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Add a preemption point when a mutex or condition variable is

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handed-off/signaled to a higher priority thread.  Note that when
there are idle KSEs that could run the higher priority thread,
we still add the preemption point because it seems to take the
kernel a while to schedule an idle KSE.  The drawbacks are that
threads will be swapped more often between CPUs (KSEs) and
that there will be an extra userland context switch (the idle
KSE is still woken and will probably resume the preempted
thread).  We'll revisit this if and when idle CPU/KSE wakeup
times improve.

Inspired by:	Petri Helenius <pete@he.iki.fi>
Reviewed by:	davidxu
This commit is contained in:
Daniel Eischen 2003-07-18 02:46:30 +00:00
parent 584a5a068d
commit 596ea21c7f
4 changed files with 36 additions and 12 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
lib/libkse/thread/thr_cond.c
View File

@ -615,6 +615,10 @@ _pthread_cond_signal(pthread_cond_t * cond)
!= NULL) {
THR_SCHED_LOCK(curthread, pthread);
cond_queue_remove(*cond, pthread);
if ((pthread->kseg == curthread->kseg) &&
(pthread->active_priority >
curthread->active_priority))
curthread->critical_yield = 1;
_thr_setrunnable_unlocked(pthread);
THR_SCHED_UNLOCK(curthread, pthread);
}
@ -674,6 +678,10 @@ _pthread_cond_broadcast(pthread_cond_t * cond)
!= NULL) {
THR_SCHED_LOCK(curthread, pthread);
cond_queue_remove(*cond, pthread);
if ((pthread->kseg == curthread->kseg) &&
(pthread->active_priority >
curthread->active_priority))
curthread->critical_yield = 1;
_thr_setrunnable_unlocked(pthread);
THR_SCHED_UNLOCK(curthread, pthread);
}

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

@ -859,8 +859,8 @@ mutex_self_lock(struct pthread *curthread, pthread_mutex_t m)
static int
mutex_unlock_common(pthread_mutex_t *m, int add_reference)
{
struct pthread *curthread = _get_curthread();
int ret = 0;
struct pthread *curthread = _get_curthread();
int ret = 0;
if (m == NULL || *m == NULL)
ret = EINVAL;
@ -997,7 +997,7 @@ mutex_unlock_common(pthread_mutex_t *m, int add_reference)
*/
THR_SCHED_LOCK(curthread, curthread);
curthread->inherited_priority =
(*m)->m_saved_prio;
(*m)->m_saved_prio;
curthread->active_priority =
MAX(curthread->inherited_priority,
curthread->base_priority);
@ -1006,7 +1006,6 @@ mutex_unlock_common(pthread_mutex_t *m, int add_reference)
* This thread now owns one less priority mutex.
*/
curthread->priority_mutex_count--;
THR_SCHED_UNLOCK(curthread, curthread);
/* Remove the mutex from the threads queue. */
MUTEX_ASSERT_IS_OWNED(*m);
@ -1464,7 +1463,7 @@ _mutex_lock_backout(struct pthread *curthread)
static void
mutex_handoff(struct pthread *curthread, struct pthread_mutex *mutex)
{
struct pthread *pthread;
struct pthread *pthread;
/* Keep dequeueing until we find a valid thread: */
mutex->m_owner = NULL;
@ -1566,8 +1565,13 @@ mutex_handoff(struct pthread *curthread, struct pthread_mutex *mutex)
/* Make the thread runnable and unlock the scheduling queue: */
_thr_setrunnable_unlocked(pthread);
THR_SCHED_UNLOCK(curthread, pthread);
/* Add a preemption point. */
if ((curthread->kseg == pthread->kseg) &&
(pthread->active_priority > curthread->active_priority))
curthread->critical_yield = 1;
THR_SCHED_UNLOCK(curthread, pthread);
if (mutex->m_owner == pthread)
/* We're done; a valid owner was found. */
break;

8
lib/libpthread/thread/thr_cond.c
View File

@ -615,6 +615,10 @@ _pthread_cond_signal(pthread_cond_t * cond)
!= NULL) {
THR_SCHED_LOCK(curthread, pthread);
cond_queue_remove(*cond, pthread);
if ((pthread->kseg == curthread->kseg) &&
(pthread->active_priority >
curthread->active_priority))
curthread->critical_yield = 1;
_thr_setrunnable_unlocked(pthread);
THR_SCHED_UNLOCK(curthread, pthread);
}
@ -674,6 +678,10 @@ _pthread_cond_broadcast(pthread_cond_t * cond)
!= NULL) {
THR_SCHED_LOCK(curthread, pthread);
cond_queue_remove(*cond, pthread);
if ((pthread->kseg == curthread->kseg) &&
(pthread->active_priority >
curthread->active_priority))
curthread->critical_yield = 1;
_thr_setrunnable_unlocked(pthread);
THR_SCHED_UNLOCK(curthread, pthread);
}

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

@ -859,8 +859,8 @@ mutex_self_lock(struct pthread *curthread, pthread_mutex_t m)
static int
mutex_unlock_common(pthread_mutex_t *m, int add_reference)
{
struct pthread *curthread = _get_curthread();
int ret = 0;
struct pthread *curthread = _get_curthread();
int ret = 0;
if (m == NULL || *m == NULL)
ret = EINVAL;
@ -997,7 +997,7 @@ mutex_unlock_common(pthread_mutex_t *m, int add_reference)
*/
THR_SCHED_LOCK(curthread, curthread);
curthread->inherited_priority =
(*m)->m_saved_prio;
(*m)->m_saved_prio;
curthread->active_priority =
MAX(curthread->inherited_priority,
curthread->base_priority);
@ -1006,7 +1006,6 @@ mutex_unlock_common(pthread_mutex_t *m, int add_reference)
* This thread now owns one less priority mutex.
*/
curthread->priority_mutex_count--;
THR_SCHED_UNLOCK(curthread, curthread);
/* Remove the mutex from the threads queue. */
MUTEX_ASSERT_IS_OWNED(*m);
@ -1464,7 +1463,7 @@ _mutex_lock_backout(struct pthread *curthread)
static void
mutex_handoff(struct pthread *curthread, struct pthread_mutex *mutex)
{
struct pthread *pthread;
struct pthread *pthread;
/* Keep dequeueing until we find a valid thread: */
mutex->m_owner = NULL;
@ -1566,8 +1565,13 @@ mutex_handoff(struct pthread *curthread, struct pthread_mutex *mutex)
/* Make the thread runnable and unlock the scheduling queue: */
_thr_setrunnable_unlocked(pthread);
THR_SCHED_UNLOCK(curthread, pthread);
/* Add a preemption point. */
if ((curthread->kseg == pthread->kseg) &&
(pthread->active_priority > curthread->active_priority))
curthread->critical_yield = 1;
THR_SCHED_UNLOCK(curthread, pthread);
if (mutex->m_owner == pthread)
/* We're done; a valid owner was found. */
break;