linux-kernel - [PATCH] lockdep: suggest the fix for "lockdep bfs error:-1" on print_bfs

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Message-ID: <ZqKdZZp7TI69DWRE@uudg.org>
Date: Thu, 25 Jul 2024 15:45:57 -0300
From: "Luis Claudio R. Goncalves" <lgoncalv@...hat.com>
To: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...hat.com>,
	Will Deacon <will@...nel.org>, Waiman Long <longman@...hat.com>,
	Boqun Feng <boqun.feng@...il.com>, linux-kernel@...r.kernel.org
Subject: [PATCH] lockdep: suggest the fix for "lockdep bfs error:-1" on
 print_bfs_bug

When lockdep fails while performing the Breadth-first-search operation
due to lack of memory, hint that increasing the value of the configuration
switch LOCKDEP_CIRCULAR_QUEUE_BITS should fix the warning.

Preface the scary bactrace with the suggestion:

    [  163.849242] Increase LOCKDEP_CIRCULAR_QUEUE_BITS to avoid this warning:
    [  163.849248] ------------[ cut here ]------------
    [  163.849250] lockdep bfs error:-1
    [  163.849263] WARNING: CPU: 24 PID: 2454 at kernel/locking/lockdep.c:2091 print_bfs_bug+0x27/0x40
    ...

Signed-off-by: Luis Claudio R. Goncalves <lgoncalv@...hat.com>
---
 kernel/locking/lockdep.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 58c88220a478a..1cf6d9fdddc9c 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -2067,6 +2067,9 @@ static noinline void print_bfs_bug(int ret)
 	/*
 	 * Breadth-first-search failed, graph got corrupted?
 	 */
+	if (ret  == BFS_EQUEUEFULL)
+		pr_warn("Increase LOCKDEP_CIRCULAR_QUEUE_BITS to avoid this warning:\n");
+
 	WARN(1, "lockdep bfs error:%d\n", ret);
 }
 
-- 
2.45.2