Commit 1eb52121 authored Jun 16, 2011 by Shaohua Li Committed by Paul E. McKenney Sep 28, 2011

rcu: Avoid unnecessary self-wakeup of per-CPU kthreads



There are a number of cases where the RCU can find additional work
for the per-CPU kthread within the context of that per-CPU kthread.
In such cases, the per-CPU kthread is already running, so attempting
to wake itself up does nothing except waste CPU cycles.  This commit
therefore checks to see if it is in the per-CPU kthread context,
omitting the wakeup in this case.

Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

parent 1f288094

kernel/rcutree_plugin.h

+3 −5

Original line number	Diff line number	Diff line
		@@ -1291,10 +1291,8 @@ static void invoke_rcu_callbacks_kthread(void)

		local_irq_save(flags);
		__this_cpu_write(rcu_cpu_has_work, 1);
		if (__this_cpu_read(rcu_cpu_kthread_task) == NULL) {
		local_irq_restore(flags);
		return;
		}
		if (__this_cpu_read(rcu_cpu_kthread_task) != NULL &&
		current != __this_cpu_read(rcu_cpu_kthread_task))
		wake_up_process(__this_cpu_read(rcu_cpu_kthread_task));
		local_irq_restore(flags);
		}

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