Messages in this thread | | | Subject | Re: [PATCH v2] arm64: Introduce IRQ stack | From | Jungseok Lee <> | Date | Fri, 18 Sep 2015 22:02:50 +0900 |
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On Sep 18, 2015, at 2:07 AM, Catalin Marinas wrote: > On Thu, Sep 17, 2015 at 09:36:04PM +0900, Jungseok Lee wrote: >> On Sep 17, 2015, at 7:33 PM, James Morse wrote: >>> On 16/09/15 12:25, Will Deacon wrote: >>>> On Sun, Sep 13, 2015 at 03:42:17PM +0100, Jungseok Lee wrote: >>>>> diff --git a/arch/arm64/include/asm/thread_info.h b/arch/arm64/include/asm/thread_info.h >>>>> index dcd06d1..44839c0 100644 >>>>> --- a/arch/arm64/include/asm/thread_info.h >>>>> +++ b/arch/arm64/include/asm/thread_info.h >>>>> @@ -73,8 +73,11 @@ static inline struct thread_info *current_thread_info(void) __attribute_const__; >>>>> >>>>> static inline struct thread_info *current_thread_info(void) >>>>> { >>>>> - return (struct thread_info *) >>>>> - (current_stack_pointer & ~(THREAD_SIZE - 1)); >>>>> + unsigned long sp_el0; >>>>> + >>>>> + asm volatile("mrs %0, sp_el0" : "=r" (sp_el0)); >>>>> + >>>>> + return (struct thread_info *)(sp_el0 & ~(THREAD_SIZE - 1)); >>>> >>>> This looks like it will generate worse code than our current implementation, >>>> thanks to the asm volatile. Maybe just add something like a global >>>> current_stack_pointer_el0? > [...] >> --- a/arch/arm64/include/asm/thread_info.h >> +++ b/arch/arm64/include/asm/thread_info.h >> @@ -77,7 +77,7 @@ static inline struct thread_info *current_thread_info(void) >> >> asm volatile("mrs %0, sp_el0" : "=r" (sp_el0)); >> >> - return (struct thread_info *)(sp_el0 & ~(THREAD_SIZE - 1)); >> + return (struct thread_info *)sp_el0; >> } > > This makes sense, since we just use sp_el0 as a scratch register, store > the current thread_info address directly. But, as James mentioned, I > don't think you need asm volatile, just asm (it has a small impact in my > tests).
I will squash this change into the original one without volatile.
Best Regards Jungseok Lee
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