On 07/29/2014 11:39 AM, Christoph Lameter wrote:
> On Tue, 29 Jul 2014, Tejun Heo wrote:
>
>> Hmmm, well, then it's something else. Either a bug in workqueue or in
>> the caller. Given the track record, the latter is more likely.
>> e.g. it looks kinda suspicious that the work func is cleared after
>> cancel_delayed_work_sync() is called. What happens if somebody tries
>> to schedule it inbetween?
>
> Here is yet another patch to also address this idea:
>
> Subject: vmstat: Clear the work.func before cancelling delayed work
>
> Looks strange to me but Tejun thinks this could do some good.
> If this really is the right thing to do then cancel_delayed_work should
> zap the work func itselt I think.
>
> Signed-off-by: Christoph Lameter <c...@linux.com>
>
>
> Index: linux/mm/vmstat.c
> ===================================================================
> --- linux.orig/mm/vmstat.c 2014-07-29 10:22:45.073884943 -0500
> +++ linux/mm/vmstat.c 2014-07-29 10:34:45.083369228 -0500
> @@ -1277,8 +1277,8 @@ static int vmstat_cpuup_callback(struct
> break;
> case CPU_DOWN_PREPARE:
> case CPU_DOWN_PREPARE_FROZEN:
> - cancel_delayed_work_sync(&per_cpu(vmstat_work, cpu));
> per_cpu(vmstat_work, cpu).work.func = NULL;
> + cancel_delayed_work_sync(&per_cpu(vmstat_work, cpu));
> break;
> case CPU_DOWN_FAILED:
> case CPU_DOWN_FAILED_FROZEN:
>
I'm slightly confused here. The on demand vmstat workers patch did this:
case CPU_DOWN_PREPARE_FROZEN:
- cancel_delayed_work_sync(&per_cpu(vmstat_work, cpu));
- per_cpu(vmstat_work, cpu).work.func = NULL;
+ if (!cpumask_test_and_set_cpu(cpu, cpu_stat_off))
+ cancel_delayed_work_sync(&per_cpu(vmstat_work, cpu));
So your new patch doesn't apply on top of it, and doesn't make sense before it.
Thanks,
Sasha
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