From: "Martin K. Petersen" <martin.petersen@oracle.com>
To: Christoph Hellwig <hch@lst.de>
Cc: James Bottomley <James.Bottomley@HansenPartnership.com>,
linux-scsi@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
Bart Van Assche <bvanassche@fusionio.com>,
Mike Christie <michaelc@cs.wisc.edu>,
"Martin K. Petersen" <martin.petersen@oracle.com>,
Robert Elliott <Elliott@hp.com>, Webb Scales <webbnh@hp.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 09/14] scsi: fix the {host,target,device}_blocked counter mess
Date: Fri, 25 Jul 2014 15:08:46 -0400 [thread overview]
Message-ID: <yq1silpgssh.fsf@sermon.lab.mkp.net> (raw)
In-Reply-To: <1405678393-11497-10-git-send-email-hch@lst.de> (Christoph Hellwig's message of "Fri, 18 Jul 2014 12:13:08 +0200")
>>>>> "Christoph" == Christoph Hellwig <hch@lst.de> writes:
Christoph> Seems like these counters are missing any sort of
Christoph> synchronization for updates, as a over 10 year old comment
Christoph> from me noted. Fix this by using atomic counters, and while
Christoph> we're at it also make sure they are in the same cacheline as
Christoph> the _busy counters and not needlessly stored to in every I/O
Christoph> completion.
Christoph> With the new model the _busy counters can temporarily go
Christoph> negative, so all the readers are updated to check for > 0
Christoph> values. Longer term every successful I/O completion will
Christoph> reset the counters to zero, so the temporarily negative
Christoph> values will not cause any harm.
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
--
Martin K. Petersen Oracle Linux Engineering
next prev parent reply other threads:[~2014-07-25 19:09 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-18 10:12 scsi-mq V4 Christoph Hellwig
2014-07-18 10:13 ` [PATCH 01/14] scsi: add scsi_setup_cmnd helper Christoph Hellwig
2014-07-22 3:42 ` Martin K. Petersen
2014-07-18 10:13 ` [PATCH 02/14] scsi: split __scsi_queue_insert Christoph Hellwig
2014-07-22 3:44 ` Martin K. Petersen
2014-07-18 10:13 ` [PATCH 03/14] scsi: centralize command re-queueing in scsi_dispatch_fn Christoph Hellwig
2014-07-22 3:46 ` Martin K. Petersen
2014-07-18 10:13 ` [PATCH 04/14] scsi: set ->scsi_done before calling scsi_dispatch_cmd Christoph Hellwig
2014-07-22 3:48 ` Martin K. Petersen
2014-07-18 10:13 ` [PATCH 05/14] scsi: push host_lock down into scsi_{host,target}_queue_ready Christoph Hellwig
2014-07-22 3:52 ` Martin K. Petersen
2014-07-18 10:13 ` [PATCH 06/14] scsi: convert target_busy to an atomic_t Christoph Hellwig
2014-07-22 3:56 ` Martin K. Petersen
2014-07-18 10:13 ` [PATCH 07/14] scsi: convert host_busy to atomic_t Christoph Hellwig
2014-07-22 4:01 ` Martin K. Petersen
2014-07-22 4:18 ` Martin K. Petersen
2014-07-25 11:38 ` Christoph Hellwig
2014-07-18 10:13 ` [PATCH 08/14] scsi: convert device_busy " Christoph Hellwig
2014-07-18 10:13 ` [PATCH 09/14] scsi: fix the {host,target,device}_blocked counter mess Christoph Hellwig
2014-07-25 19:08 ` Martin K. Petersen [this message]
2014-07-18 10:13 ` [PATCH 10/14] scsi: only maintain target_blocked if the driver has a target queue limit Christoph Hellwig
2014-07-25 19:10 ` Martin K. Petersen
2014-07-18 10:13 ` [PATCH 11/14] scsi: unwind blk_end_request_all and blk_end_request_err calls Christoph Hellwig
2014-07-25 19:12 ` Martin K. Petersen
2014-07-18 10:13 ` [PATCH 12/14] scatterlist: allow chaining to preallocated chunks Christoph Hellwig
2014-07-25 19:15 ` Martin K. Petersen
2014-07-18 10:13 ` [PATCH 13/14] scsi: add support for a blk-mq based I/O path Christoph Hellwig
2014-07-25 19:29 ` Martin K. Petersen
2014-08-18 22:21 ` Kashyap Desai
2014-08-19 15:41 ` Kashyap Desai
2014-08-19 16:06 ` Christoph Hellwig
2014-08-19 16:11 ` Kashyap Desai
2014-07-18 10:13 ` [PATCH 14/14] fnic: reject device resets without assigned tags for the blk-mq case Christoph Hellwig
2014-07-25 19:31 ` Martin K. Petersen
-- strict thread matches above, loose matches on Subject: below --
2014-06-25 16:51 scsi-mq V2 Christoph Hellwig
2014-06-25 16:51 ` [PATCH 09/14] scsi: fix the {host,target,device}_blocked counter mess Christoph Hellwig
2014-07-09 11:12 ` Hannes Reinecke
2014-07-10 6:06 ` Christoph Hellwig
2014-06-12 13:48 scsi-mq Christoph Hellwig
2014-06-12 13:49 ` [PATCH 09/14] scsi: fix the {host,target,device}_blocked counter mess Christoph Hellwig
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