From: Daniel Phillips <phillips@arcor.de>
To: Jamie Lokier <lk@tantalophile.demon.co.uk>,
Rusty Russell <rusty@rustcorp.com.au>
Cc: Oliver Neukum <oliver@neukum.name>,
Roman Zippel <zippel@linux-m68k.org>,
Alexander Viro <viro@math.psu.edu>,
kaos@ocs.com.au, linux-kernel@vger.kernel.org
Subject: Re: [RFC] Raceless module interface
Date: Thu, 12 Sep 2002 05:32:31 +0200 [thread overview]
Message-ID: <E17pKiX-0007bp-00@starship> (raw)
In-Reply-To: <20020912030933.A13608@kushida.apsleyroad.org>
On Thursday 12 September 2002 04:09, Jamie Lokier wrote:
> 1. Just before a module's cleanup_module() function is called, mark
> the module as "unloading". This should force
> try_inc_mod_use_count() to fail, causing its caller to behave like
> the associated resource (e.g. filesystem) isn't actually
> registered, and to call request_module().
My proposal produces the same effect using a slightly different
arrangement: module_cleanup() is called, and the first thing it
does is bail out with an error if there are users, or puts the
module into the inactive state (count=-1). This forces
try_inc_mod_use_count to fail, as you say.
> 2. request_module() should simply ignore modules marked as
> "unloading". It should proceed to call "insmod" etc.
>
> 3. sys_create_module() or sys_init_module() should block if there is
> a module of the same name currently in the "unloading" state.
> They should block until that module's cleanup_module() returns.
OK, this is a really good example of why replacing the lock_kernel
with a dedicated module_sem is good: if we do that, the right thing
happens. Insmod will block on the module_sem until the module is
completely unloaded and removed from the list. By the time it gets
the semaphore, everything will be in a pristine state.
The BKL on the other hand will happily relinquish control if the
cleanup sleeps, messing things up nicely.
> 4. At this point, the new instance of the module will initialise,
> request_module() calls will return and the callers which called
> try_inc_mod_use_count() in step 1 will continue with the resource
> they needed.
Yes, I don't see a problem. The problems start when you try to
shortcut this cycle. Given that a shortcut is hardly going to save
much at all, due to caching, I'd call it a waste of effort.
--
Daniel
next prev parent reply other threads:[~2002-09-12 3:26 UTC|newest]
Thread overview: 90+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-09-04 18:02 Question about pseudo filesystems Jamie Lokier
2002-09-07 12:00 ` Daniel Phillips
2002-09-07 13:36 ` Alexander Viro
2002-09-07 18:27 ` Jamie Lokier
2002-09-07 19:47 ` Alexander Viro
2002-09-08 2:21 ` Jamie Lokier
2002-09-08 2:43 ` Alexander Viro
2002-09-15 1:41 ` Moving a mount point (was Re: Question about pseudo filesystems) Rob Landley
2002-09-08 16:00 ` Question about pseudo filesystems Daniel Phillips
2002-09-09 19:48 ` Jamie Lokier
2002-09-09 20:06 ` Daniel Phillips
2002-09-10 0:44 ` Jamie Lokier
2002-09-10 1:40 ` Daniel Phillips
2002-09-10 1:56 ` Jamie Lokier
2002-09-10 2:53 ` Daniel Phillips
2002-09-10 3:26 ` Jamie Lokier
2002-09-10 3:47 ` Daniel Phillips
2002-09-10 9:15 ` Daniel Phillips
2002-09-10 10:17 ` Roman Zippel
2002-09-11 18:35 ` [RFC] Raceless module interface Daniel Phillips
2002-09-11 18:53 ` Oliver Neukum
2002-09-11 19:20 ` Daniel Phillips
2002-09-11 20:29 ` Oliver Neukum
2002-09-11 21:15 ` Daniel Phillips
2002-09-11 21:26 ` Jamie Lokier
2002-09-11 21:47 ` Daniel Phillips
2002-09-12 1:42 ` Rusty Russell
2002-09-12 2:09 ` Jamie Lokier
2002-09-12 3:13 ` Rusty Russell
2002-09-12 3:47 ` Daniel Phillips
2002-09-12 3:53 ` Alexander Viro
2002-09-12 4:11 ` Daniel Phillips
2002-09-12 4:40 ` Rusty Russell
2002-09-12 5:27 ` Daniel Phillips
2002-09-12 14:46 ` Gerhard Mack
2002-09-13 0:39 ` Rusty Russell
2002-09-13 2:23 ` Daniel Phillips
2002-09-12 5:35 ` Rusty Russell
2002-09-12 4:52 ` Rusty Russell
2002-09-12 5:58 ` Daniel Phillips
2002-09-12 7:00 ` Rusty Russell
2002-09-13 8:18 ` Helge Hafting
2002-09-12 3:32 ` Daniel Phillips [this message]
2002-09-12 1:31 ` Rusty Russell
2002-09-12 9:10 ` Oliver Neukum
2002-09-12 11:27 ` Roman Zippel
2002-09-12 13:03 ` Rusty Russell
2002-09-12 13:44 ` Roman Zippel
2002-09-13 1:30 ` Rusty Russell
2002-09-13 2:19 ` Daniel Phillips
2002-09-13 6:51 ` Rusty Russell
2002-09-13 13:34 ` Daniel Phillips
2002-09-13 13:52 ` Thunder from the hill
2002-09-13 14:09 ` Daniel Phillips
2002-09-13 14:33 ` Thunder from the hill
2002-09-13 14:44 ` Daniel Phillips
2002-09-13 14:59 ` Thunder from the hill
2002-09-13 15:17 ` Daniel Phillips
2002-09-13 15:27 ` Thunder from the hill
2002-09-13 15:37 ` Daniel Phillips
2002-09-16 2:17 ` Rusty Russell
2002-09-16 16:13 ` Daniel Phillips
2002-09-16 16:36 ` Understanding the Principles of Argumentation #3 Daniel Phillips
2002-09-16 16:42 ` Robinson Maureira Castillo
2002-09-16 17:29 ` Cort Dougan
2002-09-16 22:31 ` David Woodhouse
2002-10-01 14:13 ` Daniel Phillips
2002-10-01 14:27 ` David Woodhouse
2002-09-13 15:59 ` [RFC] Raceless module interface Daniel Phillips
2002-09-13 3:14 ` David Gibson
2002-09-13 10:35 ` Roman Zippel
2002-09-13 13:53 ` Daniel Phillips
2002-09-13 15:13 ` Roman Zippel
2002-09-13 15:30 ` Daniel Phillips
2002-09-13 15:55 ` Roman Zippel
2002-09-13 16:09 ` Daniel Phillips
2002-09-13 16:39 ` Thunder from the hill
2002-09-13 17:12 ` Daniel Phillips
2002-09-16 0:24 ` Bill Davidsen
2002-09-16 1:49 ` Rusty Russell
2002-09-16 21:36 ` Roman Zippel
2002-09-16 21:48 ` Daniel Phillips
2002-09-16 22:44 ` Roman Zippel
2002-09-11 15:28 ` Question about pseudo filesystems Bill Davidsen
2002-09-11 19:36 ` Daniel Phillips
2002-09-09 20:12 ` Daniel Phillips
2002-09-09 22:56 ` Jamie Lokier
2002-09-10 1:39 ` Alexander Viro
2002-09-09 20:18 ` Daniel Phillips
2002-09-10 6:48 ` Kai Henningsen
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