Subject: Re: workqueue thing
From: Peter Zijlstra <peterz@infradead.org>
To: Tejun Heo <tj@kernel.org>
Cc: torvalds@linux-foundation.org, awalls@radix.net,
       linux-kernel@vger.kernel.org, jeff@garzik.org, mingo@elte.hu,
       akpm@linux-foundation.org, jens.axboe@oracle.com, rusty@rustcorp.com.au,
       cl@linux-foundation.org, dhowells@redhat.com, arjan@linux.intel.com,
       avi@redhat.com, johannes@sipsolutions.net, andi@firstfloor.org
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	 <1261143924.20899.169.camel@laptop>  <4B2EE5A5.2030208@kernel.org>
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Date: Mon, 21 Dec 2009 10:22:57 +0100
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On Mon, 2009-12-21 at 12:04 +0900, Tejun Heo wrote:
> When IO goes wrong, in extreme
> cases, it can easily take over thirty secs to recover and that's
> required by the hardware specifications, so anything which ends up
> waiting on IO can take a pretty long time.  The only piece of code
> which is necessary to support that is the code necessary to migrate
> back tasks to CPUs when they come online again.  It's not a lot of
> ugly code. 

Why does it need to get migrated back, there are no affinity promises if
you allow hotplug to continue, so it might as well complete and continue
on the other cpu.

And yes, it is a lot of very ugly code.

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