Merge branch 'rcu/next' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/rcu

The major features of this series are:

 - making RCU more aggressive about entering dyntick-idle mode in order to
   improve energy efficiency

 - converting a few more call_rcu()s to kfree_rcu()s

 - applying a number of rcutree fixes and cleanups to rcutiny

 - removing CONFIG_SMP #ifdefs from treercu

 - allowing RCU CPU stall times to be set via sysfs

 - adding CPU-stall capability to rcutorture

 - adding more RCU-abuse diagnostics

 - updating documentation

 - fixing yet more issues located by the still-ongoing top-to-bottom
   inspection of RCU, this time with a special focus on the
   CPU-hotplug code path.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 19 insertions, 0 deletions

diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index 67458468f1a8..e8ee5dd0854c 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -61,6 +61,24 @@ extern void synchronize_rcu_bh(void);
 extern void synchronize_sched_expedited(void);
 extern void synchronize_rcu_expedited(void);
 
+void kfree_call_rcu(struct rcu_head *head, void (*func)(struct rcu_head *rcu));
+
+/**
+ * synchronize_rcu_bh_expedited - Brute-force RCU-bh grace period
+ *
+ * Wait for an RCU-bh grace period to elapse, but use a "big hammer"
+ * approach to force the grace period to end quickly.  This consumes
+ * significant time on all CPUs and is unfriendly to real-time workloads,
+ * so is thus not recommended for any sort of common-case code.  In fact,
+ * if you are using synchronize_rcu_bh_expedited() in a loop, please
+ * restructure your code to batch your updates, and then use a single
+ * synchronize_rcu_bh() instead.
+ *
+ * Note that it is illegal to call this function while holding any lock
+ * that is acquired by a CPU-hotplug notifier.  And yes, it is also illegal
+ * to call this function from a CPU-hotplug notifier.  Failing to observe
+ * these restriction will result in deadlock.
+ */
 static inline void synchronize_rcu_bh_expedited(void)
 {
 	synchronize_sched_expedited();
@@ -83,6 +101,7 @@ extern void rcu_sched_force_quiescent_state(void);
 /* A context switch is a grace period for RCU-sched and RCU-bh. */
 static inline int rcu_blocking_is_gp(void)
 {
+	might_sleep();  /* Check for RCU read-side critical section. */
 	return num_online_cpus() == 1;
 }