Messages in this thread | | | Date | Wed, 30 Apr 2014 18:37:24 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH v2] rwsem: Support optimistic spinning |
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On Wed, Apr 30, 2014 at 09:32:17AM -0700, Davidlohr Bueso wrote: > On Wed, 2014-04-30 at 11:21 +0200, Peter Zijlstra wrote: > > On Mon, Apr 28, 2014 at 03:09:01PM -0700, Davidlohr Bueso wrote: > > > +#ifdef CONFIG_SMP > > > > > +#else > > > +static bool rwsem_optimistic_spin(struct rw_semaphore *sem) > > > +{ > > > + return false; > > > +} > > > +#endif > > > > On the mutex side we guard this with MUTEX_SPIN_ON_OWNER, do we want to > > use that here too? > > I thought of it, but hated adding mutex naming to rwsem code -- we > already do it for cpu_relax() thanks to s390.
Yah, we need to find a better name for that thing.
> MUTEX_SPIN_ON_OWNER depends on SMP && !DEBUG_MUTEXES. > Right now rwsem optimistic spinning depends on SMP && RWSEM_XCHGADD_ALGORITHM. > > It might sense to add RWSEM_SPIN_ON_OWNER to encapsulate what we already > have. I don't think we want DEBUG_MUTEX dependencies in rwsems. Would > you accept such thing?
Ah, I remember why we have that MUTEX_SPIN_ON_OWNER, its in the comment in mutex.c right under using it. It the games we play with ->owner isn't compatible with what DEBUG_MUTEXES wants it for.
So no, you're fine with the rwsem code as is.
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