* WANG Chao <wcw...@gmail.com> wrote: > > > 在 2016年6月14日,下午6:26,Ingo Molnar <mi...@kernel.org> 写道: > > > > > > * WANG Chao <wcw...@gmail.com> wrote: > > > >> > >>> 在 2016年6月14日,下午4:56,Ingo Molnar <mi...@kernel.org> 写道: > >>> > >>> > >>> * WANG Chao <wcw...@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 <wcw...@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()? > > > > Yes. Also make sure ia64 still builds and such. > > It seems convert task_stack_end_corrupted() into inline isn’t trivial. > > In ia64, end_of_stack() is expanded to: > > (unsigned long *)((void *)(p) + ((IA64_TASK_SIZE + IA64_THREAD_INFO_SIZE + > 31) & ~31)) > > IA64_TASK_SIZE and IA64_THREAD_INFO_SIZE is defined in > arch/ia64/kernel/asm-offsets.c, > which needs to include linux/sched.h. > > So the problem is task_stack_end_corrupted() doesn’t compile before > asm-offsets.c is compiled. > asm-offsets.c also needs to include linux/sched.h to compile. I think maybe > that’s why > task_stack_end_corrupted() is introduced as marco, not inline. > > Any idea?
Oh well ... I guess we'll have to add the unlikely() to the macro itself. Thanks, Ingo