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

[Wei Fang <fangwei1@huawei.com>]

Hi, James,

On 2016/6/1 22:06, James Bottomley wrote:
> 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.
> 

OK, I'll send v3 later.

Thanks,
Wei