pm24.git/kernel/locking, branch rust-6.14

locking: rtmutex: Fix wake_q logic in task_blocks_on_rt_mutex

2024-12-02T11:01:29Z

Anders had bisected a crash using PREEMPT_RT with linux-next and isolated it down to commit 894d1b3db41c ("locking/mutex: Remove wakeups from under mutex::wait_lock"), where it seemed the wake_q structure was somehow getting corrupted causing a null pointer traversal. I was able to easily repoduce this with PREEMPT_RT and managed to isolate down that through various call stacks we were actually calling wake_up_q() twice on the same wake_q. I found that in the problematic commit, I had added the wake_up_q() call in task_blocks_on_rt_mutex() around __ww_mutex_add_waiter(), following a similar pattern in __mutex_lock_common(). However, its just wrong. We haven't dropped the lock->wait_lock, so its contrary to the point of the original patch. And it didn't match the __mutex_lock_common() logic of re-initializing the wake_q after calling it midway in the stack. Looking at it now, the wake_up_q() call is incorrect and should just be removed. So drop the erronious logic I had added. Fixes: 894d1b3db41c ("locking/mutex: Remove wakeups from under mutex::wait_lock") Closes: https://lore.kernel.org/lkml/6afb936f-17c7-43fa-90e0-b9e780866097@app.fastmail.com/ Reported-by: Anders Roxell Reported-by: Arnd Bergmann Signed-off-by: John Stultz Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Juri Lelli Tested-by: Anders Roxell Tested-by: K Prateek Nayak Link: https://lore.kernel.org/r/20241114190051.552665-1-jstultz@google.com

Merge tag 'sched-core-2024-11-18' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2024-11-19T22:16:06Z

Pull scheduler updates from Ingo Molnar: "Core facilities: - Add the "Lazy preemption" model (CONFIG_PREEMPT_LAZY=y), which optimizes fair-class preemption by delaying preemption requests to the tick boundary, while working as full preemption for RR/FIFO/DEADLINE classes. (Peter Zijlstra) - x86: Enable Lazy preemption (Peter Zijlstra) - riscv: Enable Lazy preemption (Jisheng Zhang) - Initialize idle tasks only once (Thomas Gleixner) - sched/ext: Remove sched_fork() hack (Thomas Gleixner) Fair scheduler: - Optimize the PLACE_LAG when se->vlag is zero (Huang Shijie) Idle loop: - Optimize the generic idle loop by removing unnecessary memory barrier (Zhongqiu Han) RSEQ: - Improve cache locality of RSEQ concurrency IDs for intermittent workloads (Mathieu Desnoyers) Waitqueues: - Make wake_up_{bit,var} less fragile (Neil Brown) PSI: - Pass enqueue/dequeue flags to psi callbacks directly (Johannes Weiner) Preparatory patches for proxy execution: - Add move_queued_task_locked helper (Connor O'Brien) - Consolidate pick_*_task to task_is_pushable helper (Connor O'Brien) - Split out __schedule() deactivate task logic into a helper (John Stultz) - Split scheduler and execution contexts (Peter Zijlstra) - Make mutex::wait_lock irq safe (Juri Lelli) - Expose __mutex_owner() (Juri Lelli) - Remove wakeups from under mutex::wait_lock (Peter Zijlstra) Misc fixes and cleanups: - Remove unused __HAVE_THREAD_FUNCTIONS hook support (David Disseldorp) - Update the comment for TIF_NEED_RESCHED_LAZY (Sebastian Andrzej Siewior) - Remove unused bit_wait_io_timeout (Dr. David Alan Gilbert) - remove the DOUBLE_TICK feature (Huang Shijie) - fix the comment for PREEMPT_SHORT (Huang Shijie) - Fix unnused variable warning (Christian Loehle) - No PREEMPT_RT=y for all{yes,mod}config" * tag 'sched-core-2024-11-18' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (33 commits) sched, x86: Update the comment for TIF_NEED_RESCHED_LAZY. sched: No PREEMPT_RT=y for all{yes,mod}config riscv: add PREEMPT_LAZY support sched, x86: Enable Lazy preemption sched: Enable PREEMPT_DYNAMIC for PREEMPT_RT sched: Add Lazy preemption model sched: Add TIF_NEED_RESCHED_LAZY infrastructure sched/ext: Remove sched_fork() hack sched: Initialize idle tasks only once sched: psi: pass enqueue/dequeue flags to psi callbacks directly sched/uclamp: Fix unnused variable warning sched: Split scheduler and execution contexts sched: Split out __schedule() deactivate task logic into a helper sched: Consolidate pick_*_task to task_is_pushable helper sched: Add move_queued_task_locked helper locking/mutex: Expose __mutex_owner() locking/mutex: Make mutex::wait_lock irq safe locking/mutex: Remove wakeups from under mutex::wait_lock sched: Improve cache locality of RSEQ concurrency IDs for intermittent workloads sched: idle: Optimize the generic idle loop by removing needless memory barrier ...

locking/osq_lock: Use atomic_try_cmpxchg_release() in osq_unlock()

