Author: davidxu
Date: Sat Aug 11 23:17:02 2012
New Revision: 239200
URL: http://svn.freebsd.org/changeset/base/239200
Log:
MFp4:
Further decreases unexpected context switches by defering mutex wakeup
until internal sleep queue lock is released.
Modified:
head/lib/libthr/thread/thr_cond.c
head/lib/libthr/thread/thr_kern.c
head/lib/libthr/thread/thr_mutex.c
head/lib/libthr/thread/thr_private.h
head/lib/libthr/thread/thr_umtx.h
Modified: head/lib/libthr/thread/thr_cond.c
==============================================================================
--- head/lib/libthr/thread/thr_cond.c Sat Aug 11 22:39:27 2012
(r239199)
+++ head/lib/libthr/thread/thr_cond.c Sat Aug 11 23:17:02 2012
(r239200)
@@ -217,6 +217,7 @@ cond_wait_user(struct pthread_cond *cvp,
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,
* 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);
Modified: head/lib/libthr/thread/thr_kern.c
==============================================================================
--- head/lib/libthr/thread/thr_kern.c Sat Aug 11 22:39:27 2012
(r239199)
+++ head/lib/libthr/thread/thr_kern.c Sat Aug 11 23:17:02 2012
(r239200)
@@ -199,13 +199,6 @@ _thr_sleep(struct pthread *curthread, in
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);
Modified: head/lib/libthr/thread/thr_mutex.c
==============================================================================
--- head/lib/libthr/thread/thr_mutex.c Sat Aug 11 22:39:27 2012
(r239199)
+++ head/lib/libthr/thread/thr_mutex.c Sat Aug 11 23:17:02 2012
(r239200)
@@ -92,7 +92,7 @@ int __pthread_mutex_setyieldloops_np(pth
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 *m
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
-_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
*/
*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,
}
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
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;
Modified: head/lib/libthr/thread/thr_private.h
==============================================================================
--- head/lib/libthr/thread/thr_private.h Sat Aug 11 22:39:27 2012
(r239199)
+++ head/lib/libthr/thread/thr_private.h Sat Aug 11 23:17:02 2012
(r239200)
@@ -727,10 +727,10 @@ extern struct umutex _thr_event_lock __h
*/
__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;
Modified: head/lib/libthr/thread/thr_umtx.h
==============================================================================
--- head/lib/libthr/thread/thr_umtx.h Sat Aug 11 22:39:27 2012
(r239199)
+++ head/lib/libthr/thread/thr_umtx.h Sat Aug 11 23:17:02 2012
(r239200)
@@ -120,7 +120,7 @@ _thr_umutex_timedlock(struct umutex *mtx
}
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, u
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))
@@ -142,6 +146,12 @@ _thr_umutex_unlock(struct umutex *mtx, u
}
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)
{
int32_t state;
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