linux/Documentation/RCU/Design/Requirements, branch master

rcu-tasks: Document that RCU Tasks Trace grace periods now imply RCU grace periods

2026-03-30T19:48:14Z

Now that RCU Tasks Trace is implemented in terms of SRCU-fast, the fact that each SRCU-fast grace period implies at least two RCU grace periods in turn means that each RCU Tasks Trace grace period implies at least two grace periods. This commit therefore updates the documentation accordingly. Reviewed-by: Frederic Weisbecker Reported-by: Alexei Starovoitov Signed-off-by: Paul E. McKenney Signed-off-by: Joel Fernandes

rcu: Update Requirements.rst for RCU Tasks Trace

2026-01-01T08:39:46Z

This commit updates the documentation to declare that RCU Tasks Trace is implemented as a thin wrapper around SRCU-fast. Signed-off-by: Paul E. McKenney Cc: Andrii Nakryiko Cc: Alexei Starovoitov Cc: Peter Zijlstra Cc: bpf@vger.kernel.org Reviewed-by: Joel Fernandes Signed-off-by: Boqun Feng

doc: Update for SRCU-fast definitions and initialization

2025-11-05T22:58:30Z

This commit documents the DEFINE_SRCU_FAST(), DEFINE_STATIC_SRCU_FAST(), and init_srcu_struct_fast() API members. Signed-off-by: Paul E. McKenney Cc: Mathieu Desnoyers Cc: Steven Rostedt Cc: Sebastian Andrzej Siewior Cc: Signed-off-by: Frederic Weisbecker

rcu: docs: Requirements.rst: Abide by conventions of kernel documentation

2025-08-20T18:51:28Z

Here is a list of conventions applied here: - Don't mark up function names, to be taken care of by the automarkup extension. Just say func(). - Instead of ".. code-block:: none", just say "::". - Mark inline literals by a pair of ``xxxx``. Don't use rust doc's dialect of `yyyy`. - Instead of emphasizing headings by **strong emphasis**, use sub-level title adornments, in this case "^^^^^^^^^^" and make them proper sub-sections under "Hotplug CPU". Signed-off-by: Akira Yokosawa Cc: Joel Fernandes Signed-off-by: Neeraj Upadhyay (AMD) Signed-off-by: Paul E. McKenney

rcu: Document concurrent quiescent state reporting for offline CPUs

2025-07-22T11:40:50Z

The synchronization of CPU offlining with GP initialization is confusing to put it mildly (rightfully so as the issue it deals with is complex). Recent discussions brought up a question -- what prevents the rcu_implicit_dyntick_qs() from warning about QS reports for offline CPUs (missing QS reports for offline CPUs causing indefinite hangs). QS reporting for now-offline CPUs should only happen from: - gp_init() - rcutree_cpu_report_dead() Add some documentation on this and refer to it from comments in the code explaining how QS reporting is not missed when these functions are concurrently running. I referred heavily to this post [1] about the need for the ofl_lock. [1] https://lore.kernel.org/all/20180924164443.GF4222@linux.ibm.com/ [ Applied paulmck feedback on moving documentation to Requirements.rst ] Link: https://lore.kernel.org/all/01b4d228-9416-43f8-a62e-124b92e8741a@paulmck-laptop/ Co-developed-by: "Paul E. McKenney" Signed-off-by: "Paul E. McKenney" Reviewed-by: Frederic Weisbecker Signed-off-by: Joel Fernandes Signed-off-by: Neeraj Upadhyay (AMD)

rcu: Document GP init vs hotplug-scan ordering requirements

2025-07-22T11:39:35Z

Add detailed comments explaining the critical ordering constraints during RCU grace period initialization, based on discussions with Frederic. Reviewed-by: "Paul E. McKenney" Co-developed-by: Frederic Weisbecker Signed-off-by: Frederic Weisbecker Signed-off-by: Joel Fernandes Signed-off-by: Neeraj Upadhyay (AMD)

doc: Remove RCU Tasks Rude asynchronous APIs

2024-08-14T11:15:07Z

The call_rcu_tasks_rude() and rcu_barrier_tasks_rude() APIs are no longer. This commit therefore removes them from the documentation. Signed-off-by: Paul E. McKenney Signed-off-by: Neeraj Upadhyay

doc: Update Tasks RCU and Tasks Rude RCU description in Requirements.rst

2024-06-06T18:32:04Z

This commit adds more detail to the Tasks RCU and Tasks Rude RCU descriptions in Requirements.rst. While in the area, add Tasks Trace RCU to the Tasks-RCU table of contents. Reported-by: Sebastian Andrzej Siewior Signed-off-by: Paul E. McKenney Reviewed-by: Frederic Weisbecker

rcu: Standardize explicit CPU-hotplug calls

2023-10-04T20:29:45Z

rcu_report_dead() and rcutree_migrate_callbacks() have their headers in rcupdate.h while those are pure rcutree calls, like the other CPU-hotplug functions. Also rcu_cpu_starting() and rcu_report_dead() have different naming conventions while they mirror each other's effects. Fix the headers and propose a naming that relates both functions and aligns with the prefix of other rcutree CPU-hotplug functions. Reviewed-by: Paul E. McKenney Signed-off-by: Frederic Weisbecker

rcu: Remove RCU_NONIDLE()

2023-05-11T20:42:04Z

Since there are now exactly _zero_ users of RCU_NONIDLE(), make it go away before someone else decides to (ab)use it. [ paulmck: Remove extraneous whitespace. ] Signed-off-by: Peter Zijlstra (Intel) Acked-by: Mark Rutland Acked-by: Frederic Weisbecker Signed-off-by: Paul E. McKenney