef THREAD_STACK_SIZE
31 #define THREAD_STACK_SIZE 0x400000
32 #endif
33 /* for safety, ensure a viable minimum stacksize */
34 #define THREAD_STACK_MIN 0x8000 /* 32kB */
35 #else /* !_POSIX_THREAD_ATTR_STACKSIZE */
36 #ifdef THREAD_STACK_SIZE
37 #error "THREAD_STACK_SIZE defined but _POSIX_THREAD_ATTR_STACKSIZE undefined"
38 #endif
39 #endif
40
41 /* The POSIX spec says that implementations supporting the sem_*
42 family of functions must indicate this by defining
43 _POSIX_SEMAPHORES. */
44 #ifdef _POSIX_SEMAPHORES
45 /* On FreeBSD 4.x, _POSIX_SEMAPHORES is defined empty, so
46 we need to add 0 to make it work there as well. */
47 #if (_POSIX_SEMAPHORES+0) == -1
48 #define HAVE_BROKEN_POSIX_SEMAPHORES
49 #else
50 #include <semaphore.h>
51 #include <errno.h>
52 #endif
53 #endif
54
55 /* Before FreeBSD 5.4, system scope threads was very limited resource
56 in default setting. So the process scope is preferred to get
57 enough number of threads to work. */
58 #ifdef __FreeBSD__
59 #include <osreldate.h>
60 #if __FreeBSD_version >= 500000 && __FreeBSD_version < 504101
61 #undef PTHREAD_SYSTEM_SCHED_SUPPORTED
62 #endif
63 #endif
64
65 #if !defined(pthread_attr_default)
66 # define pthread_attr_default ((pthread_attr_t *)NULL)
67 #endif
68 #if !defined(pthread_mutexattr_default)
69 # define pthread_mutexattr_default ((pthread_mutexattr_t *)NULL)
70 #endif
71 #if !defined(pthread_condattr_default)
72 # define pthread_condattr_default ((pthread_condattr_t *)NULL)
73 #endif
74
75
76 /* Whether or not to use semaphores directly rather than emulating them with
77 * mutexes and condition variables:
78 */
79 #if defined(_POSIX_SEMAPHORES) && !defined(HAVE_BROKEN_POSIX_SEMAPHORES)
80 # define USE_SEMAPHORES
81 #else
82 # undef USE_SEMAPHORES
83 #endif
84
85
86 /* On platforms that don't use standard POSIX threads pthread_sigmask()
87 * isn't present. DEC threads uses sigprocmask() instead as do most
88 * other UNIX International compliant systems that don't have the full
89 * pthread implementation.
90 */
91 #if defined(HAVE_PTHREAD_SIGMASK) && !defined(HAVE_BROKEN_PTHREAD_SIGMASK)
92 # define SET_THREAD_SIGMASK pthread_sigmask
93 #else
94 # define SET_THREAD_SIGMASK sigprocmask
95 #endif
96
97
98 /* A pthread mutex isn't sufficient to model the Python lock type
99 * because, according to Draft 5 of the docs (P1003.4a/D5), both of the
100 * following are undefined:
101 * -> a thread tries to lock a mutex it already has locked
102 * -> a thread tries to unlock a mutex locked by a different thread
103 * pthread mutexes are designed for serializing threads over short pieces
104 * of code anyway, so wouldn't be an appropriate implementation of
105 * Python's locks regardless.
106 *
107 * The pthread_lock struct implements a Python lock as a "locked?" bit
108 * and a <condition, mutex> pair. In general, if the bit can be acquired
109 * instantly, it is, else the pair is used to block the thread until the
110 * bit is cleared. 9 May 1994 tim@ksr.com
111 */
112
113 typedef struct {
114 char locked; /* 0=unlocked, 1=locked */
115 /* a <cond, mutex> pair to handle an acquire of a locked lock */
116 pthread_cond_t lock_released;
117 pthread_mutex_t mut;
118 } pthread_lock;
119
120 #define CHECK_STATUS(name) if (status != 0) { perror(name); error = 1; }
121
122 /*
123 * Initialization.
