linux-kernel - Re: [PATCH] Remove process freezer from suspend to RAM pathway

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Message-Id: <200707061916.17590.nigel@nigel.suspend2.net>
Date:	Fri, 6 Jul 2007 19:16:16 +1000
From:	Nigel Cunningham <nigel@...el.suspend2.net>
To:	Miklos Szeredi <miklos@...redi.hu>
Cc:	oliver@...kum.org, rjw@...k.pl, nigel@...pend2.net, pavel@....cz,
	benh@...nel.crashing.org, mjg59@...f.ucam.org,
	linux-kernel@...r.kernel.org, linux-pm@...ts.linux-foundation.org
Subject: Re: [PATCH] Remove process freezer from suspend to RAM pathway

Hi.

On Friday 06 July 2007 19:09:43 Miklos Szeredi wrote:
> > > > Moreover, if FUSE implements syncing, then the sync from within the 
freezer
> > > > will almost certainly deadlock.
> > > 
> > > Rafael, think positively: by the time fuse implements sync(), the
> > > freezer will be long gone ;)
> > 
> > Now you are entering really dangerous territory.
> > If you can implement a meaningfull sync method, you must have dirty
> > pages in the page cache. That means you are in the page freeing path
> > of the vm. Then we are in real trouble. Don't even think about it.
> 
> VM induced deadlocks are real nasty.  I have thought about them a lot
> already.  Suspend shouldn't introduce any big surprises.

Suspend isn't introducing the surprises. Fuse is. It creates the potential 
deadlocks simply by existing (this isn't suspend or hibernate specific).

Nigel

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