Messages in this thread | | | Date | Tue, 27 Nov 2012 08:19:25 -0800 | From | "Paul E. McKenney" <> | Subject | Re: [RFC PATCH] Fix abnormal rcu dynticks_nesting values related to async page fault |
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On Tue, Nov 27, 2012 at 04:56:30PM +0100, Frederic Weisbecker wrote: > 2012/11/27 Gleb Natapov <gleb@redhat.com>: > > For KVM_PV_REASON_PAGE_NOT_PRESENT it behaves like an exception. > > Ok. > There seem to be a bug in kvm_async_pf_task_wait(). Using > idle_cpu(cpu) to find out if the current task is the idle task may not > work if there is pending wake up. Me may schedule another task but > when that other task sleeps later we can't schedule back to idle until > the fault is completed. > > The right way is to use is_idle_task(current)
Agreed. But if you instead need to figure out whether or not RCU believes that the CPU is idle, use rcu_is_cpu_idle(). You need to figure out whether or not RCU believes that the CPU is idle if you are trying to play fast and loose with rcu_irq_enter() and rcu_irq_exit().
Thanx, Paul
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