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From: Miklos Szeredi <miklos@szeredi.hu>
To: ncunningham@crca.org.au
Cc: miklos@szeredi.hu, 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: Fri, 31 Oct 2008 13:44:41 +0100	[thread overview]
Message-ID: <E1KvtMn-0004YD-00@pomaz-ex.szeredi.hu> (raw)
In-Reply-To: <1225452484.6574.35.camel@nigel-laptop> (message from Nigel Cunningham on Fri, 31 Oct 2008 22:28:04 +1100)

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.

> 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.

Miklos

  reply	other threads:[~2008-10-31 12:45 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 [this message]
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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