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

[Andi Kleen <andi@firstfloor.org>]

> >> 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.

-Andi
-- 
ak@linux.intel.com -- Speaking for myself only.

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