Messages in this thread | | | Date | Thu, 05 Nov 2009 19:44:36 -0400 | From | Kevin Winchester <> | Subject | Re: Intermittent early panic in try_to_wake_up |
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Mike Galbraith wrote: > On Thu, 2009-10-22 at 20:33 -0300, Kevin Winchester wrote: >> Hi, >> >> A week or two ago I saw a panic on boot in try_to_wake_up, but it was not >> reproducible and I had not written down any trace information. This >> evening I saw it twice more, but then on the third boot things worked fine. >> This time I copied down the stack trace: >> >> try_to_wake_up+0x2e/0x102 >> wake_up_process+0x10/0x12 >> kthread_create+0x88/0x12c >> ?ksoftirqd+0x00/0xb7 >> cpu_callback+0x42/0x8f >> ?spawn_ksoftirqd+0x0/0x39 >> spawn_ksoftirqd+0x17/0x39 >> do_one_initcall+0x58/0x147 >> >> The first time it happened, I remember checking the git logs and it was >> shortly after: >> >> commit f5dc37530ba8a35aae0f7f4f13781d1904f71e94 >> Author: Mike Galbraith <efault@gmx.de> >> Date: Fri Oct 9 08:35:03 2009 +0200 >> >> sched: Update the clock of runqueue select_task_rq() selected >> >> In try_to_wake_up(), we update the runqueue clock, but >> select_task_rq() may select a different runqueue than the one we >> updated, leaving the new runqueue's clock stale for a bit. >> >> This patch cures occasional huge latencies reported by latencytop >> when coming out of idle on a mostly idle NO_HZ box. >> >> Signed-off-by: Mike Galbraith <efault@gmx.de> >> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> >> LKML-Reference: <1255070103.7639.30.camel@marge.simson.net> >> Signed-off-by: Ingo Molnar <mingo@elte.hu> >> >> >> ...so perhaps that has something to do with it. > > I don't think that's very likely. Box did explode near my grubby > fingerprints though. > >> Config below. Any help would be appreciated. > > Building with your config, try_to_wake_up+0x2e is around.. > > (gdb) list *try_to_wake_up+0x2e > 0xffffffff81029107 is in try_to_wake_up (kernel/sched.c:2324). > 2319 this_cpu = get_cpu(); > 2320 > 2321 smp_wmb(); > 2322 rq = orig_rq = task_rq_lock(p, &flags); > 2323 update_rq_clock(rq); > 2324 if (!(p->state & state)) > 2325 goto out; > 2326 > 2327 if (p->se.on_rq) > 2328 goto out_running; > > I don't see how any of that can explode without something very bad > having happened to ksoftirqd before we tried to wake it. >
I thought this problem had solved itself, but I've hit it again three times in the last few days.
I've expanded the CC list a little (based on get_maintainer for kernel/softirq.c, since that seems to be involved somehow, and Rafael since this definitely seems to be a regression), to see if anyone else has any ideas.
-- Kevin Winchester
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