xref: /openbmc/qemu/util/qemu-thread-posix.c (revision 795c40b8)
1 /*
2  * Wrappers around mutex/cond/thread functions
3  *
4  * Copyright Red Hat, Inc. 2009
5  *
6  * Author:
7  *  Marcelo Tosatti <mtosatti@redhat.com>
8  *
9  * This work is licensed under the terms of the GNU GPL, version 2 or later.
10  * See the COPYING file in the top-level directory.
11  *
12  */
13 #include "qemu/osdep.h"
14 #include "qemu/thread.h"
15 #include "qemu/atomic.h"
16 #include "qemu/notify.h"
17 #include "trace.h"
18 
19 static bool name_threads;
20 
21 void qemu_thread_naming(bool enable)
22 {
23     name_threads = enable;
24 
25 #ifndef CONFIG_THREAD_SETNAME_BYTHREAD
26     /* This is a debugging option, not fatal */
27     if (enable) {
28         fprintf(stderr, "qemu: thread naming not supported on this host\n");
29     }
30 #endif
31 }
32 
33 static void error_exit(int err, const char *msg)
34 {
35     fprintf(stderr, "qemu: %s: %s\n", msg, strerror(err));
36     abort();
37 }
38 
39 void qemu_mutex_init(QemuMutex *mutex)
40 {
41     int err;
42 
43     err = pthread_mutex_init(&mutex->lock, NULL);
44     if (err)
45         error_exit(err, __func__);
46 }
47 
48 void qemu_mutex_destroy(QemuMutex *mutex)
49 {
50     int err;
51 
52     err = pthread_mutex_destroy(&mutex->lock);
53     if (err)
54         error_exit(err, __func__);
55 }
56 
57 void qemu_mutex_lock(QemuMutex *mutex)
58 {
59     int err;
60 
61     err = pthread_mutex_lock(&mutex->lock);
62     if (err)
63         error_exit(err, __func__);
64 
65     trace_qemu_mutex_locked(mutex);
66 }
67 
68 int qemu_mutex_trylock(QemuMutex *mutex)
69 {
70     int err;
71 
72     err = pthread_mutex_trylock(&mutex->lock);
73     if (err == 0) {
74         trace_qemu_mutex_locked(mutex);
75         return 0;
76     }
77     if (err != EBUSY) {
78         error_exit(err, __func__);
79     }
80     return -EBUSY;
81 }
82 
83 void qemu_mutex_unlock(QemuMutex *mutex)
84 {
85     int err;
86 
87     trace_qemu_mutex_unlocked(mutex);
88     err = pthread_mutex_unlock(&mutex->lock);
89     if (err)
90         error_exit(err, __func__);
91 }
92 
93 void qemu_rec_mutex_init(QemuRecMutex *mutex)
94 {
95     int err;
96     pthread_mutexattr_t attr;
97 
98     pthread_mutexattr_init(&attr);
99     pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
100     err = pthread_mutex_init(&mutex->lock, &attr);
101     pthread_mutexattr_destroy(&attr);
102     if (err) {
103         error_exit(err, __func__);
104     }
105 }
106 
107 void qemu_cond_init(QemuCond *cond)
108 {
109     int err;
110 
111     err = pthread_cond_init(&cond->cond, NULL);
112     if (err)
113         error_exit(err, __func__);
114 }
115 
116 void qemu_cond_destroy(QemuCond *cond)
117 {
118     int err;
119 
120     err = pthread_cond_destroy(&cond->cond);
121     if (err)
122         error_exit(err, __func__);
123 }
124 
125 void qemu_cond_signal(QemuCond *cond)
126 {
127     int err;
128 
129     err = pthread_cond_signal(&cond->cond);
130     if (err)
131         error_exit(err, __func__);
132 }
133 
134 void qemu_cond_broadcast(QemuCond *cond)
135 {
136     int err;
137 
138     err = pthread_cond_broadcast(&cond->cond);
139     if (err)
140         error_exit(err, __func__);
141 }
142 
143 void qemu_cond_wait(QemuCond *cond, QemuMutex *mutex)
144 {
145     int err;
146 
