[PATCH v2 3/5] kvfree_rcu: Add a bulk-list check when a scheduler is run

From: "Uladzislau Rezki (Sony)" <urezki@gmail.com>
To: LKML <linux-kernel@vger.kernel.org>, RCU <rcu@vger.kernel.org>,
	"Paul E . McKenney" <paulmck@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>,
	Andrew Morton <akpm@linux-foundation.org>,
	Daniel Axtens <dja@axtens.net>,
	Frederic Weisbecker <frederic@kernel.org>,
	Neeraj Upadhyay <neeraju@codeaurora.org>,
	Joel Fernandes <joel@joelfernandes.org>,
	Peter Zijlstra <peterz@infradead.org>,
	Thomas Gleixner <tglx@linutronix.de>,
	"Theodore Y . Ts'o" <tytso@mit.edu>,
	Sebastian Andrzej Siewior <bigeasy@linutronix.de>,
	Uladzislau Rezki <urezki@gmail.com>,
	Oleksiy Avramchenko <oleksiy.avramchenko@sonymobile.com>
Subject: [PATCH v2 3/5] kvfree_rcu: Add a bulk-list check when a scheduler is run
Date: Thu, 15 Apr 2021 19:19:58 +0200	[thread overview]
Message-ID: <20210415172000.15086-4-urezki@gmail.com> (raw)
In-Reply-To: <20210415172000.15086-1-urezki@gmail.com>

RCU_SCHEDULER_RUNNING is set when a scheduling is available.
That signal is used in order to check and queue a "monitor work"
to reclaim freed objects(if they are) during a boot-up phase.

We have it because, the main path of the kvfree_rcu() call can
not queue the work untill the scheduler is up and running.

Currently in such helper only "krcp->head" is checked to figure
out if there are outstanding objects to be released. And this is
only one channel. After adding a bulk interface there are two
extra which have to be checked also: "krcp->bkvhead[0]" as well
as "krcp->bkvhead[1]". So, we have to queue the "monitor work"
if _any_ corresponding channel is not empty.

Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com>
---
 kernel/rcu/tree.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 07e718fdea12..3ddc9dc97487 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3712,7 +3712,8 @@ void __init kfree_rcu_scheduler_running(void)
 		struct kfree_rcu_cpu *krcp = per_cpu_ptr(&krc, cpu);
 
 		raw_spin_lock_irqsave(&krcp->lock, flags);
-		if (!krcp->head || krcp->monitor_todo) {
+		if ((!krcp->bkvhead[0] && !krcp->bkvhead[1] && !krcp->head) ||
+				krcp->monitor_todo) {
 			raw_spin_unlock_irqrestore(&krcp->lock, flags);
 			continue;
 		}
-- 
2.20.1

