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Message-ID: <1464995089.2367.7.camel@j-VirtualBox>
Subject: Re: [RFC][PATCH 0/7] locking/rwsem: Convert rwsem count to
 atomic_long_t
From: Jason Low <jason.low2@hpe.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: jason.low2@hp.com, Ingo Molnar <mingo@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
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Date: Fri, 03 Jun 2016 16:04:49 -0700
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On Sat, 2016-06-04 at 00:36 +0200, Peter Zijlstra wrote:
> On Fri, Jun 03, 2016 at 11:09:54AM -0700, Jason Low wrote:
> > --- a/arch/alpha/include/asm/rwsem.h
> > +++ b/arch/alpha/include/asm/rwsem.h
> > @@ -25,8 +25,8 @@ static inline void __down_read(struct rw_semaphore *sem)
> >  {
> >  	long oldcount;
> >  #ifndef	CONFIG_SMP
> > -	oldcount = sem->count;
> > -	sem->count += RWSEM_ACTIVE_READ_BIAS;
> > +	oldcount = atomic_long_read(&sem->count);
> > +	atomic_long_add(RWSEM_ACTIVE_READ_BIAS, &sem->count);
> >  #else
> 
> That _completely_ misses the point of the whole !SMP code.

Oh right, this defeats the purpose of the additional code path. Might as
well have removed the code entirely  :\

I can send out a new patch assuming we're still keeping all the arch/*/
rwsem.h?