linux-kernel - [PATCH] rcu/kvfree: Refactor kvfree_rcu_queue

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Message-Id: <20240930113710.637833-1-urezki@gmail.com>
Date: Mon, 30 Sep 2024 13:37:10 +0200
From: "Uladzislau Rezki (Sony)" <urezki@...il.com>
To: Vlastimil Babka <vbabka@...e.cz>
Cc: "Paul E . McKenney" <paulmck@...nel.org>,
	RCU <rcu@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Neeraj upadhyay <Neeraj.Upadhyay@....com>,
	Boqun Feng <boqun.feng@...il.com>,
	Joel Fernandes <joel@...lfernandes.org>,
	Frederic Weisbecker <frederic@...nel.org>,
	Uladzislau Rezki <urezki@...il.com>,
	Oleksiy Avramchenko <oleksiy.avramchenko@...y.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: [PATCH] rcu/kvfree: Refactor kvfree_rcu_queue_batch()

Improve readability of kvfree_rcu_queue_batch() function
in away that, after a first batch queuing, the loop is break
and success value is returned to a caller.

There is no reason to loop and check batches further as all
outstanding objects have already been picked and attached to
a certain batch to complete an offloading.

Link: https://lore.kernel.org/lkml/ZvWUt2oyXRsvJRNc@pc636/T/
Suggested-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
---
 kernel/rcu/tree.c | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index a60616e69b66..b1f883fcd918 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3607,11 +3607,12 @@ kvfree_rcu_queue_batch(struct kfree_rcu_cpu *krcp)
 			}
 
 			// One work is per one batch, so there are three
-			// "free channels", the batch can handle. It can
-			// be that the work is in the pending state when
-			// channels have been detached following by each
-			// other.
+			// "free channels", the batch can handle. Break
+			// the loop since it is done with this CPU thus
+			// queuing an RCU work is _always_ success here.
 			queued = queue_rcu_work(system_unbound_wq, &krwp->rcu_work);
+			WARN_ON_ONCE(!queued);
+			break;
 		}
 	}
 
-- 
2.39.5