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 pthread_init();
149 #endif
150 }
151
152 #endif /* !_HAVE_BSDI */
153
154 /*
155 * Thread support.
156 */
157
158
159 long
PyThread_start_new_thread(void (* func)(void *),void * arg)160 PyThread_start_new_thread(void (*func)(void *), void *arg)
161 {
162 pthread_t th;
163 int status;
164 #if defined(THREAD_STACK_SIZE) || defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
165 pthread_attr_t attrs;
166 #endif
167 #if defined(THREAD_STACK_SIZE)
168 size_t tss;
169 #endif
170
171 dprintf(("PyThread_start_new_thread called\n"));
172 if (!initialized)
173 PyThread_init_thread();
174
175 #if defined(THREAD_STACK_SIZE) || defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
176 if (pthread_attr_init(&attrs) != 0)
177 return -1;
178 #endif
179 #if defined(THREAD_STACK_SIZE)
180 tss = (_pythread_stacksize != 0) ? _pythread_stacksize
181 : THREAD_STACK_SIZE;
182 if (tss != 0) {
183 if (pthread_attr_setstacksize(&attrs, tss) != 0) {
184 pthread_attr_destroy(&attrs);
185 return -1;
186 }
187 }
188 #endif
189 #if defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
190 pthread_attr_setscope(&attrs, PTHREAD_SCOPE_SYSTEM);
191 #endif
192
193 status = pthread_create(&th,
194 #if defined(THREAD_STACK_SIZE) || defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
195 &attrs,
196 #else
197 (pthread_attr_t*)NULL,
198 #endif
199 (void* (*)(void *))func,
200 (void *)arg
201 );
202
203 #if defined(THREAD_STACK_SIZE) || defined(PTHREAD_SYSTEM_SCHED_SUPPORTED)
204 pthread_attr_destroy(&attrs);
205 #endif
206 if (status != 0)
207 return -1;
208
209 pthread_detach(th);
210
211 #if SIZEOF_PTHREAD_T <= SIZEOF_LONG
212 return (long) th;
213 #else
214 return (long) *(long *) &th;
215 #endif
216 }
217
218 /* XXX This implementation is considered (to quote Tim Peters) "inherently
219 hosed" because:
220 - It does not guarantee the promise that a non-zero integer is returned.
221 - The cast to long is inherently unsafe.
222 - It is not clear that the 'volatile' (for AIX?) and ugly casting in the
223 latter return statement (for Alpha OSF/1) are any longer necessary.
224 */
225 long
PyThread_get_thread_ident(void)226 PyThread_get_thread_ident(void)
227 {
228 volatile pthread_t threadid;
229 if (!initialized)
230 PyThread_init_thread();
231 /* Jump through some hoops for Alpha OSF/1 */
232 threadid = pthread_self();
233 #if SIZEOF_PTHREAD_T <= SIZEOF_LONG
234 return (long) threadid;
235 #else
236 return (long) *(long *) &threadid;
237 #endif
238 }
239
240 void
PyThread_exit_thread(void)241 PyThread_exit_thread(void)
242 {
243 dprintf(("PyThread_exit_thread called\n"));
244 if (!initialized) {
245 exit(0);
246 }
247 }
248
249 #ifdef USE_SEMAPHORES
250
251 /*
252 * Lock support.
