linux/kernel/locking/lockdep.c, branch v6.4

Merge tag 'core-debugobjects-2023-05-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2023-05-28T11:15:33Z

Pull debugobjects fixes from Thomas Gleixner: "Two fixes for debugobjects: - Prevent the allocation path from waking up kswapd. That's a long standing issue due to the GFP_ATOMIC allocation flag. As debug objects can be invoked from pretty much any context waking kswapd can end up in arbitrary lock chains versus the waitqueue lock - Correct the explicit lockdep wait-type violation in debug_object_fill_pool()" * tag 'core-debugobjects-2023-05-28' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: debugobjects: Don't wake up kswapd from fill_pool() debugobjects,locking: Annotate debug_object_fill_pool() wait type violation

debugobjects,locking: Annotate debug_object_fill_pool() wait type violation

2023-05-02T12:48:14Z

There is an explicit wait-type violation in debug_object_fill_pool() for PREEMPT_RT=n kernels which allows them to more easily fill the object pool and reduce the chance of allocation failures. Lockdep's wait-type checks are designed to check the PREEMPT_RT locking rules even for PREEMPT_RT=n kernels and object to this, so create a lockdep annotation to allow this to stand. Specifically, create a 'lock' type that overrides the inner wait-type while it is held -- allowing one to temporarily raise it, such that the violation is hidden. Reported-by: Vlastimil Babka Reported-by: Qi Zheng Signed-off-by: Peter Zijlstra (Intel) Tested-by: Qi Zheng Link: https://lkml.kernel.org/r/20230429100614.GA1489784@hirez.programming.kicks-ass.net

locking/lockdep: Improve the deadlock scenario print for sync and read lock

2023-03-27T18:16:04Z

Lock scenario print is always a weak spot of lockdep splats. Improvement can be made if we rework the dependency search and the error printing. However without touching the graph search, we can improve a little for the circular deadlock case, since we have the to-be-added lock dependency, and know whether these two locks are read/write/sync. In order to know whether a held_lock is sync or not, a bit was "stolen" from ->references, which reduce our limit for the same lock class nesting from 2^12 to 2^11, and it should still be good enough. Besides, since we now have bit in held_lock for sync, we don't need the "hardirqoffs being 1" trick, and also we can avoid the __lock_release() if we jump out of __lock_acquire() before the held_lock stored. With these changes, a deadlock case evolved with read lock and sync gets a better print-out from: [...] Possible unsafe locking scenario: [...] [...] CPU0 CPU1 [...] ---- ---- [...] lock(srcuA); [...] lock(srcuB); [...] lock(srcuA); [...] lock(srcuB); to [...] Possible unsafe locking scenario: [...] [...] CPU0 CPU1 [...] ---- ---- [...] rlock(srcuA); [...] lock(srcuB); [...] lock(srcuA); [...] sync(srcuB); Signed-off-by: Boqun Feng Signed-off-by: Paul E. McKenney Acked-by: Peter Zijlstra (Intel) Signed-off-by: Boqun Feng

locking/lockdep: Introduce lock_sync()

2023-03-27T18:15:23Z

Currently, functions like synchronize_srcu() do not have lockdep annotations resembling those of other write-side locking primitives. Such annotations might look as follows: lock_acquire(); lock_release(); Such annotations would tell lockdep that synchronize_srcu() acts like an empty critical section that waits for other (read-side) critical sections to finish. This would definitely catch some deadlock, but as pointed out by Paul Mckenney [1], this could also introduce false positives because of irq-safe/unsafe detection. Of course, there are tricks could help with this: might_sleep(); // Existing statement in __synchronize_srcu(). if (IS_ENABLED(CONFIG_PROVE_LOCKING)) { local_irq_disable(); lock_acquire(); lock_release(); local_irq_enable(); } But it would be better for lockdep to provide a separate annonation for functions like synchronize_srcu(), so that people won't need to repeat the ugly tricks above. Therefore introduce lock_sync(), which is simply an lock+unlock pair with no irq safe/unsafe deadlock check. This works because the to-be-annontated functions do not create real critical sections, and there is therefore no way that irq can create extra dependencies. [1]: https://lore.kernel.org/lkml/20180412021233.ewncg5jjuzjw3x62@tardis/ Signed-off-by: Boqun Feng Acked-by: Waiman Long Signed-off-by: Paul E. McKenney [ boqun: Fix typos reported by Davidlohr Bueso and Paul E. Mckenney ] Acked-by: Peter Zijlstra (Intel) Signed-off-by: Boqun Feng

cpuidle: lib/bug: Disable rcu_is_watching() during WARN/BUG

2023-01-31T14:01:45Z

In order to avoid WARN/BUG from generating nested or even recursive warnings, force rcu_is_watching() true during WARN/lockdep_rcu_suspicious(). Notably things like unwinding the stack can trigger rcu_dereference() warnings, which then triggers more unwinding which then triggers more warnings etc.. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/20230126151323.408156109@infradead.org

locking/lockdep: Print more debug information - report name and key when look_up_lock_class() got confused

2022-09-21T07:58:21Z

Printing this information will be helpful: ------------[ cut here ]------------ Looking for class "l2tp_sock" with key l2tp_socket_class, but found a different class "slock-AF_INET6" with the same key WARNING: CPU: 1 PID: 14195 at kernel/locking/lockdep.c:940 look_up_lock_class+0xcc/0x140 Modules linked in: CPU: 1 PID: 14195 Comm: a.out Not tainted 6.0.0-rc6-dirty #863 Hardware name: innotek GmbH VirtualBox/VirtualBox, BIOS VirtualBox 12/01/2006 RIP: 0010:look_up_lock_class+0xcc/0x140 Signed-off-by: Tetsuo Handa Signed-off-by: Ingo Molnar Link: https://lore.kernel.org/r/bd99391e-f787-efe9-5ec6-3c6dc4c587b0@I-love.SAKURA.ne.jp

