linux-kernel - Re: mm, vmstat: kernel BUG at mm/vmstat.c:1408!

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Date:	Wed, 13 Jan 2016 17:06:47 +0530
From:	Shiraz Hashim <shiraz.linux.kernel@...il.com>
To:	Christoph Lameter <cl@...ux.com>
Cc:	Sasha Levin <sasha.levin@...cle.com>,
	Michal Hocko <mhocko@...e.cz>,
	LKML <linux-kernel@...r.kernel.org>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: mm, vmstat: kernel BUG at mm/vmstat.c:1408!

Hi Sasha,

On Tue, Jan 12, 2016 at 5:53 PM, Christoph Lameter <cl@...ux.com> wrote:
> On Tue, 12 Jan 2016, Shiraz Hashim wrote:
>
>> > +       refresh_cpu_vm_stats(false);
>> > +       cancel_delayed_work(this_cpu_ptr(&vmstat_work));
>> >
>>
>> shouldn't this be cancel_delayed_work_sync ?
>
> Hmmm... This is executed with preemption off and the work is on the same
> cpu. If it would be able to run concurrently then we would need this.
>
> Ok but it could run from the timer interrupt if that is still on and
> occuring shortly before we go idle. Guess this needs to be similar to
> the code we execute on cpu down in the vmstat notifiers (see
> vmstat_cpuup_callback).
>
> Does this fix it? I have not been able to reproduce the issue so far.
>
> Patch against -next.
>
>
>
> Subject: vmstat: Use delayed work_sync and avoid loop.
>
> Signed-off-by: Christoph Lameter <cl@...ux.com>
>
> Index: linux/mm/vmstat.c
> ===================================================================
> --- linux.orig/mm/vmstat.c
> +++ linux/mm/vmstat.c
> @@ -1419,11 +1419,9 @@ void quiet_vmstat(void)
>         if (system_state != SYSTEM_RUNNING)
>                 return;
>
> -       do {
> -               if (!cpumask_test_and_set_cpu(smp_processor_id(), cpu_stat_off))
> -                       cancel_delayed_work(this_cpu_ptr(&vmstat_work));
> -
> -       } while (refresh_cpu_vm_stats(false));
> +       refresh_cpu_vm_stats(false);
> +       cancel_delayed_work_sync(this_cpu_ptr(&vmstat_work));
> +       cpumask_set_cpu(smp_processor_id(), cpu_stat_off);
>  }
>
>  /*

Can you please give it a try, seems it is reproducing easily at your end.

-- 
regards
Shiraz Hashim