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Date: Sat, 20 Dec 2003 20:22:38 +0100
From: Ingo Molnar <mingo@elte.hu>
To: Nick Piggin <piggin@cyberone.com.au>
Cc: Andrew Morton <akpm@osdl.org>, linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 1/5] 2.6.0 fix preempt ctx switch accounting
Message-ID: <20031220192238.GA30970@elte.hu>
References: <3FE46885.2030905@cyberone.com.au>
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* Nick Piggin <piggin@cyberone.com.au> wrote:

> Make sure to count kernel preemption as a context switch. A short cut
> has been preventing it.

i'd prefer the much simpler patch below. This also keeps the kernel
preemption logic isolated instead of mixing it into the normal path.

	Ingo

--- linux/kernel/sched.c.orig	
+++ linux/kernel/sched.c	
@@ -1520,8 +1520,10 @@ need_resched:
 	 * if entering off of a kernel preemption go straight
 	 * to picking the next task.
 	 */
-	if (unlikely(preempt_count() & PREEMPT_ACTIVE))
+	if (unlikely(preempt_count() & PREEMPT_ACTIVE)) {
+		prev->nivcsw++;
 		goto pick_next_task;
+	}
 
 	switch (prev->state) {
 	case TASK_INTERRUPTIBLE: