Messages in this thread | | | Date | Wed, 19 Sep 2007 17:29:09 -0400 | From | "Dmitry Torokhov" <> | Subject | Re: [RFC][PATCH 2/6] lockdep: validate rcu_dereference() vs rcu_read_lock() |
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On 9/19/07, Peter Zijlstra <a.p.zijlstra@chello.nl> wrote: > On Wed, 19 Sep 2007 16:41:04 -0400 "Dmitry Torokhov" > <dmitry.torokhov@gmail.com> wrote: > > > > If the IRQ handler does rcu_read_lock(),unlock() and the i8042_stop() > > > function does sync_rcu() instead of _sched(), it should be good again. > > > It will not affect anything else than the task that calls _stop(). And > > > even there the only change is that the sleep might be a tad longer. > > > > And the IRQ handler needs to do some extra job... Anyway, it looks -rt > > breaks synchronize_sched() and needs to have it fixed: > > > > "/** > > * synchronize_sched - block until all CPUs have exited any non-preemptive > > * kernel code sequences. > > * > > * This means that all preempt_disable code sequences, including NMI and > > * hardware-interrupt handlers, in progress on entry will have completed > > * before this primitive returns." > > That still does as it says in -rt. Its just that the interrupt handler > will be preemptible so the guarantees it gives are useless.
Please note "... including NMI and hardware-interrupt handlers ..."
> > > > I find it curious that a driver that is 'low performant' and does not > > > suffer lock contention pioneers locking schemes. I agree with > > > optimizing, but this is not the place to push the envelope. > > > > Please realize that evey microsecond wasted on a 'low performant' > > driver is taken from high performers and if we can help it why > > shouldn't we? > > sure, but the cache eviction caused by running the driver will have > more impact than the added rcu_read_{,un}lock() calls.
Are you saying that adding rcu_read_{,un}lock() will help with cache eviction? How?
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