Date: Tue, 2 Jul 2002 19:30:54 -0700 (PDT) From: Julian Elischer <julian@elischer.org> To: Andrew Gallatin <gallatin@cs.duke.edu> Cc: freebsd-current@freebsd.org Subject: Re: KSE signal problems still Message-ID: <Pine.BSF.4.21.0207021927590.97650-100000@InterJet.elischer.org> In-Reply-To: <15650.23048.273299.232384@grasshopper.cs.duke.edu>
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On Tue, 2 Jul 2002, Andrew Gallatin wrote:
>
> Julian Elischer writes:
> > try this:
> >
> > in tdsignal, (kern_sig.c)
> > take a lock on schedlock and release it again, just around the call to
> > forward-signal()
> >
> > forward_signal(c4445540) at forward_signal+0x1a
> > tdsignal(c4445540,2,2) at tdsignal+0x182
> > psignal(c443d558,2) at psignal+0x3c8
> >
> > hopefully this will not be called with the schedlock already locked
> >
>
> Following your suggestion, the appended patch appears to work.
>
> However, it does seem a bit silly, as we end up dropping
> and-reaquiring the sched lock quite a few times:
That's why I just asked you to test the concept..
If I know that just aquiring it here is ok,
(I presume you tried doing some work like this)
that tells me that this code isn't called from some odd place,
with the sched lock already set.
(that and code inspection of course..)
Now we know it works we can try optimise it..
I'm going home now for dinner,
so if you feel like checking this or something mor optimal in,
be my guest :-)
>
> mtx_unlock_spin(&sched_lock);
> if (td->td_state == TDS_RUNQ ||
> td->td_state == TDS_RUNNING) {
> signotify(td->td_proc); /* grabs & releases sched_lock*/
> #ifdef SMP
> if (td->td_state == TDS_RUNNING && td != curthread) {
> mtx_lock_spin(&sched_lock);
> forward_signal(td);
> mtx_unlock_spin(&sched_lock);
> }
> #endif
> }
> goto out;
>
>
>
> Wouldn't it be cleaner if there was a signotify_locked () that
> assumed you had the sched_lock held (and was called by signotify)?
>
> Drew
>
>
>
>
> Index: kern_sig.c
> ===================================================================
> RCS file: /home/ncvs/src/sys/kern/kern_sig.c,v
> retrieving revision 1.171
> diff -u -r1.171 kern_sig.c
> --- kern_sig.c 29 Jun 2002 17:26:18 -0000 1.171
> +++ kern_sig.c 3 Jul 2002 01:48:35 -0000
> @@ -1543,8 +1543,11 @@
> td->td_state == TDS_RUNNING) {
> signotify(td->td_proc);
> #ifdef SMP
> - if (td->td_state == TDS_RUNNING && td != curthread)
> + if (td->td_state == TDS_RUNNING && td != curthread) {
> + mtx_lock_spin(&sched_lock);
> forward_signal(td);
> + mtx_unlock_spin(&sched_lock);
> + }
> #endif
> }
> goto out;
>
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