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Contributions from XFS for FreeBSD project:

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- Implement cv_wait_unlock() method which has semantics compatible
  with the sv_wait() method in IRIX.  For cv_wait_unlock(), the lock
  must be held before entering the function, but is not held when the
  function is exited.

- Implement the existing cv_wait() function in terms of cv_wait_unlock().

Submitted by:	kan
Feedback from:	jhb, trhodes, Christoph Hellwig <hch at infradead dot org>
This commit is contained in:
Craig Rodrigues 2005-12-12 00:02:22 +00:00
parent 6dba929a4e
commit 92f44a3f3c
Notes: svn2git 2020-12-20 02:59:44 +00:00 
svn path=/head/; revision=153321
2 changed files with 35 additions and 15 deletions
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49
sys/kern/kern_condvar.c
View File

@ -95,17 +95,8 @@ cv_destroy(struct cv *cvp)
void
cv_wait(struct cv *cvp, struct mtx *mp)
{
struct thread *td;
WITNESS_SAVE_DECL(mp);
td = curthread;
#ifdef KTRACE
if (KTRPOINT(td, KTR_CSW))
ktrcsw(1, 0);
#endif
CV_ASSERT(cvp, mp, td);
WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, &mp->mtx_object,
"Waiting on \"%s\"", cvp->cv_description);
WITNESS_SAVE(&mp->mtx_object, mp);
if (cold || panicstr) {
@ -118,6 +109,40 @@ cv_wait(struct cv *cvp, struct mtx *mp)
return;
}
cv_wait_unlock(cvp, mp);
mtx_lock(mp);
WITNESS_RESTORE(&mp->mtx_object, mp);
}
/*
* Wait on a condition variable. This function differs from cv_wait by
* not aquiring the mutex after condition variable was signaled.
*/
void
cv_wait_unlock(struct cv *cvp, struct mtx *mp)
{
struct thread *td;
td = curthread;
#ifdef KTRACE
if (KTRPOINT(td, KTR_CSW))
ktrcsw(1, 0);
#endif
CV_ASSERT(cvp, mp, td);
WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, &mp->mtx_object,
"Waiting on \"%s\"", cvp->cv_description);
if (cold || panicstr) {
/*
* During autoconfiguration, just give interrupts
* a chance, then just return. Don't run any other
* thread or panic below, in case this is the idle
* process and already asleep.
*/
mtx_unlock(mp);
return;
}
sleepq_lock(cvp);
cvp->cv_waiters++;
@ -127,13 +152,7 @@ cv_wait(struct cv *cvp, struct mtx *mp)
sleepq_add(cvp, mp, cvp->cv_description, SLEEPQ_CONDVAR);
sleepq_wait(cvp);
#ifdef KTRACE
if (KTRPOINT(td, KTR_CSW))
ktrcsw(0, 0);
#endif
PICKUP_GIANT();
mtx_lock(mp);
WITNESS_RESTORE(&mp->mtx_object, mp);
}
/*

1
sys/sys/condvar.h
View File

@ -53,6 +53,7 @@ void cv_init(struct cv *cvp, const char *desc);
void cv_destroy(struct cv *cvp);
void cv_wait(struct cv *cvp, struct mtx *mp);
void cv_wait_unlock(struct cv *cvp, struct mtx *mp);
int cv_wait_sig(struct cv *cvp, struct mtx *mp);
int cv_timedwait(struct cv *cvp, struct mtx *mp, int timo);
int cv_timedwait_sig(struct cv *cvp, struct mtx *mp, int timo);