147     trace_qemu_mutex_unlocked(mutex);
148     err = pthread_cond_wait(&cond->cond, &mutex->lock);
149     trace_qemu_mutex_locked(mutex);
150     if (err)
151         error_exit(err, __func__);
152 }
153 
154 void qemu_sem_init(QemuSemaphore *sem, int init)
155 {
156     int rc;
157 
158 #if defined(__APPLE__) || defined(__NetBSD__)
159     rc = pthread_mutex_init(&sem->lock, NULL);
160     if (rc != 0) {
161         error_exit(rc, __func__);
162     }
163     rc = pthread_cond_init(&sem->cond, NULL);
164     if (rc != 0) {
165         error_exit(rc, __func__);
166     }
167     if (init < 0) {
168         error_exit(EINVAL, __func__);
169     }
170     sem->count = init;
171 #else
172     rc = sem_init(&sem->sem, 0, init);
173     if (rc < 0) {
174         error_exit(errno, __func__);
175     }
176 #endif
177 }
178 
179 void qemu_sem_destroy(QemuSemaphore *sem)
180 {
181     int rc;
182 
183 #if defined(__APPLE__) || defined(__NetBSD__)
184     rc = pthread_cond_destroy(&sem->cond);
185     if (rc < 0) {
186         error_exit(rc, __func__);
187     }
188     rc = pthread_mutex_destroy(&sem->lock);
189     if (rc < 0) {
190         error_exit(rc, __func__);
191     }
192 #else
193     rc = sem_destroy(&sem->sem);
194     if (rc < 0) {
195         error_exit(errno, __func__);
196     }
197 #endif
198 }
199 
200 void qemu_sem_post(QemuSemaphore *sem)
201 {
202     int rc;
203 
204 #if defined(__APPLE__) || defined(__NetBSD__)
205     pthread_mutex_lock(&sem->lock);
206     if (sem->count == UINT_MAX) {
207         rc = EINVAL;
208     } else {
209         sem->count++;
210         rc = pthread_cond_signal(&sem->cond);
211     }
212     pthread_mutex_unlock(&sem->lock);
213     if (rc != 0) {
214         error_exit(rc, __func__);
215     }
216 #else
217     rc = sem_post(&sem->sem);
218     if (rc < 0) {
219         error_exit(errno, __func__);
220     }
221 #endif
222 }
223 
224 static void compute_abs_deadline(struct timespec *ts, int ms)
225 {
226     struct timeval tv;
227     gettimeofday(&tv, NULL);
228     ts->tv_nsec = tv.tv_usec * 1000 + (ms % 1000) * 1000000;
229     ts->tv_sec = tv.tv_sec + ms / 1000;
230     if (ts->tv_nsec >= 1000000000) {
231         ts->tv_sec++;
232         ts->tv_nsec -= 1000000000;
233     }
234 }
235 
236 int qemu_sem_timedwait(QemuSemaphore *sem, int ms)
237 {
238     int rc;
239     struct timespec ts;
240 
241 #if defined(__APPLE__) || defined(__NetBSD__)
242     rc = 0;
243     compute_abs_deadline(&ts, ms);
244     pthread_mutex_lock(&sem->lock);
245     while (sem->count == 0) {
246         rc = pthread_cond_timedwait(&sem->cond, &sem->lock, &ts);
247         if (rc == ETIMEDOUT) {
248             break;
249         }
250         if (rc != 0) {
251             error_exit(rc, __func__);
252         }
253     }
254     if (rc != ETIMEDOUT) {
255         --sem->count;
256     }
257     pthread_mutex_unlock(&sem->lock);
258     return (rc == ETIMEDOUT ? -1 : 0);
259 #else
260     if (ms <= 0) {
261         /* This is cheaper than sem_timedwait.  */
262         do {
263             rc = sem_trywait(&sem->sem);
264         } while (rc == -1 && errno == EINTR);
265         if (rc == -1 && errno == EAGAIN) {
266             return -1;
267         }
268     } else {
269         compute_abs_deadline(&ts, ms);
270         do {
271             rc = sem_timedwait(&sem->sem, &ts);
