Messages in this thread | | | Subject | Re: [PATCH 05/32] nohz: Move rcu dynticks idle mode handling to idle enter/exit APIs | From | Peter Zijlstra <> | Date | Tue, 30 Aug 2011 16:13:57 +0200 |
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On Tue, 2011-08-30 at 16:11 +0200, Frederic Weisbecker wrote: > On Tue, Aug 30, 2011 at 01:17:42PM +0200, Peter Zijlstra wrote: > > On Tue, 2011-08-30 at 01:35 +0200, Frederic Weisbecker wrote: > > > But rcu read side critical sections (preemption disabled, rcu_read_lock(), > > > softirq disabled) don't need the tick to enforce the critical section > > > itself. > > > > Note that with PREEMPT_RCU only the rcu_read_lock() is actually an rcu > > read side critical section, non of the others should be used as such. > > Relying on preempt_disable(), local_bh_disable() and similar is broken > > as per a long while ago. > > Sure yeah. > > My point was that the patchset doesn't care about all that anyway. Read > side critical section still work as usual. What changes is the way we > notice periods where we are *not* in rcu read side critical sections. > This was previously partly made through the tick. Now it's still the case > but we need to remotely wake up that tick first.
But you wake up the tick for any callback - systemwide - right? That's a massive fail.
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