2 * Wrappers around mutex/cond/thread functions
4 * Copyright Red Hat, Inc. 2009
7 * Marcelo Tosatti <mtosatti@redhat.com>
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.
24 #include <sys/syscall.h>
25 #include <linux/futex.h>
27 #include "qemu/thread.h"
28 #include "qemu/atomic.h"
29 #include "qemu/notify.h"
31 static bool name_threads;
33 void qemu_thread_naming(bool enable)
35 name_threads = enable;
37 #ifndef CONFIG_THREAD_SETNAME_BYTHREAD
38 /* This is a debugging option, not fatal */
40 fprintf(stderr, "qemu: thread naming not supported on this host\n");
45 static void error_exit(int err, const char *msg)
47 fprintf(stderr, "qemu: %s: %s\n", msg, strerror(err));
51 void qemu_mutex_init(QemuMutex *mutex)
55 err = pthread_mutex_init(&mutex->lock, NULL);
57 error_exit(err, __func__);
60 void qemu_mutex_destroy(QemuMutex *mutex)
64 err = pthread_mutex_destroy(&mutex->lock);
66 error_exit(err, __func__);
69 void qemu_mutex_lock(QemuMutex *mutex)
73 err = pthread_mutex_lock(&mutex->lock);
75 error_exit(err, __func__);
78 int qemu_mutex_trylock(QemuMutex *mutex)
80 return pthread_mutex_trylock(&mutex->lock);
83 void qemu_mutex_unlock(QemuMutex *mutex)
87 err = pthread_mutex_unlock(&mutex->lock);
89 error_exit(err, __func__);
92 void qemu_cond_init(QemuCond *cond)
96 err = pthread_cond_init(&cond->cond, NULL);
98 error_exit(err, __func__);
101 void qemu_cond_destroy(QemuCond *cond)
105 err = pthread_cond_destroy(&cond->cond);
107 error_exit(err, __func__);
110 void qemu_cond_signal(QemuCond *cond)
114 err = pthread_cond_signal(&cond->cond);
116 error_exit(err, __func__);
119 void qemu_cond_broadcast(QemuCond *cond)
123 err = pthread_cond_broadcast(&cond->cond);
125 error_exit(err, __func__);
128 void qemu_cond_wait(QemuCond *cond, QemuMutex *mutex)
132 err = pthread_cond_wait(&cond->cond, &mutex->lock);
134 error_exit(err, __func__);
137 void qemu_sem_init(QemuSemaphore *sem, int init)
141 #if defined(__APPLE__) || defined(__NetBSD__)
142 rc = pthread_mutex_init(&sem->lock, NULL);
144 error_exit(rc, __func__);
146 rc = pthread_cond_init(&sem->cond, NULL);
148 error_exit(rc, __func__);
151 error_exit(EINVAL, __func__);
155 rc = sem_init(&sem->sem, 0, init);
157 error_exit(errno, __func__);
162 void qemu_sem_destroy(QemuSemaphore *sem)
166 #if defined(__APPLE__) || defined(__NetBSD__)
167 rc = pthread_cond_destroy(&sem->cond);
169 error_exit(rc, __func__);
171 rc = pthread_mutex_destroy(&sem->lock);
173 error_exit(rc, __func__);
176 rc = sem_destroy(&sem->sem);
178 error_exit(errno, __func__);
183 void qemu_sem_post(QemuSemaphore *sem)
187 #if defined(__APPLE__) || defined(__NetBSD__)
188 pthread_mutex_lock(&sem->lock);
189 if (sem->count == UINT_MAX) {
193 rc = pthread_cond_signal(&sem->cond);
195 pthread_mutex_unlock(&sem->lock);
197 error_exit(rc, __func__);
200 rc = sem_post(&sem->sem);
202 error_exit(errno, __func__);
207 static void compute_abs_deadline(struct timespec *ts, int ms)
210 gettimeofday(&tv, NULL);
211 ts->tv_nsec = tv.tv_usec * 1000 + (ms % 1000) * 1000000;
212 ts->tv_sec = tv.tv_sec + ms / 1000;
213 if (ts->tv_nsec >= 1000000000) {
215 ts->tv_nsec -= 1000000000;
219 int qemu_sem_timedwait(QemuSemaphore *sem, int ms)
224 #if defined(__APPLE__) || defined(__NetBSD__)
226 compute_abs_deadline(&ts, ms);
227 pthread_mutex_lock(&sem->lock);
228 while (sem->count == 0) {
229 rc = pthread_cond_timedwait(&sem->cond, &sem->lock, &ts);
230 if (rc == ETIMEDOUT) {
234 error_exit(rc, __func__);
237 if (rc != ETIMEDOUT) {
240 pthread_mutex_unlock(&sem->lock);
241 return (rc == ETIMEDOUT ? -1 : 0);
244 /* This is cheaper than sem_timedwait. */
246 rc = sem_trywait(&sem->sem);
247 } while (rc == -1 && errno == EINTR);
248 if (rc == -1 && errno == EAGAIN) {
252 compute_abs_deadline(&ts, ms);
254 rc = sem_timedwait(&sem->sem, &ts);
255 } while (rc == -1 && errno == EINTR);
256 if (rc == -1 && errno == ETIMEDOUT) {
261 error_exit(errno, __func__);
267 void qemu_sem_wait(QemuSemaphore *sem)
271 #if defined(__APPLE__) || defined(__NetBSD__)
272 pthread_mutex_lock(&sem->lock);
273 while (sem->count == 0) {
274 rc = pthread_cond_wait(&sem->cond, &sem->lock);
276 error_exit(rc, __func__);
280 pthread_mutex_unlock(&sem->lock);
283 rc = sem_wait(&sem->sem);
284 } while (rc == -1 && errno == EINTR);
286 error_exit(errno, __func__);
292 #define futex(...) syscall(__NR_futex, __VA_ARGS__)
294 static inline void futex_wake(QemuEvent *ev, int n)
296 futex(ev, FUTEX_WAKE, n, NULL, NULL, 0);
299 static inline void futex_wait(QemuEvent *ev, unsigned val)
301 futex(ev, FUTEX_WAIT, (int) val, NULL, NULL, 0);
304 static inline void futex_wake(QemuEvent *ev, int n)
306 pthread_mutex_lock(&ev->lock);
308 pthread_cond_signal(&ev->cond);
310 pthread_cond_broadcast(&ev->cond);
312 pthread_mutex_unlock(&ev->lock);
315 static inline void futex_wait(QemuEvent *ev, unsigned val)
317 pthread_mutex_lock(&ev->lock);
318 if (ev->value == val) {
319 pthread_cond_wait(&ev->cond, &ev->lock);
321 pthread_mutex_unlock(&ev->lock);
325 /* Valid transitions:
326 * - free->set, when setting the event
327 * - busy->set, when setting the event, followed by futex_wake
328 * - set->free, when resetting the event
329 * - free->busy, when waiting
331 * set->busy does not happen (it can be observed from the outside but
332 * it really is set->free->busy).