272         } while (rc == -1 && errno == EINTR);
273         if (rc == -1 && errno == ETIMEDOUT) {
274             return -1;
275         }
276     }
277     if (rc < 0) {
278         error_exit(errno, __func__);
279     }
280     return 0;
281 #endif
282 }
283 
284 void qemu_sem_wait(QemuSemaphore *sem)
285 {
286     int rc;
287 
288 #if defined(__APPLE__) || defined(__NetBSD__)
289     pthread_mutex_lock(&sem->lock);
290     while (sem->count == 0) {
291         rc = pthread_cond_wait(&sem->cond, &sem->lock);
292         if (rc != 0) {
293             error_exit(rc, __func__);
294         }
295     }
296     --sem->count;
297     pthread_mutex_unlock(&sem->lock);
298 #else
299     do {
300         rc = sem_wait(&sem->sem);
301     } while (rc == -1 && errno == EINTR);
302     if (rc < 0) {
303         error_exit(errno, __func__);
304     }
305 #endif
306 }
307 
308 #ifdef __linux__
309 #include "qemu/futex.h"
310 #else
311 static inline void qemu_futex_wake(QemuEvent *ev, int n)
312 {
313     pthread_mutex_lock(&ev->lock);
314     if (n == 1) {
315         pthread_cond_signal(&ev->cond);
316     } else {
317         pthread_cond_broadcast(&ev->cond);
318     }
319     pthread_mutex_unlock(&ev->lock);
320 }
321 
322 static inline void qemu_futex_wait(QemuEvent *ev, unsigned val)
323 {
324     pthread_mutex_lock(&ev->lock);
325     if (ev->value == val) {
326         pthread_cond_wait(&ev->cond, &ev->lock);
327     }
328     pthread_mutex_unlock(&ev->lock);
329 }
330 #endif
331 
332 /* Valid transitions:
333  * - free->set, when setting the event
334  * - busy->set, when setting the event, followed by qemu_futex_wake
335  * - set->free, when resetting the event
336  * - free->busy, when waiting
337  *
338  * set->busy does not happen (it can be observed from the outside but
339  * it really is set->free->busy).
340  *
341  * busy->free provably cannot happen; to enforce it, the set->free transition
342  * is done with an OR, which becomes a no-op if the event has concurrently
343  * transitioned to free or busy.
344  */
345 
346 #define EV_SET         0
347 #define EV_FREE        1
348 #define EV_BUSY       -1
349 
350 void qemu_event_init(QemuEvent *ev, bool init)
351 {
352 #ifndef __linux__
353     pthread_mutex_init(&ev->lock, NULL);
354     pthread_cond_init(&ev->cond, NULL);
355 #endif
356 
357     ev->value = (init ? EV_SET : EV_FREE);
358 }
359 
360 void qemu_event_destroy(QemuEvent *ev)
361 {
362 #ifndef __linux__
363     pthread_mutex_destroy(&ev->lock);
364     pthread_cond_destroy(&ev->cond);
365 #endif
366 }
367 
368 void qemu_event_set(QemuEvent *ev)
369 {
370     /* qemu_event_set has release semantics, but because it *loads*
371      * ev->value we need a full memory barrier here.
372      */
373     smp_mb();
374     if (atomic_read(&ev->value) != EV_SET) {
375         if (atomic_xchg(&ev->value, EV_SET) == EV_BUSY) {
376             /* There were waiters, wake them up.  */
377             qemu_futex_wake(ev, INT_MAX);
378         }
379     }
380 }
381 
382 void qemu_event_reset(QemuEvent *ev)
383 {
384     unsigned value;
385 
386     value = atomic_read(&ev->value);
387     smp_mb_acquire();
388     if (value == EV_SET) {
389         /*
390          * If there was a concurrent reset (or even reset+wait),
391          * do nothing.  Otherwise change EV_SET->EV_FREE.
