Re: [PATCH 2/2] stop_machine: dequeue work before signal completion

From: Tejun Heo
Date: Tue Feb 12 2013 - 12:38:22 EST

On Sun, Feb 10, 2013 at 01:26:11PM +0800, Hillf Danton wrote:
> When a CPU is finally put down in either CPU_UP_CANCELLED or
> CPU_POST_DEAD, cpu_stop_cpu_callback() signals immediate completion on
> all cpu_stop_works still queued on the dead CPU; unfortunately, this
> code is buggy in that it doesn't remove the canceled work items off
> the stopper->works leaving it corrupted, which will trigger BUG_ON()
> during CPU_UP_PREPARE if the CPU is brought back online.
> This bug isn't easily triggered because CPU_DOWN has to race against
> cpu_stop calls and most, if not all, cpu stop users pin target CPUs.
> Fix it by popping each work item off stopper->works.
> Thanks Tejun for sharing commit message, again.
> Signed-off-by: Hillf Danton <dhillf@xxxxxxxxx>
> Reviewed-by: Namhyung Kim <namhyung@xxxxxxxxxx>
> Cc: stable@xxxxxxxxxxxxxxx

Acked-by: Tejun Heo <tj@xxxxxxxxxx>

Andrew, this one too.

Thank you!

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