linux-kernel - [PATCH v3 tip/core/rcu 03/40] srcu: Consolidate batch checking into rcu_all_batches

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Date:   Wed, 19 Apr 2017 09:58:00 -0700
From:   "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
To:     linux-kernel@...r.kernel.org
Cc:     mingo@...nel.org, jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
        fweisbec@...il.com, oleg@...hat.com, bobby.prani@...il.com,
        "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Subject: [PATCH v3 tip/core/rcu 03/40] srcu: Consolidate batch checking into rcu_all_batches_empty()

The srcu_reschedule() function invokes rcu_batch_empty() on each of
the four rcu_batch structures in the srcu_struct in question twice.
Given that this check will also be needed in cleanup_srcu_struct(), this
commit consolidates these four checks into a new rcu_all_batches_empty()
function.

Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@...htriplett.org>
---
 kernel/rcu/srcu.c | 21 +++++++++++++--------
 1 file changed, 13 insertions(+), 8 deletions(-)

diff --git a/kernel/rcu/srcu.c b/kernel/rcu/srcu.c
index ef3bcfb15b39..ba41a5d04b49 100644
--- a/kernel/rcu/srcu.c
+++ b/kernel/rcu/srcu.c
@@ -65,6 +65,17 @@ static inline bool rcu_batch_empty(struct rcu_batch *b)
 }
 
 /*
+ * Are all batches empty for the specified srcu_struct?
+ */
+static inline bool rcu_all_batches_empty(struct srcu_struct *sp)
+{
+	return rcu_batch_empty(&sp->batch_done) &&
+	       rcu_batch_empty(&sp->batch_check1) &&
+	       rcu_batch_empty(&sp->batch_check0) &&
+	       rcu_batch_empty(&sp->batch_queue);
+}
+
+/*
  * Remove the callback at the head of the specified rcu_batch structure
  * and return a pointer to it, or return NULL if the structure is empty.
  */
@@ -619,15 +630,9 @@ static void srcu_reschedule(struct srcu_struct *sp)
 {
 	bool pending = true;
 
-	if (rcu_batch_empty(&sp->batch_done) &&
-	    rcu_batch_empty(&sp->batch_check1) &&
-	    rcu_batch_empty(&sp->batch_check0) &&
-	    rcu_batch_empty(&sp->batch_queue)) {
+	if (rcu_all_batches_empty(sp)) {
 		spin_lock_irq(&sp->queue_lock);
-		if (rcu_batch_empty(&sp->batch_done) &&
-		    rcu_batch_empty(&sp->batch_check1) &&
-		    rcu_batch_empty(&sp->batch_check0) &&
-		    rcu_batch_empty(&sp->batch_queue)) {
+		if (rcu_all_batches_empty(sp)) {
 			sp->running = false;
 			pending = false;
 		}
-- 
2.5.2