124 */
125
126 #ifdef _HAVE_BSDI
127 static
_noop(void)128 void _noop(void)
129 {
130 }
131
132 static void
PyThread__init_thread(void)133 PyThread__init_thread(void)
134 {
135 /* DO AN INIT BY STARTING THE THREAD */
136 static int dummy = 0;
137 pthread_t thread1;
138 pthread_create(&thread1, NULL, (void *) _noop, &dummy);
139 pthread_join(thread1, NULL);
140 }
141
142 #else /* !_HAVE_BSDI */
143
144 static void
PyThread__init_thread(void)145 PyThread__init_thread(void)
146 {
147 #if defined(_AIX) && defined(__GNUC__)
148 extern void pthread_init(void);
149 pthread_init();
150 #endif
151 }
152
153 #endif /* !_HAVE_BSDI */
154
155 /*
156 * Thread support.
157 */
158
159
160 long
PyThread_start_new_thread(void (* func)(void *),void * arg)161 PyThread_start_new_thread(void (*func)(void *), void *arg)
162 {
163 pthread_t th;
164 int status;
165 #if defined(THREAD_STACK_SIZE) || defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
166 pthread_attr_t attrs;
167 #endif
168 #if defined(THREAD_STACK_SIZE)
169 size_t tss;
170 #endif
171
172 dprintf(("PyThread_start_new_thread called\n"));
173 if (!initialized)
174 PyThread_init_thread();
175
176 #if defined(THREAD_STACK_SIZE) || defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
177 if (pthread_attr_init(&attrs) != 0)
178 return -1;
179 #endif
180 #if defined(THREAD_STACK_SIZE)
181 tss = (_pythread_stacksize != 0) ? _pythread_stacksize
182 : THREAD_STACK_SIZE;
183 if (tss != 0) {
184 if (pthread_attr_setstacksize(&attrs, tss) != 0) {
185 pthread_attr_destroy(&attrs);
186 return -1;
187 }
188 }
189 #endif
190 #if defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
191 pthread_attr_setscope(&attrs, PTHREAD_SCOPE_SYSTEM);
192 #endif
193
194 status = pthread_create(&th,
195 #if defined(THREAD_STACK_SIZE) || defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
196 &attrs,
197 #else
198 (pthread_attr_t*)NULL,
199 #endif
200 (void* (*)(void *))func,
201 (void *)arg
202 );
203
204 #if defined(THREAD_STACK_SIZE) || defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
205 pthread_attr_destroy(&attrs);
206 #endif
207 if (status != 0)
208 return -1;
209
210 pthread_detach(th);
211
212 #if SIZEOF_PTHREAD_T <= SIZEOF_LONG
213 return (long) th;
214 #else
215 return (long) *(long *) &th;
216 #endif
217 }
218
219 /* XXX This implementation is considered (to quote Tim Peters) "inherently
220 hosed" because:
221 - It does not guarantee the promise that a non-zero integer is returned.
222 - The cast to long is inherently unsafe.
223 - It is not clear that the 'volatile' (for AIX?) and ugly casting in the
224 latter return statement (for Alpha OSF/1) are any longer necessary.
225 */
226 long
PyThread_get_thread_ident(void)227 PyThread_get_thread_ident(void)
228 {
229 volatile pthread_t threadid;
230 if (!initialized)
231 PyThread_init_thread();
232 /* Jump through some hoops for Alpha OSF/1 */
233 threadid = pthread_self();
234 #if SIZEOF_PTHREAD_T <= SIZEOF_LONG
235 return (long) threadid;
236 #else
237 return (long) *(long *) &threadid;
238 #endif
239 }
240
241 void
PyThread_exit_thread(void)242 PyThread_exit_thread(void)
243 {
244 dprintf(("PyThread_exit_thread called\n"));
245 if (!initialized) {
246 exit(0);
247 }
248 }
249
250 #ifdef USE_SEMAPHORES
251
252 /*
253 * Lock support.
