[lkml]   [2011]   [May]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
    SubjectRe: [BUG] "sched: Remove rq->lock from the first half of ttwu()" locks up on ARM
    On Tue, 2011-05-24 at 19:13 +0100, Marc Zyngier wrote:
    > Peter,
    > I've experienced all kind of lock-ups on ARM SMP platforms recently, and
    > finally tracked it down to the following patch:
    > e4a52bcb9a18142d79e231b6733cabdbf2e67c1f [sched: Remove rq->lock from the first half of ttwu()].
    > Even on moderate load, the machine locks up, often silently, and
    > sometimes with a few messages like:
    > INFO: rcu_preempt_state detected stalls on CPUs/tasks: { 0} (detected by 1, t=12002 jiffies)
    > Another side effect of this patch is that the load average is always 0,
    > whatever load I throw at the system.
    > Reverting the sched changes up to that patch (included) gives me a
    > working system again, which happily survives parallel kernel
    > compilations without complaining.
    > My knowledge of the scheduler being rather limited, I haven't been able
    > to pinpoint the exact problem (though it probably have something to do
    > with __ARCH_WANT_INTERRUPTS_ON_CTXSW being defined on ARM). The enclosed
    > patch somehow papers over the load average problem, but the system ends
    > up locking up anyway:

    Hurm.. I'll try and make x86 use __ARCH_WANT_INTERRUPTS_ON_CTXSW, IIRC
    Ingo once said that that is possible and try to see if I can reproduce.
    No clear ideas atm.

    Thanks for reporting.

     \ /
      Last update: 2011-05-24 23:31    [W:0.038 / U:8.924 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site