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

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Date:   Wed, 30 Jun 2021 13:47:59 -0000
From:   "tip-bot2 for Uladzislau Rezki (Sony)" <tip-bot2@...utronix.de>
To:     linux-tip-commits@...r.kernel.org
Cc:     "Uladzislau Rezki (Sony)" <urezki@...il.com>,
        "Paul E. McKenney" <paulmck@...nel.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: [tip: core/rcu] kvfree_rcu: Add a bulk-list check when a scheduler is run

The following commit has been merged into the core/rcu branch of tip:

Commit-ID:     d434c00fa3ac476ca6295b8310d097dd71984624
Gitweb:        https://git.kernel.org/tip/d434c00fa3ac476ca6295b8310d097dd71984624
Author:        Uladzislau Rezki (Sony) <urezki@...il.com>
AuthorDate:    Thu, 15 Apr 2021 19:19:58 +02:00
Committer:     Paul E. McKenney <paulmck@...nel.org>
CommitterDate: Mon, 10 May 2021 16:00:48 -07:00

kvfree_rcu: Add a bulk-list check when a scheduler is run

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 676a49a..e86f32d 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;
 		}