[PATCH 2/8] refscale: Add local_irq_disable() and local_irq_save() readers

[Paul E. McKenney]

This commit adds refscale readers based on local_irq_disable() and
local_irq_enable() ("refscale.scale_type=irq") and on local_irq_save()
and local_irq_restore ("refscale.scale_type=irqsave").  On my x86 laptop,
these are about 2.8ns and 7.5ns per enable/disable pair, respectively.

Signed-off-by: Paul E. McKenney <paul...@kernel.org>
---
 kernel/rcu/refscale.c | 66 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 65 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/refscale.c b/kernel/rcu/refscale.c
index ece77f6d055b..266a3fa94b54 100644
--- a/kernel/rcu/refscale.c
+++ b/kernel/rcu/refscale.c
@@ -636,6 +636,70 @@ static const struct ref_scale_ops jiffies_ops = {
        .name           = "jiffies"
 };
 
+static void ref_irq_section(const int nloops)
+{
+       int i;
+
+       preempt_disable();
+       for (i = nloops; i >= 0; i--) {
+               local_irq_disable();
+               local_irq_enable();
+       }
+       preempt_enable();
+}
+
+static void ref_irq_delay_section(const int nloops, const int udl, const int 
ndl)
+{
+       int i;
+
+       preempt_disable();
+       for (i = nloops; i >= 0; i--) {
+               local_irq_disable();
+               un_delay(udl, ndl);
+               local_irq_enable();
+       }
+       preempt_enable();
+}
+
+static const struct ref_scale_ops irq_ops = {
+       .readsection    = ref_irq_section,
+       .delaysection   = ref_irq_delay_section,
+       .name           = "irq"
+};
+
+static void ref_irqsave_section(const int nloops)
+{
+       unsigned long flags;
+       int i;
+
+       preempt_disable();
+       for (i = nloops; i >= 0; i--) {
+               local_irq_save(flags);
+               local_irq_restore(flags);
+       }
+       preempt_enable();
+}
+
+static void ref_irqsave_delay_section(const int nloops, const int udl, const 
int ndl)
+{
+       unsigned long flags;
+       int i;
+
+       preempt_disable();
+       for (i = nloops; i >= 0; i--) {
+               local_irq_save(flags);
+               un_delay(udl, ndl);
+               local_irq_restore(flags);
+       }
+       preempt_enable();
+}
+
+static const struct ref_scale_ops irqsave_ops = {
+       .readsection    = ref_irqsave_section,
+       .delaysection   = ref_irqsave_delay_section,
+       .name           = "irqsave"
+};
+
 ////////////////////////////////////////////////////////////////////////
 //
 // Methods leveraging SLAB_TYPESAFE_BY_RCU.
@@ -1172,7 +1236,7 @@ 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,
+               &acqrel_ops, &sched_clock_ops, &clock_ops, &jiffies_ops, 
&irq_ops, &irqsave_ops,
                &typesafe_ref_ops, &typesafe_lock_ops, &typesafe_seqlock_ops,
        };
 
-- 
2.40.1