From: Nigel Cunningham <nigel@suspend2.net>
Organization: Suspend2.net
To: "Rafael J. Wysocki" <rjw@sisk.pl>
Subject: Re: [ 00/23] [Suspend2] Freezer Upgrade Patches
Date: Fri, 27 Jan 2006 14:04:08 +1000
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Cc: linux-kernel@vger.kernel.org, Pavel Machek <pavel@suse.cz>
References: <20060126034518.3178.55397.stgit@localhost.localdomain> <200601270010.22702.rjw@sisk.pl>
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Hi.

On Friday 27 January 2006 09:10, Rafael J. Wysocki wrote:
> Hi,
>
> On Thursday, 26 January 2006 04:45, Nigel Cunningham wrote:
> > Hi everyone.
> >
> > This set of patches represents the freezer upgrade patches from Suspend2.
> >
> > The key features of this changeset are:
> >
> > - Use of Christoph Lameter's todo list notifiers, which help with SMP
> >   cleanness.
> > - Splitting the freezing of kernel and userspace processes. Freezing
> >   currently suffers from a race because userspace processes can be
> >   submitting work for kernel threads, thereby stopping them from
> >   responding to freeze messages in a timely manner. The freezer can
> >   thus give up when it doesn't really need to. (This is not normally
> >   a problem only because load is not usually high).
>
> Could you please describe specific situation?

The simplest example would be:

dd if=/dev/hda of=/dev/null
echo disk > /sys/power/state

> > - The use of bdev freezing to ensure filesystems are properly frozen,
> >   thereby increasing the integrity of on-disk data in the case where
> >   a resume doesn't occur. This is also helpful in the case of Suspend2,
> >   where we don't atomically copy all memory, instead writing LRU pages
> >   separately.
>
> Is this also needed when we do atomically copy all memory?

I'm not thawing the bdevs until the end of resuming, so no.

Regards,

Nigel

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