lkml.org 
[lkml]   [2011]   [May]   [25]   [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
    From
    Date
    On Tue, 2011-05-24 at 23:39 +0200, Ingo Molnar wrote:
    > * Peter Zijlstra <a.p.zijlstra@chello.nl> wrote:
    >
    > > 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.
    >
    > Yes, should be possible to just disable it on x86 - no further tricks needed.
    > It's been a long time since i tested that though.

    I can confirm this is SMP only. UP is fine. SMP+nosmp locks up as well.

    M.
    --
    Reality is an implementation detail.




    \
     
     \ /
      Last update: 2011-05-25 14:25    [W:0.026 / U:0.040 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site