Merge tag 'rcu.2022.07.26a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu

2022-08-03T02:12:45Z

Pull RCU updates from Paul McKenney: - Documentation updates - Miscellaneous fixes - Callback-offload updates, perhaps most notably a new RCU_NOCB_CPU_DEFAULT_ALL Kconfig option that causes all CPUs to be offloaded at boot time, regardless of kernel boot parameters. This is useful to battery-powered systems such as ChromeOS and Android. In addition, a new RCU_NOCB_CPU_CB_BOOST kernel boot parameter prevents offloaded callbacks from interfering with real-time workloads and with energy-efficiency mechanisms - Polled grace-period updates, perhaps most notably making these APIs account for both normal and expedited grace periods - Tasks RCU updates, perhaps most notably reducing the CPU overhead of RCU tasks trace grace periods by more than a factor of two on a system with 15,000 tasks. The reduction is expected to increase with the number of tasks, so it seems reasonable to hypothesize that a system with 150,000 tasks might see a 20-fold reduction in CPU overhead - Torture-test updates - Updates that merge RCU's dyntick-idle tracking into context tracking, thus reducing the overhead of transitioning to kernel mode from either idle or nohz_full userspace execution for kernels that track context independently of RCU. This is expected to be helpful primarily for kernels built with CONFIG_NO_HZ_FULL=y * tag 'rcu.2022.07.26a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu: (98 commits) rcu: Add irqs-disabled indicator to expedited RCU CPU stall warnings rcu: Diagnose extended sync_rcu_do_polled_gp() loops rcu: Put panic_on_rcu_stall() after expedited RCU CPU stall warnings rcutorture: Test polled expedited grace-period primitives rcu: Add polled expedited grace-period primitives rcutorture: Verify that polled GP API sees synchronous grace periods rcu: Make Tiny RCU grace periods visible to polled APIs rcu: Make polled grace-period API account for expedited grace periods rcu: Switch polled grace-period APIs to ->gp_seq_polled rcu/nocb: Avoid polling when my_rdp->nocb_head_rdp list is empty rcu/nocb: Add option to opt rcuo kthreads out of RT priority rcu: Add nocb_cb_kthread check to rcu_is_callbacks_kthread() rcu/nocb: Add an option to offload all CPUs on boot rcu/nocb: Fix NOCB kthreads spawn failure with rcu_nocb_rdp_deoffload() direct call rcu/nocb: Invert rcu_state.barrier_mutex VS hotplug lock locking order rcu/nocb: Add/del rdp to iterate from rcuog itself rcu/tree: Add comment to describe GP-done condition in fqs loop rcu: Initialize first_gp_fqs at declaration in rcu_gp_fqs() rcu/kvfree: Remove useless monitor_todo flag rcu: Cleanup RCU urgency state for offline CPU ...

context_tracking: Take idle eqs entrypoints over RCU

2022-07-05T20:32:16Z

The RCU dynticks counter is going to be merged into the context tracking subsystem. Start with moving the idle extended quiescent states entrypoints to context tracking. For now those are dumb redirections to existing RCU calls. [ paulmck: Apply kernel test robot feedback. ] Signed-off-by: Frederic Weisbecker Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Neeraj Upadhyay Cc: Uladzislau Rezki Cc: Joel Fernandes Cc: Boqun Feng Cc: Nicolas Saenz Julienne Cc: Marcelo Tosatti Cc: Xiongfeng Wang Cc: Yu Liao Cc: Phil Auld Cc: Paul Gortmaker Cc: Alex Belits Signed-off-by: Paul E. McKenney Reviewed-by: Nicolas Saenz Julienne Tested-by: Nicolas Saenz Julienne

locking/lockdep: Fix lockdep_init_map_*() confusion

2022-06-24T07:48:56Z

Commit dfd5e3f5fe27 ("locking/lockdep: Mark local_lock_t") added yet another lockdep_init_map_*() variant, but forgot to update all the existing users of the most complicated version. This could lead to a loss of lock_type and hence an incorrect report. Given the relative rarity of both local_lock and these annotations, this is unlikely to happen in practise, still, best fix things. Fixes: dfd5e3f5fe27 ("locking/lockdep: Mark local_lock_t") Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/YqyEDtoan20K0CVD@worktop.programming.kicks-ass.net

locking/lockdep: Use sched_clock() for random numbers

2022-06-13T08:29:57Z

Since the rewrote of prandom_u32(), in the commit mentioned below, the function uses sleeping locks which extracing random numbers and filling the batch. This breaks lockdep on PREEMPT_RT because lock_pin_lock() disables interrupts while calling __lock_pin_lock(). This can't be moved earlier because the main user of the function (rq_pin_lock()) invokes that function after disabling interrupts in order to acquire the lock. The cookie does not require random numbers as its goal is to provide a random value in order to notice unexpected "unlock + lock" sites. Use sched_clock() to provide random numbers. Fixes: a0103f4d86f88 ("random32: use real rng for non-deterministic randomness") Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Peter Zijlstra (Intel) Link: https://lkml.kernel.org/r/YoNn3pTkm5+QzE5k@linutronix.de