[ltt-dev] [PATCH] fix the "unknown" case

[Paul E. McKenney]

On Sun, Jun 13, 2010 at 05:20:34PM -0400, Mathieu Desnoyers wrote:
> * Paul E. McKenney (paulmck at linux.vnet.ibm.com) wrote:
> > On Thu, Jun 10, 2010 at 09:46:31PM -0400, Mathieu Desnoyers wrote:
> 
> [...]
> 
> (will reply to the rest in the individual patches)
> 
> > > Can we trust __sync_lock_test_and_set/__sync_add_and_fetch given that
> > > __sync_synchronize is broken ?
> > 
> > I don't know yet.  If it turns out that we cannot, then I will use some
> > form of global locking.  But the __sync_lock_test_and_set() do at least
> > generate instructions, unlike __sync_synchronize().  ;-)
> 
> I'm concerned about the fact that their synchronization primitives might have
> the assembly all with, except for the memory barriers.

OK.  How about if I used a hashed array of locks, indexed by a hash of
the cacheline number of the access in question?  Then the "unknown" case
doesn't depend at all on the __sync_ primitives.

							Thanx, Paul

> Thanks,
> 
> Mathieu
> 
> > 
> > I will send two patches, one that incorporates your suggestions, and
> > another that removes sync_core().
> > 
> > 							Thanx, Paul
> > 
> > > Thanks,
> > > 
> > > Mathieu
> > > 
> > > > +
> > > > +#ifdef __cplusplus 
> > > > +}
> > > > +#endif
> > > > +
> > > > +#include <urcu/uatomic_generic.h>
> > > > +
> > > > +#endif /* _URCU_ARCH_UATOMIC_ARMV7_H */
> > > 
> > > -- 
> > > Mathieu Desnoyers
> > > Operating System Efficiency R&D Consultant
> > > EfficiOS Inc.
> > > http://www.efficios.com
> 
> -- 
> Mathieu Desnoyers
> Operating System Efficiency R&D Consultant
> EfficiOS Inc.
> http://www.efficios.com