On Tue, May 31, 2016 at 1:38 AM, Wei Fang <fangwei1@xxxxxxxxxx> wrote:
> sas_ata_strategy_handler() adds the works of the ata error handler
> to system_unbound_wq. This workqueue asynchronously runs work items,
> so the ata error handler will be performed concurrently on different
> CPUs. In this case, ->host_failed will be decreased simultaneously in
> scsi_eh_finish_cmd() on different CPUs, and become abnormal.
>
> It will lead to permanently inequal between ->host_failed and
> ->host_busy, and scsi error handler thread won't become running.
> IO errors after that won't be handled forever.
>
> Use atomic type for ->host_failed to fix this race.
>
> This fixes the problem introduced in
> commit 50824d6c5657 ("[SCSI] libsas: async ata-eh").
>
> Reviewed-by: Christoph Hellwig <hch@xxxxxxxxxxxxx>
> Signed-off-by: Wei Fang <fangwei1@xxxxxxxxxx>
Acked-by: Dan Williams <dan.j.williams@xxxxxxxxx>
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