From: Joe Korty <joe.korty@ccur.com>
To: Linus Torvalds <torvalds@osdl.org>
Cc: Jamie Lokier <jamie@shareable.org>, Andrew Morton <akpm@osdl.org>,
Olof Johansson <olof@austin.ibm.com>,
linux-kernel@vger.kernel.org, rusty@rustcorp.com.au
Subject: Re: [PATCH/RFC] Futex mmap_sem deadlock
Date: Wed, 23 Feb 2005 09:49:40 -0500 [thread overview]
Message-ID: <20050223144940.GA880@tsunami.ccur.com> (raw)
In-Reply-To: <Pine.LNX.4.58.0502221317270.2378@ppc970.osdl.org>
On Tue, Feb 22, 2005 at 01:30:27PM -0800, Linus Torvalds wrote:
>
> We really have this already, and it's called "current->preempt". It
> handles any lock at all, and doesn't add yet another special case to all
> the architectures.
>
> Just do
>
> repeat:
> down_read(¤t->mm->mmap_sem);
> get_futex_key(...) etc.
> queue_me(...) etc.
> inc_preempt_count();
> ret = get_user(...);
> dec_preempt_count();
Perhaps this should be preempt_disable .... preempt_enable.
Otherwise, a preempt attempt in get_user would not be seen
until some future preempt_enable was executed.
Regards,
Joe
--
"Money can buy bandwidth, but latency is forever" -- John Mashey
next prev parent reply other threads:[~2005-02-23 14:50 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-02-22 19:06 [PATCH/RFC] Futex mmap_sem deadlock Olof Johansson
2005-02-22 19:36 ` Linus Torvalds
2005-02-22 21:16 ` Benjamin Herrenschmidt
2005-02-22 21:19 ` Benjamin Herrenschmidt
2005-02-22 21:31 ` Linus Torvalds
2005-02-22 21:42 ` Benjamin Herrenschmidt
2005-02-22 22:10 ` Linus Torvalds
2005-02-22 22:24 ` Benjamin Herrenschmidt
2005-02-22 23:08 ` Greg KH
2005-02-23 11:24 ` David Howells
2005-02-22 19:55 ` Andrew Morton
2005-02-22 21:07 ` Jamie Lokier
2005-02-22 21:19 ` Olof Johansson
2005-02-22 22:09 ` Jamie Lokier
2005-02-22 21:19 ` Chris Friesen
2005-02-22 21:27 ` Jamie Lokier
2005-02-22 21:30 ` Linus Torvalds
2005-02-22 22:34 ` Jamie Lokier
2005-02-22 22:42 ` Olof Johansson
2005-02-22 23:20 ` Andrew Morton
2005-02-22 23:23 ` Olof Johansson
2005-02-23 11:39 ` David Howells
2005-02-23 16:22 ` Olof Johansson
2005-02-23 18:44 ` David Howells
2005-02-23 14:49 ` Joe Korty [this message]
2005-02-23 15:54 ` Linus Torvalds
2005-02-23 17:10 ` Olof Johansson
2005-02-23 17:37 ` Arjan van de Ven
2005-02-23 18:22 ` Jamie Lokier
2005-02-23 18:34 ` Linus Torvalds
2005-02-23 18:49 ` Jamie Lokier
2005-02-23 19:12 ` Olof Johansson
2005-02-23 22:00 ` Linus Torvalds
2005-02-24 0:00 ` Jamie Lokier
2005-02-23 18:37 ` Olof Johansson
2005-02-22 21:40 ` Andrew Morton
2005-02-22 21:59 ` Linus Torvalds
2005-02-23 11:42 ` David Howells
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