Commit 11bbb235 authored Sep 04, 2014 by Paul E. McKenney

rcu: Use DEFINE_PER_CPU_SHARED_ALIGNED for rcu_data



The rcu_data per-CPU variable has a number of fields that are atomically
manipulated, potentially by any CPU.  This situation can result in false
sharing with per-CPU variables that have the misfortune of being allocated
adjacent to rcu_data in memory.  This commit therefore changes the
DEFINE_PER_CPU() to DEFINE_PER_CPU_SHARED_ALIGNED() in order to avoid
this false sharing.

Reported-by: Christoph Lameter <cl@linux.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Christoph Lameter <cl@linux.com>
Reviewed-by: Pranith Kumar <bobby.prani@gmail.com>

parent 28ced795

kernel/rcu/tree.c

+1 −1

Original line number	Diff line number	Diff line
		@@ -105,7 +105,7 @@ struct rcu_state sname##_state = { \
		.name = RCU_STATE_NAME(sname), \
		.abbr = sabbr, \
		}; \
		DEFINE_PER_CPU(struct rcu_data, sname##_data)
		DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, sname##_data)

		RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched);
		RCU_STATE_INITIALIZER(rcu_bh, 'b', call_rcu_bh);