Re: [9fans] wait hang

[erik quanstrom <quanstro@coraid.com>]

On Mon Dec 18 11:49:41 EST 2006, rsc@swtch.com wrote:
> You're right.  I forgot about "wait".
> I reverted the change to rc.
> 
> Note that if you add "wait" to your hanging example
> it will not necessarily wait for all of the echos, only
> the first 128 or so.
> 
> Russ

if i'm reading pwait correctly, it will actually wait for all if them because nwait
is now properly incremented and decremented, but the wait message will be
discarded if the waitlist is >= 128 when the child exits.

do i have this wrong?

- erik

from port/proc.c

1195 	lock(&up->exl);
1196 	if(up->nchild == 0 && up->waitq == 0) {
1197 		unlock(&up->exl);
1198 		error(Enochild);
1199 	}
1200 	unlock(&up->exl);
1201 
1202 	sleep(&up->waitr, haswaitq, up);
1203 
1204 	lock(&up->exl);
1205 	wq = up->waitq;
1206 	up->waitq = wq->next;
1207 	up->nwait--;
1208 	unlock(&up->exl);
1209 
1210 	qunlock(&up->qwaitr);
1211 	poperror();
1212 
1213 	if(w)
1214 		memmove(w, &wq->w, sizeof(Waitmsg));