Date: Thu, 16 Dec 2004 15:21:44 -0500 From: John Baldwin <jhb@FreeBSD.org> To: Peter Holm <peter@holm.cc> Cc: jeffr@FreeBSD.org Subject: Re: Freeze Message-ID: <200412161521.44026.jhb@FreeBSD.org> In-Reply-To: <20041206135934.GA24238@peter.osted.lan> References: <20041112123343.GA12048@peter.osted.lan> <200411191710.19215.jhb@FreeBSD.org> <20041206135934.GA24238@peter.osted.lan>
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On Monday 06 December 2004 08:59 am, Peter Holm wrote: > On Fri, Nov 19, 2004 at 05:10:19PM -0500, John Baldwin wrote: > > On Friday 19 November 2004 02:59 am, Peter Holm wrote: > > > On Mon, Nov 15, 2004 at 03:46:15PM -0500, John Baldwin wrote: > > > > On Friday 12 November 2004 07:33 am, Peter Holm wrote: > > > > > GENERIC HEAD from Nov 11 08:05 UTC > > > > > > > > > > The following stack traces etc. was done before my first > > > > > cup of coffee, so it's not so informative as it could have been :-( > > > > > > > > > > The test box appeared to have been frozen for more than 6 hours, > > > > > but was pingable. > > > > > > > > > > http://www.holm.cc/stress/log/cons86.html > > > > > > > > A weak guess is that you have the system in some sort of livelock due > > > > to fork()? Have you tried running with 'debug.mpsafevm=1' set from > > > > the loader? > > > > > > > > -- > > > > John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ > > > > "Power Users Use the Power to Serve" = http://www.FreeBSD.org > > > > > > OK, I've got some more info: > > > > > > http://www.holm.cc/stress/log/cons88.html > > > > > > Looks like a spin in uma_zone_slab() when slab_zalloc() fails? > > > > Yes, I think if you specify M_WAITOK, then that might happen. > > slab_zalloc() can fail if any of the init functions fail for example, in > > which case it would loop forever. You can try this hack (though it may > > very well be wrong) to return failure if that is what is triggering: > > > > Index: uma_core.c > > =================================================================== > > RCS file: /usr/cvs/src/sys/vm/uma_core.c,v > > retrieving revision 1.110 > > diff -u -r1.110 uma_core.c > > --- uma_core.c 6 Nov 2004 11:43:30 -0000 1.110 > > +++ uma_core.c 19 Nov 2004 22:08:26 -0000 > > @@ -1998,6 +1998,10 @@ > > */ > > if (flags & M_NOWAIT) > > flags |= M_NOVM; > > + > > + /* XXXHACK */ > > + if (flags & M_WAITOK) > > + break; > > } > > return (slab); > > } > > > > -- > > John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ > > "Power Users Use the Power to Serve" = http://www.FreeBSD.org > > I instrumented the code with this: > $ cvs diff -u > cvs diff: Diffing . > Index: uma_core.c > =================================================================== > RCS file: /home/ncvs/src/sys/vm/uma_core.c,v > retrieving revision 1.110 > diff -u -r1.110 uma_core.c > --- uma_core.c 6 Nov 2004 11:43:30 -0000 1.110 > +++ uma_core.c 6 Dec 2004 13:49:36 -0000 > @@ -1926,6 +1926,7 @@ > { > uma_slab_t slab; > uma_keg_t keg; > + int i; > > keg = zone->uz_keg; > > @@ -1943,7 +1944,8 @@ > > slab = NULL; > > - for (;;) { > + for (i = 0;;i++) { > + KASSERT(i < 10000, ("uma_zone_slab is looping")); > /* > * Find a slab with some space. Prefer slabs that are > partially * used over those that are totally full. This helps to reduce > > and now during test of Jeff Roberson's "SMP FFS" patch the assert > triggered: http://www.holm.cc/stress/log/cons92.html Hmm. Does the hack patch above make the hang go away or does it just break things worse? -- John Baldwin <jhb@FreeBSD.org> <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve" = http://www.FreeBSD.org
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