Re: [PATCH v9 05/19] qspinlock: Optimize for smaller NR_CPUS

[Waiman Long]

On 04/18/2014 03:46 AM, Ingo Molnar wrote:
> * Waiman Long<waiman.long@xxxxxx>  wrote:
>
> > On 04/17/2014 11:58 AM, Peter Zijlstra wrote:
> > > On Thu, Apr 17, 2014 at 11:03:57AM -0400, Waiman Long wrote:
> > > > +static __always_inline void
> > > > +clear_pending_set_locked(struct qspinlock *lock, u32 val)
> > > > +{
> > > > +	struct __qspinlock *l = (void *)lock;
> > > > +
> > > > +	ACCESS_ONCE(l->locked_pending) = 1;
> > > > +}
> > > > @@ -157,8 +251,13 @@ static inline int trylock_pending(struct qspinlock *lock, u32 *pval)
> > > >   	 * we're pending, wait for the owner to go away.
> > > >   	 *
> > > >   	 * *,1,1 ->   *,1,0
> > > > +	 *
> > > > +	 * this wait loop must be a load-acquire such that we match the
> > > > +	 * store-release that clears the locked bit and create lock
> > > > +	 * sequentiality; this because not all try_clear_pending_set_locked()
> > > > +	 * implementations imply full barriers.
> > > You renamed the function referred in the above comment.
> > Sorry, will fix the comments.
> I suggest not renaming the function instead.
> try_clear_pending_set_locked() tells the intent in a clearer fashion.
>
> Thanks,
>
> 	Ingo

I usually use the word "try" if there is a possibility of failure. 
However, the function will always succeed, albeit by waiting a bit in 
some cases. That is why I remove "try" from the name.

-Longman
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