linux-kernel - Re: [PATCH v2] sched: unlikely corrupted stack end

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Message-Id: <AAC81E50-769F-4C37-A180-46BAD20EE89E@gmail.com>
Date:	Tue, 14 Jun 2016 18:17:29 +0800
From:	WANG Chao <wcwxyz@...il.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] sched: unlikely corrupted stack end


> 在 2016年6月14日，下午4:56，Ingo Molnar <mingo@...nel.org> 写道：
> 
> 
> * WANG Chao <wcwxyz@...il.com> wrote:
> 
>> unlikely() was dropped in commit ce03e4137bb2 ("sched/core: Drop
>> unlikely behind BUG_ON()"), but commit 29d6455178a0 ("sched: panic on
>> corrupted stack end") dropped BUG_ON() and called panic directly.
>> 
>> Now we should bring unlikely() back for branch prediction. While we're
>> at it, it's better and cleaner to turn task_stack_end_corrupted() into
>> inline function.
>> 
>> Signed-off-by: WANG Chao <wcwxyz@...il.com>
>> ---
>> include/linux/sched.h | 7 +++++--
>> 1 file changed, 5 insertions(+), 2 deletions(-)
>> 
>> diff --git a/include/linux/sched.h b/include/linux/sched.h
>> index 6e42ada26345..797ca1975431 100644
>> --- a/include/linux/sched.h
>> +++ b/include/linux/sched.h
>> @@ -2997,8 +2997,11 @@ static inline unsigned long *end_of_stack(struct task_struct *p)
>> }
>> 
>> #endif
>> -#define task_stack_end_corrupted(task) \
>> -		(*(end_of_stack(task)) != STACK_END_MAGIC)
>> +
>> +static inline int task_stack_end_corrupted(struct task_struct *p)
>> +{
>> +	return unlikely(*(end_of_stack(p)) != STACK_END_MAGIC);
>> +}
> 
> The passed in pointer should be const, and the extra parentheses around the 
> end_of_stack() call are not needed anymore (since it's now proper C code now).

end_of_stack() will discard const and cause an compiler warning.
Should I add const to end_of_stack()?