Merge tag 'rcu.2022.01.09a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu
Pull RCU updates from Paul McKenney:
- Documentation updates, perhaps most notably Neil Brown's writeup of
the reference-counting analogy to RCU.
- Expedited grace-period cleanups.
- Remove CONFIG_RCU_FAST_NO_HZ due to lack of valid users. I have asked
around, posted a blog entry, and sent this series to LKML without
result.
- Miscellaneous fixes.
- RCU callback offloading updates, perhaps most notably Frederic
Weisbecker's updates allowing CPUs booted in the de-offloaded state
to be offloaded at runtime.
- nolibc fixes from Willy Tarreau and Anmar Faizi, but also including
Mark Brown's addition of gettid().
- RCU Tasks Trace fixes, including changes that increase the
scalability of call_rcu_tasks_trace() for the BPF folks (Martin Lau
and KP Singh).
- Various fixes including those from Wander Lairson Costa and Li
Zhijian.
- Fixes plus addition of tests for the increased call_rcu_tasks_trace()
scalability.
* tag 'rcu.2022.01.09a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu: (87 commits)
rcu/nocb: Merge rcu_spawn_cpu_nocb_kthread() and rcu_spawn_one_nocb_kthread()
rcu/nocb: Allow empty "rcu_nocbs" kernel parameter
rcu/nocb: Create kthreads on all CPUs if "rcu_nocbs=" or "nohz_full=" are passed
rcu/nocb: Optimize kthreads and rdp initialization
rcu/nocb: Prepare nocb_cb_wait() to start with a non-offloaded rdp
rcu/nocb: Remove rcu_node structure from nocb list when de-offloaded
rcu-tasks: Use fewer callbacks queues if callback flood ends
rcu-tasks: Use separate ->percpu_dequeue_lim for callback dequeueing
rcu-tasks: Use more callback queues if contention encountered
rcu-tasks: Avoid raw-spinlocked wakeups from call_rcu_tasks_generic()
rcu-tasks: Count trylocks to estimate call_rcu_tasks() contention
rcu-tasks: Add rcupdate.rcu_task_enqueue_lim to set initial queueing
rcu-tasks: Make rcu_barrier_tasks*() handle multiple callback queues
rcu-tasks: Use workqueues for multiple rcu_tasks_invoke_cbs() invocations
rcu-tasks: Abstract invocations of callbacks
rcu-tasks: Abstract checking of callback lists
rcu-tasks: Add a ->percpu_enqueue_lim to the rcu_tasks structure
rcu-tasks: Inspect stalled task's trc state in locked state
rcu-tasks: Use spin_lock_rcu_node() and friends
rcutorture: Combine n_max_cbs from all kthreads in a callback flood
...
