kernel/linux.git/include/linux/percpu-rwsem.h, branch v6.12.80

percpu-rwsem: remove the unused parameter 'read'

2024-08-19T11:45:03+00:00

In the function percpu_rwsem_release, the parameter `read` is unused, so remove it. Signed-off-by: Wang Long Link: https://lore.kernel.org/r/20240802091901.2546797-1-w@laoqinren.net Reviewed-by: Jan Kara Signed-off-by: Christian Brauner

locking/percpu-rwsem: Add percpu_is_write_locked() and percpu_is_read_locked()

2022-08-30T08:56:23+00:00

Implement simple accessors to probe percpu-rwsem's locked state: percpu_is_write_locked(), percpu_is_read_locked(). Signed-off-by: Marco Elver Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Dmitry Vyukov Acked-by: Ian Rogers Link: https://lore.kernel.org/r/20220829124719.675715-11-elver@google.com

locking/percpu-rwsem: Use this_cpu_{inc,dec}() for read_count

2020-09-16T14:26:56+00:00

The __this_cpu*() accessors are (in general) IRQ-unsafe which, given that percpu-rwsem is a blocking primitive, should be just fine. However, file_end_write() is used from IRQ context and will cause load-store issues on architectures where the per-cpu accessors are not natively irq-safe. Fix it by using the IRQ-safe this_cpu_*() for operations on read_count. This will generate more expensive code on a number of platforms, which might cause a performance regression for some of the other percpu-rwsem users. If any such is reported, we can consider alternative solutions. Fixes: 70fe2f48152e ("aio: fix freeze protection of aio writes") Signed-off-by: Hou Tao Signed-off-by: Peter Zijlstra (Intel) Acked-by: Will Deacon Acked-by: Oleg Nesterov Link: https://lkml.kernel.org/r/20200915140750.137881-1-houtao1@huawei.com

locking/percpu-rwsem: Fold __percpu_up_read()

2020-02-11T12:10:58+00:00

Now that __percpu_up_read() is only ever used from percpu_up_read() merge them, it's a small function. Signed-off-by: Davidlohr Bueso Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Acked-by: Will Deacon Acked-by: Waiman Long Link: https://lkml.kernel.org/r/20200131151540.212415454@infradead.org

locking/percpu-rwsem: Remove the embedded rwsem

2020-02-11T12:10:56+00:00

The filesystem freezer uses percpu-rwsem in a way that is effectively write_non_owner() and achieves this with a few horrible hacks that rely on the rwsem (!percpu) implementation. When PREEMPT_RT replaces the rwsem implementation with a PI aware variant this comes apart. Remove the embedded rwsem and implement it using a waitqueue and an atomic_t. - make readers_block an atomic, and use it, with the waitqueue for a blocking test-and-set write-side. - have the read-side wait for the 'lock' state to clear. Have the waiters use FIFO queueing and mark them (reader/writer) with a new WQ_FLAG. Use a custom wake_function to wake either a single writer or all readers until a writer. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Davidlohr Bueso Acked-by: Will Deacon Acked-by: Waiman Long Tested-by: Juri Lelli Link: https://lkml.kernel.org/r/20200204092403.GB14879@hirez.programming.kicks-ass.net

locking/percpu-rwsem: Move __this_cpu_inc() into the slowpath

2020-02-11T12:10:54+00:00

As preparation to rework __percpu_down_read() move the __this_cpu_inc() into it. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Davidlohr Bueso Acked-by: Will Deacon Acked-by: Waiman Long Tested-by: Juri Lelli Link: https://lkml.kernel.org/r/20200131151540.041600199@infradead.org

locking/percpu-rwsem: Convert to bool

2020-02-11T12:10:54+00:00

Use bool where possible. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Davidlohr Bueso Acked-by: Will Deacon Acked-by: Waiman Long Tested-by: Juri Lelli Link: https://lkml.kernel.org/r/20200131151539.984626569@infradead.org

locking/percpu-rwsem, lockdep: Make percpu-rwsem use its own lockdep_map

2020-02-11T12:10:53+00:00

As preparation for replacing the embedded rwsem, give percpu-rwsem its own lockdep_map. Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Davidlohr Bueso Acked-by: Will Deacon Acked-by: Waiman Long Tested-by: Juri Lelli Link: https://lkml.kernel.org/r/20200131151539.927625541@infradead.org

locking/lockdep: Remove unused @nested argument from lock_release()

