From becb41bfe0544f1f7f494f48d6f68cbdb2e1ed0e Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Mon, 7 Apr 2014 13:34:07 -0700 Subject: [PATCH] rcu: Make large and small sysidle systems use same state machine Currently, small systems move back into RCU_SYSIDLE_NOT from RCU_SYSIDLE_SHORT and large systems do not. This works because moving aggressively to RCU_SYSIDLE_NOT affects only performance, not correctness, and on small systems, the performance impact should be negligible. That said, this difference does make RCU a bit more complex, and RCU does not seem to be suffering from any lack of complexity. This commit therefore adjusts small-system operation to match that of large systems, so that the state never moves back to RCU_SYSIDLE_NOT from RCU_SYSIDLE_SHORT. Reported-by: Frederic Weisbecker Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- kernel/rcu/tree_plugin.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 045c6d04ed3f..f7593c2536b0 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -2659,7 +2659,8 @@ static void rcu_sysidle(unsigned long j) static void rcu_sysidle_cancel(void) { smp_mb(); - ACCESS_ONCE(full_sysidle_state) = RCU_SYSIDLE_NOT; + if (full_sysidle_state > RCU_SYSIDLE_SHORT) + ACCESS_ONCE(full_sysidle_state) = RCU_SYSIDLE_NOT; } /*