linux-kernel - Re: [PATCH] sched: unlikely corrupted stack end

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Message-ID: <20160614074346.GA9689@gmail.com>
Date:	Tue, 14 Jun 2016 09:43:46 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	WANG Chao <wcwxyz@...il.com>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] sched: unlikely corrupted stack end


* WANG Chao <wcwxyz@...il.com> wrote:

> unlikely() was dropped in commit ce03e41 ("sched/core: Drop unlikely
> behind BUG_ON()"), but commit 29d6455 ("sched: panic on corrupted stack
> end") dropped BUG_ON() and called panic directly.
> 
> Now we should bring unlikely() back for branch prediction.
> 
> Signed-off-by: WANG Chao <wcwxyz@...il.com>
> ---
>  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 017d539..7db442c 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -3170,7 +3170,7 @@ static noinline void __schedule_bug(struct task_struct *prev)
>  static inline void schedule_debug(struct task_struct *prev)
>  {
>  #ifdef CONFIG_SCHED_STACK_END_CHECK
> -	if (task_stack_end_corrupted(prev))
> +	if (unlikely(task_stack_end_corrupted(prev)))
>  		panic("corrupted stack end detected inside scheduler\n");
>  #endif

It would be better and cleaner to push that into the task_stack_end_corrupted() 
definition. (and to turn it into an inline function while we are touching it.)

Thanks,

	Ingo