254 */
255
256 PyThread_type_lock
PyThread_allocate_lock(void)257 PyThread_allocate_lock(void)
258 {
259 sem_t *lock;
260 int status, error = 0;
261
262 dprintf(("PyThread_allocate_lock called\n"));
263 if (!initialized)
264 PyThread_init_thread();
265
266 lock = (sem_t *)malloc(sizeof(sem_t));
267
268 if (lock) {
269 status = sem_init(lock,0,1);
270 CHECK_STATUS("sem_init");
271
272 if (error) {
273 free((void *)lock);
274 lock = NULL;
275 }
276 }
277
278 dprintf(("PyThread_allocate_lock() -> %p\n", lock));
279 return (PyThread_type_lock)lock;
280 }
281
282 void
PyThread_free_lock(PyThread_type_lock lock)283 PyThread_free_lock(PyThread_type_lock lock)
284 {
285 sem_t *thelock = (sem_t *)lock;
286 int status, error = 0;
287
288 (void) error; /* silence unused-but-set-variable warning */
289 dprintf(("PyThread_free_lock(%p) called\n", lock));
290
291 if (!thelock)
292 return;
293
294 status = sem_destroy(thelock);
295 CHECK_STATUS("sem_destroy");
296
297 free((void *)thelock);
298 }
299
300 /*
301 * As of February 2002, Cygwin thread implementations mistakenly report error
302 * codes in the return value of the sem_ calls (like the pthread_ functions).
303 * Correct implementations return -1 and put the code in errno. This supports
304 * either.
305 */
306 static int
fix_status(int status)307 fix_status(int status)
308 {
309 return (status == -1) ? errno : status;
310 }
311
312 int
PyThread_acquire_lock(PyThread_type_lock lock,int waitflag)313 PyThread_acquire_lock(PyThread_type_lock lock, int waitflag)
314 {
315 int success;
316 sem_t *thelock = (sem_t *)lock;
317 int status, error = 0;
318
319 (void) error; /* silence unused-but-set-variable warning */
320 dprintf(("PyThread_acquire_lock(%p, %d) called\n", lock, waitflag));
321
322 do {
323 if (waitflag)
324 status = fix_status(sem_wait(thelock));
325 else
326 status = fix_status(sem_trywait(thelock));
327 } while (status == EINTR); /* Retry if interrupted by a signal */
328
329 if (waitflag) {
330 CHECK_STATUS("sem_wait");
331 } else if (status != EAGAIN) {
332 CHECK_STATUS("sem_trywait");
333 }
334
335 success = (status == 0) ? 1 : 0;
336
337 dprintf(("PyThread_acquire_lock(%p, %d) -> %d\n", lock, waitflag, success));
338 return success;
339 }
340
341 void
PyThread_release_lock(PyThread_type_lock lock)342 PyThread_release_lock(PyThread_type_lock lock)
343 {
344 sem_t *thelock = (sem_t *)lock;
345 int status, error = 0;
346
347 (void) error; /* silence unused-but-set-variable warning */
348 dprintf(("PyThread_release_lock(%p) called\n", lock));
349
350 status = sem_post(thelock);
351 CHECK_STATUS("sem_post");
352 }
353
354 #else /* USE_SEMAPHORES */
355
356 /*
357 * Lock support.
358 */
359 PyThread_type_lock
PyThread_allocate_lock(void)360 PyThread_allocate_lock(void)
361 {
362 pthread_lock *lock;
363 int status, error = 0;
364
365 dprintf(("PyThread_allocate_lock called\n"));
366 if (!initialized)
367 PyThread_init_thread();
368
369 lock = (pthread_lock *) malloc(sizeof(pthread_lock));
370 if (lock) {
371 memset((void *)lock, '\0', sizeof(pthread_lock));
372 lock->locked = 0;
373
374 status = pthread_mutex_init(&lock->mut,
375 pthread_mutexattr_default);
376 CHECK_STATUS("pthread_mutex_init");
377
378 status = pthread_cond_init(&lock->lock_released,
379 pthread_condattr_default);
380 CHECK_STATUS("pthread_cond_init");
381
382 if (error) {
383 free((void *)lock);
384 lock = 0;
385 }
386 }
387
388 dprintf(("PyThread_allocate_lock() -> %p\n", lock));
389 return (PyThread_type_lock) lock;
