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Re: Atomicity & preemptive kernels

To: Jun Sun <jsun@mvista.com>
Subject: Re: Atomicity & preemptive kernels
From: Justin Carlson <justin@cs.cmu.edu>
Date: 11 Jun 2002 12:56:59 -0700
Cc: linux-mips@oss.sgi.com
In-reply-to: <3D0644F4.8070902@mvista.com>
References: <1023738247.1133.56.camel@localhost.localdomain> <3D0524B5.403@mvista.com> <1023753603.1152.28.camel@localhost.localdomain> <3D0644F4.8070902@mvista.com>
Sender: owner-linux-mips@oss.sgi.com
On Tue, 2002-06-11 at 11:44, Jun Sun wrote:

> I see your point now.
> 
> However, the race is not there.  switch_mm() is only called from inside 
> schedule() function, which as a whole is preemption-safe.  In other words, 
> the 
> above event sequence won't cause a context switch until we exit from 
> schedule() function.
> 

Yes, but the initial code I cited was explicitly not in the schedule
function.  It was an icache_flush_page() implementation.

Just something to be careful of.  I think it's going to bite more than a
few people as a bug that's about impossible to track down...

-Justin

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