Subject: [PATCH 2/2] ARM: include: asm: use 'int' instead of 'unsigned long' for normal register variables within atomic.h

From: [email-masked] (Chen Gang)
Date: Fri, 04 Oct 2013 17:51:56 +0800

On 10/04/2013 12:32 AM, Will Deacon wrote:
> On Thu, Oct 03, 2013 at 11:05:31AM +0100, Chen Gang wrote:
>> If need send patch v2 for it, I should try (if so, need patch 1 also
>> send again?).
> 
> Almost, comments below.
> 
>>> So the related patch is below (still based on Patch 1):
>>>
>>> -----------------------------patch begin--------------------------------
>>>
>>> arm/include/asm/atomic.h: use 'int' instead of 'unsigned long' for 'oldval' in atomic_cmpxchg().
>>>
>>>   For atomic_cmpxchg(), the type of 'oldval' need be 'int' to match the
>>>   type of "*ptr" (used by 'ldrex' instruction) and 'old' (used by 'teq'
>>>   instruction).
>>>
>>>
>>> Signed-off-by: Chen Gang <[email-masked]>
>>> ---
>>>  arch/arm/include/asm/atomic.h |    3 ++-
>>>  1 files changed, 2 insertions(+), 1 deletions(-)
>>>
>>> diff --git a/arch/arm/include/asm/atomic.h b/arch/arm/include/asm/atomic.h
>>> index a715ac0..9ee7e01 100644
>>> --- a/arch/arm/include/asm/atomic.h
>>> +++ b/arch/arm/include/asm/atomic.h
>>> @@ -114,7 +114,8 @@ static inline int atomic_sub_return(int i, atomic_t *v)
>>>  
>>>  static inline int atomic_cmpxchg(atomic_t *ptr, int old, int new)
>>>  {
>>> -	unsigned long oldval, res;
>>> +	int oldval;
>>> +	unsigned long res;
>>>  
>>>  	smp_mb();
> 
> I think you should also fix atomic_clear_mask to take (unsigned int mask,
> atomic_t *v). That would require a third patch fixing asm-generic, where
> atomic_clear_mask and atomic_set_mask have different types for the mask
> parameter.
> 
> The problem with arm64 is that we're using *unsigned long* for 32-bit
> clear_mask, which is definitely wrong because it's 64-bit (another patch to
> fix this!).
> 

At least, that is not a bug.

In fact, in my opinion, atomic_set/clear_mask() can be for both 32-bit
and 64-bit (no 'atomic64_set/clear_mask' in 'asm-generic').

> Finally, is atomic_clear_mask even used anywhere outside of
> drivers/s390/scsi/? If not, perhaps we can just drop this function from arm
> and arm64 after all.
> 

Please see my original patch which may related for our discussion:
https://lkml.org/lkml/2013/6/9/4

In fact, that already included my opinion which may related with our
discussion, and has get acked-by for s390, but still suspending :-(

> Will

Thanks.
-- 
Chen Gang