Date: Wed, 18 May 2011 17:34:55 -0400 From: John Baldwin <jhb@freebsd.org> To: Max Laier <max@love2party.net> Cc: neel@freebsd.org, Andriy Gapon <avg@freebsd.org>, Attilio Rao <attilio@freebsd.org>, FreeBSD current <freebsd-current@freebsd.org>, Stephan Uphoff <ups@freebsd.org>, Peter Grehan <grehan@freebsd.org> Subject: Re: proposed smp_rendezvous change Message-ID: <201105181734.55988.jhb@freebsd.org> In-Reply-To: <4DD42BC6.80104@love2party.net> References: <4DCD357D.6000109@FreeBSD.org> <201105171635.17704.jhb@freebsd.org> <4DD42BC6.80104@love2party.net>
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On Wednesday, May 18, 2011 4:27:50 pm Max Laier wrote:
> On 05/17/2011 01:35 PM, John Baldwin wrote:
> ...
> > Yeah, I already have a patch to do that, but hadn't added atomic ops to
> > critical_enter() and critical_exit(). But it also wasn't as fancy in the
> > critical_exit() case. Here is what I have and I think it might actually
> > be ok (it doesn't use an atomic read and clear, but I think it is safe).
> > Hmm, actually, it will need to use the read and clear:
>
> Looks good to me. I was slightly surprised by this:
>
> > Index: kern/kern_synch.c
> > ===================================================================
> > --- kern/kern_synch.c (revision 222024)
> > +++ kern/kern_synch.c (working copy)
> > @@ -400,9 +400,7 @@
> > if (!TD_ON_LOCK(td)&& !TD_IS_RUNNING(td))
> > mtx_assert(&Giant, MA_NOTOWNED);
> > #endif
> > - KASSERT(td->td_critnest == 1 || (td->td_critnest == 2&&
> > - (td->td_owepreempt)&& (flags& SW_INVOL) != 0&&
> > - newtd == NULL) || panicstr,
> > + KASSERT(td->td_critnest == 1 || panicstr,
> > ("mi_switch: switch in a critical section"));
> > KASSERT((flags& (SW_INVOL | SW_VOL)) != 0,
> > ("mi_switch: switch must be voluntary or involuntary"));
>
> part of the patch. But that is in fact correct and much more expressive
> and safe than the version we had before.
Ok, I need to stress test this some first.
> Thanks,
> Max
>
> P.S. I'd like to see this and the rendezvous changes in stable/7 in the
> not too distant future. Mind if I MFH these when you are done - unless
> you are planing to do it already, anyways.
I will merge them certainly. These are critical fixes. :(
--
John Baldwin
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