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Re: [PATCH] xfs: re-enable xfsaild idle mode and fix associated races

To: Mark Tinguely <tinguely@xxxxxxx>
Subject: Re: [PATCH] xfs: re-enable xfsaild idle mode and fix associated races
From: Dave Chinner <david@xxxxxxxxxxxxx>
Date: Thu, 7 Jun 2012 12:13:53 +1000
Cc: Brian Foster <bfoster@xxxxxxxxxx>, xfs@xxxxxxxxxxx
In-reply-to: <4FCCEF94.7020501@xxxxxxx>
References: <1337875602-63025-1-git-send-email-bfoster@xxxxxxxxxx> <4FCCEF94.7020501@xxxxxxx>
User-agent: Mutt/1.5.21 (2010-09-15)
On Mon, Jun 04, 2012 at 12:25:40PM -0500, Mark Tinguely wrote:
> On 05/24/12 11:06, Brian Foster wrote:
> >xfsaild idle mode logic currently leads to a couple hangs:
> >
> >1.) If xfsaild is rescheduled in during an incremental scan
> >     (i.e., tout != 0) and the target has been updated since
> >     the previous run, we can hit the new target and go into
> >     idle mode with a still populated ail.
> >2.) A wake up is only issued when the target is pushed forward.
> >     The wake up can race with xfsaild if it is currently in the
> >     process of entering idle mode, causing future wake up
> >     events to be lost.
> >
> >Both hangs are reproducible by running xfstests 273 in a loop.
> >Modify xfsaild to enter idle mode only when the ail is empty
> >and the push target has not been moved forward since the last
> >push.
> >
> >Signed-off-by: Brian Foster<bfoster@xxxxxxxxxx>
> >---
> 
> I wouldn't mind keeping an large (a few minutes) wake up value for the
> empty AIL case to be paranoid.

And then we'll never hear about hangs....

Cheers,

Dave.
-- 
Dave Chinner
david@xxxxxxxxxxxxx

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