253 */
254
255 PyThread_type_lock
PyThread_allocate_lock(void)256 PyThread_allocate_lock(void)
257 {
258 sem_t *lock;
259 int status, error = 0;
260
261 dprintf(("PyThread_allocate_lock called\n"));
262 if (!initialized)
263 PyThread_init_thread();
264
265 lock = (sem_t *)malloc(sizeof(sem_t));
266
267 if (lock) {
268 status = sem_init(lock,0,1);
269 CHECK_STATUS("sem_init");
270
271 if (error) {
272 free((void *)lock);
273 lock = NULL;
274 }
275 }
276
277 dprintf(("PyThread_allocate_lock() -> %p\n", lock));
278 return (PyThread_type_lock)lock;
279 }
280
281 void
PyThread_free_lock(PyThread_type_lock lock)282 PyThread_free_lock(PyThread_type_lock lock)
283 {
284 sem_t *thelock = (sem_t *)lock;
285 int status, error = 0;
286
287 dprintf(("PyThread_free_lock(%p) called\n", lock));
288
289 if (!thelock)
290 return;
291
292 status = sem_destroy(thelock);
293 CHECK_STATUS("sem_destroy");
294
295 free((void *)thelock);
296 }
297
298 /*
299 * As of February 2002, Cygwin thread implementations mistakenly report error
300 * codes in the return value of the sem_ calls (like the pthread_ functions).
301 * Correct implementations return -1 and put the code in errno. This supports
302 * either.
303 */
304 static int
fix_status(int status)305 fix_status(int status)
306 {
307 return (status == -1) ? errno : status;
308 }
309
310 int
PyThread_acquire_lock(PyThread_type_lock lock,int waitflag)311 PyThread_acquire_lock(PyThread_type_lock lock, int waitflag)
312 {
313 int success;
314 sem_t *thelock = (sem_t *)lock;
315 int status, error = 0;
316
317 dprintf(("PyThread_acquire_lock(%p, %d) called\n", lock, waitflag));
318
319 do {
320 if (waitflag)
321 status = fix_status(sem_wait(thelock));
322 else
323 status = fix_status(sem_trywait(thelock));
324 } while (status == EINTR); /* Retry if interrupted by a signal */
325
326 if (waitflag) {
327 CHECK_STATUS("sem_wait");
328 } else if (status != EAGAIN) {
329 CHECK_STATUS("sem_trywait");
330 }
331
332 success = (status == 0) ? 1 : 0;
333
334 dprintf(("PyThread_acquire_lock(%p, %d) -> %d\n", lock, waitflag, success));
335 return success;
336 }
337
338 void
PyThread_release_lock(PyThread_type_lock lock)339 PyThread_release_lock(PyThread_type_lock lock)
340 {
341 sem_t *thelock = (sem_t *)lock;
342 int status, error = 0;
343
344 dprintf(("PyThread_release_lock(%p) called\n", lock));
345
346 status = sem_post(thelock);
347 CHECK_STATUS("sem_post");
348 }
349
350 #else /* USE_SEMAPHORES */
351
352 /*
353 * Lock support.
354 */
355 PyThread_type_lock
PyThread_allocate_lock(void)356 PyThread_allocate_lock(void)
357 {
358 pthread_lock *lock;
359 int status, error = 0;
360
361 dprintf(("PyThread_allocate_lock called\n"));
362 if (!initialized)
363 PyThread_init_thread();
364
365 lock = (pthread_lock *) malloc(sizeof(pthread_lock));
366 if (lock) {
367 memset((void *)lock, '\0', sizeof(pthread_lock));
368 lock->locked = 0;
369
370 status = pthread_mutex_init(&lock->mut,
371 pthread_mutexattr_default);
372 CHECK_STATUS("pthread_mutex_init");
373
374 status = pthread_cond_init(&lock->lock_released,
375 pthread_condattr_default);
376 CHECK_STATUS("pthread_cond_init");
377
378 if (error) {
379 free((void *)lock);
380 lock = 0;
381 }
382 }
383
384 dprintf(("PyThread_allocate_lock() -> %p\n", lock));
385 return (PyThread_type_lock) lock;
386 }
387
388 void
