linux-next.git/kernel/locking/lockdep.c, branch master

Merge branch 'master' of git://git.code.sf.net/p/tomoyo/tomoyo.git

2026-07-06T13:53:42+00:00

locking/lockdep: add sequence counter to held_lock

2026-07-05T23:23:27+00:00

Add an 8 bit small sequence counter to the held_lock struct to detect if the lock as been dropped and reacquired. This is useful when a data structure depends on a constant locking context, but is not able to detect locking and unlocking of the lock through its own API. Since the __lock_unpin_lock() will no longer detect underflow by casting the unsigned int to a signed int, update the casting code to use a temp variable for calculations using a signed int. Link: https://lore.kernel.org/20260630190843.3563858-3-liam@infradead.org Link: https://lore.kernel.org/all/h3tpnj5kzcrxms5picmimtkpg4aypcpip5wbd6bt2rpdj5k7eb@nhtzs3lefrkq/ Signed-off-by: Liam R. Howlett (Oracle) Suggested-by: Peter Zijlstra Cc: Ingo Molnar Cc: Will Deacon Cc: Boqun Feng Cc: Waiman Long Cc: Chris Mason Cc: Chuck Lever Cc: Jason Gunthorpe Cc: Joe Perches Cc: Rik van Riel Signed-off-by: Andrew Morton

locking/lockdep: make lockdep_print_held_locks() always print if CONFIG_DEBUG_AID_FOR_SYZBOT=y

2026-06-29T11:24:18+00:00

This change is not for upstream. This change is for linux-next only. When executing syzkaller testcases, many threads run on few number of CPUs. It is more helpful for syzbot reports to also include locks held by "waiting for CPU" tasks. Signed-off-by: Tetsuo Handa

lockdep: Speed up lockdep_unregister_key() with expedited RCU synchronization

2025-07-15T04:57:29+00:00

lockdep_unregister_key() is called from critical code paths, including sections where rtnl_lock() is held. For example, when replacing a qdisc in a network device, network egress traffic is disabled while __qdisc_destroy() is called for every network queue. If lockdep is enabled, __qdisc_destroy() calls lockdep_unregister_key(), which gets blocked waiting for synchronize_rcu() to complete. For example, a simple tc command to replace a qdisc could take 13 seconds: # time /usr/sbin/tc qdisc replace dev eth0 root handle 0x1: mq real 0m13.195s user 0m0.001s sys 0m2.746s During this time, network egress is completely frozen while waiting for RCU synchronization. Use synchronize_rcu_expedited() instead to minimize the impact on critical operations like network connectivity changes. This improves 10x the function call to tc, when replacing the qdisc for a network card. # time /usr/sbin/tc qdisc replace dev eth0 root handle 0x1: mq real 0m1.789s user 0m0.000s sys 0m1.613s [boqun: Fixed the comment and add more information for the temporary workaround, and add TODO information for hazptr] Reported-by: Erik Lundgren Signed-off-by: Breno Leitao Reviewed-by: Paul E. McKenney Reviewed-by: Eric Dumazet Signed-off-by: Boqun Feng Link: https://lore.kernel.org/r/20250321-lockdep-v1-1-78b732d195fb@debian.org

locking/lockdep: Avoid struct return in lock_stats()

2025-07-15T04:57:20+00:00

Returning a large structure from the lock_stats() function causes clang to have multiple copies of it on the stack and copy between them, which can end up exceeding the frame size warning limit: kernel/locking/lockdep.c:300:25: error: stack frame size (1464) exceeds limit (1280) in 'lock_stats' [-Werror,-Wframe-larger-than] 300 | struct lock_class_stats lock_stats(struct lock_class *class) Change the calling conventions to directly operate on the caller's copy, which apparently is what gcc does already. Signed-off-by: Arnd Bergmann Signed-off-by: Boqun Feng Link: https://lore.kernel.org/r/20250610092941.2642847-1-arnd@kernel.org

locking/lockdep: Add number of dynamic keys to /proc/lockdep_stats

2025-05-06T16:34:43+00:00

There have been recent reports about running out of lockdep keys: MAX_LOCKDEP_KEYS too low! One possible reason is that too many dynamic keys have been registered. A possible culprit is the lockdep_register_key() call in qdisc_alloc() of net/sched/sch_generic.c. Currently, there is no way to find out how many dynamic keys have been registered. Add such a stat to the /proc/lockdep_stats to get better clarity. Signed-off-by: Waiman Long Signed-off-by: Boqun Feng Signed-off-by: Ingo Molnar Cc: Bill Wendling Cc: Justin Stitt Cc: Nathan Chancellor Cc: Nick Desaulniers Cc: Peter Zijlstra Cc: Will Deacon Cc: llvm@lists.linux.dev Link: https://lore.kernel.org/r/20250506042049.50060-4-boqun.feng@gmail.com

