linux-kernel - [PATCH tip/core/rcu 3/7] kvfree_rcu: Add a bulk-list check when a scheduler is run

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Message-Id: <20210511225516.2893420-3-paulmck@kernel.org>
Date:   Tue, 11 May 2021 15:55:12 -0700
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     rcu@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, kernel-team@...com, mingo@...nel.org,
        jiangshanlai@...il.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, joel@...lfernandes.org,
        "Uladzislau Rezki (Sony)" <urezki@...il.com>,
        "Paul E . McKenney" <paulmck@...nel.org>
Subject: [PATCH tip/core/rcu 3/7] kvfree_rcu: Add a bulk-list check when a scheduler is run

From: "Uladzislau Rezki (Sony)" <urezki@...il.com>

The rcu_scheduler_active flag is set to RCU_SCHEDULER_RUNNING once the
scheduler is up and running.  That signal is used in order to check
and queue a "monitor work" to reclaim freed objects (if there are any)
during early boot.  This flag is used by kvfree_rcu() to determine when
work can safely be queued, at which point memory passed to earlier
invocations of kvfree_rcu() can be processed.

However, only "krcp->head" is checked for objects that need to be
released, and there are now two more, namely, "krcp->bkvhead[0]" and
"krcp->bkvhead[1]".  Therefore, check these two additional channels.

Signed-off-by: Uladzislau Rezki (Sony) <urezki@...il.com>
Signed-off-by: Paul E. McKenney <paulmck@...nel.org>
---
 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 676a49ab5b2b..e86f32d6b8f9 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -3739,7 +3739,8 @@ 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;
 		}
-- 
2.31.1.189.g2e36527f23