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

[mathieu.desnoyers@efficios.com (Mathieu Desnoyers)]

* Paul E. McKenney (paulmck at linux.vnet.ibm.com) wrote:
> 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.

I'm afraid this won't work with signal handlers. :-/ It would be a shame to have
to make these primitives non-signal-safe just for the sake of the "unknown"
arch. Or maybe it could make sense to disable signals around these, even though
it will be really slow ?

Thanks,

Mathieu

> 
> 							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

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com