locking/lockdep: Prevent abuse of lockdep subclass

2025-05-06T16:34:35+00:00

To catch the code trying to use a subclass value >= MAX_LOCKDEP_SUBCLASSES (8), add a DEBUG_LOCKS_WARN_ON() statement to notify the users that such a large value is not allowed. [ boqun: Reword the commit log with a more objective tone ] Signed-off-by: Waiman Long Signed-off-by: Boqun Feng Signed-off-by: Ingo Molnar Cc: Bill Wendling Cc: Justin Stitt Cc: Nathan Chancellor Cc: Nick Desaulniers Cc: Peter Zijlstra Cc: Will Deacon Cc: llvm@lists.linux.dev Link: https://lore.kernel.org/r/20250506042049.50060-3-boqun.feng@gmail.com

locking/lockdep: Move hlock_equal() to the respective #ifdeffery

2025-05-06T16:34:31+00:00

When hlock_equal() is unused, it prevents kernel builds with clang, `make W=1` and CONFIG_WERROR=y, CONFIG_LOCKDEP=y and CONFIG_LOCKDEP_SMALL=n: lockdep.c:2005:20: error: unused function 'hlock_equal' [-Werror,-Wunused-function] Fix this by moving the function to the respective existing ifdeffery for its the only user. See also: 6863f5643dd7 ("kbuild: allow Clang to find unused static inline functions for W=1 build") Fixes: 68e305678583 ("lockdep: Adjust check_redundant() for recursive read change") Signed-off-by: Andy Shevchenko Signed-off-by: Boqun Feng Signed-off-by: Ingo Molnar Cc: Bill Wendling Cc: Justin Stitt Cc: Nathan Chancellor Cc: Nick Desaulniers Cc: Peter Zijlstra Cc: Waiman Long Cc: Will Deacon Cc: llvm@lists.linux.dev Link: https://lore.kernel.org/r/20250506042049.50060-2-boqun.feng@gmail.com

locking/lockdep: Decrease nr_unused_locks if lock unused in zap_class()

2025-03-27T07:23:17+00:00

Currently, when a lock class is allocated, nr_unused_locks will be increased by 1, until it gets used: nr_unused_locks will be decreased by 1 in mark_lock(). However, one scenario is missed: a lock class may be zapped without even being used once. This could result into a situation that nr_unused_locks != 0 but no unused lock class is active in the system, and when `cat /proc/lockdep_stats`, a WARN_ON() will be triggered in a CONFIG_DEBUG_LOCKDEP=y kernel: [...] DEBUG_LOCKS_WARN_ON(debug_atomic_read(nr_unused_locks) != nr_unused) [...] WARNING: CPU: 41 PID: 1121 at kernel/locking/lockdep_proc.c:283 lockdep_stats_show+0xba9/0xbd0 And as a result, lockdep will be disabled after this. Therefore, nr_unused_locks needs to be accounted correctly at zap_class() time. Signed-off-by: Boqun Feng Signed-off-by: Ingo Molnar Reviewed-by: Waiman Long Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20250326180831.510348-1-boqun.feng@gmail.com

locking/lockdep: Add kasan_check_byte() check in lock_acquire()

2025-03-07T23:55:04+00:00

KASAN instrumentation of lockdep has been disabled, as we don't need KASAN to check the validity of lockdep internal data structures and incur unnecessary performance overhead. However, the lockdep_map pointer passed in externally may not be valid (e.g. use-after-free) and we run the risk of using garbage data resulting in false lockdep reports. Add kasan_check_byte() call in lock_acquire() for non kernel core data object to catch invalid lockdep_map and print out a KASAN report before any lockdep splat, if any. Suggested-by: Marco Elver Signed-off-by: Waiman Long Signed-off-by: Boqun Feng Signed-off-by: Ingo Molnar Reviewed-by: Marco Elver Reviewed-by: Andrey Konovalov Link: https://lore.kernel.org/r/20250214195242.2480920-1-longman@redhat.com Link: https://lore.kernel.org/r/20250307232717.1759087-7-boqun.feng@gmail.com