linux-kernel - Re: [linux-pm] Freezer: Don't count threads waiting for frozen filesystems.

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Message-Id: <E1KuyFq-0006Sc-PC@pomaz-ex.szeredi.hu>
Date:	Wed, 29 Oct 2008 00:45:42 +0100
From:	Miklos Szeredi <miklos@...redi.hu>
To:	ncunningham@...a.org.au
CC:	miklos@...redi.hu, linux-pm@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [linux-pm] Freezer: Don't count threads waiting for
	frozen	filesystems.

On Wed, 29 Oct 2008, Nigel Cunningham wrote:
> Hi.
> 
> On Wed, 2008-10-29 at 00:24 +0100, Miklos Szeredi wrote:
> > On Wed, 29 Oct 2008, Nigel Cunningham wrote:
> > > Remember, though, that we're only freezing fuse at the moment, and
> > > strictly one filesystem at a time. We can thus happily wait for the
> > > i_mutex taken by some other process to be released.
> > 
> > Not going to work: you need to wait for all requests to be finished,
> > but those might depend on some other fuse filesystem which has already
> > been frozen.
> 
> Okay. In that case, am I right in thinking that the request waiting on
> the frozen filesystem will be stuck in request_wait_answer,

Yes.

> and the
> userspace process that was trying to satisfy the request will be stuck
> in the FUSE_MIGHT_FREEZE call that was invoked for the frozen
> filesystem?

No, it already passed that, before the filesystem got frozen.  But it
doesn't matter, in either case i_mutex will already have been taken by
the VFS and it won't be released until the request completely
finishes.

Miklos
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