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Subject[PATCH v5] lockdep: Allow tuning tracing capacity constants.
Date
Since syzkaller continues various test cases until the kernel crashes,
syzkaller tends to examine more locking dependencies than normal systems.
As a result, syzbot is reporting that the fuzz testing was terminated
due to hitting upper limits lockdep can track [1] [2] [3]. Since analysis
via /proc/lockdep* did not show any obvious culprit [4] [5], we have no
choice but allow tuning tracing capacity constants.

[1] https://syzkaller.appspot.com/bug?id=3d97ba93fb3566000c1c59691ea427370d33ea1b
[2] https://syzkaller.appspot.com/bug?id=381cb436fe60dc03d7fd2a092b46d7f09542a72a
[3] https://syzkaller.appspot.com/bug?id=a588183ac34c1437fc0785e8f220e88282e5a29f
[4] https://lkml.kernel.org/r/4b8f7a57-fa20-47bd-48a0-ae35d860f233@i-love.sakura.ne.jp
[5] https://lkml.kernel.org/r/1c351187-253b-2d49-acaf-4563c63ae7d2@i-love.sakura.ne.jp

Reported-by: syzbot <syzbot+cd0ec5211ac07c18c049@syzkaller.appspotmail.com>
Reported-by: syzbot <syzbot+91fd909b6e62ebe06131@syzkaller.appspotmail.com>
Reported-by: syzbot <syzbot+62ebe501c1ce9a91f68c@syzkaller.appspotmail.com>
References: https://lkml.kernel.org/r/1595640639-9310-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Dmitry Vyukov <dvyukov@google.com>
---
kernel/locking/lockdep.c | 2 +-
kernel/locking/lockdep_internals.h | 8 +++---
lib/Kconfig.debug | 40 ++++++++++++++++++++++++++++++
3 files changed, 45 insertions(+), 5 deletions(-)

diff --git a/kernel/locking/lockdep.c b/kernel/locking/lockdep.c
index bdaf4829098c..65b3777e8089 100644
--- a/kernel/locking/lockdep.c
+++ b/kernel/locking/lockdep.c
@@ -1391,7 +1391,7 @@ static int add_lock_to_list(struct lock_class *this,
/*
* For good efficiency of modular, we use power of 2
*/
-#define MAX_CIRCULAR_QUEUE_SIZE 4096UL
+#define MAX_CIRCULAR_QUEUE_SIZE (1UL << CONFIG_LOCKDEP_CIRCULAR_QUEUE_BITS)
#define CQ_MASK (MAX_CIRCULAR_QUEUE_SIZE-1)

/*
diff --git a/kernel/locking/lockdep_internals.h b/kernel/locking/lockdep_internals.h
index de49f9e1c11b..ecb8662e7a4e 100644
--- a/kernel/locking/lockdep_internals.h
+++ b/kernel/locking/lockdep_internals.h
@@ -99,16 +99,16 @@ static const unsigned long LOCKF_USED_IN_IRQ_READ =
#define MAX_STACK_TRACE_ENTRIES 262144UL
#define STACK_TRACE_HASH_SIZE 8192
#else
-#define MAX_LOCKDEP_ENTRIES 32768UL
+#define MAX_LOCKDEP_ENTRIES (1UL << CONFIG_LOCKDEP_BITS)

-#define MAX_LOCKDEP_CHAINS_BITS 16
+#define MAX_LOCKDEP_CHAINS_BITS CONFIG_LOCKDEP_CHAINS_BITS

/*
* Stack-trace: tightly packed array of stack backtrace
* addresses. Protected by the hash_lock.
*/
-#define MAX_STACK_TRACE_ENTRIES 524288UL
-#define STACK_TRACE_HASH_SIZE 16384
+#define MAX_STACK_TRACE_ENTRIES (1UL << CONFIG_LOCKDEP_STACK_TRACE_BITS)
+#define STACK_TRACE_HASH_SIZE (1 << CONFIG_LOCKDEP_STACK_TRACE_HASH_BITS)
#endif

/*
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 7937265ef879..4cb84b499636 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1332,6 +1332,46 @@ config LOCKDEP
config LOCKDEP_SMALL
bool

+config LOCKDEP_BITS
+ int "Bitsize for MAX_LOCKDEP_ENTRIES"
+ depends on LOCKDEP && !LOCKDEP_SMALL
+ range 10 30
+ default 15
+ help
+ Try increasing this value if you hit "BUG: MAX_LOCKDEP_ENTRIES too low!" message.
+
+config LOCKDEP_CHAINS_BITS
+ int "Bitsize for MAX_LOCKDEP_CHAINS"
+ depends on LOCKDEP && !LOCKDEP_SMALL
+ range 10 30
+ default 16
+ help
+ Try increasing this value if you hit "BUG: MAX_LOCKDEP_CHAINS too low!" message.
+
+config LOCKDEP_STACK_TRACE_BITS
+ int "Bitsize for MAX_STACK_TRACE_ENTRIES"
+ depends on LOCKDEP && !LOCKDEP_SMALL
+ range 10 30
+ default 19
+ help
+ Try increasing this value if you hit "BUG: MAX_STACK_TRACE_ENTRIES too low!" message.
+
+config LOCKDEP_STACK_TRACE_HASH_BITS
+ int "Bitsize for STACK_TRACE_HASH_SIZE"
+ depends on LOCKDEP && !LOCKDEP_SMALL
+ range 10 30
+ default 14
+ help
+ Try increasing this value if you need large MAX_STACK_TRACE_ENTRIES.
+
+config LOCKDEP_CIRCULAR_QUEUE_BITS
+ int "Bitsize for elements in circular_queue struct"
+ depends on LOCKDEP
+ range 10 30
+ default 12
+ help
+ Try increasing this value if you hit "lockdep bfs error:-1" warning due to __cq_enqueue() failure.
+
config DEBUG_LOCKDEP
bool "Lock dependency engine debugging"
depends on DEBUG_KERNEL && LOCKDEP
--
2.18.4
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