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.
13 #include "qemu/osdep.h"
14 #include "qemu/thread.h"
15 #include "qemu/atomic.h"
16 #include "qemu/notify.h"
17 #include "qemu-thread-common.h"
18 #include "qemu/tsan.h"
19 #include "qemu/bitmap.h"
21 #ifdef CONFIG_PTHREAD_SET_NAME_NP
22 #include <pthread_np.h>
25 static bool name_threads;
27 void qemu_thread_naming(bool enable)
29 name_threads = enable;
31 #if !defined CONFIG_PTHREAD_SETNAME_NP_W_TID && \
32 !defined CONFIG_PTHREAD_SETNAME_NP_WO_TID && \
33 !defined CONFIG_PTHREAD_SET_NAME_NP
34 /* This is a debugging option, not fatal */
36 fprintf(stderr, "qemu: thread naming not supported on this host\n");
41 static void error_exit(int err, const char *msg)
43 fprintf(stderr, "qemu: %s: %s\n", msg, strerror(err));
47 static inline clockid_t qemu_timedwait_clockid(void)
49 #ifdef CONFIG_PTHREAD_CONDATTR_SETCLOCK
50 return CLOCK_MONOTONIC;
52 return CLOCK_REALTIME;
56 static void compute_abs_deadline(struct timespec *ts, int ms)
58 clock_gettime(qemu_timedwait_clockid(), ts);
59 ts->tv_nsec += (ms % 1000) * 1000000;
60 ts->tv_sec += ms / 1000;
61 if (ts->tv_nsec >= 1000000000) {
63 ts->tv_nsec -= 1000000000;
67 void qemu_mutex_init(QemuMutex *mutex)
71 err = pthread_mutex_init(&mutex->lock, NULL);
73 error_exit(err, __func__);
74 qemu_mutex_post_init(mutex);
77 void qemu_mutex_destroy(QemuMutex *mutex)
81 assert(mutex->initialized);
82 mutex->initialized = false;
83 err = pthread_mutex_destroy(&mutex->lock);
85 error_exit(err, __func__);
88 void qemu_mutex_lock_impl(QemuMutex *mutex, const char *file, const int line)
92 assert(mutex->initialized);
93 qemu_mutex_pre_lock(mutex, file, line);
94 err = pthread_mutex_lock(&mutex->lock);
96 error_exit(err, __func__);
97 qemu_mutex_post_lock(mutex, file, line);
100 int qemu_mutex_trylock_impl(QemuMutex *mutex, const char *file, const int line)
104 assert(mutex->initialized);
105 err = pthread_mutex_trylock(&mutex->lock);
107 qemu_mutex_post_lock(mutex, file, line);
111 error_exit(err, __func__);
116 void qemu_mutex_unlock_impl(QemuMutex *mutex, const char *file, const int line)
120 assert(mutex->initialized);
121 qemu_mutex_pre_unlock(mutex, file, line);
122 err = pthread_mutex_unlock(&mutex->lock);
124 error_exit(err, __func__);
127 void qemu_rec_mutex_init(QemuRecMutex *mutex)
130 pthread_mutexattr_t attr;
132 pthread_mutexattr_init(&attr);
133 pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
134 err = pthread_mutex_init(&mutex->m.lock, &attr);
135 pthread_mutexattr_destroy(&attr);
137 error_exit(err, __func__);
139 mutex->m.initialized = true;
142 void qemu_rec_mutex_destroy(QemuRecMutex *mutex)
144 qemu_mutex_destroy(&mutex->m);
147 void qemu_rec_mutex_lock_impl(QemuRecMutex *mutex, const char *file, int line)
149 qemu_mutex_lock_impl(&mutex->m, file, line);
152 int qemu_rec_mutex_trylock_impl(QemuRecMutex *mutex, const char *file, int line)
154 return qemu_mutex_trylock_impl(&mutex->m, file, line);
157 void qemu_rec_mutex_unlock_impl(QemuRecMutex *mutex, const char *file, int line)
159 qemu_mutex_unlock_impl(&mutex->m, file, line);
162 void qemu_cond_init(QemuCond *cond)
164 pthread_condattr_t attr;
167 err = pthread_condattr_init(&attr);
169 error_exit(err, __func__);
171 #ifdef CONFIG_PTHREAD_CONDATTR_SETCLOCK
172 err = pthread_condattr_setclock(&attr, qemu_timedwait_clockid());
174 error_exit(err, __func__);
177 err = pthread_cond_init(&cond->cond, &attr);
