From a26ac2455ffcf3be5c6ef92bc6df7182700f2114 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Wed, 12 Jan 2011 14:10:23 -0800 Subject: rcu: move TREE_RCU from softirq to kthread If RCU priority boosting is to be meaningful, callback invocation must be boosted in addition to preempted RCU readers. Otherwise, in presence of CPU real-time threads, the grace period ends, but the callbacks don't get invoked. If the callbacks don't get invoked, the associated memory doesn't get freed, so the system is still subject to OOM. But it is not reasonable to priority-boost RCU_SOFTIRQ, so this commit moves the callback invocations to a kthread, which can be boosted easily. Also add comments and properly synchronized all accesses to rcu_cpu_kthread_task, as suggested by Lai Jiangshan. Signed-off-by: Paul E. McKenney Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- kernel/rcutree_plugin.h | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'kernel/rcutree_plugin.h') diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h index 774f010a4619..b9bd69a5a4fe 100644 --- a/kernel/rcutree_plugin.h +++ b/kernel/rcutree_plugin.h @@ -1206,7 +1206,7 @@ static DEFINE_PER_CPU(unsigned long, rcu_dyntick_holdoff); * * Because it is not legal to invoke rcu_process_callbacks() with irqs * disabled, we do one pass of force_quiescent_state(), then do a - * raise_softirq() to cause rcu_process_callbacks() to be invoked later. + * invoke_rcu_kthread() to cause rcu_process_callbacks() to be invoked later. * The per-cpu rcu_dyntick_drain variable controls the sequencing. */ int rcu_needs_cpu(int cpu) @@ -1257,7 +1257,7 @@ int rcu_needs_cpu(int cpu) /* If RCU callbacks are still pending, RCU still needs this CPU. */ if (c) - raise_softirq(RCU_SOFTIRQ); + invoke_rcu_kthread(); return c; } -- cgit v1.2.1