9vx/OSX: attempt at fixing spurious pthread wakeups - vx32 - Local 9vx git repository for patches.
(DIR) Log
(DIR) Files
(DIR) Refs
---
(DIR) commit b73f901985b9aaada2c11d977276a2d064555048
(DIR) parent f4b577eb84fd57b6e5835b3776ac2976f9302ed9
(HTM) Author: Russ Cox <rsc@swtch.com>
Date: Sat, 28 Jun 2008 11:37:35 -0400
9vx/OSX: attempt at fixing spurious pthread wakeups
Diffstat:
src/9vx/sched.c | 20 +++++++++++++++++++-
1 file changed, 19 insertions(+), 1 deletion(-)
---
(DIR) diff --git a/src/9vx/sched.c b/src/9vx/sched.c
@@ -44,6 +44,17 @@ punlock(Psleep *p)
static void
psleep(Psleep *p)
{
+ /*
+ * OS X is trying to be helpful and has changed the behavior
+ * of pthreads condition variables. After pthread_cond_signal
+ * any subsequent pthread_cond_wait returns immediately.
+ * This is perhaps more sensible behavior than the standard,
+ * but it's not actually what the standard requires.
+ * So we have to pthread_cond_init to clear any pre-existing
+ * condition. This is okay because we hold the lock that
+ * protects the condition in the first place. Sigh.
+ */
+ pthread_cond_init(&p->cond, nil);
pthread_cond_wait(&p->cond, &p->mutex);
}
@@ -69,8 +80,10 @@ void
idlehands(void)
{
plock(&idling);
- while(!idlewakeup)
+ while(!idlewakeup){
psleep(&idling);
+ iprint("idlehands spurious wakeup\n");
+ }
idlewakeup = 0;
punlock(&idling);
}
@@ -124,6 +137,7 @@ ready(Proc *p)
kprocq.n++;
if(kprocq.n > nrunproc)
newmach();
+iprint("ready p\n");
pwakeup(&run);
unlock(&kprocq.lk);
punlock(&run);
@@ -137,11 +151,13 @@ ready(Proc *p)
Proc*
runproc(void)
{
+ int nbad;
Proc *p;
if(m->machno == 0)
return _runproc();
+ nbad = 0;
plock(&run);
lock(&kprocq.lk); /* redundant but fine */
while((p = kprocq.head) == nil){
@@ -149,6 +165,8 @@ runproc(void)
unlock(&kprocq.lk);
psleep(&run);
lock(&kprocq.lk);
+ if(kprocq.head == nil && ++nbad%1000 == 0)
+ iprint("cpu%d: runproc spurious wakeup\n", m->machno);
nrunproc--;
}
kprocq.head = p->rnext;