Re: [PATCH RFC tip/core/rcu 11/11] rcu: move TREE_RCU from softirqto kthread

From: Paul E. McKenney
Date: Wed Feb 23 2011 - 15:45:42 EST


On Wed, Feb 23, 2011 at 01:24:34PM -0600, Christoph Lameter wrote:
> On Wed, 23 Feb 2011, Paul E. McKenney wrote:
>
> > Reschedules can happen in this case due to CPU hotplug events. :-(
>
> Lockout cpu hotplug instead of disabling interrupts? Systems that support
> cpu hotplug in hardware are rare and so the cpu hotplug locking may be
> become noop.

Good point!

However, the local_irq_save() is doing two things here: (1) blocking
CPU hotplug and (2) synchronizing with concurrent invocations of
invoke_rcu_cpu_kthread() from irq handlers.

Thanx, Paul
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