linux-kernel - [PATCH 2/3] rcu/tree: move locking/unlocking to separate functions

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Date:   Thu,  2 Apr 2020 14:32:52 +0200
From:   "Uladzislau Rezki (Sony)" <urezki@...il.com>
To:     LKML <linux-kernel@...r.kernel.org>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Joel Fernandes <joel@...lfernandes.org>
Cc:     RCU <rcu@...r.kernel.org>, linux-mm@...ck.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Uladzislau Rezki <urezki@...il.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Oleksiy Avramchenko <oleksiy.avramchenko@...ymobile.com>
Subject: [PATCH 2/3] rcu/tree: move locking/unlocking to separate functions

Introduce two helpers to lock and unlock an access to the
per-cpu "kfree_rcu_cpu" structure. The reason is to make
kvfree_call_rcu() function to be more readable.

Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
---
 kernel/rcu/tree.c | 39 +++++++++++++++++++++++++--------------
 1 file changed, 25 insertions(+), 14 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 24f620a06219..5e26145e9ead 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3159,6 +3159,27 @@ static inline struct rcu_head *attach_rcu_head_to_object(void *obj)
 	return ((struct rcu_head *) ++ptr);
 }
 
+static inline struct kfree_rcu_cpu *
+krc_this_cpu_lock(unsigned long *flags)
+{
+	struct kfree_rcu_cpu *krcp;
+
+	local_irq_save(*flags);	// For safely calling this_cpu_ptr().
+	krcp = this_cpu_ptr(&krc);
+	if (likely(krcp->initialized))
+		spin_lock(&krcp->lock);
+
+	return krcp;
+}
+
+static inline void
+krc_this_cpu_unlock(struct kfree_rcu_cpu *krcp, unsigned long flags)
+{
+	if (likely(krcp->initialized))
+		spin_unlock(&krcp->lock);
+	local_irq_restore(flags);
+}
+
 /*
  * Queue a request for lazy invocation of appropriate free routine after a
  * grace period. Please note there are three paths are maintained, two are the
@@ -3195,10 +3216,7 @@ void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
 		ptr = (unsigned long *) func;
 	}
 
-	local_irq_save(flags);	// For safely calling this_cpu_ptr().
-	krcp = this_cpu_ptr(&krc);
-	if (krcp->initialized)
-		spin_lock(&krcp->lock);
+	krcp = krc_this_cpu_lock(&flags);
 
 	// Queue the object but don't yet schedule the batch.
 	if (debug_rcu_head_queue(ptr)) {
@@ -3220,19 +3238,14 @@ void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
 		/* Is headless object? */
 		if (head == NULL) {
 			/* Drop the lock. */
-			if (krcp->initialized)
-				spin_unlock(&krcp->lock);
-			local_irq_restore(flags);
+			krc_this_cpu_unlock(krcp, flags);
 
 			head = attach_rcu_head_to_object(ptr);
 			if (head == NULL)
 				goto inline_return;
 
 			/* Take it back. */
-			local_irq_save(flags);
-			krcp = this_cpu_ptr(&krc);
-			if (krcp->initialized)
-				spin_lock(&krcp->lock);
+			krcp = krc_this_cpu_lock(&flags);
 
 			/*
 			 * Tag the headless object. Such objects have a back-pointer
@@ -3267,9 +3280,7 @@ void kvfree_call_rcu(struct rcu_head *head, rcu_callback_t func)
 	}
 
 unlock_return:
-	if (krcp->initialized)
-		spin_unlock(&krcp->lock);
-	local_irq_restore(flags);
+	krc_this_cpu_unlock(krcp, flags);
 
 inline_return:
 	/*
-- 
2.20.1