linux-kernel - Re: [linux-pm] Is it supposed to be ok to call del

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Date:	Thu, 22 Apr 2010 16:40:58 -0700
From:	Matt Reimer <mattjreimer@...il.com>
To:	linux-kernel <linux-kernel@...r.kernel.org>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Alan Stern <stern@...land.harvard.edu>,
	Jens Axboe <jens.axboe@...cle.com>,
	Maxim Levitsky <maximlevitsky@...il.com>,
	linux-pm <linux-pm@...ts.linux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Pavel Machek <pavel@....cz>
Subject: Re: [linux-pm] Is it supposed to be ok to call del_gendisk while 
	userspace is frozen?

On Thu, Mar 4, 2010 at 1:15 PM, Pavel Machek <pavel@....cz> wrote:
> Hi!
>
>> > My thought exactly.  This is the only approach that also solves the
>> > following race:
>> >
>> >     A driver is unloaded at the same time as a suspend starts.
>> >
>> >     The writeback thread gets frozen.
>> >
>> >     Then before the rmmod thread is frozen, it calls del_gendisk.
>> >
>> > Delaying things by means of a workqueue (or the equivalent) might also
>> > work, but it doesn't seem as safe.  For example, some important
>> > writebacks might end up getting delayed until too late.
>
> Delaying writebacks during sleep should be ok... That's why we do
> sync() after userspace is frozen -- nothing really important should be
> waiting for writeback after that point.

Has this been fixed, or has a consensus about how to fix this been
achieved? I'm hitting the same problem and have some time to work on a
fix.

Matt
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