From: olof@austin.ibm.com (Olof Johansson)
To: Jamie Lokier <jamie@shareable.org>
Cc: Andrew Morton <akpm@osdl.org>,
linux-kernel@vger.kernel.org, torvalds@osdl.org,
rusty@rustcorp.com.au
Subject: Re: [PATCH/RFC] Futex mmap_sem deadlock
Date: Tue, 22 Feb 2005 15:19:38 -0600 [thread overview]
Message-ID: <20050222211938.GB7079@austin.ibm.com> (raw)
In-Reply-To: <20050222210752.GG22555@mail.shareable.org>
On Tue, Feb 22, 2005 at 09:07:52PM +0000, Jamie Lokier wrote:
>
> That won't work because the vma lock must be help between key
> calculation and get_user() - otherwise futex is not reliable. It
> would work if the futex key calculation was inside the loop.
Sure, but that's still true: It's just that the get_user() is done twice
instead. The semaphore is never released between the key calculation and
the "real" get_user().
> A much simpler solution (and sorry for not offering it earlier,
> because Andrew Morton pointed out this bug long ago, but I was busy), is:
Either way works for me. Andrew/Linus, got a preference? I'll either
post my refresh based on Andrews comments, or code up Jamie's
suggestion.
-Olof
next prev parent reply other threads:[~2005-02-22 21:23 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-02-22 19:06 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
2005-02-22 19:55 ` Andrew Morton
2005-02-22 21:07 ` Jamie Lokier
2005-02-22 21:19 ` Olof Johansson [this message]
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 14:49 ` Joe Korty
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 11:39 ` David Howells
2005-02-23 16:22 ` Olof Johansson
2005-02-23 18:44 ` David Howells
2005-02-23 11:42 ` David Howells
2005-02-23 11:24 ` David Howells
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