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From: Jeff Garzik on 28 Jun 2010 18:40
On 06/28/2010 05:04 PM, Tejun Heo wrote:
> libata has two concurrency related limitations.
>
> a. ata_wq which is used for polling PIO has single thread per CPU. If
> there are multiple devices doing polling PIO on the same CPU, they
> can't be executed simultaneously.
>
> b. ata_aux_wq which is used for SCSI probing has single thread. In
> cases where SCSI probing is stalled for extended period of time
> which is possible for ATAPI devices, this will stall all probing.
>
> #a is solved by increasing maximum concurrency of ata_wq. Please note
> that polling PIO might be used under allocation path and thus needs to
> be served by a separate wq with a rescuer.
>
> #b is solved by using the default wq instead and achieving exclusion
> via per-port mutex.
>
> Signed-off-by: Tejun Heo<tj(a)kernel.org>
> Cc: Jeff Garzik<jgarzik(a)pobox.com>

Acked-by: Jeff Garzik <jgarzik(a)redhat.com>


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From: Tejun Heo on 29 Jun 2010 03:10
On 06/29/2010 12:32 AM, Jeff Garzik wrote:
>> Signed-off-by: Tejun Heo<tj(a)kernel.org>
>> Cc: Jeff Garzik<jgarzik(a)pobox.com>
>
> Acked-by: Jeff Garzik <jgarzik(a)redhat.com>

Thanks, Jeff.

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tejun
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