Messages in this thread | | | Date | Tue, 17 Jun 2014 11:55:10 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH RFC] percpu: add data dependency barrier in percpu accessors and operations |
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On Tue, Jun 17, 2014 at 01:47:01PM -0500, Christoph Lameter wrote: > > On Tue, 17 Jun 2014, Linus Torvalds wrote: > > > On Jun 17, 2014 6:28 AM, "Christoph Lameter" <cl@gentwo.org> wrote: > > > > > > Even alpha maintains the illusion of changes becoming visible in the > > > proper order for the currently executing thread. No barriers are needed. > > > > No Christoph, alpha really doesn't. Barriers needed. > > Everythig breaks if a single hardware execution thread can no longer > observe a consistent view of the world of the data it modifies. > > We are not talking about synchronization here between multiple hardware > threads. This is simply code running on a single hardware thread and all > architectures maintain the uniprocessor illusion there.
We are talking about one CPU initializing all CPUs' portions of dynamically allocated per-CPU memory, so there really is more than one CPU involved.
Thanx, Paul
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