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From: Oliver Neukum <oliver@neukum.name>
To: Daniel Phillips <phillips@arcor.de>,
	Roman Zippel <zippel@linux-m68k.org>
Cc: Jamie Lokier <lk@tantalophile.demon.co.uk>,
	Alexander Viro <viro@math.psu.edu>,
	Rusty Russell <rusty@rustcorp.com.au>,
	<linux-kernel@vger.kernel.org>
Subject: Re: [RFC] Raceless module interface
Date: Thu, 12 Sep 2002 11:10:47 +0200	[thread overview]
Message-ID: <200209121110.47246.oliver@neukum.name> (raw)
In-Reply-To: <E17pCKQ-0007Sz-00@starship>


> To make this work, we rely on the rule that no module code may
> sleep/schedule unless it first increments a counter.  The counter
> incremented will, at present, be the module->count, but that is entirely
> up to the module itself; module.c will no longer care how it keeps
> track, as long as it does.
>
> With config_preempt code, we must additionally disable preemption until
> the module quiescence test has completed.  I'm not going to go further
> into this, because this is deep scheduling-fu, and I haven't got working
> code to show yet.  Suffice to say that we have the technology to build a
> magic_wait_for_quiescence, and we must now proceed to do that.  (Robert,
> are you reading?)  A noncounting module uses the test as follows, in its
> cleanup_function:
>
> 	unregister_callpoints(...);
> 	magic_wait_for_quiescence();
> 	return cleanup_foo(...);

Please correct me if I am wrong, but ...

Task A					Task B					counter
call_module()										+1
schedule()											still 1
						unregister_callpoints()		still 1
						magic_wait_for_quiescence();	still 1
call_module_second_func() -> Won't work

So by trying to unregister a module you make a module unusable
for an unspecified amount of time.

	Regards
		Oliver



  parent reply	other threads:[~2002-09-12  8:35 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
2002-09-12  1:31                         ` Rusty Russell
2002-09-12  9:10                         ` Oliver Neukum [this message]
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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