rcu: Define RCU-bh update API in terms of RCU

Now that the main RCU API knows about softirq disabling and softirq's
quiescent states, the RCU-bh update code can be dispensed with.
This commit therefore removes the RCU-bh update-side implementation and
defines RCU-bh's update-side API in terms of that of either RCU-preempt or
RCU-sched, depending on the setting of the CONFIG_PREEMPT Kconfig option.

In kernels built with CONFIG_RCU_NOCB_CPU=y this has the knock-on effect
of reducing by one the number of rcuo kthreads per CPU.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/include/linux/rcutree.h b/include/linux/rcutree.h
index 664b580695d6..c789c302a2c9 100644
--- a/include/linux/rcutree.h
+++ b/include/linux/rcutree.h
@@ -45,7 +45,11 @@ static inline void rcu_virt_note_context_switch(int cpu)
 	rcu_note_context_switch(false);
 }
 
-void synchronize_rcu_bh(void);
+static inline void synchronize_rcu_bh(void)
+{
+	synchronize_rcu();
+}
+
 void synchronize_sched_expedited(void);
 void synchronize_rcu_expedited(void);
 
@@ -69,7 +73,7 @@ void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func);
  */
 static inline void synchronize_rcu_bh_expedited(void)
 {
-	synchronize_sched_expedited();
+	synchronize_rcu_expedited();
 }
 
 void rcu_barrier(void);