linux-kernel - [PATCH] lockdep: Allow tuning tracing keys constant.

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Date:   Fri, 30 Sep 2022 10:00:58 -0700
From:   Ryan Huang <tzukui@...gle.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>,
        Sasha Levin <sashal@...nel.org>
Cc:     linux-kernel@...r.kernel.org, Ryan Huang <tzukui@...gle.com>
Subject: [PATCH] lockdep: Allow tuning tracing keys constant.

Tetsuo Handa made a change for tuning lockdep tracing capacity constants
[1]. He created following tracing config constants:
  - LOCKDEP_BITS
  - LOCKDEP_CHAINS_BITS
  - LOCKDEP_STACK_TRACE_BITS
However there is a missing one for LOCKDEP_KEYS_BITS. We can see this is
also hitting the upper limits in [2].

[1] https://github.com/torvalds/linux/commit/5dc33592e95534dc8455ce3e9baaaf3dae0fff82
[2] https://syzkaller.appspot.com/bug?id=df466e1151a7e45dd880d8c7033f1ad48acebfb4

Fixes: 5dc33592e955 ("lockdep: Allow tuning tracing capacity constants.")
Signed-off-by: Ryan Huang <tzukui@...gle.com>
---
 include/linux/lockdep.h | 2 +-
 lib/Kconfig.debug       | 8 ++++++++
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/include/linux/lockdep.h b/include/linux/lockdep.h
index 1f1099dac3f05..3bb1740296559 100644
--- a/include/linux/lockdep.h
+++ b/include/linux/lockdep.h
@@ -82,7 +82,7 @@ struct lock_chain {
 	u64				chain_key;
 };
 
-#define MAX_LOCKDEP_KEYS_BITS		13
+#define MAX_LOCKDEP_KEYS_BITS		CONFIG_LOCKDEP_KEYS_BITS
 #define MAX_LOCKDEP_KEYS		(1UL << MAX_LOCKDEP_KEYS_BITS)
 #define INITIAL_CHAIN_KEY		-1
 
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index d3e5f36bb01e0..d15024bd14f1d 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1398,6 +1398,14 @@ config LOCKDEP_CHAINS_BITS
 	help
 	  Try increasing this value if you hit "BUG: MAX_LOCKDEP_CHAINS too low!" message.
 
+config LOCKDEP_KEYS_BITS
+	int "Bitsize for MAX_LOCKDEP_KEYS"
+	depends on LOCKDEP && !LOCKDEP_SMALL
+	range 10 30
+	default 13
+	help
+	  Try increasing this value if you hit "BUG: MAX_LOCKDEP_KEYS too low!" message.
+
 config LOCKDEP_STACK_TRACE_BITS
 	int "Bitsize for MAX_STACK_TRACE_ENTRIES"
 	depends on LOCKDEP && !LOCKDEP_SMALL
-- 
2.38.0.rc1.362.ged0d419d3c-goog