Date: Mon, 23 Jul 2001 15:26:12 -0700 (PDT) From: Julian Elischer <julian@elischer.org> To: John Baldwin <jhb@FreeBSD.org> Cc: current@FreeBSD.org Subject: RE: mutex blocking queues.. Message-ID: <Pine.BSF.4.21.0107231525030.19434-100000@InterJet.elischer.org> In-Reply-To: <XFMail.010723110257.jhb@FreeBSD.org>
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this strikes me as avoidable. I'll think about it.. Until then
I guess I'll just have two lists in the thread.. one for sleep and one for
mutexes.
On Mon, 23 Jul 2001, John Baldwin wrote:
>
> On 23-Jul-01 Julian Elischer wrote:
> > Why does the mutex not link blocked processes though the
> > sleep queue linked list entry? Why does it use the run queue entry?
> > In KSEs the sleep queue and run queue enties go into different
> > sub structures and ahve different types so this breaks...
> > do I need to do something sleazy or can I just link them together using the
> > equivalemt of the p_slpq entry?
>
> You can block on a mutex when processing signals in the catch case in msleep()
> after you have put the process on the sleep queue:
>
> int
> msleep(ident, mtx, priority, wmesg, timo)
> {
> ...
> p->p_wchan = ident;
> p->p_wmesg = wmesg;
> p->p_slptime = 0;
> p->p_pri.pri_level = priority & PRIMASK;
> CTR5(KTR_PROC, "msleep: proc %p (pid %d, %s) on %s (%p)", p, p->p_pid,
> p->p_comm, wmesg, ident);
> TAILQ_INSERT_TAIL(&slpque[LOOKUP(ident)], p, p_slpq);
> ...
> /*
> * We put ourselves on the sleep queue and start our timeout
> * before calling CURSIG, as we could stop there, and a wakeup
> * or a SIGCONT (or both) could occur while we were stopped.
> * A SIGCONT would cause us to be marked as SSLEEP
> * without resuming us, thus we must be ready for sleep
> * when CURSIG is called. If the wakeup happens while we're
> * stopped, p->p_wchan will be 0 upon return from CURSIG.
> */
> if (catch) {
> CTR3(KTR_PROC, "msleep caught: proc %p (pid %d, %s)", p,
> p->p_pid, p->p_comm);
> p->p_sflag |= PS_SINTR;
> mtx_unlock_spin(&sched_lock);
> PROC_LOCK(p);
> sig = CURSIG(p);
> mtx_lock_spin(&sched_lock);
> PROC_UNLOCK_NOSWITCH(p);
> ...
>
> If that proc_lock blocks then we don't want to clobber the sleep queue.
>
> --
>
> John Baldwin <jhb@FreeBSD.org> -- http://www.FreeBSD.org/~jhb/
> PGP Key: http://www.baldwin.cx/~john/pgpkey.asc
> "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/
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