From: Heiko Carstens <heiko.carstens@de.ibm.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org, mm-commits@vger.kernel.org,
buytenh@wantstofly.org, mingo@elte.hu, riku.voipio@movial.fi,
stable@kernel.org, schwidefsky@de.ibm.com
Subject: Re: + futex-runtime-enable-pi-and-robust-functionality.patch added to -mm tree
Date: Sat, 16 Feb 2008 15:04:44 +0100 [thread overview]
Message-ID: <20080216140444.GC4900@osiris.boeblingen.de.ibm.com> (raw)
In-Reply-To: <alpine.LFD.1.00.0802161444510.7583@apollo.tec.linutronix.de>
On Sat, Feb 16, 2008 at 02:48:17PM +0100, Thomas Gleixner wrote:
> On Sat, 16 Feb 2008, Heiko Carstens wrote:
>
> > > Well, NULL pointer dereferencing is supposed to fail, isn't it ?
> >
> > I wasn't sure that this is true for all architectures, but...
>
> It's an requirement for futex support.
To be more precise: dereferencing alone won't cause an exception for
NULL pointers on s390. Only writes will do so.
That is very architecture specific since we cannot unmap page 0,
it contains per-cpu data -- like exception pointers and all such stuff
that the cpu needs.
Just in case there is any code that relies on the fact that also reads
via a NULL pointer are supposed to failed.
next prev parent reply other threads:[~2008-02-16 14:04 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <200802150149.m1F1n8Gx013909@imap1.linux-foundation.org>
2008-02-16 12:42 ` Heiko Carstens
2008-02-16 13:05 ` Thomas Gleixner
2008-02-16 13:41 ` Heiko Carstens
2008-02-16 13:48 ` Thomas Gleixner
2008-02-16 14:04 ` Heiko Carstens [this message]
2008-02-16 14:29 ` Thomas Gleixner
2008-03-27 3:32 ` Benjamin Herrenschmidt
2008-03-27 3:48 ` Benjamin Herrenschmidt
2008-03-27 12:03 ` Josh Boyer
2008-02-18 13:00 ` Andrew Morton
2008-02-18 13:10 ` Heiko Carstens
2008-02-18 13:18 ` Heiko Carstens
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