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From:   "Paul E. McKenney" <paulmck@kernel.org>
To:     rcu@vger.kernel.org
Cc:     linux-kernel@vger.kernel.org, kernel-team@meta.com,
        rostedt@goodmis.org, Zqiang <qiang1.zhang@intel.com>,
        "Paul E . McKenney" <paulmck@kernel.org>
Subject: [PATCH rcu 4/8] rcu/kvfree: Invoke debug_rcu_bhead_unqueue() after checking bnode->gp_snap
Date:   Wed, 10 May 2023 10:02:38 -0700
Message-Id: <20230510170242.2187714-4-paulmck@kernel.org>
In-Reply-To: <1c01c38f-3783-44d7-8c11-7416cd5b849c@paulmck-laptop>
References: <1c01c38f-3783-44d7-8c11-7416cd5b849c@paulmck-laptop>
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From: Zqiang <qiang1.zhang@intel.com>

If kvfree_rcu_bulk() sees that the required grace period has failed to
elapse, it leaks the memory because readers might still be using it.
But in that case, the debug-objects subsystem still marks the relevant
structures as having been freed, even though they are instead being
leaked.

This commit fixes this mismatch by invoking debug_rcu_bhead_unqueue()
only when we are actually going to free the objects.

Signed-off-by: Zqiang <qiang1.zhang@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 kernel/rcu/tree.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 7452ba97ba34..426f1f3bb5f2 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -2922,8 +2922,8 @@ kvfree_rcu_bulk(struct kfree_rcu_cpu *krcp,
 	unsigned long flags;
 	int i;
 
-	debug_rcu_bhead_unqueue(bnode);
 	if (!WARN_ON_ONCE(!poll_state_synchronize_rcu_full(&bnode->gp_snap))) {
+		debug_rcu_bhead_unqueue(bnode);
 		rcu_lock_acquire(&rcu_callback_map);
 		if (idx == 0) { // kmalloc() / kfree().
 			trace_rcu_invoke_kfree_bulk_callback(
-- 
2.40.1