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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
Date: Wed, 23 Jan 2002 16:31:18 +1100	[thread overview]
Message-ID: <20020123053118.GB14366@krispykreme> (raw)
In-Reply-To: <E16TFDk-0007wc-00@wagner.rustcorp.com.au>
In-Reply-To: <E16TFDk-0007wc-00@wagner.rustcorp.com.au>


> 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

  reply	other threads:[~2002-01-23  5:35 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2002-01-23  4:41 [PATCH] One-liner typo 2.5.3-pre3 in ppc/kernel/idle.c Rusty Russell
2002-01-23  5:31 ` Anton Blanchard [this message]
2002-01-23  6:00   ` Rusty Russell

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