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From: Nigel Cunningham <ncunningham@crca.org.au>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: rjw@sisk.pl, linux-pm@lists.linux-foundation.org,
	linux-kernel@vger.kernel.org
Subject: Re: [linux-pm] Freezer: Don't count threads waiting for frozen filesystems.
Date: Mon, 27 Oct 2008 22:20:27 +1100	[thread overview]
Message-ID: <1225106427.26724.5.camel@nigel-laptop> (raw)
In-Reply-To: <E1KuQ1J-0002Vw-9Q@pomaz-ex.szeredi.hu>

Hi Miklos.

On Mon, 2008-10-27 at 12:12 +0100, Miklos Szeredi wrote:
> On Sun, 26 Oct 2008, Rafael J. Wysocki wrote:
> > On Saturday, 25 of October 2008, Nigel Cunningham wrote:
> > > While working on freezing fuse filesystems, I found that if a filesystem
> > > is frozen when we try to freeze processes, freezing can fail because
> > > threads are waiting in vfs_check_frozen for the filesystem to be thawed.
> > > We should thus not count such threads.
> > > 
> > > The check will be safe if a filesystem is thawed while we're freezing
> > > processes because filesystem thaws are only invoked from userspace. Any
> > > waiting processes will be woken and frozen prior to us completing the
> > > freezing of userspace (the caller invoking the filesystem thaw will be
> > > freezing) or - in the worst case - together with kernel threads.
> 
> The description is missing some details: why is the filesystem frozen
> before suspend?  AFAICS this can happen when DM calls bdev_freeze() on
> the device before the task freezing begins.  Is this the case?

It doesn't matter why a process is sitting in that wait_event call. What
does matter is that one can be there. In the case where I saw it, I was
working on fuse freezing. I don't remember the details, as it's a year
since I made this patch, but I don't think I wasn't using fuse or DM.

> Also, while the patch might solve some of the symptoms of the fuse
> vs. process freezer interaction, it will not fully fix that problem.
> As such it's just a hack to hide the problem, making it less likely to
> appear.

No, it's part of the solution. I haven't posted the full fuse freezing
patch because I thought this could be profitably merged without the rest
of the patch.

Regards,

Nigel


  reply	other threads:[~2008-10-27 11:20 UTC|newest]

Thread overview: 59+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
     [not found] <1224886068.6478.21.camel@nigel-laptop>
2008-10-26 20:01 ` Rafael J. Wysocki
2008-10-27 11:12   ` Miklos Szeredi
2008-10-27 11:20     ` Nigel Cunningham [this message]
2008-10-27 11:37       ` Rafael J. Wysocki
2008-10-27 11:40         ` Nigel Cunningham
2008-10-27 12:38           ` Miklos Szeredi
2008-10-27 20:59             ` Nigel Cunningham
2008-10-27 21:09               ` Miklos Szeredi
2008-10-27 22:13                 ` Nigel Cunningham
2008-10-28 20:25                   ` Miklos Szeredi
2008-10-28 21:29                     ` Nigel Cunningham
2008-10-28 21:51                       ` Miklos Szeredi
2008-10-28 22:00                         ` Rafael J. Wysocki
2008-10-28 22:02                           ` Miklos Szeredi
2008-10-28 22:21                             ` Rafael J. Wysocki
2008-10-28 23:21                               ` Miklos Szeredi
2008-10-28 23:59                                 ` Rafael J. Wysocki
2008-10-29  8:10                                   ` Miklos Szeredi
2008-10-29 13:51                                     ` Alan Stern
2008-10-29 14:50                                       ` Miklos Szeredi
2008-10-29 15:28                                         ` Alan Stern
2008-10-29 15:50                                           ` Miklos Szeredi
2008-10-29 16:17                                             ` Alan Stern
2008-10-29 16:10                                           ` Miklos Szeredi
2008-10-29 20:37                                             ` Alan Stern
2008-10-29 21:11                                               ` Rafael J. Wysocki
2008-10-29 21:45                                                 ` Nigel Cunningham
2008-10-29 22:07                                                   ` Rafael J. Wysocki
2008-10-29 23:53                                                     ` Miklos Szeredi
2008-11-09 13:44                                                       ` Pavel Machek
2008-10-29 23:48                                                   ` Miklos Szeredi
2008-10-30 13:04                                                     ` Nigel Cunningham
2008-10-30 13:56                                                       ` Alan Stern
2008-10-30 21:44                                                         ` Nigel Cunningham
2008-10-31  8:49                                                           ` Miklos Szeredi
2008-10-31  9:10                                                             ` Nigel Cunningham
2008-10-31  9:16                                                               ` Miklos Szeredi
2008-10-31 11:28                                                                 ` Nigel Cunningham
2008-10-31 12:44                                                                   ` Miklos Szeredi
2008-10-31 21:11                                                                     ` Nigel Cunningham
2008-10-29 23:43                                               ` Miklos Szeredi
2008-10-30 13:54                                                 ` Alan Stern
2008-10-30 14:39                                                   ` Miklos Szeredi
2008-10-30 17:07                                                     ` Alan Stern
2008-10-30 17:43                                                       ` Miklos Szeredi
2008-10-30 20:17                                                     ` Rafael J. Wysocki
2008-11-15 16:58                                                     ` Pavel Machek
2008-10-29 23:56                                               ` Matthew Garrett
2008-10-28 22:03                         ` Nigel Cunningham
2008-10-28 23:04                     ` Nigel Cunningham
2008-10-28 23:12                       ` Miklos Szeredi
2008-10-28 23:17                         ` Nigel Cunningham
2008-10-28 23:24                           ` Miklos Szeredi
2008-10-28 23:41                             ` Nigel Cunningham
2008-10-28 23:45                               ` Miklos Szeredi
2008-10-28 23:50                                 ` Miklos Szeredi
2008-10-28 23:58                                   ` Nigel Cunningham
2008-10-28 23:54                                 ` Nigel Cunningham
2008-10-27 11:37       ` Miklos Szeredi

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