On Wed, Apr 13, 2016 at 01:49:04PM -0700, Jason Low wrote: > On Wed, 2016-04-13 at 10:43 -0700, Will Deacon wrote: > > On Tue, Apr 12, 2016 at 08:02:17PM -0700, Jason Low wrote: > > > For qspinlocks on ARM64, we would like to use WFE instead > > > of purely spinning. Qspinlocks internally have lock > > > contenders spin on an MCS lock. > > > > > > Update arch_mcs_spin_lock_contended() such that it uses > > > the new smp_cond_load_acquire() so that ARM64 can also > > > override this spin loop with its own implementation using WFE. > > > > > > On x86, it can also cheaper to use this than spinning on > > > smp_load_acquire(). > > > > > > Signed-off-by: Jason Low <[email protected]> > > > > FWIW, we just override arch_mcs_spin_lock_contended entirely for arch/arm/ > > and use wfe there so we could do the same for arm64 in mainline already. > > Right, I was also thinking about that, although when we use > smp_cond_load_acquire() in the generic implementation, would we just end > up overriding it for the arch/arm64 version with the same thing? :)
Sure, and we can convert to smp_cond_load_acquire then. I was just thinking that you can avoid the immediate dependency on Peter's stuff, that's all. Will