179 error_exit(err, __func__);
181 err = pthread_condattr_destroy(&attr);
183 error_exit(err, __func__);
185 cond->initialized = true;
188 void qemu_cond_destroy(QemuCond *cond)
192 assert(cond->initialized);
193 cond->initialized = false;
194 err = pthread_cond_destroy(&cond->cond);
196 error_exit(err, __func__);
199 void qemu_cond_signal(QemuCond *cond)
203 assert(cond->initialized);
204 err = pthread_cond_signal(&cond->cond);
206 error_exit(err, __func__);
209 void qemu_cond_broadcast(QemuCond *cond)
213 assert(cond->initialized);
214 err = pthread_cond_broadcast(&cond->cond);
216 error_exit(err, __func__);
219 void qemu_cond_wait_impl(QemuCond *cond, QemuMutex *mutex, const char *file, const int line)
223 assert(cond->initialized);
224 qemu_mutex_pre_unlock(mutex, file, line);
225 err = pthread_cond_wait(&cond->cond, &mutex->lock);
226 qemu_mutex_post_lock(mutex, file, line);
228 error_exit(err, __func__);
231 static bool TSA_NO_TSA
232 qemu_cond_timedwait_ts(QemuCond *cond, QemuMutex *mutex, struct timespec *ts,
233 const char *file, const int line)
237 assert(cond->initialized);
238 trace_qemu_mutex_unlock(mutex, file, line);
239 err = pthread_cond_timedwait(&cond->cond, &mutex->lock, ts);
240 trace_qemu_mutex_locked(mutex, file, line);
241 if (err && err != ETIMEDOUT) {
242 error_exit(err, __func__);
244 return err != ETIMEDOUT;
247 bool qemu_cond_timedwait_impl(QemuCond *cond, QemuMutex *mutex, int ms,
248 const char *file, const int line)
252 compute_abs_deadline(&ts, ms);
253 return qemu_cond_timedwait_ts(cond, mutex, &ts, file, line);
256 void qemu_sem_init(QemuSemaphore *sem, int init)
258 qemu_mutex_init(&sem->mutex);
259 qemu_cond_init(&sem->cond);
262 error_exit(EINVAL, __func__);
267 void qemu_sem_destroy(QemuSemaphore *sem)
269 qemu_cond_destroy(&sem->cond);
270 qemu_mutex_destroy(&sem->mutex);
273 void qemu_sem_post(QemuSemaphore *sem)
275 qemu_mutex_lock(&sem->mutex);
276 if (sem->count == UINT_MAX) {
277 error_exit(EINVAL, __func__);
280 qemu_cond_signal(&sem->cond);
282 qemu_mutex_unlock(&sem->mutex);
285 int qemu_sem_timedwait(QemuSemaphore *sem, int ms)
290 compute_abs_deadline(&ts, ms);
291 qemu_mutex_lock(&sem->mutex);
292 while (sem->count == 0) {
296 rc = qemu_cond_timedwait_ts(&sem->cond, &sem->mutex, &ts,
299 if (!rc) { /* timeout */
306 qemu_mutex_unlock(&sem->mutex);
307 return (rc ? 0 : -1);
310 void qemu_sem_wait(QemuSemaphore *sem)
312 qemu_mutex_lock(&sem->mutex);
313 while (sem->count == 0) {
314 qemu_cond_wait(&sem->cond, &sem->mutex);
317 qemu_mutex_unlock(&sem->mutex);
321 #include "qemu/futex.h"
323 static inline void qemu_futex_wake(QemuEvent *ev, int n)
325 assert(ev->initialized);
326 pthread_mutex_lock(&ev->lock);
328 pthread_cond_signal(&ev->cond);
330 pthread_cond_broadcast(&ev->cond);
332 pthread_mutex_unlock(&ev->lock);
335 static inline void qemu_futex_wait(QemuEvent *ev, unsigned val)
337 assert(ev->initialized);
338 pthread_mutex_lock(&ev->lock);
339 if (ev->value == val) {
340 pthread_cond_wait(&ev->cond, &ev->lock);
342 pthread_mutex_unlock(&ev->lock);
346 /* Valid transitions:
347 * - free->set, when setting the event
348 * - busy->set, when setting the event, followed by qemu_futex_wake
349 * - set->free, when resetting the event
350 * - free->busy, when waiting
352 * set->busy does not happen (it can be observed from the outside but
353 * it really is set->free->busy).
