Date: Sun, 23 Jun 2002 13:19:33 -0700 From: Alfred Perlstein <bright@mu.org> To: Matthew Dillon <dillon@apollo.backplane.com> Cc: freebsd-hackers@freebsd.org, Julian Elischer <julian@elischer.org>, Alan Cox <alc@cs.rice.edu>, Tor.Egge@cvsup.no.freebsd.org Subject: Re: Bug in wakeup() (stable and current) ? Message-ID: <20020623201933.GM53232@elvis.mu.org> In-Reply-To: <200206232014.g5NKE5x3058562@apollo.backplane.com> References: <200206232014.g5NKE5x3058562@apollo.backplane.com>
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* Matthew Dillon <dillon@apollo.backplane.com> [020623 13:14] wrote:
> This doesn't look right at all. It looks like wakeup is not restarting
> properly:
>
> s = splhigh();
> qp = &slpque[LOOKUP(ident)];
> restart:
> TAILQ_FOREACH(p, qp, p_procq) {
> if (p->p_wchan == ident) {
> TAILQ_REMOVE(qp, p, p_procq);
> p->p_wchan = 0;
> if (p->p_stat == SSLEEP) {
> ...
> goto restart;
> }
> /* XXXXXX goto restart should occur HERE XXXXXX */
> }
> }
>
> The goto restart condition should occur one level up, as I show in
> the comment.
>
> Could someone take a look at this and tell me if I am blowing smoke?
I'm pretty sure you only need to 'goto restart' if you call into
maybe_resched() as someone else may have manipulated the queues.
The 'restart' label is only in there for restarting in case one of
the functions called may change the lists, if we restart _every_
time we'll traverse the same procs where p->p_wchan != ident over
and over needlessly.
-Alfred
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