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Date: Thu, 04 Apr 2002 15:10:21 -0800
From: Andrew Morton <akpm@zip.com.au>
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To: Robert Love <rml@tech9.net>
CC: Roger Larsson <roger.larsson@norran.net>,
        Linus Torvalds <torvalds@transmeta.com>,
        Dave Hansen <haveblue@us.ibm.com>,
        "Adam J. Richter" <adam@yggdrasil.com>, linux-kernel@vger.kernel.org
Subject: Re: Patch: linux-2.5.8-pre1/kernel/exit.c change caused BUG() atboot  
 time
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Robert Love wrote:
> 
> ...
> This allows us to preempt tasks in any state, without problems or
> special cases.  It also wasn't too much overhead - compared to now,
> basically just:
> 
>         if (unlikely(current->preempt_count() & PREEMPT_ACTIVE))
>                 goto pick_next_task;
> 
> at the top of schedule().
> 

That's changing schedule().  Seems that I'd ruled out that
option prematurely.  As current->preempt_count() and PREEMPT_ACTIVE
can both evaluate to constant zero if CONFIG_PREEMPT=n, it can
be done ifdeflessly.

Everything happens inside rq->lock.  Looks solid to me.

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