2019-10-09T10:46:10+00:00

Since the following commit: b4adfe8e05f1 ("locking/lockdep: Remove unused argument in __lock_release") @nested is no longer used in lock_release(), so remove it from all lock_release() calls and friends. Signed-off-by: Qian Cai Signed-off-by: Peter Zijlstra (Intel) Acked-by: Will Deacon Acked-by: Daniel Vetter Cc: Linus Torvalds Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: airlied@linux.ie Cc: akpm@linux-foundation.org Cc: alexander.levin@microsoft.com Cc: daniel@iogearbox.net Cc: davem@davemloft.net Cc: dri-devel@lists.freedesktop.org Cc: duyuyang@gmail.com Cc: gregkh@linuxfoundation.org Cc: hannes@cmpxchg.org Cc: intel-gfx@lists.freedesktop.org Cc: jack@suse.com Cc: jlbec@evilplan.or Cc: joonas.lahtinen@linux.intel.com Cc: joseph.qi@linux.alibaba.com Cc: jslaby@suse.com Cc: juri.lelli@redhat.com Cc: maarten.lankhorst@linux.intel.com Cc: mark@fasheh.com Cc: mhocko@kernel.org Cc: mripard@kernel.org Cc: ocfs2-devel@oss.oracle.com Cc: rodrigo.vivi@intel.com Cc: sean@poorly.run Cc: st@kernel.org Cc: tj@kernel.org Cc: tytso@mit.edu Cc: vdavydov.dev@gmail.com Cc: vincent.guittot@linaro.org Cc: viro@zeniv.linux.org.uk Link: https://lkml.kernel.org/r/1568909380-32199-1-git-send-email-cai@lca.pw Signed-off-by: Ingo Molnar

Merge branch 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2019-07-08T23:12:03+00:00

Pull locking updates from Ingo Molnar: "The main changes in this cycle are: - rwsem scalability improvements, phase #2, by Waiman Long, which are rather impressive: "On a 2-socket 40-core 80-thread Skylake system with 40 reader and writer locking threads, the min/mean/max locking operations done in a 5-second testing window before the patchset were: 40 readers, Iterations Min/Mean/Max = 1,807/1,808/1,810 40 writers, Iterations Min/Mean/Max = 1,807/50,344/151,255 After the patchset, they became: 40 readers, Iterations Min/Mean/Max = 30,057/31,359/32,741 40 writers, Iterations Min/Mean/Max = 94,466/95,845/97,098" There's a lot of changes to the locking implementation that makes it similar to qrwlock, including owner handoff for more fair locking. Another microbenchmark shows how across the spectrum the improvements are: "With a locking microbenchmark running on 5.1 based kernel, the total locking rates (in kops/s) on a 2-socket Skylake system with equal numbers of readers and writers (mixed) before and after this patchset were: # of Threads Before Patch After Patch ------------ ------------ ----------- 2 2,618 4,193 4 1,202 3,726 8 802 3,622 16 729 3,359 32 319 2,826 64 102 2,744" The changes are extensive and the patch-set has been through several iterations addressing various locking workloads. There might be more regressions, but unless they are pathological I believe we want to use this new implementation as the baseline going forward. - jump-label optimizations by Daniel Bristot de Oliveira: the primary motivation was to remove IPI disturbance of isolated RT-workload CPUs, which resulted in the implementation of batched jump-label updates. Beyond the improvement of the real-time characteristics kernel, in one test this patchset improved static key update overhead from 57 msecs to just 1.4 msecs - which is a nice speedup as well. - atomic64_t cross-arch type cleanups by Mark Rutland: over the last ~10 years of atomic64_t existence the various types used by the APIs only had to be self-consistent within each architecture - which means they became wildly inconsistent across architectures. Mark puts and end to this by reworking all the atomic64 implementations to use 's64' as the base type for atomic64_t, and to ensure that this type is consistently used for parameters and return values in the API, avoiding further problems in this area. - A large set of small improvements to lockdep by Yuyang Du: type cleanups, output cleanups, function return type and othr cleanups all around the place. - A set of percpu ops cleanups and fixes by Peter Zijlstra. - Misc other changes - please see the Git log for more details" * 'locking-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (82 commits) locking/lockdep: increase size of counters for lockdep statistics locking/atomics: Use sed(1) instead of non-standard head(1) option locking/lockdep: Move mark_lock() inside CONFIG_TRACE_IRQFLAGS && CONFIG_PROVE_LOCKING x86/jump_label: Make tp_vec_nr static x86/percpu: Optimize raw_cpu_xchg() x86/percpu, sched/fair: Avoid local_clock() x86/percpu, x86/irq: Relax {set,get}_irq_regs() x86/percpu: Relax smp_processor_id() x86/percpu: Differentiate this_cpu_{}() and __this_cpu_{}() locking/rwsem: Guard against making count negative locking/rwsem: Adaptive disabling of reader optimistic spinning locking/rwsem: Enable time-based spinning on reader-owned rwsem locking/rwsem: Make rwsem->owner an atomic_long_t locking/rwsem: Enable readers spinning on writer locking/rwsem: Clarify usage of owner's nonspinaable bit locking/rwsem: Wake up almost all readers in wait queue locking/rwsem: More optimal RT task handling of null owner locking/rwsem: Always release wait_lock before waking up tasks locking/rwsem: Implement lock handoff to prevent lock starvation locking/rwsem: Make rwsem_spin_on_owner() return owner state ...