[PATCH] sched: reassign prev and switch_count when reacquire_kernel_lock() fail

[Yong Zhang <yong.zhang0@gmail.com>]

>From 4c04fbbd43f3fef7a3b9471a0000c399c2e045ed Mon Sep 17 00:00:00 2001
From: Yong Zhang <yong.zhang0@gmail.com>
Date: Mon, 11 Jan 2010 14:21:25 +0800
Subject: [PATCH] sched: reassign prev and switch_count when
reacquire_kernel_lock() fail

Assume A->B schedule is processing, if B have acquired BKL before and
it need reschedule this time. Then on B's context, it will go to
need_resched_nonpreemptible for reschedule. But at this time, prev
and switch_count are related to A. It's wrong and will lead to
incorrect scheduler statistics.

Signed-off-by: Yong Zhang <yong.zhang0@gmail.com>
---
 kernel/sched.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)

diff --git a/kernel/sched.c b/kernel/sched.c
index c535cc4..4508fe7 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -5530,8 +5530,11 @@ need_resched_nonpreemptible:

 	post_schedule(rq);

-	if (unlikely(reacquire_kernel_lock(current) < 0))
+	if (unlikely(reacquire_kernel_lock(current) < 0)) {
+		prev = rq->curr;
+		switch_count = &prev->nivcsw;
 		goto need_resched_nonpreemptible;
+	}

 	preempt_enable_no_resched();
 	if (need_resched())
-- 
1.6.3.3