Commit-ID: becb41bfe0544f1f7f494f48d6f68cbdb2e1ed0e
Gitweb: http://git.kernel.org/tip/becb41bfe0544f1f7f494f48d6f68cbdb2e1ed0e
Author: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
AuthorDate: Mon, 7 Apr 2014 13:34:07 -0700
Committer: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
CommitDate: Tue, 29 Apr 2014 08:45:24 -0700
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 <fweisbec@xxxxxxxxx>
Signed-off-by: Paul E. McKenney <paulmck@xxxxxxxxxxxxxxxxxx>
Reviewed-by: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
---
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 045c6d0..f7593c2 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;
}
/*
--
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