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Date: Wed, 23 Jan 2002 16:31:18 +1100
From: Anton Blanchard <anton@samba.org>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: paulus@samba.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] One-liner typo 2.5.3-pre3 in ppc/kernel/idle.c
Message-ID: <20020123053118.GB14366@krispykreme>
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> Looks like need_resched conversion error.

Actually there is a (badly commented) optimisation here. (OK so it isn't
commented at all :)

The code used to say: 

        int oldval = xchg(&current->need_resched, -1);

	if (!oldval) {
		while(current->need_resched == -1)
			; /* Do Nothing */
	}

We atomically grab the current value of need_resched and replace it with
-1. The -1 tells the scheduler that we are busy looping and it doesnt need
to send an IPI to force a reschedule.

Anton