From: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
To: Ingo Molnar <mingo@elte.hu>
Cc: akpm@osdl.org, "H. Peter Anvin" <hpa@zytor.com>,
Jeremy Fitzhardinge <jeremy@goop.org>,
Steven Rostedt <rostedt@goodmis.org>,
"Frank Ch. Eigler" <fche@redhat.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Fix x86_64 page fault scheduler race
Date: Tue, 22 Apr 2008 10:06:36 -0400 [thread overview]
Message-ID: <20080422140636.GA1683@Krystal> (raw)
In-Reply-To: <20080422132614.GC7311@elte.hu>
* Ingo Molnar (mingo@elte.hu) wrote:
>
> * Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote:
>
> > You are right in that x86_64 does not seems to play as safely as
> > x86_32 on this matter; it uses current->mm. Probably it shouldn't
> > assume "current" is valid. Actually, I don't see where x86_64 disables
> > interrupts around __switch_to, so this would seem to be a race
> > condition. Or have I missed something ?
>
> the scheduler disables interrupts around __switch_to(). (x86 does not
> set __ARCH_WANT_INTERRUPTS_ON_CTXSW)
>
> Ingo
Ok, so I guess it's only useful to NMIs then. However, it makes me
wonder why this comment was there in the first place on x86_32
vmalloc_fault() and why it uses read_cr3() :
* Do _not_ use "current" here. We might be inside
* an interrupt in the middle of a task switch..
Mathieu
--
Mathieu Desnoyers
Computer Engineering Ph.D. Student, Ecole Polytechnique de Montreal
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F BA06 3F25 A8FE 3BAE 9A68
next prev parent reply other threads:[~2008-04-22 14:06 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-04-22 13:21 [PATCH] Fix x86_64 page fault scheduler race Mathieu Desnoyers
2008-04-22 13:26 ` Ingo Molnar
2008-04-22 14:06 ` Mathieu Desnoyers [this message]
2008-04-22 14:19 ` Ingo Molnar
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