linux-kernel - Re: [PATCH 1/3] Make the IDE DMA timeout modifiable

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Message-ID: <4693D9B6.4090408@ru.mvista.com>
Date:	Tue, 10 Jul 2007 23:10:46 +0400
From:	Sergei Shtylyov <sshtylyov@...mvista.com>
To:	Bartlomiej Zolnierkiewicz <bzolnier@...il.com>
Cc:	Suleiman Souhlal <ssouhlal@...ebsd.org>, linux-ide@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] Make the IDE DMA timeout modifiable

Hello.

Bartlomiej Zolnierkiewicz wrote:

>>>>On Feb 20, 2007, at 5:44 PM, Bartlomiej Zolnierkiewicz wrote:

>>>>>On Wednesday 21 February 2007 02:19, Suleiman Souhlal wrote:

>>>>>>It can be changed via /proc/ide/hd?/settings.

>>>>>Why do we need to change IDE DMA timeout dynamically?

>>>>I've used it to test error recovery (for example).

>>>Seems quite useable for developers but I would prefer not to
>>>expose it in production kernels for end users.

>>    It seems that I have counter example of a customer asking if this timeout 
>>can be done configurable. :-)

> May I ask what was the rationale for this request?

    Their system seems to become unschedulable for this period of time (DMA 
timeouts happen from time to time) -- at least the keepalive daemon stopped 
replying during this period...

> I have no strong feelings about adding this /proc/ide/ setting but I worry
> that it could be (mis)used just to (unreliably) work-around problems...

>>    BTW, why the timeout is so damn long? 2*WAIT_CMD is 20 secs, and if DMA is 
>>not complete or interrupt pending, it may wait 10 more secs...

> I really don't remember... :)

> Maybe Mark or Alan could help with figuring this out.

    They also have probably forgotten. :-)

> Thanks,
> Bart

MBR, Sergei
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