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authorPaul E. McKenney <paul.mckenney@linaro.org>2012-03-01 13:18:08 -0800
committerPaul E. McKenney <paulmck@linux.vnet.ibm.com>2012-05-09 14:27:54 -0700
commitb1420f1c8bfc30ecf6380a31d0f686884834b599 (patch)
tree56eb378bcd64175a7302a1031b388ecf569a30bb /kernel/rcutree.h
parent98248a0e24327bc64eb7518145c44bff7bebebc3 (diff)
downloadlinux-b1420f1c8bfc30ecf6380a31d0f686884834b599.tar.bz2
rcu: Make rcu_barrier() less disruptive
The rcu_barrier() primitive interrupts each and every CPU, registering a callback on every CPU. Once all of these callbacks have been invoked, rcu_barrier() knows that every callback that was registered before the call to rcu_barrier() has also been invoked. However, there is no point in registering a callback on a CPU that currently has no callbacks, most especially if that CPU is in a deep idle state. This commit therefore makes rcu_barrier() avoid interrupting CPUs that have no callbacks. Doing this requires reworking the handling of orphaned callbacks, otherwise callbacks could slip through rcu_barrier()'s net by being orphaned from a CPU that rcu_barrier() had not yet interrupted to a CPU that rcu_barrier() had already interrupted. This reworking was needed anyway to take a first step towards weaning RCU from the CPU_DYING notifier's use of stop_cpu(). Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcutree.h')
-rw-r--r--kernel/rcutree.h11
1 files changed, 11 insertions, 0 deletions
diff --git a/kernel/rcutree.h b/kernel/rcutree.h
index 36ca28ecedc6..1e49c5685960 100644
--- a/kernel/rcutree.h
+++ b/kernel/rcutree.h
@@ -371,6 +371,17 @@ struct rcu_state {
raw_spinlock_t onofflock; /* exclude on/offline and */
/* starting new GP. */
+ struct rcu_head *orphan_nxtlist; /* Orphaned callbacks that */
+ /* need a grace period. */
+ struct rcu_head **orphan_nxttail; /* Tail of above. */
+ struct rcu_head *orphan_donelist; /* Orphaned callbacks that */
+ /* are ready to invoke. */
+ struct rcu_head **orphan_donetail; /* Tail of above. */
+ long qlen_lazy; /* Number of lazy callbacks. */
+ long qlen; /* Total number of callbacks. */
+ struct task_struct *rcu_barrier_in_progress;
+ /* Task doing rcu_barrier(), */
+ /* or NULL if no barrier. */
raw_spinlock_t fqslock; /* Only one task forcing */
/* quiescent states. */
unsigned long jiffies_force_qs; /* Time at which to invoke */