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From: Nigel Cunningham <ncunningham@crca.org.au>
To: Miklos Szeredi <miklos@szeredi.hu>
Cc: 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: Sat, 01 Nov 2008 08:11:38 +1100	[thread overview]
Message-ID: <1225487498.6574.40.camel@nigel-laptop> (raw)
In-Reply-To: <E1KvtMn-0004YD-00@pomaz-ex.szeredi.hu>

Hi.

On Fri, 2008-10-31 at 13:44 +0100, Miklos Szeredi wrote:
> On Fri, 31 Oct 2008, Nigel Cunningham wrote:
> > You don't. You just use FUSE_MIGHT_FREEZE to stop them before they take
> > locks that might cause problems. So my suggestion is:
> 
> Before?  FUSE_MIGHT_FREEZE is called _after_ i_mutex is taken by the
> VFS.

Ok. So I'll shift it backwards in the calling chain a bit.

> > 1) Stop new requests at FUSE_MIGHT_FREEZE
> > 2) Handle existing requests by using freezer_do_not_count in
> > request_send and request_send_nowait before the spin_lock and
> > freezer_count after the spin_unlock.
> > 
> > With #2, we don't need to care about whether the request is completed
> > before freezing completes or post-resume.
> > 
> > If the userspace process tries to use an already frozen fuse filesystem
> > and gets frozen, that's okay because we'll sit waiting for an answer,
> > not be counted by the freezer and so not contribute to any failure to
> > freeze processes.
> > 
> > If the userspace process completes its work, we'll either get caught at
> > the freezer_count (if we've already been told to freeze) or be gotten
> > later, after exiting the fuse code.
> 
> Yes, this is the variant of categorizing sleeps to freezing and
> non-freezing.  The problem is, you need to do that with all
> mutex_lock(&inode->i_mutex) instances as well.  Try grepping for that
> in fs/*.c!
> 
> It _is_ possible, it's just not practical.

Let's get practical. You know fuse a lot better than me. Can you give me
the most complicated, ugly configuration you can think of, and I'll work
on making it freeze first time, every time.

Regards,

Nigel


  reply	other threads:[~2008-10-31 21:11 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
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 [this message]
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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