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[tip/core/rcu,02/55] rcu: Avoid unnecessary self-wakeup of per-CPU kthreads

Message ID 1315332049-2604-2-git-send-email-paulmck@linux.vnet.ibm.com
State Accepted
Commit 1eb521210a8c9823038abe4ddfe8c69e713ec17d
Headers show

Commit Message

Paul E. McKenney Sept. 6, 2011, 5:59 p.m. UTC 
From: Shaohua Li <shaohua.li@intel.com>

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>
---
 kernel/rcutree_plugin.h |    8 +++-----
 1 files changed, 3 insertions(+), 5 deletions(-)
diff mbox

Patch

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 7b850cd..9703298 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -1291,11 +1291,9 @@  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;
-	}
-	wake_up_process(__this_cpu_read(rcu_cpu_kthread_task));
+	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);
 }