user/sven/linux.git/kernel/locking, branch v6.14.6

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

2025-04-20T08:23:03Z

commit 495f53d5cca0f939eaed9dca90b67e7e6fb0e30c upstream. 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 Signed-off-by: Greg Kroah-Hartman

locking/semaphore: Use wake_q to wake up processes outside lock critical section

2025-03-07T23:52:01Z

A circular lock dependency splat has been seen involving down_trylock(): ====================================================== WARNING: possible circular locking dependency detected 6.12.0-41.el10.s390x+debug ------------------------------------------------------ dd/32479 is trying to acquire lock: 0015a20accd0d4f8 ((console_sem).lock){-.-.}-{2:2}, at: down_trylock+0x26/0x90 but task is already holding lock: 000000017e461698 (&zone->lock){-.-.}-{2:2}, at: rmqueue_bulk+0xac/0x8f0 the existing dependency chain (in reverse order) is: -> #4 (&zone->lock){-.-.}-{2:2}: -> #3 (hrtimer_bases.lock){-.-.}-{2:2}: -> #2 (&rq->__lock){-.-.}-{2:2}: -> #1 (&p->pi_lock){-.-.}-{2:2}: -> #0 ((console_sem).lock){-.-.}-{2:2}: The console_sem -> pi_lock dependency is due to calling try_to_wake_up() while holding the console_sem raw_spinlock. This dependency can be broken by using wake_q to do the wakeup instead of calling try_to_wake_up() under the console_sem lock. This will also make the semaphore's raw_spinlock become a terminal lock without taking any further locks underneath it. The hrtimer_bases.lock is a raw_spinlock while zone->lock is a spinlock. The hrtimer_bases.lock -> zone->lock dependency happens via the debug_objects_fill_pool() helper function in the debugobjects code. -> #4 (&zone->lock){-.-.}-{2:2}: __lock_acquire+0xe86/0x1cc0 lock_acquire.part.0+0x258/0x630 lock_acquire+0xb8/0xe0 _raw_spin_lock_irqsave+0xb4/0x120 rmqueue_bulk+0xac/0x8f0 __rmqueue_pcplist+0x580/0x830 rmqueue_pcplist+0xfc/0x470 rmqueue.isra.0+0xdec/0x11b0 get_page_from_freelist+0x2ee/0xeb0 __alloc_pages_noprof+0x2c2/0x520 alloc_pages_mpol_noprof+0x1fc/0x4d0 alloc_pages_noprof+0x8c/0xe0 allocate_slab+0x320/0x460 ___slab_alloc+0xa58/0x12b0 __slab_alloc.isra.0+0x42/0x60 kmem_cache_alloc_noprof+0x304/0x350 fill_pool+0xf6/0x450 debug_object_activate+0xfe/0x360 enqueue_hrtimer+0x34/0x190 __run_hrtimer+0x3c8/0x4c0 __hrtimer_run_queues+0x1b2/0x260 hrtimer_interrupt+0x316/0x760 do_IRQ+0x9a/0xe0 do_irq_async+0xf6/0x160 Normally a raw_spinlock to spinlock dependency is not legitimate and will be warned if CONFIG_PROVE_RAW_LOCK_NESTING is enabled, but debug_objects_fill_pool() is an exception as it explicitly allows this dependency for non-PREEMPT_RT kernel without causing PROVE_RAW_LOCK_NESTING lockdep splat. As a result, this dependency is legitimate and not a bug. Anyway, semaphore is the only locking primitive left that is still using try_to_wake_up() to do wakeup inside critical section, all the other locking primitives had been migrated to use wake_q to do wakeup outside of the critical section. It is also possible that there are other circular locking dependencies involving printk/console_sem or other existing/new semaphores lurking somewhere which may show up in the future. Let just do the migration now to wake_q to avoid headache like this. Reported-by: yzbot+ed801a886dfdbfe7136d@syzkaller.appspotmail.com Signed-off-by: Waiman Long Signed-off-by: Boqun Feng Signed-off-by: Ingo Molnar Cc: Linus Torvalds Link: https://lore.kernel.org/r/20250307232717.1759087-3-boqun.feng@gmail.com

