git: 9front

Info  •  Files  •  Log  •  Branches

wait: always check up->nchild before going to sleep

always make sure that there are child processes we can wait for
before sleeping.

put pwait() sleep into a loop and recheck. this is not strictly
neccesary but prevents accidents if there are spurious wakeups
or a bug.

--- a/sys/src/9/port/devproc.c

+++ b/sys/src/9/port/devproc.c

@@ -908,12 +908,12 @@

 		}

 		lock(&p->exl);

-		if(up == p && p->nchild == 0 && p->waitq == 0) {

-			unlock(&p->exl);

-			error(Enochild);

-		}

 		pid = p->pid;

 		while(p->waitq == 0) {

+			if(up == p && p->nchild == 0) {

+				unlock(&p->exl);

+				error(Enochild);

+			}

 			unlock(&p->exl);

 			sleep(&p->waitr, haswaitq, p);

 			if(p->pid != pid)

--- a/sys/src/9/port/proc.c

+++ b/sys/src/9/port/proc.c

@@ -1229,15 +1229,15 @@

 	}

 	lock(&up->exl);

-	if(up->nchild == 0 && up->waitq == 0) {

+	while(up->waitq == 0) {

+		if(up->nchild == 0) {

+			unlock(&up->exl);

+			error(Enochild);

+		}

 		unlock(&up->exl);

-		error(Enochild);

+		sleep(&up->waitr, haswaitq, up);

+		lock(&up->exl);

 	}

-	unlock(&up->exl);

-

-	sleep(&up->waitr, haswaitq, up);

-

-	lock(&up->exl);

 	wq = up->waitq;

 	up->waitq = wq->next;

 	up->nwait--;

-- 

⑨