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Date: Tue, 22 Apr 2008 16:19:09 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
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
Message-ID: <20080422141909.GE24966@elte.hu>
References: <20080422132151.GA32120@Krystal> <20080422132614.GC7311@elte.hu> <20080422140636.GA1683@Krystal>
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* Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> wrote:

> > the scheduler disables interrupts around __switch_to(). (x86 does 
> > not set __ARCH_WANT_INTERRUPTS_ON_CTXSW)
> 
> 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..

hm, i guess it's still useful to keep the 
__ARCH_WANT_INTERRUPTS_ON_CTXSW case working too. On -rt we used to 
enable it to squeeze a tiny bit more latency out of the system.

	Ingo