locking/rtmutex: Use the 'struct' keyword in kernel-doc comment

2025-03-07T23:52:01Z

Add the "struct" keyword to prevent a kernel-doc warning: rtmutex_common.h:67: warning: cannot understand function prototype: 'struct rt_wake_q_head ' Signed-off-by: Randy Dunlap Signed-off-by: Boqun Feng Signed-off-by: Ingo Molnar Acked-by: Waiman Long Link: https://lore.kernel.org/r/20250307232717.1759087-2-boqun.feng@gmail.com

treewide: const qualify ctl_tables where applicable

2025-01-28T12:48:37Z

Add the const qualifier to all the ctl_tables in the tree except for watchdog_hardlockup_sysctl, memory_allocation_profiling_sysctls, loadpin_sysctl_table and the ones calling register_net_sysctl (./net, drivers/inifiniband dirs). These are special cases as they use a registration function with a non-const qualified ctl_table argument or modify the arrays before passing them on to the registration function. Constifying ctl_table structs will prevent the modification of proc_handler function pointers as the arrays would reside in .rodata. This is made possible after commit 78eb4ea25cd5 ("sysctl: treewide: constify the ctl_table argument of proc_handlers") constified all the proc_handlers. Created this by running an spatch followed by a sed command: Spatch: virtual patch @ depends on !(file in "net") disable optional_qualifier @ identifier table_name != { watchdog_hardlockup_sysctl, iwcm_ctl_table, ucma_ctl_table, memory_allocation_profiling_sysctls, loadpin_sysctl_table }; @@ + const struct ctl_table table_name [] = { ... }; sed: sed --in-place \ -e "s/struct ctl_table .table = &uts_kern/const struct ctl_table *table = \&uts_kern/" \ kernel/utsname_sysctl.c Reviewed-by: Song Liu Acked-by: Steven Rostedt (Google) # for kernel/trace/ Reviewed-by: Martin K. Petersen # SCSI Reviewed-by: Darrick J. Wong # xfs Acked-by: Jani Nikula Acked-by: Corey Minyard Acked-by: Wei Liu Acked-by: Thomas Gleixner Reviewed-by: Bill O'Donnell Acked-by: Baoquan He Acked-by: Ashutosh Dixit Acked-by: Anna Schumaker Signed-off-by: Joel Granados

Merge tag 'rcu.release.v6.14' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux

2025-01-21T22:39:21Z

Pull RCU updates from Uladzislau Rezki: "Misc fixes: - check if IRQs are disabled in rcu_exp_need_qs() - instrument KCSAN exclusive-writer assertions - add extra WARN_ON_ONCE() check - set the cpu_no_qs.b.exp under lock - warn if callback enqueued on offline CPU Torture-test updates: - add rcutorture.preempt_duration kernel module parameter - make the TREE03 scenario do preemption - improve pooling timeouts for rcu_torture_writer() - improve output of "Failure/close-call rcutorture reader segments" - add some reader-state debugging checks - update doc of polled APIs - add extra diagnostics for per-reader-segment preemption - add an extra test for sched_clock() - improve testing on unresponsive systems SRCU updates: - improve doc for srcu_read_lock() in terms of return value - fix typo in comments - remove redundant GP sequence checks in the srcu_funnel_gp_start" * tag 'rcu.release.v6.14' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux: (31 commits) srcu: Remove redundant GP sequence checks in srcu_funnel_gp_start srcu: Fix typo s/srcu_check_read_flavor()/__srcu_check_read_flavor()/ srcu: Guarantee non-negative return value from srcu_read_lock() MAINTAINERS: Update RCU git tree rcu: Add lockdep_assert_irqs_disabled() to rcu_exp_need_qs() rcu: Add KCSAN exclusive-writer assertions for rdp->cpu_no_qs.b.exp rcu: Make preemptible rcu_exp_handler() check idempotency rcu: Replace open-coded rcu_exp_need_qs() from rcu_exp_handler() with call rcu: Move rcu_report_exp_rdp() setting of ->cpu_no_qs.b.exp under lock rcu: Make rcu_report_exp_cpu_mult() caller acquire lock rcu: Report callbacks enqueued on offline CPU blind spot rcutorture: Use symbols for SRCU reader flavors rcutorture: Add per-reader-segment preemption diagnostics rcutorture: Read CPU ID for decoration protected by both reader types rcutorture: Add preempt_count() to rcutorture_one_extend_check() diagnostics rcutorture: Add parameters to control polled/conditional wait interval rcutorture: Add documentation for recent conditional and polled APIs rcutorture: Ignore attempts to test preemption and forward progress rcutorture: Make rcutorture_one_extend() check reader state rcutorture: Pretty-print rcutorture reader segments ...

