Re: [PATCH v3 1/9] block: Fix a race in the runtime power management code

[Hannes Reinecke <hare@suse.de>]

On 11/23/20 4:17 AM, Bart Van Assche wrote:
> With the current implementation the following race can happen:
> * blk_pre_runtime_suspend() calls blk_freeze_queue_start() and
>    blk_mq_unfreeze_queue().
> * blk_queue_enter() calls blk_queue_pm_only() and that function returns
>    true.
> * blk_queue_enter() calls blk_pm_request_resume() and that function does
>    not call pm_request_resume() because the queue runtime status is
>    RPM_ACTIVE.
> * blk_pre_runtime_suspend() changes the queue status into RPM_SUSPENDING.
> 
> Fix this race by changing the queue runtime status into RPM_SUSPENDING
> before switching q_usage_counter to atomic mode.
> 
> Acked-by: Alan Stern <stern@rowland.harvard.edu>
> Acked-by: Stanley Chu <stanley.chu@mediatek.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Cc: Ming Lei <ming.lei@redhat.com>
> Cc: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
> Cc: stable <stable@vger.kernel.org>
> Fixes: 986d413b7c15 ("blk-mq: Enable support for runtime power management")
> Signed-off-by: Can Guo <cang@codeaurora.org>
> Signed-off-by: Bart Van Assche <bvanassche@acm.org>
> ---
>   block/blk-pm.c | 15 +++++++++------
>   1 file changed, 9 insertions(+), 6 deletions(-)
> 
Reviewed-by: Hannes Reinecke <hare@suse.de>

Cheers,

Hannes
-- 
Dr. Hannes Reinecke                Kernel Storage Architect
hare@suse.de                              +49 911 74053 688
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