Am 26.03.2015 um 18:23 schrieb Christian Borntraeger:
> Am 26.03.2015 um 18:07 schrieb Peter Zijlstra:
>> On Thu, Mar 26, 2015 at 09:45:07AM -0700, Linus Torvalds wrote:
>>
>>> Stop this idiocy.
>>
>> Yeah, clearly I can type faster than I can think straight :/
>>
>>
>> In any case, I've the below patch; do you want to take it now or do you
>> want me to route it through tip/locking/urgent or something like that?
>
> Its not urgent. Current upstream has a broken check (gcc will not emit the
> warning if the function is static). I just fixed the check in my next tree
> but I can certainly drop that tree.
>
Thinking more about that, the removal of the ifdef for 64bit data might be
a reason to schedule that for 4.0.
>>
>> ---
>> Subject: kernel: Remove atomicy checks from {READ,WRITE}_ONCE
>> From: Peter Zijlstra <pet...@infradead.org>
>> Date: Thu, 26 Mar 2015 17:45:37 +0100
>>
>> The fact that volatile allows for atomic load/stores is a special case
>> not a requirement for {READ,WRITE}_ONCE(). Their primary purpose is to
>> force the compiler to emit load/stores _once_.
>>
>> So remove the warning as it is correct behaviour. This also implies that
>> the u64 case is not 64bit only, so remove the #ifdef so we can generate
>> better code in that case.
>>
>> Cc: Stephen Rothwell <s...@canb.auug.org.au>
>> Cc: Christian Borntraeger <borntrae...@de.ibm.com>
>> Cc: Thomas Gleixner <t...@linutronix.de>
>> Cc: Ingo Molnar <mi...@elte.hu>
>> Cc: "H. Peter Anvin" <h...@zytor.com>
>> Cc: Davidlohr Bueso <d...@stgolabs.net>
>> Cc: Paul McKenney <paul...@linux.vnet.ibm.com>
>> Cc: Will Deacon <will.dea...@arm.com>
>> Acked-by: Linus Torvalds <torva...@linux-foundation.org>
>> Signed-off-by: Peter Zijlstra (Intel) <pet...@infradead.org>
>
> Acked-by: Christian Borntraeger <borntrae...@de.ibm.com>
>
>
>> ---
>> include/linux/compiler.h | 16 ----------------
>> 1 file changed, 16 deletions(-)
>>
>> diff --git a/include/linux/compiler.h b/include/linux/compiler.h
>> index 1b45e4a0519b..0e41ca0e5927 100644
>> --- a/include/linux/compiler.h
>> +++ b/include/linux/compiler.h
>> @@ -192,29 +192,16 @@ void ftrace_likely_update(struct ftrace_branch_data
>> *f, int val, int expect);
>>
>> #include <uapi/linux/types.h>
>>
>> -static __always_inline void data_access_exceeds_word_size(void)
>> -#ifdef __compiletime_warning
>> -__compiletime_warning("data access exceeds word size and won't be atomic")
>> -#endif
>> -;
>> -
>> -static __always_inline void data_access_exceeds_word_size(void)
>> -{
>> -}
>> -
>> static __always_inline void __read_once_size(const volatile void *p, void
>> *res, int size)
>> {
>> switch (size) {
>> case 1: *(__u8 *)res = *(volatile __u8 *)p; break;
>> case 2: *(__u16 *)res = *(volatile __u16 *)p; break;
>> case 4: *(__u32 *)res = *(volatile __u32 *)p; break;
>> -#ifdef CONFIG_64BIT
>> case 8: *(__u64 *)res = *(volatile __u64 *)p; break;
>> -#endif
>> default:
>> barrier();
>> __builtin_memcpy((void *)res, (const void *)p, size);
>> - data_access_exceeds_word_size();
>> barrier();
>> }
>> }
>> @@ -225,13 +212,10 @@ static __always_inline void __write_once_size(volatile
>> void *p, void *res, int s
>> case 1: *(volatile __u8 *)p = *(__u8 *)res; break;
>> case 2: *(volatile __u16 *)p = *(__u16 *)res; break;
>> case 4: *(volatile __u32 *)p = *(__u32 *)res; break;
>> -#ifdef CONFIG_64BIT
>> case 8: *(volatile __u64 *)p = *(__u64 *)res; break;
>> -#endif
>> default:
>> barrier();
>> __builtin_memcpy((void *)p, (const void *)res, size);
>> - data_access_exceeds_word_size();
>> barrier();
>> }
>> }
>>
>
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