Merge tag 'lockdep-for-tip.20241220' of git://git.kernel.org/pub/scm/linux/kernel/git/boqun/linux into locking/core

2024-12-22T11:43:31Z

Lockdep changes for v6.14: - Use swap() macro in the ww_mutex test. - Minor fixes and documentation for lockdep configs on internal data structure sizes. - Some "-Wunused-function" warning fixes for Clang. Rust locking changes for v6.14: - Add Rust locking files into LOCKING PRIMITIVES maintainer entry. - Add `Lock<(), ..>::from_raw()` function to support abstraction on low level locking. - Expose `Guard::new()` for public usage and add type alias for spinlock and mutex guards. - Add lockdep checking when creating a new lock `Guard`.

sched/wake_q: Add helper to call wake_up_q after unlock with preemption disabled

2024-12-20T14:31:21Z

A common pattern seen when wake_qs are used to defer a wakeup until after a lock is released is something like: preempt_disable(); raw_spin_unlock(lock); wake_up_q(wake_q); preempt_enable(); So create some raw_spin_unlock*_wake() helper functions to clean this up. Applies on top of the fix I submitted here: https://lore.kernel.org/lkml/20241212222138.2400498-1-jstultz@google.com/ NOTE: I recognise the unlock()/unlock_irq()/unlock_irqrestore() variants creates its own duplication, which we could use a macro to generate the similar functions, but I often dislike how those generation macros making finding the actual implementation harder, so I left the three functions as is. If folks would prefer otherwise, let me know and I'll switch it. Suggested-by: Peter Zijlstra Signed-off-by: John Stultz Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20241217040803.243420-1-jstultz@google.com

lockdep: Move lockdep_assert_locked() under #ifdef CONFIG_PROVE_LOCKING

2024-12-19T22:04:03Z

When lockdep_assert_locked() is unused, it prevents kernel builds with clang, `make W=1` and CONFIG_WERROR=y, CONFIG_LOCKDEP=y and CONFIG_PROVE_LOCKING=n: kernel/locking/lockdep.c:160:20: error: unused function 'lockdep_assert_locked' [-Werror,-Wunused-function] Fix this by moving it under the respective ifdeffery. See also commit 6863f5643dd7 ("kbuild: allow Clang to find unused static inline functions for W=1 build"). [Boqun: add more config information of the error] Signed-off-by: Andy Shevchenko Signed-off-by: Boqun Feng Link: https://lore.kernel.org/r/20241202193445.769567-1-andriy.shevchenko@linux.intel.com

lockdep: Mark chain_hlock_class_idx() with __maybe_unused

2024-12-19T21:57:53Z

When chain_hlock_class_idx() is unused, it prevents kernel builds with clang, `make W=1` and CONFIG_WERROR=y, CONFIG_LOCKDEP=y and CONFIG_PROVE_LOCKING=n: kernel/locking/lockdep.c:435:28: error: unused function 'chain_hlock_class_idx' [-Werror,-Wunused-function] Fix this by marking it with __maybe_unused. See also commit 6863f5643dd7 ("kbuild: allow Clang to find unused static inline functions for W=1 build"). [Boqun: add more config information of the error] Signed-off-by: Andy Shevchenko Signed-off-by: Boqun Feng Link: https://lore.kernel.org/r/20241209170810.1485183-1-andriy.shevchenko@linux.intel.com

locking/rtmutex: Make sure we wake anything on the wake_q when we release the lock->wait_lock

2024-12-17T16:47:24Z

Bert reported seeing occasional boot hangs when running with PREEPT_RT and bisected it down to commit 894d1b3db41c ("locking/mutex: Remove wakeups from under mutex::wait_lock"). It looks like I missed a few spots where we drop the wait_lock and potentially call into schedule without waking up the tasks on the wake_q structure. Since the tasks being woken are ww_mutex tasks they need to be able to run to release the mutex and unblock the task that currently is planning to wake them. Thus we can deadlock. So make sure we wake the wake_q tasks when we unlock the wait_lock. Closes: https://lore.kernel.org/lkml/20241211182502.2915-1-spasswolf@web.de Fixes: 894d1b3db41c ("locking/mutex: Remove wakeups from under mutex::wait_lock") Reported-by: Bert Karwatzki Signed-off-by: John Stultz Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/20241212222138.2400498-1-jstultz@google.com