/*
* 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"
#include "qemu/thread.h"
#include "qemu/atomic.h"
#include "qemu/notify.h"
#include "qemu-thread-common.h"
#include "qemu/tsan.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();
}
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;
}
}
void qemu_mutex_init(QemuMutex *mutex)
{
int err;
err = pthread_mutex_init(&mutex->lock, NULL);
if (err)
error_exit(err, __func__);
qemu_mutex_post_init(mutex);
}
void qemu_mutex_destroy(QemuMutex *mutex)
{
int err;
assert(mutex->initialized);
mutex->initialized = false;
err = pthread_mutex_destroy(&mutex->lock);
if (err)
error_exit(err, __func__);
}
void qemu_mutex_lock_impl(QemuMutex *mutex, const char *file, const int line)
{
int err;
assert(mutex->initialized);
qemu_mutex_pre_lock(mutex, file, line);
err = pthread_mutex_lock(&mutex->lock);
if (err)
error_exit(err, __func__);
qemu_mutex_post_lock(mutex, file, line);
}
int qemu_mutex_trylock_impl(QemuMutex *mutex, const char *file, const int line)
{
int err;
assert(mutex->initialized);
err = pthread_mutex_trylock(&mutex->lock);
if (err == 0) {
qemu_mutex_post_lock(mutex, file, line);
return 0;
}
if (err != EBUSY) {
error_exit(err, __func__);
}
return -EBUSY;
}
void qemu_mutex_unlock_impl(QemuMutex *mutex, const char *file, const int line)
{
int err;
assert(mutex->initialized);
qemu_mutex_pre_unlock(mutex, file, line);
err = pthread_mutex_unlock(&mutex->lock);
if (err)
error_exit(err, __func__);
}
void qemu_rec_mutex_init(QemuRecMutex *mutex)
{
int err;
pthread_mutexattr_t attr;
pthread_mutexattr_init(&attr);
pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE);
err = pthread_mutex_init(&mutex->lock, &attr);
pthread_mutexattr_destroy(&attr);
if (err) {
error_exit(err, __func__);
}
mutex->initialized = true;
}
void qemu_cond_init(QemuCond *cond)
{
int err;
err = pthread_cond_init(&cond->cond, NULL);
if (err)
error_exit(err, __func__);
cond->initialized = true;
}
void qemu_cond_destroy(QemuCond *cond)
{
int err;
assert(cond->initialized);
cond->initialized = false;
err = pthread_cond_destroy(&cond->cond);
if (err)
error_exit(err, __func__);
}
void qemu_cond_signal(QemuCond *cond)
{
int err;
assert(cond->initialized);
err = pthread_cond_signal(&cond->cond);
if (err)
error_exit(err, __func__);
}
void qemu_cond_broadcast(QemuCond *cond)
{
int err;
assert(cond->initialized);
err = pthread_cond_broadcast(&cond->cond);
if (err)
error_exit(err, __func__);
}
void qemu_cond_wait_impl(QemuCond *cond, QemuMutex *mutex, const char *file, const int line)
{
int err;
assert(cond->initialized);
qemu_mutex_pre_unlock(mutex, file, line);
err = pthread_cond_wait(&cond->cond, &mutex->lock);
qemu_mutex_post_lock(mutex, file, line);
if (err)
error_exit(err, __func__);
}
bool qemu_cond_timedwait_impl(QemuCond *cond, QemuMutex *mutex, int ms,
const char *file, const int line)
{
int err;
struct timespec ts;
assert(cond->initialized);
trace_qemu_mutex_unlock(mutex, file, line);
compute_abs_deadline(&ts, ms);
err = pthread_cond_timedwait(&cond->cond, &mutex->lock, &ts);
trace_qemu_mutex_locked(mutex, file, line);
if (err && err != ETIMEDOUT) {
error_exit(err, __func__);
}
return err != ETIMEDOUT;
}
void qemu_sem_init(QemuSemaphore *sem, int init)
{
int rc;
#ifndef CONFIG_SEM_TIMEDWAIT
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
sem->initialized = true;
}
void qemu_sem_destroy(QemuSemaphore *sem)
{
int rc;
assert(sem->initialized);
sem->initialized = false;
#ifndef CONFIG_SEM_TIMEDWAIT
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;
assert(sem->initialized);
#ifndef CONFIG_SEM_TIMEDWAIT
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
}
int qemu_sem_timedwait(QemuSemaphore *sem, int ms)
{
int rc;
struct timespec ts;
assert(sem->initialized);
#ifndef CONFIG_SEM_TIMEDWAIT
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;
assert(sem->initialized);
#ifndef CONFIG_SEM_TIMEDWAIT
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__
#include "qemu/futex.h"
#else
static inline void qemu_futex_wake(QemuEvent *ev, int n)
{
assert(ev->initialized);
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 qemu_futex_wait(QemuEvent *ev, unsigned val)
{
assert(ev->initialized);
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 qemu_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);
ev->initialized = true;
}
void qemu_event_destroy(QemuEvent *ev)
{
assert(ev->initialized);
ev->initialized = false;
#ifndef __linux__
pthread_mutex_destroy(&ev->lock);
pthread_cond_destroy(&ev->cond);
#endif
}
void qemu_event_set(QemuEvent *ev)
{
/* qemu_event_set has release semantics, but because it *loads*
* ev->value we need a full memory barrier here.
