From 31915ab4cbf507aadab40847cf9989da5e88b090 Mon Sep 17 00:00:00 2001
From: Heiko Carstens <heiko.carstens@de.ibm.com>
Date: Thu, 16 Sep 2010 14:42:25 +0200
Subject: [PATCH] sched: Remove branch hints within context_switch()
With 710390d9 "sched: Optimize branch hint in context_switch()"
the branch hint logic within context_switch() got inversed.
In fact the hints "if (likely(!mm))" and "if (likely(!prev->mm))"
mean that it is likely that the previous and next task are kernel
threads.
That assumption is certainly counter intuitive, but Tim has shown
that at least with his workload this is true. Nevertheless the
truth is: it depends on the current workload. So just remove the
annotations which also improves readability.
Reported-by: Tim Blechmann <tim@klingt.org>
Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
LKML-Reference: <20100916124225.GA2209@osiris.boeblingen.de.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
kernel/sched.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
diff --git a/kernel/sched.c b/kernel/sched.c
index b40b82e33590d..16a1129f51ec4 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -2845,14 +2845,14 @@ context_switch(struct rq *rq, struct task_struct *prev,
*/
arch_start_context_switch(prev);
- if (likely(!mm)) {
+ if (!mm) {
next->active_mm = oldmm;
atomic_inc(&oldmm->mm_count);
enter_lazy_tlb(oldmm, next);
} else
switch_mm(oldmm, mm, next);
- if (likely(!prev->mm)) {
+ if (!prev->mm) {
prev->active_mm = NULL;
rq->prev_mm = oldmm;
}