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fix race.

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rsc 2004-05-20 21:39:24 +00:00
parent 52aeb2f9b9
commit 1c39bb5919
1 changed files with 15 additions and 1 deletions
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16
src/lib9/rendez-signal.c
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@ -45,6 +45,7 @@ struct Vous
Vous *link;
Lock lk;
int pid;
int wakeup;
ulong val;
ulong tag;
};
@ -149,8 +150,20 @@ rendezvous(ulong tag, ulong val)
sigaddset(&mask, SIGUSR1);
sigprocmask(SIG_SETMASK, &mask, NULL);
sigdelset(&mask, SIGUSR1);
v->wakeup = 0;
unlock(&v->lk);
sigsuspend(&mask);
for(;;){
/*
* There may well be random signals flying around,
* so we can't be sure why we woke up. If we weren't
* properly awakened, we need to go back to sleep.
*/
sigsuspend(&mask);
lock(&v->lk); /* do some memory synchronization */
unlock(&v->lk);
if(v->wakeup == 1)
break;
}
rval = v->val;
if(DBG)fprint(2, "pid is %d, awake\n", me);
putvous(v);
@ -169,6 +182,7 @@ rendezvous(ulong tag, ulong val)
lock(&v->lk);
rval = v->val;
v->val = val;
v->wakeup = 1;
unlock(&v->lk);
if(kill(vpid, SIGUSR1) < 0){
if(DBG)fprint(2, "pid is %d, kill %d failed: %r\n", me, vpid);