Date: Wed, 8 Jul 2009 10:18:56 +0300 From: Dan Naumov <dan.naumov@gmail.com> To: Attilio Rao <attilio@freebsd.org> Cc: FreeBSD-STABLE Mailing List <freebsd-stable@freebsd.org> Subject: Re: 7.2-release/amd64: panic, spin lock held too long Message-ID: <cf9b1ee00907080018s3f32c8afr4f65f01ce9ff1f25@mail.gmail.com> In-Reply-To: <cf9b1ee00907071757i169d2a82la260798f364054f9@mail.gmail.com> References: <cf9b1ee00907061812r3da70018i1c8d8d12bb038a80@mail.gmail.com> <3bbf2fe10907061818v245abd0cgc3ca5073cb93aea4@mail.gmail.com> <cf9b1ee00907061825r34165c48x6727c50b3219d5fb@mail.gmail.com> <3bbf2fe10907061827g35eaeb49g26cf6fdb64436ca7@mail.gmail.com> <cf9b1ee00907071757i169d2a82la260798f364054f9@mail.gmail.com>
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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 =A07 03:49:38 atom syslogd: kernel boot file is /boot/kernel/kern= el >>>>> Jul =A07 03:49:38 atom kernel: spin lock 0xffffffff80b3edc0 (sched lo= ck >>>>> 1) held by 0xffffff00017d8370 (tid 100054) too long >>>>> Jul =A07 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 =A08 03:03:49 atom kernel: ssppiinn =A0lloocckk > 00xxffffffffffffffff8800bb33eeddc400 =A0((sscchheedd =A0lloocck k1 )0 )h > ehledl db yb y 0x0xfffffffffff0f00001081735339760e 0( t(itdi d > 10100006070)5 )t otoo ol olnogng > Jul =A08 03:03:49 atom kernel: p > Jul =A08 03:03:49 atom kernel: anic: spin lock held too long > Jul =A08 03:03:49 atom kernel: cpuid =3D 0 > Jul =A08 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. The only other things running on the system are: sshd, ntpd, smartd, smbd/nmdb and a few instances of irssi in screens. - Sincerely, Dan Naumov
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