refscale: Add local_bh_disable() readers

This commit adds refscale readers based on local_bh_disable() and
local_bh_enable() ("refscale.scale_type=bh").  On my x86 laptop, these
are about 4.9ns.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>

diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index f956e0b3c097356acfa9939fe6ab009e55ddb9bb..995c189efaf08d8942ff249292d5b08d64b6551c 100644 (file)
--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -629,6 +629,37 @@ static const struct ref_scale_ops jiffies_ops = {
        .name           = "jiffies"
 };
 
+static void ref_bh_section(const int nloops)
+{
+       int i;
+
+       preempt_disable();
+       for (i = nloops; i >= 0; i--) {
+               local_bh_disable();
+               local_bh_enable();
+       }
+       preempt_enable();
+}
+
+static void ref_bh_delay_section(const int nloops, const int udl, const int ndl)
+{
+       int i;
+
+       preempt_disable();
+       for (i = nloops; i >= 0; i--) {
+               local_bh_disable();
+               un_delay(udl, ndl);
+               local_bh_enable();
+       }
+       preempt_enable();
+}
+
+static const struct ref_scale_ops bh_ops = {
+       .readsection    = ref_bh_section,
+       .delaysection   = ref_bh_delay_section,
+       .name           = "bh"
+};
+
 static void ref_irq_section(const int nloops)
 {
        int i;
@@ -1229,7 +1260,8 @@ ref_scale_init(void)
        static const struct ref_scale_ops *scale_ops[] = {
                &rcu_ops, &srcu_ops, &srcu_fast_ops, RCU_TRACE_OPS RCU_TASKS_OPS
                &refcnt_ops, &rwlock_ops, &rwsem_ops, &lock_ops, &lock_irq_ops,
-               &acqrel_ops, &sched_clock_ops, &clock_ops, &jiffies_ops, &irq_ops, &irqsave_ops,
+               &acqrel_ops, &sched_clock_ops, &clock_ops, &jiffies_ops,
+               &bh_ops, &irq_ops, &irqsave_ops,
                &typesafe_ref_ops, &typesafe_lock_ops, &typesafe_seqlock_ops,
        };