/* * Wrappers around mutex/cond/thread functions * * Copyright Red Hat, Inc. 2009 * * Author: * Marcelo Tosatti <mtosatti@redhat.com> * * This work is licensed under the terms of the GNU GPL, version 2 or later. * See the COPYING file in the top-level directory. * */ #include "qemu/osdep.h" #ifdef __linux__ #include <sys/syscall.h> #include <linux/futex.h> #endif #include "qemu/thread.h" #include "qemu/atomic.h" #include "qemu/notify.h" static bool name_threads; void qemu_thread_naming(bool enable) { name_threads = enable; #ifndef CONFIG_THREAD_SETNAME_BYTHREAD /* This is a debugging option, not fatal */ if (enable) { fprintf(stderr, "qemu: thread naming not supported on this host\n"); } #endif } static void error_exit(int err, const char *msg) { fprintf(stderr, "qemu: %s: %s\n", msg, strerror(err)); abort(); } void qemu_mutex_init(QemuMutex *mutex) { int err; err = pthread_mutex_init(&mutex->lock, NULL); if (err) error_exit(err, __func__); } void qemu_mutex_destroy(QemuMutex *mutex) { int err; err = pthread_mutex_destroy(&mutex->lock); if (err) error_exit(err, __func__); } void qemu_mutex_lock(QemuMutex *mutex) { int err; err = pthread_mutex_lock(&mutex->lock); if (err) error_exit(err, __func__); } int qemu_mutex_trylock(QemuMutex *mutex) { return pthread_mutex_trylock(&mutex->lock); } void qemu_mutex_unlock(QemuMutex *mutex) { int err; err = pthread_mutex_unlock(&mutex->lock); if (err) error_exit(err, __func__); } void qemu_cond_init(QemuCond *cond) { int err; err = pthread_cond_init(&cond->cond, NULL); if (err) error_exit(err, __func__); } void qemu_cond_destroy(QemuCond *cond) { int err; err = pthread_cond_destroy(&cond->cond); if (err) error_exit(err, __func__); } void qemu_cond_signal(QemuCond *cond) { int err; err = pthread_cond_signal(&cond->cond); if (err) error_exit(err, __func__); } void qemu_cond_broadcast(QemuCond *cond) { int err; err = pthread_cond_broadcast(&cond->cond); if (err) error_exit(err, __func__); } void qemu_cond_wait(QemuCond *cond, QemuMutex *mutex) { int err; err = pthread_cond_wait(&cond->cond, &mutex->lock); if (err) error_exit(err, __func__); } void qemu_sem_init(QemuSemaphore *sem, int init) { int rc; #if defined(__APPLE__) || defined(__NetBSD__) rc = pthread_mutex_init(&sem->lock, NULL); if (rc != 0) { error_exit(rc, __func__); } rc = pthread_cond_init(&sem->cond, NULL); if (rc != 0) { error_exit(rc, __func__); } if (init < 0) { error_exit(EINVAL, __func__); } sem->count = init; #else rc = sem_init(&sem->sem, 0, init); if (rc < 0) { error_exit(errno, __func__); } #endif } void qemu_sem_destroy(QemuSemaphore *sem) { int rc; #if defined(__APPLE__) || defined(__NetBSD__) rc = pthread_cond_destroy(&sem->cond); if (rc < 0) { error_exit(rc, __func__); } rc = pthread_mutex_destroy(&sem->lock); if (rc < 0) { error_exit(rc, __func__); } #else rc = sem_destroy(&sem->sem); if (rc < 0) { error_exit(errno, __func__); } #endif } void qemu_sem_post(QemuSemaphore *sem) { int rc; #if defined(__APPLE__) || defined(__NetBSD__) pthread_mutex_lock(&sem->lock); if (sem->count == UINT_MAX) { rc = EINVAL; } else { sem->count++; rc = pthread_cond_signal(&sem->cond); } pthread_mutex_unlock(&sem->lock); if (rc != 0) { error_exit(rc, __func__); } #else rc = sem_post(&sem->sem); if (rc < 0) { error_exit(errno, __func__); } #endif } static void compute_abs_deadline(struct timespec *ts, int ms) { struct timeval tv; gettimeofday(&tv, NULL); ts->tv_nsec = tv.tv_usec * 1000 + (ms % 1000) * 1000000; ts->tv_sec = tv.tv_sec + ms / 1000; if (ts->tv_nsec >= 1000000000) { ts->tv_sec++; ts->tv_nsec -= 1000000000; } } int qemu_sem_timedwait(QemuSemaphore *sem, int ms) { int rc; struct timespec ts; #if defined(__APPLE__) || defined(__NetBSD__) rc = 0; compute_abs_deadline(&ts, ms); pthread_mutex_lock(&sem->lock); while (sem->count == 0) { rc = pthread_cond_timedwait(&sem->cond, &sem->lock, &ts); if (rc == ETIMEDOUT) { break; } if (rc != 0) { error_exit(rc, __func__); } } if (rc != ETIMEDOUT) { --sem->count; } pthread_mutex_unlock(&sem->lock); return (rc == ETIMEDOUT ? -1 : 0); #else if (ms <= 0) { /* This is cheaper than sem_timedwait. */ do { rc = sem_trywait(&sem->sem); } while (rc == -1 && errno == EINTR); if (rc == -1 && errno == EAGAIN) { return -1; } } else { compute_abs_deadline(&ts, ms); do { rc = sem_timedwait(&sem->sem, &ts); } while (rc == -1 && errno == EINTR); if (rc == -1 && errno == ETIMEDOUT) { return -1; } } if (rc < 0) { error_exit(errno, __func__); } return 0; #endif } void qemu_sem_wait(QemuSemaphore *sem) { int rc; #if defined(__APPLE__) || defined(__NetBSD__) pthread_mutex_lock(&sem->lock); while (sem->count == 0) { rc = pthread_cond_wait(&sem->cond, &sem->lock); if (rc != 0) { error_exit(rc, __func__); } } --sem->count; pthread_mutex_unlock(&sem->lock); #else do { rc = sem_wait(&sem->sem); } while (rc == -1 && errno == EINTR); if (rc < 0) { error_exit(errno, __func__); } #endif } #ifdef __linux__ #define futex(...) syscall(__NR_futex, __VA_ARGS__) static inline void futex_wake(QemuEvent *ev, int n) { futex(ev, FUTEX_WAKE, n, NULL, NULL, 0); } static inline void futex_wait(QemuEvent *ev, unsigned val) { while (futex(ev, FUTEX_WAIT, (int) val, NULL, NULL, 0)) { switch (errno) { case EWOULDBLOCK: return; case EINTR: break; /* get out of switch and retry */ default: abort(); } } } #else static inline void futex_wake(QemuEvent *ev, int n) { pthread_mutex_lock(&ev->lock); if (n == 1) { pthread_cond_signal(&ev->cond); } else { pthread_cond_broadcast(&ev->cond); } pthread_mutex_unlock(&ev->lock); } static inline void futex_wait(QemuEvent *ev, unsigned val) { pthread_mutex_lock(&ev->lock); if (ev->value == val) { pthread_cond_wait(&ev->cond, &ev->lock); } pthread_mutex_unlock(&ev->lock); } #endif /* Valid transitions: * - free->set, when setting the event * - busy->set, when setting the event, followed by futex_wake * - set->free, when resetting the event * - free->busy, when waiting * * set->busy does not happen (it can be observed from the outside but * it really is set->free->busy). * * busy->free provably cannot happen; to enforce it, the set->free transition * is done with an OR, which becomes a no-op if the event has concurrently * transitioned to free or busy. */ #define EV_SET 0 #define EV_FREE 1 #define EV_BUSY -1 void qemu_event_init(QemuEvent *ev, bool init) { #ifndef __linux__ pthread_mutex_init(&ev->lock, NULL); pthread_cond_init(&ev->cond, NULL); #endif ev->value = (init ? EV_SET : EV_FREE); } void qemu_event_destroy(QemuEvent *ev) { #ifndef __linux__ pthread_mutex_destroy(&ev->lock); pthread_cond_destroy(&ev->cond); #endif } void qemu_event_set(QemuEvent *ev) { if (atomic_mb_read(&ev->value) != EV_SET) { if (atomic_xchg(&ev->value, EV_SET) == EV_BUSY) { /* There were waiters, wake them up. */ futex_wake(ev, INT_MAX); } } } void qemu_event_reset(QemuEvent *ev) { if (atomic_mb_read(&ev->value) == EV_SET) { /* * If there was a concurrent reset (or even reset+wait), * do nothing. Otherwise change EV_SET->EV_FREE. */ atomic_or(&ev->value, EV_FREE); } } void qemu_event_wait(QemuEvent *ev) { unsigned value; value = atomic_mb_read(&ev->value); if (value != EV_SET) { if (value == EV_FREE) { /* * Leave the event reset and tell qemu_event_set that there * are waiters. No need to retry, because there cannot be * a concurrent busy->free transition. After the CAS, the * event will be either set or busy. */ if (atomic_cmpxchg(&ev->value, EV_FREE, EV_BUSY) == EV_SET) { return; } } futex_wait(ev, EV_BUSY); } } static pthread_key_t exit_key; union NotifierThreadData { void *ptr; NotifierList list; }; QEMU_BUILD_BUG_ON(sizeof(union NotifierThreadData) != sizeof(void *)); void qemu_thread_atexit_add(Notifier *notifier) { union NotifierThreadData ntd; ntd.ptr = pthread_getspecific(exit_key); notifier_list_add(&ntd.list, notifier); pthread_setspecific(exit_key, ntd.ptr); } void qemu_thread_atexit_remove(Notifier *notifier) { union NotifierThreadData ntd; ntd.ptr = pthread_getspecific(exit_key); notifier_remove(notifier); pthread_setspecific(exit_key, ntd.ptr); } static void qemu_thread_atexit_run(void *arg) { union NotifierThreadData ntd = { .ptr = arg }; notifier_list_notify(&ntd.list, NULL); } static void __attribute__((constructor)) qemu_thread_atexit_init(void) { pthread_key_create(&exit_key, qemu_thread_atexit_run); } /* Attempt to set the threads name; note that this is for debug, so * we're not going to fail if we can't set it. */ static void qemu_thread_set_name(QemuThread *thread, const char *name) { #ifdef CONFIG_PTHREAD_SETNAME_NP pthread_setname_np(thread->thread, name); #endif } void qemu_thread_create(QemuThread *thread, const char *name, void *(*start_routine)(void*), void *arg, int mode) { sigset_t set, oldset; int err; pthread_attr_t attr; err = pthread_attr_init(&attr); if (err) { error_exit(err, __func__); } if (mode == QEMU_THREAD_DETACHED) { err = pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED); if (err) { error_exit(err, __func__); } } /* Leave signal handling to the iothread. */ sigfillset(&set); pthread_sigmask(SIG_SETMASK, &set, &oldset); err = pthread_create(&thread->thread, &attr, start_routine, arg); if (err) error_exit(err, __func__); if (name_threads) { qemu_thread_set_name(thread, name); } pthread_sigmask(SIG_SETMASK, &oldset, NULL); pthread_attr_destroy(&attr); } void qemu_thread_get_self(QemuThread *thread) { thread->thread = pthread_self(); } bool qemu_thread_is_self(QemuThread *thread) { return pthread_equal(pthread_self(), thread->thread); } void qemu_thread_exit(void *retval) { pthread_exit(retval); } void *qemu_thread_join(QemuThread *thread) { int err; void *ret; err = pthread_join(thread->thread, &ret); if (err) { error_exit(err, __func__); } return ret; }