Re: [Xen-devel] [PATCH v2 6/6] x86/time: relax barriers

2016-08-03 Thread Jan Beulich
>>> On 03.08.16 at 15:11, wrote: > On 03/08/16 14:04, Jan Beulich wrote: >> On x86 there's no need for full barriers in loops waiting for some >> memory location to change. Nor do we need full barriers between two >> reads and two writes - SMP ones fully suffice (and I actually think >> they could

Re: [Xen-devel] [PATCH v2 6/6] x86/time: relax barriers

2016-08-03 Thread Andrew Cooper
On 03/08/16 14:04, Jan Beulich wrote: > On x86 there's no need for full barriers in loops waiting for some > memory location to change. Nor do we need full barriers between two > reads and two writes - SMP ones fully suffice (and I actually think > they could in fact be dropped, since atomic_*() op

[Xen-devel] [PATCH v2 6/6] x86/time: relax barriers

2016-08-03 Thread Jan Beulich
On x86 there's no need for full barriers in loops waiting for some memory location to change. Nor do we need full barriers between two reads and two writes - SMP ones fully suffice (and I actually think they could in fact be dropped, since atomic_*() operations should already provide enough orderin