355 * busy->free provably cannot happen; to enforce it, the set->free transition
356 * is done with an OR, which becomes a no-op if the event has concurrently
357 * transitioned to free or busy.
364 void qemu_event_init(QemuEvent *ev, bool init)
367 pthread_mutex_init(&ev->lock, NULL);
368 pthread_cond_init(&ev->cond, NULL);
371 ev->value = (init ? EV_SET : EV_FREE);
372 ev->initialized = true;
375 void qemu_event_destroy(QemuEvent *ev)
377 assert(ev->initialized);
378 ev->initialized = false;
380 pthread_mutex_destroy(&ev->lock);
381 pthread_cond_destroy(&ev->cond);
385 void qemu_event_set(QemuEvent *ev)
387 assert(ev->initialized);
390 * Pairs with both qemu_event_reset() and qemu_event_wait().
392 * qemu_event_set has release semantics, but because it *loads*
393 * ev->value we need a full memory barrier here.
396 if (qatomic_read(&ev->value) != EV_SET) {
397 int old = qatomic_xchg(&ev->value, EV_SET);
399 /* Pairs with memory barrier in kernel futex_wait system call. */
401 if (old == EV_BUSY) {
402 /* There were waiters, wake them up. */
403 qemu_futex_wake(ev, INT_MAX);
408 void qemu_event_reset(QemuEvent *ev)
410 assert(ev->initialized);
413 * If there was a concurrent reset (or even reset+wait),
414 * do nothing. Otherwise change EV_SET->EV_FREE.
416 qatomic_or(&ev->value, EV_FREE);
419 * Order reset before checking the condition in the caller.
420 * Pairs with the first memory barrier in qemu_event_set().
425 void qemu_event_wait(QemuEvent *ev)
429 assert(ev->initialized);
432 * qemu_event_wait must synchronize with qemu_event_set even if it does
433 * not go down the slow path, so this load-acquire is needed that
434 * synchronizes with the first memory barrier in qemu_event_set().
436 * If we do go down the slow path, there is no requirement at all: we
437 * might miss a qemu_event_set() here but ultimately the memory barrier in
438 * qemu_futex_wait() will ensure the check is done correctly.
440 value = qatomic_load_acquire(&ev->value);
441 if (value != EV_SET) {
442 if (value == EV_FREE) {
444 * Leave the event reset and tell qemu_event_set that there are
445 * waiters. No need to retry, because there cannot be a concurrent
446 * busy->free transition. After the CAS, the event will be either
449 * This cmpxchg doesn't have particular ordering requirements if it
450 * succeeds (moving the store earlier can only cause qemu_event_set()
451 * to issue _more_ wakeups), the failing case needs acquire semantics
452 * like the load above.
454 if (qatomic_cmpxchg(&ev->value, EV_FREE, EV_BUSY) == EV_SET) {
460 * This is the final check for a concurrent set, so it does need
461 * a smp_mb() pairing with the second barrier of qemu_event_set().
462 * The barrier is inside the FUTEX_WAIT system call.
464 qemu_futex_wait(ev, EV_BUSY);
468 static __thread NotifierList thread_exit;
471 * Note that in this implementation you can register a thread-exit
472 * notifier for the main thread, but it will never be called.
473 * This is OK because main thread exit can only happen when the
474 * entire process is exiting, and the API allows notifiers to not
475 * be called on process exit.
477 void qemu_thread_atexit_add(Notifier *notifier)
479 notifier_list_add(&thread_exit, notifier);
482 void qemu_thread_atexit_remove(Notifier *notifier)
484 notifier_remove(notifier);
487 static void qemu_thread_atexit_notify(void *arg)
490 * Called when non-main thread exits (via qemu_thread_exit()
491 * or by returning from its start routine.)
493 notifier_list_notify(&thread_exit, NULL);
497 void *(*start_routine)(void *);
502 static void *qemu_thread_start(void *args)
504 QemuThreadArgs *qemu_thread_args = args;
505 void *(*start_routine)(void *) = qemu_thread_args->start_routine;
506 void *arg = qemu_thread_args->arg;
509 /* Attempt to set the threads name; note that this is for debug, so
510 * we're not going to fail if we can't set it.
