Messages in this thread | | | Date | Tue, 6 Jan 2015 04:01:21 -0800 | From | Kent Overstreet <> | Subject | Re: Linux 3.19-rc3 |
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On Tue, Jan 06, 2015 at 12:48:42PM +0100, Peter Zijlstra wrote: > > > Looking at that closure stuff, why is there an smp_mb() in > closure_wake_up() ? Typically wakeup only needs to imply a wmb. > > Also note that __closure_wake_up() starts with a fully serializing > instruction (xchg) and thereby already implies the full barrier.
Probably no good reason, that code is pretty old :)
If I was to hazard a guess, I had my own lockless linked lists before llist.h existed and perhaps I did it with atomic_xchg() - which was at least documented to not imply a barrier. I suppose it should just be dropped.
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