392          */
393         atomic_or(&ev->value, EV_FREE);
394     }
395 }
396 
397 void qemu_event_wait(QemuEvent *ev)
398 {
399     unsigned value;
400 
401     value = atomic_read(&ev->value);
402     smp_mb_acquire();
403     if (value != EV_SET) {
404         if (value == EV_FREE) {
405             /*
406              * Leave the event reset and tell qemu_event_set that there
407              * are waiters.  No need to retry, because there cannot be
408              * a concurrent busy->free transition.  After the CAS, the
409              * event will be either set or busy.
410              */
411             if (atomic_cmpxchg(&ev->value, EV_FREE, EV_BUSY) == EV_SET) {
412                 return;
413             }
414         }
415         qemu_futex_wait(ev, EV_BUSY);
416     }
417 }
418 
419 static pthread_key_t exit_key;
420 
421 union NotifierThreadData {
422     void *ptr;
423     NotifierList list;
424 };
425 QEMU_BUILD_BUG_ON(sizeof(union NotifierThreadData) != sizeof(void *));
426 
427 void qemu_thread_atexit_add(Notifier *notifier)
428 {
429     union NotifierThreadData ntd;
430     ntd.ptr = pthread_getspecific(exit_key);
431     notifier_list_add(&ntd.list, notifier);
432     pthread_setspecific(exit_key, ntd.ptr);
433 }
434 
435 void qemu_thread_atexit_remove(Notifier *notifier)
436 {
437     union NotifierThreadData ntd;
438     ntd.ptr = pthread_getspecific(exit_key);
439     notifier_remove(notifier);
440     pthread_setspecific(exit_key, ntd.ptr);
441 }
442 
443 static void qemu_thread_atexit_run(void *arg)
444 {
445     union NotifierThreadData ntd = { .ptr = arg };
446     notifier_list_notify(&ntd.list, NULL);
447 }
448 
449 static void __attribute__((constructor)) qemu_thread_atexit_init(void)
450 {
451     pthread_key_create(&exit_key, qemu_thread_atexit_run);
452 }
453 
454 
455 /* Attempt to set the threads name; note that this is for debug, so
456  * we're not going to fail if we can't set it.
457  */
458 static void qemu_thread_set_name(QemuThread *thread, const char *name)
459 {
460 #ifdef CONFIG_PTHREAD_SETNAME_NP
461     pthread_setname_np(thread->thread, name);
462 #endif
463 }
464 
465 void qemu_thread_create(QemuThread *thread, const char *name,
466                        void *(*start_routine)(void*),
467                        void *arg, int mode)
468 {
469     sigset_t set, oldset;
470     int err;
471     pthread_attr_t attr;
472 
473     err = pthread_attr_init(&attr);
474     if (err) {
475         error_exit(err, __func__);
476     }
477 
478     /* Leave signal handling to the iothread.  */
479     sigfillset(&set);
480     pthread_sigmask(SIG_SETMASK, &set, &oldset);
481     err = pthread_create(&thread->thread, &attr, start_routine, arg);
482     if (err)
483         error_exit(err, __func__);
484 
485     if (name_threads) {
486         qemu_thread_set_name(thread, name);
487     }
488 
489     if (mode == QEMU_THREAD_DETACHED) {
490         err = pthread_detach(thread->thread);
491         if (err) {
492             error_exit(err, __func__);
493         }
494     }
495     pthread_sigmask(SIG_SETMASK, &oldset, NULL);
496 
497     pthread_attr_destroy(&attr);
498 }
499 
500 void qemu_thread_get_self(QemuThread *thread)
501 {
502     thread->thread = pthread_self();
503 }
504 
505 bool qemu_thread_is_self(QemuThread *thread)
506 {
507    return pthread_equal(pthread_self(), thread->thread);
508 }
509 
510 void qemu_thread_exit(void *retval)
511 {
512     pthread_exit(retval);
513 }
514 
515 void *qemu_thread_join(QemuThread *thread)
516 {
517     int err;
518     void *ret;
519 
520     err = pthread_join(thread->thread, &ret);
521     if (err) {
522         error_exit(err, __func__);
523     }
524     return ret;
525 }
526