390 }
391
392 void
PyThread_free_lock(PyThread_type_lock lock)393 PyThread_free_lock(PyThread_type_lock lock)
394 {
395 pthread_lock *thelock = (pthread_lock *)lock;
396 int status, error = 0;
397
398 (void) error; /* silence unused-but-set-variable warning */
399 dprintf(("PyThread_free_lock(%p) called\n", lock));
400
401 status = pthread_mutex_destroy( &thelock->mut );
402 CHECK_STATUS("pthread_mutex_destroy");
403
404 status = pthread_cond_destroy( &thelock->lock_released );
405 CHECK_STATUS("pthread_cond_destroy");
406
407 free((void *)thelock);
408 }
409
410 int
PyThread_acquire_lock(PyThread_type_lock lock,int waitflag)411 PyThread_acquire_lock(PyThread_type_lock lock, int waitflag)
412 {
413 int success;
414 pthread_lock *thelock = (pthread_lock *)lock;
415 int status, error = 0;
416
417 dprintf(("PyThread_acquire_lock(%p, %d) called\n", lock, waitflag));
418
419 status = pthread_mutex_lock( &thelock->mut );
420 CHECK_STATUS("pthread_mutex_lock[1]");
421 success = thelock->locked == 0;
422
423 if ( !success && waitflag ) {
424 /* continue trying until we get the lock */
425
426 /* mut must be locked by me -- part of the condition
427 * protocol */
428 while ( thelock->locked ) {
429 status = pthread_cond_wait(&thelock->lock_released,
430 &thelock->mut);
431 CHECK_STATUS("pthread_cond_wait");
432 }
433 success = 1;
434 }
435 if (success) thelock->locked = 1;
436 status = pthread_mutex_unlock( &thelock->mut );
437 CHECK_STATUS("pthread_mutex_unlock[1]");
438
439 if (error) success = 0;
440 dprintf(("PyThread_acquire_lock(%p, %d) -> %d\n", lock, waitflag, success));
441 return success;
442 }
443
444 void
PyThread_release_lock(PyThread_type_lock lock)445 PyThread_release_lock(PyThread_type_lock lock)
446 {
447 pthread_lock *thelock = (pthread_lock *)lock;
448 int status, error = 0;
449
450 (void) error; /* silence unused-but-set-variable warning */
451 dprintf(("PyThread_release_lock(%p) called\n", lock));
452
453 status = pthread_mutex_lock( &thelock->mut );
454 CHECK_STATUS("pthread_mutex_lock[3]");
455
456 thelock->locked = 0;
457
458 status = pthread_mutex_unlock( &thelock->mut );
459 CHECK_STATUS("pthread_mutex_unlock[3]");
460
461 /* wake up someone (anyone, if any) waiting on the lock */
462 status = pthread_cond_signal( &thelock->lock_released );
463 CHECK_STATUS("pthread_cond_signal");
464 }
465
466 #endif /* USE_SEMAPHORES */
467
468 /* set the thread stack size.
469 * Return 0 if size is valid, -1 if size is invalid,
470 * -2 if setting stack size is not supported.
471 */
472 static int
_pythread_pthread_set_stacksize(size_t size)473 _pythread_pthread_set_stacksize(size_t size)
474 {
475 #if defined(THREAD_STACK_SIZE)
476 pthread_attr_t attrs;
477 size_t tss_min;
478 int rc = 0;
479 #endif
480
481 /* set to default */
482 if (size == 0) {
483 _pythread_stacksize = 0;
484 return 0;
485 }
486
487 #if defined(THREAD_STACK_SIZE)
488 #if defined(PTHREAD_STACK_MIN)
489 tss_min = PTHREAD_STACK_MIN > THREAD_STACK_MIN ? PTHREAD_STACK_MIN
490 : THREAD_STACK_MIN;
491 #else
492 tss_min = THREAD_STACK_MIN;
493 #endif
494 if (size >= tss_min) {
495 /* validate stack size by setting thread attribute */
496 if (pthread_attr_init(&attrs) == 0) {
497 rc = pthread_attr_setstacksize(&attrs, size);
498 pthread_attr_destroy(&attrs);
499 if (rc == 0) {
500 _pythread_stacksize = size;
501 return 0;
502 }
503 }
504 }
505 return -1;
506 #else
507 return -2;
508 #endif
509 }
510
511 #define THREAD_SET_STACKSIZE(x) _pythread_pthread_set_stacksize(x)
512