Messages in this thread Patch in this message | | | Subject | Re: [BUG] "sched: Remove rq->lock from the first half of ttwu()" locks up on ARM | From | Peter Zijlstra <> | Date | Wed, 25 May 2011 23:15:28 +0200 |
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On Wed, 2011-05-25 at 19:08 +0200, Peter Zijlstra wrote: > Ooh, shiny, whilst typing this I got an NMI-watchdog error reporting me > that CPU1 got stuck in try_to_wake_up(), so it looks like I can indeed > reproduce some funnies. > > /me goes dig in.
Does the below make your ARM box happy again?
It restores the old ttwu behaviour for this case and seems to not mess up my x86 with __ARCH_WANT_INTERRUPTS_ON_CTXSW.
Figuring out why the existing condition failed and writing a proper changelog requires a mind that is slightly less deprived of sleep and I shall attempt that tomorrow -- provided this does indeed work for you.
--- diff --git a/kernel/sched.c b/kernel/sched.c index 2d12893..6976eac 100644 --- a/kernel/sched.c +++ b/kernel/sched.c @@ -2573,7 +2573,19 @@ static void ttwu_queue_remote(struct task_struct *p, int cpu) if (!next) smp_send_reschedule(cpu); } -#endif + +#ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW +static void ttwu_activate_remote(struct task_struct *p, int wake_flags) +{ + struct rq *rq = __task_rq_lock(p); + + ttwu_activate(rq, p, ENQUEUE_WAKEUP | ENQUEUE_WAKING); + ttwu_do_wakeup(rq, p, wake_flags); + + __task_rq_unlock(rq); +} +#endif /* __ARCH_WANT_INTERRUPTS_ON_CTXSW */ +#endif /* CONFIG_SMP */ static void ttwu_queue(struct task_struct *p, int cpu) { @@ -2630,18 +2642,11 @@ try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) */ while (p->on_cpu) { #ifdef __ARCH_WANT_INTERRUPTS_ON_CTXSW - /* - * If called from interrupt context we could have landed in the - * middle of schedule(), in this case we should take care not - * to spin on ->on_cpu if p is current, since that would - * deadlock. - */ - if (p == current) { - ttwu_queue(p, cpu); - goto stat; - } -#endif + ttwu_activate_remote(p, wake_flags); + goto stat; +#else cpu_relax(); +#endif } /* * Pairs with the smp_wmb() in finish_lock_switch().
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