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From:   Xiongwei Song <sxwjean@me.com>
To:     peterz@infradead.org, mingo@redhat.com, will@kernel.org,
        longman@redhat.com, boqun.feng@gmail.com
Cc:     linux-kernel@vger.kernel.org, Xiongwei Song <sxwjean@gmail.com>
Subject: [PATCH] locking/lockdep: print possible warning after counting deps
Date:   Wed, 16 Jun 2021 22:42:10 +0800
Message-Id: <20210616144210.278662-2-sxwjean@me.com>
In-Reply-To: <20210616144210.278662-1-sxwjean@me.com>
References: <20210616144210.278662-1-sxwjean@me.com>
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From: Xiongwei Song <sxwjean@gmail.com>

The graph walk might hit error when counting dependencies. Once the
return value is negative, print a warning to reminder users.

Signed-off-by: Xiongwei Song <sxwjean@gmail.com>
---
 kernel/locking/lockdep.c | 12 ++++++++++--
 1 file changed, 10 insertions(+), 2 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 7641bd407239..074fd6418c20 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -2028,8 +2028,12 @@ static unsigned long __lockdep_count_forward_deps(struct lock_list *this)
 {
 	unsigned long  count = 0;
 	struct lock_list *target_entry;
+	enum bfs_result ret;
+
+	ret = __bfs_forwards(this, (void *)&count, noop_count, NULL, &target_entry);
 
-	__bfs_forwards(this, (void *)&count, noop_count, NULL, &target_entry);
+	if (unlikely(bfs_error(ret)))
+		print_bfs_bug(ret);
 
 	return count;
 }
@@ -2053,8 +2057,12 @@ static unsigned long __lockdep_count_backward_deps(struct lock_list *this)
 {
 	unsigned long  count = 0;
 	struct lock_list *target_entry;
+	enum bfs_result ret;
+
+	ret = __bfs_backwards(this, (void *)&count, noop_count, NULL, &target_entry);
 
-	__bfs_backwards(this, (void *)&count, noop_count, NULL, &target_entry);
+	if (unlikely(bfs_error(ret)))
+		print_bfs_bug(ret);
 
 	return count;
 }
-- 
2.30.2