Re: [PATCH v2] sched: unlikely corrupted stack end

WANG Chao
2016-06-14T10:17:51Z

> 在 2016年6月14日，下午4:56，Ingo Molnar <mingo@kernel.org> 写道：
>
>
> * WANG Chao <wcwxyz@gmail.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@gmail.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()?