512 if (name_threads && qemu_thread_args->name) {
513 # if defined(CONFIG_PTHREAD_SETNAME_NP_W_TID)
514 pthread_setname_np(pthread_self(), qemu_thread_args->name);
515 # elif defined(CONFIG_PTHREAD_SETNAME_NP_WO_TID)
516 pthread_setname_np(qemu_thread_args->name);
517 # elif defined(CONFIG_PTHREAD_SET_NAME_NP)
518 pthread_set_name_np(pthread_self(), qemu_thread_args->name);
521 QEMU_TSAN_ANNOTATE_THREAD_NAME(qemu_thread_args->name);
522 g_free(qemu_thread_args->name);
523 g_free(qemu_thread_args);
526 * GCC 11 with glibc 2.17 on PowerPC reports
528 * qemu-thread-posix.c:540:5: error: ‘__sigsetjmp’ accessing 656 bytes
529 * in a region of size 528 [-Werror=stringop-overflow=]
530 * 540 | pthread_cleanup_push(qemu_thread_atexit_notify, NULL);
531 * | ^~~~~~~~~~~~~~~~~~~~
533 * which is clearly nonsense.
535 #pragma GCC diagnostic push
537 #pragma GCC diagnostic ignored "-Wstringop-overflow"
540 pthread_cleanup_push(qemu_thread_atexit_notify, NULL);
541 r = start_routine(arg);
542 pthread_cleanup_pop(1);
544 #pragma GCC diagnostic pop
549 void qemu_thread_create(QemuThread *thread, const char *name,
550 void *(*start_routine)(void*),
553 sigset_t set, oldset;
556 QemuThreadArgs *qemu_thread_args;
558 err = pthread_attr_init(&attr);
560 error_exit(err, __func__);
563 if (mode == QEMU_THREAD_DETACHED) {
564 pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
567 /* Leave signal handling to the iothread. */
569 /* Blocking the signals can result in undefined behaviour. */
570 sigdelset(&set, SIGSEGV);
571 sigdelset(&set, SIGFPE);
572 sigdelset(&set, SIGILL);
573 /* TODO avoid SIGBUS loss on macOS */
574 pthread_sigmask(SIG_SETMASK, &set, &oldset);
576 qemu_thread_args = g_new0(QemuThreadArgs, 1);
577 qemu_thread_args->name = g_strdup(name);
578 qemu_thread_args->start_routine = start_routine;
579 qemu_thread_args->arg = arg;
581 err = pthread_create(&thread->thread, &attr,
582 qemu_thread_start, qemu_thread_args);
585 error_exit(err, __func__);
587 pthread_sigmask(SIG_SETMASK, &oldset, NULL);
589 pthread_attr_destroy(&attr);
592 int qemu_thread_set_affinity(QemuThread *thread, unsigned long *host_cpus,
595 #if defined(CONFIG_PTHREAD_AFFINITY_NP)
596 const size_t setsize = CPU_ALLOC_SIZE(nbits);
601 cpuset = CPU_ALLOC(nbits);
604 CPU_ZERO_S(setsize, cpuset);
605 value = find_first_bit(host_cpus, nbits);
606 while (value < nbits) {
607 CPU_SET_S(value, setsize, cpuset);
608 value = find_next_bit(host_cpus, nbits, value + 1);
611 err = pthread_setaffinity_np(thread->thread, setsize, cpuset);
619 int qemu_thread_get_affinity(QemuThread *thread, unsigned long **host_cpus,
620 unsigned long *nbits)
622 #if defined(CONFIG_PTHREAD_AFFINITY_NP)
623 unsigned long tmpbits;
628 tmpbits = CPU_SETSIZE;
630 setsize = CPU_ALLOC_SIZE(tmpbits);
631 cpuset = CPU_ALLOC(tmpbits);
634 err = pthread_getaffinity_np(thread->thread, setsize, cpuset);
637 if (err != -EINVAL) {
646 /* Convert the result into a proper bitmap. */
648 *host_cpus = bitmap_new(tmpbits);
649 for (i = 0; i < tmpbits; i++) {
650 if (CPU_ISSET(i, cpuset)) {
651 set_bit(i, *host_cpus);
661 void qemu_thread_get_self(QemuThread *thread)
663 thread->thread = pthread_self();
666 bool qemu_thread_is_self(QemuThread *thread)
668 return pthread_equal(pthread_self(), thread->thread);
671 void qemu_thread_exit(void *retval)
673 pthread_exit(retval);
676 void *qemu_thread_join(QemuThread *thread)
681 err = pthread_join(thread->thread, &ret);
683 error_exit(err, __func__);