Merge tag 'rcu.2026.08.18a' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux

Pull RCU updates from Paul McKenney:
 "Make expedited grace periods expedite normal RCU callbacks

  Miscellaneous fixes:
   - Improve diagnostic output with character task states
   - Mark accesses to inform KCSAN of concurrency design
   - Move from kmalloc() to kmalloc_obj()
   - Documentation updates
   - Improve handling of RCU deferred quiescent states
   - Clean up unused function arguments and structure fields
   - Reduce show_rcu_gp_kthreads() stack space

  Tasks RCU updates:
   - Clean up after SRCU re-implementation of Tasks Trace RCU
   - Mark accesses to inform KCSAN of concurrency design
   - Add ->lazy_timer status to diagnostic output
   - Remove an unnecessary memory barrier
   - Fix a data race, courtesy of KCSAN
   - Documentation updates
   - Convert cond_resched_tasks_rcu_qs() from macro to static inline
     function

  SRCU updates:
   - Add Rust helpers for SRCU
   - Avoid losing queued work at cleanup_srcu_struct() time

  Torture-test updates:
   - Preparation work for immediate RCU priority deboosting
   - Test RCU readers from real interrupt handlers (as opposed to
     softirq)
   - Simplify code through use of cpumask_next_wrap()
   - Improve diagnostic output with character task states
   - Add rcutorture.nwriters parameter to allow lightweight stall
     testing, and rcutorture.stall_only to make doing so easier
   - Test an RCU Tasks Trace grace period implying an RCU grace period
   - Make RCU Tasks Trace torturing track reader batches
   - Fix a data race, courtesy of KCSAN
   - Plug a shuffle_tmp_mask memory leak on kthread spawn failure"

* tag 'rcu.2026.08.18a' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux: (59 commits)
  rcu: Add closing parenthesis in comment in rcu_read_unlock_strict()
  rcutorture: Make {,s}rcu_read_delay() better handle forward-progress testing
  rcutorture: Announce declining to forward-progress test
  torture: Don't leak shuffle_tmp_mask when shuffler kthread fails to start
  rcutorture: Use this_cpu_inc() for rcu_torture_count[] and rcu_torture_batch[]
  rcutorture: Make RCU Tasks Trace track Reader Batches
  rcutorture: Test RCU Tasks Trace GP implying RCU GP
  rcutorture: Add a stall_only module parameter
  rcutorture: Add nwriters module parameter
  rcutorture: Use task_state_to_char() for task-state reporting
  rcutorture: Use cpumask_next_wrap() in rcu_torture_preempt()
  rcutorture: Test RCU readers from hardware interrupt handlers
  rcutorture: Check for immediate deboosting at reader end
  srcu: Queue sdp->work when the delay timer is successfully deleted
  rcu-tasks: Convert cond_resched_tasks_rcu_qs() to static inline
  rcu-tasks: Fix some comments for call_rcu_tasks() and call_rcu_tasks_rude()
  rcu-tasks: Rename tasks_rcu_exit_srcu_stall_timer to tasks_rcu_exit_stall_timer
  rcu: Mark interrupts-enabled accesses to rdp->cpu_no_qs.s
  rcu: Reduce stack usage in show_rcu_gp_kthreads()
  rcu: Mark accesses to ->rcu_urgent_qs and ->rcu_need_heavy_qs
  ...

1 files changed, 14 insertions, 0 deletions

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 4a12805a5..66c1c879a 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -6157,6 +6157,11 @@ Kernel parameters
 			the number of CPUs.  For example, -2 selects N
 			(the number of CPUs), -3 selects N+1, and so on.
 
+	rcutorture.nwriters= [KNL]
+			Set number of RCU writers, which must be either
+			zero or one.  For additional writers, use instead
+			the rcutorture.nfakewriters parameter.
+
 	rcutorture.object_debug= [KNL]
 			Enable debug-object double-call_rcu() testing.
 
@@ -6246,6 +6251,15 @@ Kernel parameters
 			and stall_gp_kthread are specified, the
 			kthread is starved first, then the CPU.
 
+	rcutorture.stall_only= [KNL]
+			Shut off all rcutorture kthreads other than the
+			RCU CPU stall-warning test kthreads.  The purpose
+			of this is to test production applictions'
+			reactions to CPU stalls, and with minimal
+			additional overhead.  Or you can omit the
+			stall-warning tests as well and get a heavy
+			no-op, your choice!
+
 	rcutorture.stat_interval= [KNL]
 			Time (s) between statistics printk()s.