Commit becb41bf authored Apr 07, 2014 by Paul E. McKenney

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@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

parent 5057f55e

kernel/rcu/tree_plugin.h

+2 −1

Original line number	Diff line number	Diff line
		@@ -2659,6 +2659,7 @@ static void rcu_sysidle(unsigned long j)
		static void rcu_sysidle_cancel(void)
		{
		smp_mb();
		if (full_sysidle_state > RCU_SYSIDLE_SHORT)
		ACCESS_ONCE(full_sysidle_state) = RCU_SYSIDLE_NOT;
		}

Admin message