kernel/linux.git/Documentation/RCU, branch v6.18.21

Merge tag 'rcu.2025.09.26a' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux

2025-10-04T18:28:45+00:00

Pull RCU updates from Paul McKenney: "Documentation updates: - Update whatisRCU.rst and checklist.rst for recent RCU API additions - Fix RCU documentation formatting and typos - Replace dead Ottawa Linux Symposium links in RTFP.txt Miscellaneous RCU updates: - Document that rcu_barrier() hurries RCU_LAZY callbacks - Remove redundant interrupt disabling from rcu_preempt_deferred_qs_handler() - Move list_for_each_rcu from list.h to rculist.h, and adjust the include directive in kernel/cgroup/dmem.c accordingly - Make initial set of changes to accommodate upcoming system_percpu_wq changes SRCU updates: - Create an srcu_read_lock_fast_notrace() for eventual use in tracing, including adding guards - Document the reliance on per-CPU operations as implicit RCU readers in __srcu_read_{,un}lock_fast() - Document the srcu_flip() function's memory-barrier D's relationship to SRCU-fast readers - Remove a redundant preempt_disable() and preempt_enable() pair from srcu_gp_start_if_needed() Torture-test updates: - Fix jitter.sh spin time so that it actually varies as advertised. It is still quite coarse-grained, but at least it does now vary - Update torture.sh help text to include the not-so-new --do-normal parameter, which permits (for example) testing KCSAN kernels without doing non-debug kernels - Fix a number of false-positive diagnostics that were being triggered by rcutorture starting before boot completed. Running multiple near-CPU-bound rcutorture processes when there is only the boot CPU is after all a bit excessive - Substitute kcalloc() for kzalloc() - Remove a redundant kfree() and NULL out kfree()ed objects" * tag 'rcu.2025.09.26a' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux: (31 commits) rcu: WQ_UNBOUND added to sync_wq workqueue rcu: WQ_PERCPU added to alloc_workqueue users rcu: replace use of system_wq with system_percpu_wq refperf: Set reader_tasks to NULL after kfree() refperf: Remove redundant kfree() after torture_stop_kthread() srcu/tiny: Remove preempt_disable/enable() in srcu_gp_start_if_needed() srcu: Document srcu_flip() memory-barrier D relation to SRCU-fast srcu: Document __srcu_read_{,un}lock_fast() implicit RCU readers rculist: move list_for_each_rcu() to where it belongs refscale: Use kcalloc() instead of kzalloc() rcutorture: Use kcalloc() instead of kzalloc() docs: rcu: Replace multiple dead OLS links in RTFP.txt doc: Fix typo in RCU's torture.rst documentation Documentation: RCU: Retitle toctree index Documentation: RCU: Reduce toctree depth Documentation: RCU: Wrap kvm-remote.sh rerun snippet in literal code block rcu: docs: Requirements.rst: Abide by conventions of kernel documentation doc: Add RCU guards to checklist.rst doc: Update whatisRCU.rst for recent RCU API additions rcutorture: Delay forward-progress testing until boot completes ...

docs: rcu: Replace multiple dead OLS links in RTFP.txt

2025-08-22T13:25:47+00:00

This patch updates several dead OLS links in RTFP.txt, replacing them with working copies hosted on kernel.org. Originally posted as part of a 2-patch series, this is now being sent as a standalone v4 patch to avoid confusion. Signed-off-by: Nikil Paul S Signed-off-by: Paul E. McKenney

doc: Fix typo in RCU's torture.rst documentation

2025-08-22T13:25:47+00:00

s/you// Reported-by: Randy Dunlap Signed-off-by: Paul E. McKenney

Documentation: RCU: Retitle toctree index

2025-08-22T13:25:47+00:00

toctree index title ("RCU concepts") is rather a misnomer: RCU concepts is already described in rcu.rst, whereas the toctree suggests that the docs themes about handbook on RCU subsystem instead. Edit the title to reflect the fact. Signed-off-by: Bagas Sanjaya Signed-off-by: Paul E. McKenney

Documentation: RCU: Reduce toctree depth

2025-08-22T13:25:47+00:00

toctree index for RCU currently has maximum depth of 3. Since no docs currently use more than 3 section heading levels, this effectively spills the entire docs hierarchy. Tidy up by reducing toctree depth to 2 (only showing docs title and second-level sections). Signed-off-by: Bagas Sanjaya Signed-off-by: Paul E. McKenney

Documentation: RCU: Wrap kvm-remote.sh rerun snippet in literal code block

2025-08-22T13:25:47+00:00

Unlike other kvm*.sh snippets in RCU torture test documentation, kvm-remote.sh rerun snippet isn't formatted as literal code block, causing it to be definition list instead in htmldocs output. Wrap it like the rest. Fixes: 0c208a793022 ("doc: Update torture.rst") Signed-off-by: Bagas Sanjaya Signed-off-by: Paul E. McKenney Reviewed-by: Randy Dunlap

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

2025-08-20T18:51:28+00:00

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

doc: Add RCU guards to checklist.rst

2025-08-20T18:51:28+00:00

Also note that RCU guards can be easier to use. Signed-off-by: Paul E. McKenney

doc: Update whatisRCU.rst for recent RCU API additions

2025-08-20T18:51:02+00:00

Bring this file kicking and screaming into the year 2025! [ paulmck: Apply feedback from Bagas Sanjaya. ] Signed-off-by: Paul E. McKenney

Documentation: Fix RCU typos

2025-08-18T16:31:19+00:00

Fix typos. Signed-off-by: Bjorn Helgaas Reviewed-by: Randy Dunlap Signed-off-by: Jonathan Corbet Link: https://lore.kernel.org/r/20250813200526.290420-3-helgaas@kernel.org