Re: [PATCH 1/2] rwsem: check the lock before cpmxchg in down_write_trylockand rwsem_do_wake

[Alex Shi]

On 06/23/2013 01:10 PM, Andi Kleen wrote:
>>>> diff --git a/include/asm-generic/rwsem.h b/include/asm-generic/rwsem.h
>>>> > >> index bb1e2cd..052d973 100644
>>>> > >> --- a/include/asm-generic/rwsem.h
>>>> > >> +++ b/include/asm-generic/rwsem.h
>>>> > >> @@ -70,11 +70,11 @@ static inline void __down_write(struct
>>>> > >> rw_semaphore *sem)
>>>> > >>
>>>> > >>   static inline int __down_write_trylock(struct rw_semaphore *sem)
>>>> > >>   {
>>>> > >> -    long tmp;
>>>> > >> +    if (unlikely(&sem->count != RWSEM_UNLOCKED_VALUE))
>>> > >                      ^^^^^^^^^^^
>>> > > 
>>> > > This is probably not what you want.
>>> > > 
>> > 
>> > this function logical is quite simple. check the sem->count before
>> > cmpxchg is no harm this logical.
>> > 
>> > So could you like to tell us what should we want?
> You are comparing the address, not the value. Remove the &
> This was a nop too.

ops, So stupid I am! :(

-- 
Thanks
    Alex
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