From: Christoph Hellwig <hch@infradead.org>
To: James Bottomley <jejb@linux.vnet.ibm.com>
Cc: Wei Fang <fangwei1@huawei.com>,
tj@kernel.org, martin.petersen@oracle.com,
linux-ide@vger.kernel.org, linux-scsi@vger.kernel.org
Subject: Re: [PATCH] scsi: fix race between simultaneous decrements of ->host_failed
Date: Sun, 29 May 2016 11:06:49 -0700 [thread overview]
Message-ID: <20160529180649.GA6486@infradead.org> (raw)
In-Reply-To: <1464536473.2287.6.camel@linux.vnet.ibm.com>
On Sun, May 29, 2016 at 08:41:13AM -0700, James Bottomley wrote:
> Actually, it doesn't look fine at all. The same mechanism that's
> supposed to protect the host_failed decrement is also supposed to
> protect the list_move_tail(). If there's a problem with the former
> then we're also in danger of corrupting the list.
No, that's not the case. eh_entry is used for two things:
a) shost->eh_cmd_q, which is used to queue up command for the EH
thread, and is locked using the host lock.
b) various on-stack lists in the EH thread
scsi_eh_finish_cmd is only called for case b) as all EH thread
implementations move the commands from eh_cmd_q to a local list
as the very first thing.
host_fail on the other hand is incremented under the host_lock
in scsi_eh_scmd_add, but decremented without any lock from the
EH thread.
next prev parent reply other threads:[~2016-05-29 18:06 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-05-28 3:51 [PATCH] scsi: fix race between simultaneous decrements of ->host_failed Wei Fang
2016-05-29 6:54 ` Christoph Hellwig
2016-05-29 15:41 ` James Bottomley
2016-05-29 18:06 ` Christoph Hellwig [this message]
2016-05-29 19:15 ` James Bottomley
2016-05-30 7:27 ` Wei Fang
2016-05-30 16:04 ` James Bottomley
2016-05-30 7:43 ` Wei Fang
2016-05-30 19:10 ` Christoph Hellwig
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