Re: [PATCH v2 1/2] scsi: fix race between simultaneous decrements of ->host_failed

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On Tue, 2016-05-31 at 16:38 +0800, Wei Fang 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.

As I said previously, you don't need atomics to do this, could you just
remove the decrement in scsi_eh_finish_command() and zero the counter
after the strategy handler completes.

Thanks,

James


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