2024-10-25T08:01:50Z

Replace this pattern in osq_unlock(): atomic_cmpxchg(*ptr, old, new) == old ... with the simpler and faster: atomic_try_cmpxchg(*ptr, &old, new) The x86 CMPXCHG instruction returns success in the ZF flag, so this change saves a compare after the CMPXCHG. The code in the fast path of osq_unlock() improves from: 11b: 31 c9 xor %ecx,%ecx 11d: 8d 50 01 lea 0x1(%rax),%edx 120: 89 d0 mov %edx,%eax 122: f0 0f b1 0f lock cmpxchg %ecx,(%rdi) 126: 39 c2 cmp %eax,%edx 128: 75 05 jne 12f <...> to: 12b: 31 d2 xor %edx,%edx 12d: 83 c0 01 add $0x1,%eax 130: f0 0f b1 17 lock cmpxchg %edx,(%rdi) 134: 75 05 jne 13b <...> Signed-off-by: Uros Bizjak Signed-off-by: Peter Zijlstra (Intel) Acked-by: Waiman Long Link: https://lore.kernel.org/r/20241001114606.820277-1-ubizjak@gmail.com

locking/rtmutex: Fix misleading comment

2024-10-24T21:03:30Z

Going through the RCU-boost and rtmutex code, I ran into this utterly confusing comment. Fix it to avoid confusing future readers. [ tglx: Wordsmithed the comment ] Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Thomas Gleixner Reviewed-by: Sebastian Andrzej Siewior Link: https://lore.kernel.org/all/20241008092606.GJ33184@noisy.programming.kicks-ass.net

locking/rt: Annotate unlock followed by lock for sparse.

2024-10-24T09:27:02Z

rt_mutex_slowlock_block() and rtlock_slowlock_locked() both unlock lock::wait_lock and then lock it later. This is unusual and sparse complains about it. Add __releases() + __acquires() annotation to mark that it is expected. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/20240812104200.2239232-5-bigeasy@linutronix.de

locking/rt: Add sparse annotation for RCU.

2024-10-24T09:27:02Z

Every lock, that becomes a sleeping lock on PREEMPT_RT, starts a RCU read side critical section. There is no sparse annotation for this and sparse complains about unbalanced locking. Add __acquires/ __releases for the RCU lock. This covers all but the trylock functions. A __cond_acquires() annotation didn't work. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Thomas Gleixner Link: https://lore.kernel.org/all/20240812104200.2239232-4-bigeasy@linutronix.de

locking/pvqspinlock: Convert fields of 'enum vcpu_state' to uppercase

2024-10-18T04:21:16Z

Convert the fields of 'enum vcpu_state' to uppercase for better readability. No functional changes intended. Acked-by: Waiman Long Signed-off-by: Qiuxu Zhuo Signed-off-by: Boqun Feng Link: https://lore.kernel.org/r/20240809014802.15320-1-qiuxu.zhuo@intel.com

lockdep: Use info level for lockdep initial info messages

2024-10-18T04:21:16Z

All those: Lock dependency validator: Copyright (c) 2006 Red Hat, Inc., Ingo Molnar ... MAX_LOCKDEP_SUBCLASSES: 8 ... MAX_LOCK_DEPTH: 48 ... MAX_LOCKDEP_KEYS: 8192 and so on are dumped with the KERN_WARNING level. It is due to missing KERN_* annotation. Use pr_info() instead of bare printk() to dump the info with the info level. Signed-off-by: Jiri Slaby (SUSE) Cc: Peter Zijlstra Cc: Ingo Molnar Cc: Will Deacon Cc: Waiman Long Cc: Boqun Feng Reviewed-by: Waiman Long Signed-off-by: Boqun Feng Link: https://lore.kernel.org/r/20241007065457.20128-1-jirislaby@kernel.org

lockdep: Add lockdep_cleanup_dead_cpu()

2024-10-18T03:07:22Z

Add a function to check that an offline CPU has left the tracing infrastructure in a sane state. Commit 9bb69ba4c177 ("ACPI: processor_idle: use raw_safe_halt() in acpi_idle_play_dead()") fixed an issue where the acpi_idle_play_dead() function called safe_halt() instead of raw_safe_halt(), which had the side-effect of setting the hardirqs_enabled flag for the offline CPU. On x86 this triggered warnings from lockdep_assert_irqs_disabled() when the CPU was brought back online again later. These warnings were too early for the exception to be handled correctly, leading to a triple-fault. Add lockdep_cleanup_dead_cpu() to check for this kind of failure mode, print the events leading up to it, and correct it so that the CPU can come online again correctly. Re-introducing the original bug now merely results in this warning instead: [ 61.556652] smpboot: CPU 1 is now offline [ 61.556769] CPU 1 left hardirqs enabled! [ 61.556915] irq event stamp: 128149 [ 61.556965] hardirqs last enabled at (128149): [] acpi_idle_play_dead+0x46/0x70 [ 61.557055] hardirqs last disabled at (128148): [] do_idle+0x90/0xe0 [ 61.557117] softirqs last enabled at (128078): [] __do_softirq+0x31c/0x423 [ 61.557199] softirqs last disabled at (128065): [] __irq_exit_rcu+0x91/0x100 [boqun: Capitalize the title and reword the message a bit] Signed-off-by: David Woodhouse Reviewed-by: Thomas Gleixner Signed-off-by: Boqun Feng Link: https://lore.kernel.org/r/f7bd2b3b999051bb3ef4be34526a9262008285f5.camel@infradead.org

locking/mutex: Expose __mutex_owner()

2024-10-14T10:52:41Z

Implementing proxy execution requires that scheduler code be able to identify the current owner of a mutex. Expose __mutex_owner() for this purpose (alone!). Includes a null mutex check, so that users of the function can be simplified. [Removed the EXPORT_SYMBOL] [jstultz: Reworked per Peter's suggestions] Signed-off-by: Juri Lelli Signed-off-by: Valentin Schneider Signed-off-by: Connor O'Brien Signed-off-by: John Stultz Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Metin Kaya Reviewed-by: Valentin Schneider Tested-by: K Prateek Nayak Tested-by: Metin Kaya Link: https://lore.kernel.org/r/20241009235352.1614323-4-jstultz@google.com