Commit-ID: e3995a25fa361ce987a7d0ade00b17e3151519d7
Gitweb: http://git.kernel.org/tip/e3995a25fa361ce987a7d0ade00b17e3151519d7
Author: Paul E. McKenney <paul.mckenney@xxxxxxxxxx>
AuthorDate: Mon, 18 Apr 2011 15:31:26 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Thu, 5 May 2011 23:16:55 -0700
rcu: put per-CPU kthread at non-RT priority during CPU hotplug operations
If you are doing CPU hotplug operations, it is best not to have
CPU-bound realtime tasks running CPU-bound on the outgoing CPU.
So this commit makes per-CPU kthreads run at non-realtime priority
during that time.
Signed-off-by: Paul E. McKenney <paul.mckenney@xxxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
---
kernel/rcutree.c | 26 ++++++++++++++++++++++++++
1 files changed, 26 insertions(+), 0 deletions(-)
diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 51eef41..198e4df 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1464,6 +1464,30 @@ static void invoke_rcu_node_kthread(struct rcu_node *rnp)
}
/*
+ * Set the specified CPU's kthread to run RT or not, as specified by
+ * the to_rt argument. The CPU-hotplug locks are held, so the task
+ * is not going away.
+ */
+static void rcu_cpu_kthread_setrt(int cpu, int to_rt)
+{
+ int policy;
+ struct sched_param sp;
+ struct task_struct *t;
+
+ t = per_cpu(rcu_cpu_kthread_task, cpu);
+ if (t == NULL)
+ return;
+ if (to_rt) {
+ policy = SCHED_FIFO;
+ sp.sched_priority = RCU_KTHREAD_PRIO;
+ } else {
+ policy = SCHED_NORMAL;
+ sp.sched_priority = 0;
+ }
+ sched_setscheduler_nocheck(t, policy, &sp);
+}
+
+/*
* Timer handler to initiate the waking up of per-CPU kthreads that
* have yielded the CPU due to excess numbers of RCU callbacks.
* We wake up the per-rcu_node kthread, which in turn will wake up
@@ -2166,9 +2190,11 @@ static int __cpuinit rcu_cpu_notify(struct notifier_block *self,
case CPU_ONLINE:
case CPU_DOWN_FAILED:
rcu_node_kthread_setaffinity(rnp, -1);
+ rcu_cpu_kthread_setrt(cpu, 1);
break;
case CPU_DOWN_PREPARE:
rcu_node_kthread_setaffinity(rnp, cpu);
+ rcu_cpu_kthread_setrt(cpu, 0);
break;
case CPU_DYING:
case CPU_DYING_FROZEN:
--
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