334 * busy->free provably cannot happen; to enforce it, the set->free transition
335 * is done with an OR, which becomes a no-op if the event has concurrently
336 * transitioned to free or busy.
343 void qemu_event_init(QemuEvent *ev, bool init)
346 pthread_mutex_init(&ev->lock, NULL);
347 pthread_cond_init(&ev->cond, NULL);
350 ev->value = (init ? EV_SET : EV_FREE);
353 void qemu_event_destroy(QemuEvent *ev)
356 pthread_mutex_destroy(&ev->lock);
357 pthread_cond_destroy(&ev->cond);
361 void qemu_event_set(QemuEvent *ev)
363 if (atomic_mb_read(&ev->value) != EV_SET) {
364 if (atomic_xchg(&ev->value, EV_SET) == EV_BUSY) {
365 /* There were waiters, wake them up. */
366 futex_wake(ev, INT_MAX);
371 void qemu_event_reset(QemuEvent *ev)
373 if (atomic_mb_read(&ev->value) == EV_SET) {
375 * If there was a concurrent reset (or even reset+wait),
376 * do nothing. Otherwise change EV_SET->EV_FREE.
378 atomic_or(&ev->value, EV_FREE);
382 void qemu_event_wait(QemuEvent *ev)
386 value = atomic_mb_read(&ev->value);
387 if (value != EV_SET) {
388 if (value == EV_FREE) {
390 * Leave the event reset and tell qemu_event_set that there
391 * are waiters. No need to retry, because there cannot be
392 * a concurent busy->free transition. After the CAS, the
393 * event will be either set or busy.
395 if (atomic_cmpxchg(&ev->value, EV_FREE, EV_BUSY) == EV_SET) {
399 futex_wait(ev, EV_BUSY);
403 static pthread_key_t exit_key;
405 union NotifierThreadData {
409 QEMU_BUILD_BUG_ON(sizeof(union NotifierThreadData) != sizeof(void *));
411 void qemu_thread_atexit_add(Notifier *notifier)
413 union NotifierThreadData ntd;
414 ntd.ptr = pthread_getspecific(exit_key);
415 notifier_list_add(&ntd.list, notifier);
416 pthread_setspecific(exit_key, ntd.ptr);
419 void qemu_thread_atexit_remove(Notifier *notifier)
421 union NotifierThreadData ntd;
422 ntd.ptr = pthread_getspecific(exit_key);
423 notifier_remove(notifier);
424 pthread_setspecific(exit_key, ntd.ptr);
427 static void qemu_thread_atexit_run(void *arg)
429 union NotifierThreadData ntd = { .ptr = arg };
430 notifier_list_notify(&ntd.list, NULL);
433 static void __attribute__((constructor)) qemu_thread_atexit_init(void)
435 pthread_key_create(&exit_key, qemu_thread_atexit_run);
439 /* Attempt to set the threads name; note that this is for debug, so
440 * we're not going to fail if we can't set it.
442 static void qemu_thread_set_name(QemuThread *thread, const char *name)
444 #ifdef CONFIG_PTHREAD_SETNAME_NP
445 pthread_setname_np(thread->thread, name);
449 void qemu_thread_create(QemuThread *thread, const char *name,
450 void *(*start_routine)(void*),
453 sigset_t set, oldset;
457 err = pthread_attr_init(&attr);
459 error_exit(err, __func__);
461 if (mode == QEMU_THREAD_DETACHED) {
462 err = pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
464 error_exit(err, __func__);
468 /* Leave signal handling to the iothread. */
470 pthread_sigmask(SIG_SETMASK, &set, &oldset);
471 err = pthread_create(&thread->thread, &attr, start_routine, arg);
473 error_exit(err, __func__);
476 qemu_thread_set_name(thread, name);
479 pthread_sigmask(SIG_SETMASK, &oldset, NULL);
481 pthread_attr_destroy(&attr);
484 void qemu_thread_get_self(QemuThread *thread)
486 thread->thread = pthread_self();
489 bool qemu_thread_is_self(QemuThread *thread)
491 return pthread_equal(pthread_self(), thread->thread);
494 void qemu_thread_exit(void *retval)
496 pthread_exit(retval);
499 void *qemu_thread_join(QemuThread *thread)
504 err = pthread_join(thread->thread, &ret);
506 error_exit(err, __func__);