[RFC 1/2] rcu: Do prepare and cleanup idle depending on in_nmi()

[Byungchul Park]

Get rid of dependency on ->dynticks_nmi_nesting.

Signed-off-by: Byungchul Park <byungchul.p...@lge.com>
---
 kernel/rcu/tree.c | 22 ++++++++++------------
 1 file changed, 10 insertions(+), 12 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index deb2508..59ae94e 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -797,6 +797,11 @@ void rcu_nmi_exit(void)
                return;
        }
 
+       if (!in_nmi()) {
+               rcu_prepare_for_idle();
+               rcu_dynticks_task_enter();
+       }
+
        /* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */
        trace_rcu_dyntick(TPS("Startirq"), rdtp->dynticks_nmi_nesting, 0, 
rdtp->dynticks);
        WRITE_ONCE(rdtp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */
@@ -824,14 +829,8 @@ void rcu_nmi_exit(void)
  */
 void rcu_irq_exit(void)
 {
-       struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
-
        lockdep_assert_irqs_disabled();
-       if (rdtp->dynticks_nmi_nesting == 1)
-               rcu_prepare_for_idle();
        rcu_nmi_exit();
-       if (rdtp->dynticks_nmi_nesting == 0)
-               rcu_dynticks_task_enter();
 }
 
 /*
@@ -944,6 +943,11 @@ void rcu_nmi_enter(void)
        if (rcu_dynticks_curr_cpu_in_eqs()) {
                rcu_dynticks_eqs_exit();
                incby = 1;
+
+               if (!in_nmi()) {
+                       rcu_dynticks_task_exit();
+                       rcu_cleanup_after_idle();
+               }
        }
        trace_rcu_dyntick(incby == 1 ? TPS("Endirq") : TPS("++="),
                          rdtp->dynticks_nmi_nesting,
@@ -977,14 +981,8 @@ void rcu_nmi_enter(void)
  */
 void rcu_irq_enter(void)
 {
-       struct rcu_dynticks *rdtp = this_cpu_ptr(&rcu_dynticks);
-
        lockdep_assert_irqs_disabled();
-       if (rdtp->dynticks_nmi_nesting == 0)
-               rcu_dynticks_task_exit();
        rcu_nmi_enter();
-       if (rdtp->dynticks_nmi_nesting == 1)
-               rcu_cleanup_after_idle();
 }
 
 /*
-- 
1.9.1