Re: timer code oops when calling mod_delayed_work

From: Jeff Layton
Date: Wed Nov 04 2015 - 06:48:45 EST


On Tue, 3 Nov 2015 19:06:58 -0500
Tejun Heo <tj@xxxxxxxxxx> wrote:

> Hello, Jeff.
>
> Can you please verify whether the following patch fixes the issue?
>
> Thanks.
>
> diff --git a/kernel/time/timer.c b/kernel/time/timer.c
> index 84190f0..566a282 100644
> --- a/kernel/time/timer.c
> +++ b/kernel/time/timer.c
> @@ -970,12 +970,21 @@ EXPORT_SYMBOL(add_timer);
> */
> void add_timer_on(struct timer_list *timer, int cpu)
> {
> - struct tvec_base *base = per_cpu_ptr(&tvec_bases, cpu);
> + struct tvec_base *new_base = per_cpu_ptr(&tvec_bases, cpu);
> + struct tvec_base *base;
> unsigned long flags;
>
> timer_stats_timer_set_start_info(timer);
> BUG_ON(timer_pending(timer) || !timer->function);
> - spin_lock_irqsave(&base->lock, flags);
> +
> + base = lock_timer_base(timer, &flags);
> + if (base != new_base) {
> + timer->flags |= TIMER_MIGRATING;
> + spin_unlock(&base->lock);
> + base = new_base;
> + spin_lock(&base->lock);
> + }
> +
> timer->flags = (timer->flags & ~TIMER_BASEMASK) | cpu;
> debug_activate(timer, timer->expires);
> internal_add_timer(base, timer);

Yes, thanks! That fixes my reproducer and Chris also said he was unable
to reproduce the bug after applying that patch. You can add this if you
like:

Tested-by: Jeff Layton <jlayton@xxxxxxxxxxxxxxx>
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