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From: James Bottomley <jejb@linux.vnet.ibm.com>
To: Wei Fang <fangwei1@huawei.com>,
	tj@kernel.org, martin.petersen@oracle.com, corbet@lwn.net
Cc: hch@infradead.org, dan.j.williams@intel.com,
	linux-ide@vger.kernel.org, linux-scsi@vger.kernel.org,
	linux-doc@vger.kernel.org
Subject: Re: [PATCH v2 1/2] scsi: fix race between simultaneous decrements of ->host_failed
Date: Wed, 01 Jun 2016 10:06:11 -0400	[thread overview]
Message-ID: <1464789971.23285.1.camel@linux.vnet.ibm.com> (raw)
In-Reply-To: <1464683898-9877-1-git-send-email-fangwei1@huawei.com>

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



  parent reply	other threads:[~2016-06-01 14:06 UTC|newest]

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-05-31  8:38 [PATCH v2 1/2] scsi: fix race between simultaneous decrements of ->host_failed Wei Fang
2016-05-31  8:38 ` [PATCH v2 2/2] Documentation/scsi: update scsi_eh.txt about ->host_failed Wei Fang
2016-05-31 14:33 ` [PATCH v2 1/2] scsi: fix race between simultaneous decrements of ->host_failed Tejun Heo
2016-06-01  1:20   ` Wei Fang
2016-06-01  3:21 ` Dan Williams
2016-06-01  3:30   ` Dan Williams
2016-06-01 14:06 ` James Bottomley [this message]
2016-06-02  1:58   ` Wei Fang
2016-06-01 14:36 ` Kevin Groeneveld
2016-06-01 15:29   ` Bart Van Assche
2016-06-01 15:38     ` James Bottomley
2016-06-02  2:37   ` Wei Fang
2016-06-02  3:09     ` Wei Fang
2016-06-06 12:48     ` Kevin Groeneveld

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