*/
assert(ev->initialized);
smp_mb();
if (qatomic_read(&ev->value) != EV_SET) {
if (qatomic_xchg(&ev->value, EV_SET) == EV_BUSY) {
/* There were waiters, wake them up. */
qemu_futex_wake(ev, INT_MAX);
}
}
}
void qemu_event_reset(QemuEvent *ev)
{
unsigned value;
assert(ev->initialized);
value = qatomic_read(&ev->value);
smp_mb_acquire();
if (value == EV_SET) {
/*
* If there was a concurrent reset (or even reset+wait),
* do nothing. Otherwise change EV_SET->EV_FREE.
*/
qatomic_or(&ev->value, EV_FREE);
}
}
void qemu_event_wait(QemuEvent *ev)
{
unsigned value;
assert(ev->initialized);
value = qatomic_read(&ev->value);
smp_mb_acquire();
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 (qatomic_cmpxchg(&ev->value, EV_FREE, EV_BUSY) == EV_SET) {
return;
}
}
qemu_futex_wait(ev, EV_BUSY);
}
}
static __thread NotifierList thread_exit;
/*
* Note that in this implementation you can register a thread-exit
* notifier for the main thread, but it will never be called.
* This is OK because main thread exit can only happen when the
* entire process is exiting, and the API allows notifiers to not
* be called on process exit.
*/
void qemu_thread_atexit_add(Notifier *notifier)
{
notifier_list_add(&thread_exit, notifier);
}
void qemu_thread_atexit_remove(Notifier *notifier)
{
notifier_remove(notifier);
}
static void qemu_thread_atexit_notify(void *arg)
{
/*
* Called when non-main thread exits (via qemu_thread_exit()
* or by returning from its start routine.)
*/
notifier_list_notify(&thread_exit, NULL);
}
typedef struct {
void *(*start_routine)(void *);
void *arg;
char *name;
} QemuThreadArgs;
static void *qemu_thread_start(void *args)
{
QemuThreadArgs *qemu_thread_args = args;
void *(*start_routine)(void *) = qemu_thread_args->start_routine;
void *arg = qemu_thread_args->arg;
void *r;
#ifdef CONFIG_THREAD_SETNAME_BYTHREAD
/* 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.
*/
if (name_threads && qemu_thread_args->name) {
# if defined(CONFIG_PTHREAD_SETNAME_NP_W_TID)
pthread_setname_np(pthread_self(), qemu_thread_args->name);
# elif defined(CONFIG_PTHREAD_SETNAME_NP_WO_TID)
pthread_setname_np(qemu_thread_args->name);
# endif
}
#endif
QEMU_TSAN_ANNOTATE_THREAD_NAME(qemu_thread_args->name);
g_free(qemu_thread_args->name);
g_free(qemu_thread_args);
pthread_cleanup_push(qemu_thread_atexit_notify, NULL);
r = start_routine(arg);
pthread_cleanup_pop(1);
return r;
}
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;
QemuThreadArgs *qemu_thread_args;
err = pthread_attr_init(&attr);
if (err) {
error_exit(err, __func__);
}
if (mode == QEMU_THREAD_DETACHED) {
pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);
}
/* Leave signal handling to the iothread. */
sigfillset(&set);
/* Blocking the signals can result in undefined behaviour. */
sigdelset(&set, SIGSEGV);
sigdelset(&set, SIGFPE);
sigdelset(&set, SIGILL);
/* TODO avoid SIGBUS loss on macOS */
pthread_sigmask(SIG_SETMASK, &set, &oldset);
qemu_thread_args = g_new0(QemuThreadArgs, 1);
qemu_thread_args->name = g_strdup(name);
qemu_thread_args->start_routine = start_routine;
qemu_thread_args->arg = arg;
err = pthread_create(&thread->thread, &attr,
qemu_thread_start, qemu_thread_args);
if (err)
error_exit(err, __func__);
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;
}
