Date: Wed, 8 Jul 2009 11:50:36 +0200 From: Attilio Rao <attilio@freebsd.org> To: Dan Naumov <dan.naumov@gmail.com> Cc: FreeBSD-STABLE Mailing List <freebsd-stable@freebsd.org> Subject: Re: 7.2-release/amd64: panic, spin lock held too long Message-ID: <3bbf2fe10907080250q35899d3dhc2f101b62c6e5306@mail.gmail.com> In-Reply-To: <cf9b1ee00907080018s3f32c8afr4f65f01ce9ff1f25@mail.gmail.com> References: <cf9b1ee00907061812r3da70018i1c8d8d12bb038a80@mail.gmail.com> <3bbf2fe10907061818v245abd0cgc3ca5073cb93aea4@mail.gmail.com> <cf9b1ee00907061825r34165c48x6727c50b3219d5fb@mail.gmail.com> <3bbf2fe10907061827g35eaeb49g26cf6fdb64436ca7@mail.gmail.com> <cf9b1ee00907071757i169d2a82la260798f364054f9@mail.gmail.com> <cf9b1ee00907080018s3f32c8afr4f65f01ce9ff1f25@mail.gmail.com>
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2009/7/8 Dan Naumov <dan.naumov@gmail.com>: > On Wed, Jul 8, 2009 at 3:57 AM, Dan Naumov<dan.naumov@gmail.com> wrote: >> On Tue, Jul 7, 2009 at 4:27 AM, Attilio Rao<attilio@freebsd.org> wrote: >>> 2009/7/7 Dan Naumov <dan.naumov@gmail.com>: >>>> On Tue, Jul 7, 2009 at 4:18 AM, Attilio Rao<attilio@freebsd.org> wrote: >>>>> 2009/7/7 Dan Naumov <dan.naumov@gmail.com>: >>>>>> I just got a panic following by a reboot a few seconds after running >>>>>> "portsnap update", /var/log/messages shows the following: >>>>>> >>>>>> Jul 7 03:49:38 atom syslogd: kernel boot file is /boot/kernel/kernel >>>>>> Jul 7 03:49:38 atom kernel: spin lock 0xffffffff80b3edc0 (sched lock >>>>>> 1) held by 0xffffff00017d8370 (tid 100054) too long >>>>>> Jul 7 03:49:38 atom kernel: panic: spin lock held too long >>>>> >>>>> That's a known bug, affecting -CURRENT as well. >>>>> The cpustop IPI is handled though an NMI, which means it could >>>>> interrupt a CPU in any moment, even while holding a spinlock, >>>>> violating one well known FreeBSD rule. >>>>> That means that the cpu can stop itself while the thread was holding >>>>> the sched lock spinlock and not releasing it (there is no way, modulo >>>>> highly hackish, to fix that). >>>>> In the while hardclock() wants to schedule something else to run and >>>>> got stuck on the thread lock. >>>>> >>>>> Ideal fix would involve not using a NMI for serving the cpustop while >>>>> having a cheap way (not making the common path too hard) to tell >>>>> hardclock() to avoid scheduling while cpustop is in flight. >>>>> >>>>> Thanks, >>>>> Attilio >>>> >>>> Any idea if a fix is being worked on and how unlucky must one be to >>>> run into this issue, should I expect it to happen again? Is it >>>> basically completely random? >>> >>> I'd like to work on that issue before BETA3 (and backport to >>> STABLE_7), I'm just time-constrained right now. >>> it is completely random. >>> >>> Thanks, >>> Attilio >> >> Ok, this is getting pretty bad, 23 hours later, I get the same kind of >> panic, the only difference is that instead of "portsnap update", this >> was triggered by "portsnap cron" which I have running between 3 and 4 >> am every day: >> >> Jul 8 03:03:49 atom kernel: ssppiinn lloocckk >> 00xxffffffffffffffff8800bb33eeddc400 ((sscchheedd lloocck k1 )0 )h >> ehledl db yb y 0x0xfffffffffff0f00001081735339760e 0( t(itdi d >> 10100006070)5 )t otoo ol olnogng >> Jul 8 03:03:49 atom kernel: p >> Jul 8 03:03:49 atom kernel: anic: spin lock held too long >> Jul 8 03:03:49 atom kernel: cpuid = 0 >> Jul 8 03:03:49 atom kernel: Uptime: 23h2m38s > > I have now tried repeating the problem by running "stress --cpu 8 --io > 8 --vm 4 --vm-bytes 1024M --timeout 600s --verbose" which pushed > system load into the 15.50 ballpark and simultaneously running > "portsnap fetch" and "portsnap update" but I couldn't manually trigger > the panic, it seems that this problem is indeed random (although it > baffles me why is it specifically portsnap triggering it). I have now > disabled powerd to check whether that makes any difference to system > stability. But is that happening at reboot time? Thanks, Attilio -- Peace can only be achieved by understanding - A. Einstein
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