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From: Miklos Szeredi <miklos@szeredi.hu>
To: stern@rowland.harvard.edu
Cc: miklos@szeredi.hu, rjw@sisk.pl, linux-kernel@vger.kernel.org,
	ncunningham@crca.org.au, linux-pm@lists.linux-foundation.org
Subject: Re: [linux-pm] Freezer: Don't count threads waiting for frozen filesystems.
Date: Wed, 29 Oct 2008 17:10:27 +0100	[thread overview]
Message-ID: <E1KvDcp-0008B7-SR@pomaz-ex.szeredi.hu> (raw)
In-Reply-To: <Pine.LNX.4.44L0.0810291122220.2189-100000@iolanthe.rowland.org> (message from Alan Stern on Wed, 29 Oct 2008 11:28:34 -0400 (EDT))

On Wed, 29 Oct 2008, Alan Stern wrote:
> On Wed, 29 Oct 2008, Miklos Szeredi wrote:
> 
> > Actually I was thinking of an rw-semaphore, not a mutex.  But yeah
> > that still has scalability problems.  But it could be done with custom
> > locking primitives, optimized for this case:
> > 
> >    suspend_disable();
> >    /* driver stuff */
> >    suspend_enable();
> 
> Yes, it could be done.  And the overhead could be minimized by using
> per-CPU variables.  It would still be an awful lot of work, and easy to
> get wrong.

OK, getting back to this, as it seems to be the only way that we agree
is doable.

How about this,

 a) identify syscalls that may make drivers do I/O:

 - read
 - write
 - ioctl
 ???

 b) add the suspend_disable/enable() primitives to these syscalls

 c) push primitives inside the implementation

c) is slightly tricky, but could be done for example by setting a flag
on open: FMODE_NO_SUSPEND_DISABLE (better name required), saying that
implementation is responsible for getting the suspend disable magic
right.

For starters this flag could be set for all non-device opens (maybe all
non-char-dev opens?), solving the fuse vs. freezer issues without any
complicated trickery.

Miklos

  parent reply	other threads:[~2008-10-29 16:10 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 [this message]
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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