PyThread_free_lock(PyThread_type_lock lock)389 PyThread_free_lock(PyThread_type_lock lock)
390 {
391 pthread_lock *thelock = (pthread_lock *)lock;
392 int status, error = 0;
393
394 dprintf(("PyThread_free_lock(%p) called\n", lock));
395
396 status = pthread_mutex_destroy( &thelock->mut );
397 CHECK_STATUS("pthread_mutex_destroy");
398
399 status = pthread_cond_destroy( &thelock->lock_released );
400 CHECK_STATUS("pthread_cond_destroy");
401
402 free((void *)thelock);
403 }
404
405 int
PyThread_acquire_lock(PyThread_type_lock lock,int waitflag)406 PyThread_acquire_lock(PyThread_type_lock lock, int waitflag)
407 {
408 int success;
409 pthread_lock *thelock = (pthread_lock *)lock;
410 int status, error = 0;
411
412 dprintf(("PyThread_acquire_lock(%p, %d) called\n", lock, waitflag));
413
414 status = pthread_mutex_lock( &thelock->mut );
415 CHECK_STATUS("pthread_mutex_lock[1]");
416 success = thelock->locked == 0;
417
418 if ( !success && waitflag ) {
419 /* continue trying until we get the lock */
420
421 /* mut must be locked by me -- part of the condition
422 * protocol */
423 while ( thelock->locked ) {
424 status = pthread_cond_wait(&thelock->lock_released,
425 &thelock->mut);
426 CHECK_STATUS("pthread_cond_wait");
427 }
428 success = 1;
429 }
430 if (success) thelock->locked = 1;
431 status = pthread_mutex_unlock( &thelock->mut );
432 CHECK_STATUS("pthread_mutex_unlock[1]");
433
434 if (error) success = 0;
435 dprintf(("PyThread_acquire_lock(%p, %d) -> %d\n", lock, waitflag, success));
436 return success;
437 }
438
439 void
PyThread_release_lock(PyThread_type_lock lock)440 PyThread_release_lock(PyThread_type_lock lock)
441 {
442 pthread_lock *thelock = (pthread_lock *)lock;
443 int status, error = 0;
444
445 dprintf(("PyThread_release_lock(%p) called\n", lock));
446
447 status = pthread_mutex_lock( &thelock->mut );
448 CHECK_STATUS("pthread_mutex_lock[3]");
449
450 thelock->locked = 0;
451
452 status = pthread_mutex_unlock( &thelock->mut );
453 CHECK_STATUS("pthread_mutex_unlock[3]");
454
455 /* wake up someone (anyone, if any) waiting on the lock */
456 status = pthread_cond_signal( &thelock->lock_released );
457 CHECK_STATUS("pthread_cond_signal");
458 }
459
460 #endif /* USE_SEMAPHORES */
461
462 /* set the thread stack size.
463 * Return 0 if size is valid, -1 if size is invalid,
464 * -2 if setting stack size is not supported.
465 */
466 static int
_pythread_pthread_set_stacksize(size_t size)467 _pythread_pthread_set_stacksize(size_t size)
468 {
469 #if defined(THREAD_STACK_SIZE)
470 pthread_attr_t attrs;
471 size_t tss_min;
472 int rc = 0;
473 #endif
474
475 /* set to default */
476 if (size == 0) {
477 _pythread_stacksize = 0;
478 return 0;
479 }
480
481 #if defined(THREAD_STACK_SIZE)
482 #if defined(PTHREAD_STACK_MIN)
483 tss_min = PTHREAD_STACK_MIN > THREAD_STACK_MIN ? PTHREAD_STACK_MIN
484 : THREAD_STACK_MIN;
485 #else
486 tss_min = THREAD_STACK_MIN;
487 #endif
488 if (size >= tss_min) {
489 /* validate stack size by setting thread attribute */
490 if (pthread_attr_init(&attrs) == 0) {
491 rc = pthread_attr_setstacksize(&attrs, size);
492 pthread_attr_destroy(&attrs);
493 if (rc == 0) {
494 _pythread_stacksize = size;
495 return 0;
496 }
497 }
498 }
499 return -1;
500 #else
501 return -2;
502 #endif
503 }
504
505 #define THREAD_SET_STACKSIZE(x) _pythread_pthread_set_stacksize(x)
506