#include <limits.h>
#include <unistd.h>
#include <sys/time.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)
{
void qemu_mutex_init(QemuMutex *mutex)
{
int err;
- pthread_mutexattr_t mutexattr;
- pthread_mutexattr_init(&mutexattr);
- pthread_mutexattr_settype(&mutexattr, PTHREAD_MUTEX_ERRORCHECK);
- err = pthread_mutex_init(&mutex->lock, &mutexattr);
- pthread_mutexattr_destroy(&mutexattr);
+ err = pthread_mutex_init(&mutex->lock, NULL);
if (err)
error_exit(err, __func__);
}
#if defined(__APPLE__) || defined(__NetBSD__)
pthread_mutex_lock(&sem->lock);
- if (sem->count == INT_MAX) {
+ if (sem->count == UINT_MAX) {
rc = EINVAL;
- } else if (sem->count++ < 0) {
- rc = pthread_cond_signal(&sem->cond);
} else {
- rc = 0;
+ sem->count++;
+ rc = pthread_cond_signal(&sem->cond);
}
pthread_mutex_unlock(&sem->lock);
if (rc != 0) {
struct timespec ts;
#if defined(__APPLE__) || defined(__NetBSD__)
+ rc = 0;
compute_abs_deadline(&ts, ms);
pthread_mutex_lock(&sem->lock);
- --sem->count;
- while (sem->count < 0) {
+ while (sem->count == 0) {
rc = pthread_cond_timedwait(&sem->cond, &sem->lock, &ts);
if (rc == ETIMEDOUT) {
- ++sem->count;
break;
}
if (rc != 0) {
error_exit(rc, __func__);
}
}
+ if (rc != ETIMEDOUT) {
+ --sem->count;
+ }
pthread_mutex_unlock(&sem->lock);
return (rc == ETIMEDOUT ? -1 : 0);
#else
void qemu_sem_wait(QemuSemaphore *sem)
{
+ int rc;
+
#if defined(__APPLE__) || defined(__NetBSD__)
pthread_mutex_lock(&sem->lock);
- --sem->count;
- while (sem->count < 0) {
- pthread_cond_wait(&sem->cond, &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
- int rc;
-
do {
rc = sem_wait(&sem->sem);
} while (rc == -1 && errno == EINTR);
#endif
}
-void qemu_thread_create(QemuThread *thread,
+#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)
{
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);
projects / qemu.git / blobdiff