Merge tag 'rcu.2026.03.31a' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux

Pull RCU updates from Joel Fernandes:
 "NOCB CPU management:

   - Consolidate rcu_nocb_cpu_offload() and rcu_nocb_cpu_deoffload() to
     reduce code duplication

   - Extract nocb_bypass_needs_flush() helper to reduce duplication in
     NOCB bypass path

  rcutorture/torture infrastructure:

   - Add NOCB01 config for RCU_LAZY torture testing

   - Add NOCB02 config for NOCB poll mode testing

   - Add TRIVIAL-PREEMPT config for textbook-style preemptible RCU
     torture

   - Test call_srcu() with preemption both disabled and enabled

   - Remove kvm-check-branches.sh in favor of kvm-series.sh

   - Make hangs more visible in torture.sh output

   - Add informative message for tests without a recheck file

   - Fix numeric test comparison in srcu_lockdep.sh

   - Use torture_shutdown_init() in refscale and rcuscale instead of
     open-coded shutdown functions

   - Fix modulo-zero error in torture_hrtimeout_ns().

  SRCU:

   - Fix SRCU read flavor macro comments

   - Fix s/they disables/they disable/ typo in srcu_read_unlock_fast()

  RCU Tasks:

   - Document that RCU Tasks Trace grace periods now imply RCU grace
     periods

   - Remove unnecessary smp_store_release() in cblist_init_generic()"

* tag 'rcu.2026.03.31a' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux:
  rcutorture: Test call_srcu() with preemption disabled and not
  rcu: Add BOOTPARAM_RCU_STALL_PANIC Kconfig option
  torture: Avoid modulo-zero error in torture_hrtimeout_ns()
  rcu/nocb: Extract nocb_bypass_needs_flush() to reduce duplication
  rcu/nocb: Consolidate rcu_nocb_cpu_offload/deoffload functions
  rcu-tasks: Remove unnecessary smp_store_release() in cblist_init_generic()
  rcutorture: Add NOCB02 config for nocb poll mode testing
  rcutorture: Add NOCB01 config for RCU_LAZY torture testing
  rcu-tasks: Document that RCU Tasks Trace grace periods now imply RCU grace periods
  srcu: Fix s/they disables/they disable/ typo in srcu_read_unlock_fast()
  srcu: Fix SRCU read flavor macro comments
  rcuscale: Ditch rcu_scale_shutdown in favor of torture_shutdown_init()
  refscale: Ditch ref_scale_shutdown in favor of torture_shutdown_init()
  rcutorture: Fix numeric "test" comparison in srcu_lockdep.sh
  torture: Print informative message for test without recheck file
  torture: Make hangs more visible in torture.sh output
  kvm-check-branches.sh: Remove in favor of kvm-series.sh
  rcutorture: Add a textbook-style trivial preemptible RCU

4 files changed, 10 insertions, 9 deletions

diff --git a/include/linux/rcupdate.h b/include/linux/rcupdate.h
index 04f3f86a41450..18a85c30fd4f3 100644
--- a/include/linux/rcupdate.h
+++ b/include/linux/rcupdate.h
@@ -208,12 +208,9 @@ static inline void exit_tasks_rcu_finish(void) { }
 /**
  * rcu_trace_implies_rcu_gp - does an RCU Tasks Trace grace period imply an RCU grace period?
  *
- * As an accident of implementation, an RCU Tasks Trace grace period also
- * acts as an RCU grace period.  However, this could change at any time.
- * Code relying on this accident must call this function to verify that
- * this accident is still happening.
- *
- * You have been warned!
+ * Now that RCU Tasks Trace is implemented in terms of SRCU-fast, a
+ * call to synchronize_rcu_tasks_trace() is guaranteed to imply at least
+ * one call to synchronize_rcu().
  */
 static inline bool rcu_trace_implies_rcu_gp(void) { return true; }
 
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 5a5d3dbc9cdf3..ffb2ad9716f05 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -949,6 +949,10 @@ struct task_struct {
 	struct srcu_ctr __percpu	*trc_reader_scp;
 #endif /* #ifdef CONFIG_TASKS_TRACE_RCU */
 
+#ifdef CONFIG_TRIVIAL_PREEMPT_RCU
+	int				rcu_trivial_preempt_nesting;
+#endif /* #ifdef CONFIG_TRIVIAL_PREEMPT_RCU */
+
 	struct sched_info		sched_info;
 
 	struct list_head		tasks;
diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index bb44a0bd76968..81b1938512d5d 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -69,8 +69,8 @@ int init_srcu_struct_fast_updown(struct srcu_struct *ssp);
 #define SRCU_READ_FLAVOR_NORMAL		0x1		// srcu_read_lock().
 #define SRCU_READ_FLAVOR_NMI		0x2		// srcu_read_lock_nmisafe().
 //					0x4		// SRCU-lite is no longer with us.
-#define SRCU_READ_FLAVOR_FAST		0x4		// srcu_read_lock_fast().
-#define SRCU_READ_FLAVOR_FAST_UPDOWN	0x8		// srcu_read_lock_fast().
+#define SRCU_READ_FLAVOR_FAST		0x4		// srcu_read_lock_fast(), also NMI-safe.
+#define SRCU_READ_FLAVOR_FAST_UPDOWN	0x8		// srcu_read_lock_fast_updown().
 #define SRCU_READ_FLAVOR_ALL		(SRCU_READ_FLAVOR_NORMAL | SRCU_READ_FLAVOR_NMI | \
 					 SRCU_READ_FLAVOR_FAST | SRCU_READ_FLAVOR_FAST_UPDOWN)
 						// All of the above.
diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
index be76fa4fc1700..fd1a9270cb9a8 100644
--- a/include/linux/srcutree.h
+++ b/include/linux/srcutree.h
@@ -260,7 +260,7 @@ static inline struct srcu_ctr __percpu *__srcu_ctr_to_ptr(struct srcu_struct *ss
  * srcu_read_unlock_fast().
  *
  * Note that both this_cpu_inc() and atomic_long_inc() are RCU read-side
- * critical sections either because they disables interrupts, because
+ * critical sections either because they disable interrupts, because
  * they are a single instruction, or because they are read-modify-write
  * atomic operations, depending on the whims of the architecture.
  * This matters because the SRCU-fast grace-period mechanism uses either