linux-kernel - [PATCH v2 2/3] sched/core: drop unlikely behind BUG

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Date:	Mon,  5 Oct 2015 21:26:05 +0800
From:	Geliang Tang <geliangtang@....com>
To:	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>
Cc:	Geliang Tang <geliangtang@....com>, linux-kernel@...r.kernel.org
Subject: [PATCH v2 2/3] sched/core: drop unlikely behind BUG_ON()

(1) For !CONFIG_BUG cases, the bug call is a no-op, so we couldn't care
less and the change is ok.

(2) ppc and mips, which HAVE_ARCH_BUG_ON, do not rely on branch predictions
as it seems to be pointless[1] and thus callers should not be trying to
push an optimization in the first place.

(3) For CONFIG_BUG and !HAVE_ARCH_BUG_ON cases, BUG_ON() contains an
unlikely compiler flag already.

Hence, we can drop unlikely behind BUG_ON().

[1] http://lkml.iu.edu/hypermail/linux/kernel/1101.3/02289.html

Signed-off-by: Geliang Tang <geliangtang@....com>
---
Changes in v2:
 - Just rewrite the commit log.
---
 kernel/sched/core.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index fe81929..a3518789 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -2947,7 +2947,7 @@ static noinline void __schedule_bug(struct task_struct *prev)
 static inline void schedule_debug(struct task_struct *prev)
 {
 #ifdef CONFIG_SCHED_STACK_END_CHECK
-	BUG_ON(unlikely(task_stack_end_corrupted(prev)));
+	BUG_ON(task_stack_end_corrupted(prev));
 #endif
 	/*
 	 * Test if we are atomic. Since do_exit() needs to call into
-- 
2.5.0


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