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Further decreases unexpected context switches by defering mutex wakeup
until internal sleep queue lock is released.
This commit is contained in:
davidxu 2012-08-11 23:17:02 +00:00
parent decb55dbb5
commit 72ce06de36
5 changed files with 38 additions and 24 deletions
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15
lib/libthr/thread/thr_cond.c
View File

@ -217,6 +217,7 @@ cond_wait_user(struct pthread_cond *cvp, struct pthread_mutex *mp,
struct sleepqueue *sq;
int recurse;
int error;
int defered;
if (curthread->wchan != NULL)
PANIC("thread was already on queue.");
@ -230,13 +231,23 @@ cond_wait_user(struct pthread_cond *cvp, struct pthread_mutex *mp,
* us to check it without locking in pthread_cond_signal().
*/
cvp->__has_user_waiters = 1;
curthread->will_sleep = 1;
(void)_mutex_cv_unlock(mp, &recurse);
defered = 0;
(void)_mutex_cv_unlock(mp, &recurse, &defered);
curthread->mutex_obj = mp;
_sleepq_add(cvp, curthread);
for(;;) {
_thr_clear_wake(curthread);
_sleepq_unlock(cvp);
if (defered) {
if ((mp->m_lock.m_owner & UMUTEX_CONTESTED) == 0)
(void)_umtx_op_err(&mp->m_lock, UMTX_OP_MUTEX_WAKE2,
mp->m_lock.m_flags, 0, 0);
}
if (curthread->nwaiter_defer > 0) {
_thr_wake_all(curthread->defer_waiters,
curthread->nwaiter_defer);
curthread->nwaiter_defer = 0;
}
if (cancel) {
_thr_cancel_enter2(curthread, 0);

7
lib/libthr/thread/thr_kern.c
View File

@ -199,13 +199,6 @@ _thr_sleep(struct pthread *curthread, int clockid,
const struct timespec *abstime)
{
curthread->will_sleep = 0;
if (curthread->nwaiter_defer > 0) {
_thr_wake_all(curthread->defer_waiters,
curthread->nwaiter_defer);
curthread->nwaiter_defer = 0;
}
if (curthread->wake_addr->value != 0)
return (0);

16
lib/libthr/thread/thr_mutex.c
View File

@ -92,7 +92,7 @@ int __pthread_mutex_setyieldloops_np(pthread_mutex_t *mutex, int count);
static int mutex_self_trylock(pthread_mutex_t);
static int mutex_self_lock(pthread_mutex_t,
const struct timespec *abstime);
static int mutex_unlock_common(struct pthread_mutex *, int);
static int mutex_unlock_common(struct pthread_mutex *, int, int *);
static int mutex_lock_sleep(struct pthread *, pthread_mutex_t,
const struct timespec *);
@ -461,7 +461,7 @@ _pthread_mutex_unlock(pthread_mutex_t *mutex)
struct pthread_mutex *mp;
mp = *mutex;
return (mutex_unlock_common(mp, 0));
return (mutex_unlock_common(mp, 0, NULL));
}
int
@ -476,7 +476,7 @@ _mutex_cv_lock(struct pthread_mutex *m, int count)
}
int
_mutex_cv_unlock(struct pthread_mutex *m, int *count)
_mutex_cv_unlock(struct pthread_mutex *m, int *count, int *defer)
{
/*
@ -484,7 +484,7 @@ _mutex_cv_unlock(struct pthread_mutex *m, int *count)
*/
*count = m->m_count;
m->m_count = 0;
(void)mutex_unlock_common(m, 1);
(void)mutex_unlock_common(m, 1, defer);
return (0);
}
@ -629,7 +629,7 @@ mutex_self_lock(struct pthread_mutex *m, const struct timespec *abstime)
}
static int
mutex_unlock_common(struct pthread_mutex *m, int cv)
mutex_unlock_common(struct pthread_mutex *m, int cv, int *mtx_defer)
{
struct pthread *curthread = _get_curthread();
uint32_t id;
@ -657,12 +657,12 @@ mutex_unlock_common(struct pthread_mutex *m, int cv)
defered = 1;
m->m_flags &= ~PMUTEX_FLAG_DEFERED;
} else
defered = 0;
defered = 0;
DEQUEUE_MUTEX(curthread, m);
_thr_umutex_unlock(&m->m_lock, id);
_thr_umutex_unlock2(&m->m_lock, id, mtx_defer);
if (curthread->will_sleep == 0 && defered) {
if (mtx_defer == NULL && defered) {
_thr_wake_all(curthread->defer_waiters,
curthread->nwaiter_defer);
curthread->nwaiter_defer = 0;

8
lib/libthr/thread/thr_private.h
View File

@ -727,10 +727,10 @@ extern struct umutex _thr_event_lock __hidden;
*/
__BEGIN_DECLS
int _thr_setthreaded(int) __hidden;
int _mutex_cv_lock(struct pthread_mutex *, int count) __hidden;
int _mutex_cv_unlock(struct pthread_mutex *, int *count) __hidden;
int _mutex_cv_attach(struct pthread_mutex *, int count) __hidden;
int _mutex_cv_detach(struct pthread_mutex *, int *count) __hidden;
int _mutex_cv_lock(struct pthread_mutex *, int) __hidden;
int _mutex_cv_unlock(struct pthread_mutex *, int *, int *) __hidden;
int _mutex_cv_attach(struct pthread_mutex *, int) __hidden;
int _mutex_cv_detach(struct pthread_mutex *, int *) __hidden;
int _mutex_owned(struct pthread *, const struct pthread_mutex *) __hidden;
int _mutex_reinit(pthread_mutex_t *) __hidden;
void _mutex_fork(struct pthread *curthread) __hidden;

16
lib/libthr/thread/thr_umtx.h
View File

@ -120,7 +120,7 @@ _thr_umutex_timedlock(struct umutex *mtx, uint32_t id,
}
static inline int
_thr_umutex_unlock(struct umutex *mtx, uint32_t id)
_thr_umutex_unlock2(struct umutex *mtx, uint32_t id, int *defer)
{
uint32_t flags = mtx->m_flags;
@ -132,8 +132,12 @@ _thr_umutex_unlock(struct umutex *mtx, uint32_t id)
return (EPERM);
} while (__predict_false(!atomic_cmpset_rel_32(&mtx->m_owner,
owner, UMUTEX_UNOWNED)));
if ((owner & UMUTEX_CONTESTED))
(void)_umtx_op_err(mtx, UMTX_OP_MUTEX_WAKE2, flags, 0, 0);
if ((owner & UMUTEX_CONTESTED)) {
if (defer == NULL)
(void)_umtx_op_err(mtx, UMTX_OP_MUTEX_WAKE2, flags, 0, 0);
else
*defer = 1;
}
return (0);
}
if (atomic_cmpset_rel_32(&mtx->m_owner, id, UMUTEX_UNOWNED))
@ -141,6 +145,12 @@ _thr_umutex_unlock(struct umutex *mtx, uint32_t id)
return (__thr_umutex_unlock(mtx, id));
}
static inline int
_thr_umutex_unlock(struct umutex *mtx, uint32_t id)
{
return _thr_umutex_unlock2(mtx, id, NULL);
}
static inline int
_thr_rwlock_tryrdlock(struct urwlock *rwlock, int flags)
{