linux-kernel - [tip: locking/core] lockdep: suggest the fix for "lockdep bfs error:-1" on print_bfs

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Message-ID: <172294149671.2215.14897146884400480880.tip-bot2@tip-bot2>
Date: Tue, 06 Aug 2024 10:51:36 -0000
From: "tip-bot2 for Luis Claudio R. Goncalves" <tip-bot2@...utronix.de>
To: linux-tip-commits@...r.kernel.org
Cc: "Luis Claudio R. Goncalves" <lgoncalv@...hat.com>,
 "Peter Zijlstra (Intel)" <peterz@...radead.org>,
 Boqun Feng <boqun.feng@...il.com>, Waiman Long <longman@...hat.com>,
 x86@...nel.org, linux-kernel@...r.kernel.org
Subject: [tip: locking/core] lockdep: suggest the fix for "lockdep bfs
 error:-1" on print_bfs_bug

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

Commit-ID:     7886a61ebc1f3998df5950299cbe17272bf32c59
Gitweb:        https://git.kernel.org/tip/7886a61ebc1f3998df5950299cbe17272bf32c59
Author:        Luis Claudio R. Goncalves <lgoncalv@...hat.com>
AuthorDate:    Tue, 30 Jul 2024 14:45:47 -03:00
Committer:     Peter Zijlstra <peterz@...radead.org>
CommitterDate: Mon, 05 Aug 2024 16:54:41 +02:00

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 config
switch LOCKDEP_CIRCULAR_QUEUE_BITS should fix the warning.

Preface the scary backtrace 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>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Reviewed-by: Boqun Feng <boqun.feng@...il.com>
Reviewed-by: Waiman Long <longman@...hat.com>
Link: https://lkml.kernel.org/r/Zqkmy0lS-9Sw0M9j@uudg.org
---
 kernel/locking/lockdep.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index 726b22c..fee21f3 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);
 }