Messages in this thread | | | Date | Tue, 29 Jul 2014 23:54:00 +0200 | From | Frederic Weisbecker <> | Subject | Re: [PATCH 05/10] smp: Fast path check on IPI list |
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On Tue, Jul 29, 2014 at 02:07:39PM +0200, Peter Zijlstra wrote: > On Mon, Jul 28, 2014 at 07:37:31PM +0200, Frederic Weisbecker wrote: > > When we enqueue a remote irq work, we trigger the same IPI as those > > raised by smp_call_function_*() family. > > > > So when we receive such IPI, we check both irq_work and smp_call_function > > queues. Thus if we trigger a remote irq work, we'll likely find the > > smp_call_function queue empty unless we collide with concurrent enqueuers > > but the probability is low. > > > > Meanwhile, checking the smp_call_function queue can be costly because > > we use llist_del_all() which relies on cmpxchg(). > > xchg()
Ah, right!
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