Merge tag 'rcu.release.v6.14' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux

Pull RCU updates from Uladzislau Rezki:
 "Misc fixes:
   - check if IRQs are disabled in rcu_exp_need_qs()
   - instrument KCSAN exclusive-writer assertions
   - add extra WARN_ON_ONCE() check
   - set the cpu_no_qs.b.exp under lock
   - warn if callback enqueued on offline CPU

  Torture-test updates:
   - add rcutorture.preempt_duration kernel module parameter
   - make the TREE03 scenario do preemption
   - improve pooling timeouts for rcu_torture_writer()
   - improve output of "Failure/close-call rcutorture reader segments"
   - add some reader-state debugging checks
   - update doc of polled APIs
   - add extra diagnostics for per-reader-segment preemption
   - add an extra test for sched_clock()
   - improve testing on unresponsive systems

  SRCU updates:
   - improve doc for srcu_read_lock() in terms of return value
   - fix typo in comments
   - remove redundant GP sequence checks in the srcu_funnel_gp_start"

* tag 'rcu.release.v6.14' of git://git.kernel.org/pub/scm/linux/kernel/git/rcu/linux: (31 commits)
  srcu: Remove redundant GP sequence checks in srcu_funnel_gp_start
  srcu: Fix typo s/srcu_check_read_flavor()/__srcu_check_read_flavor()/
  srcu: Guarantee non-negative return value from srcu_read_lock()
  MAINTAINERS: Update RCU git tree
  rcu: Add lockdep_assert_irqs_disabled() to rcu_exp_need_qs()
  rcu: Add KCSAN exclusive-writer assertions for rdp->cpu_no_qs.b.exp
  rcu: Make preemptible rcu_exp_handler() check idempotency
  rcu: Replace open-coded rcu_exp_need_qs() from rcu_exp_handler() with call
  rcu: Move rcu_report_exp_rdp() setting of ->cpu_no_qs.b.exp under lock
  rcu: Make rcu_report_exp_cpu_mult() caller acquire lock
  rcu: Report callbacks enqueued on offline CPU blind spot
  rcutorture: Use symbols for SRCU reader flavors
  rcutorture: Add per-reader-segment preemption diagnostics
  rcutorture: Read CPU ID for decoration protected by both reader types
  rcutorture: Add preempt_count() to rcutorture_one_extend_check() diagnostics
  rcutorture: Add parameters to control polled/conditional wait interval
  rcutorture: Add documentation for recent conditional and polled APIs
  rcutorture: Ignore attempts to test preemption and forward progress
  rcutorture: Make rcutorture_one_extend() check reader state
  rcutorture: Pretty-print rcutorture reader segments
  ...

4 files changed, 28 insertions, 14 deletions

diff --git a/include/linux/rcupdate_wait.h b/include/linux/rcupdate_wait.h
index 303ab9bee155..f9bed3d3f78d 100644
--- a/include/linux/rcupdate_wait.h
+++ b/include/linux/rcupdate_wait.h
@@ -65,4 +65,15 @@ static inline void cond_resched_rcu(void)
 #endif
 }
 
+// Has the current task blocked within its current RCU read-side
+// critical section?
+static inline bool has_rcu_reader_blocked(void)
+{
+#ifdef CONFIG_PREEMPT_RCU
+	return !list_empty(&current->rcu_node_entry);
+#else
+	return false;
+#endif
+}
+
 #endif /* _LINUX_SCHED_RCUPDATE_WAIT_H */
diff --git a/include/linux/srcu.h b/include/linux/srcu.h
index 08339eb8a01c..d7ba46e74f58 100644
--- a/include/linux/srcu.h
+++ b/include/linux/srcu.h
@@ -43,6 +43,12 @@ int init_srcu_struct(struct srcu_struct *ssp);
 #define __SRCU_DEP_MAP_INIT(srcu_name)
 #endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
 
+/* Values for SRCU Tree srcu_data ->srcu_reader_flavor, but also used by rcutorture. */
+#define SRCU_READ_FLAVOR_NORMAL	0x1		// srcu_read_lock().
+#define SRCU_READ_FLAVOR_NMI	0x2		// srcu_read_lock_nmisafe().
+#define SRCU_READ_FLAVOR_LITE	0x4		// srcu_read_lock_lite().
+#define SRCU_READ_FLAVOR_ALL	0x7		// All of the above.
+
 #ifdef CONFIG_TINY_SRCU
 #include <linux/srcutiny.h>
 #elif defined(CONFIG_TREE_SRCU)
@@ -232,13 +238,14 @@ static inline int srcu_read_lock_held(const struct srcu_struct *ssp)
  * a mutex that is held elsewhere while calling synchronize_srcu() or
  * synchronize_srcu_expedited().
  *
- * The return value from srcu_read_lock() must be passed unaltered
- * to the matching srcu_read_unlock().  Note that srcu_read_lock() and
- * the matching srcu_read_unlock() must occur in the same context, for
- * example, it is illegal to invoke srcu_read_unlock() in an irq handler
- * if the matching srcu_read_lock() was invoked in process context.  Or,
- * for that matter to invoke srcu_read_unlock() from one task and the
- * matching srcu_read_lock() from another.
+ * The return value from srcu_read_lock() is guaranteed to be
+ * non-negative.  This value must be passed unaltered to the matching
+ * srcu_read_unlock().  Note that srcu_read_lock() and the matching
+ * srcu_read_unlock() must occur in the same context, for example, it is
+ * illegal to invoke srcu_read_unlock() in an irq handler if the matching
+ * srcu_read_lock() was invoked in process context.  Or, for that matter to
+ * invoke srcu_read_unlock() from one task and the matching srcu_read_lock()
+ * from another.
  */
 static inline int srcu_read_lock(struct srcu_struct *ssp) __acquires(ssp)
 {
diff --git a/include/linux/srcutree.h b/include/linux/srcutree.h
index 490aeecc6bb4..b17814c9d1c7 100644
--- a/include/linux/srcutree.h
+++ b/include/linux/srcutree.h
@@ -26,6 +26,7 @@ struct srcu_data {
 	atomic_long_t srcu_lock_count[2];	/* Locks per CPU. */
 	atomic_long_t srcu_unlock_count[2];	/* Unlocks per CPU. */
 	int srcu_reader_flavor;			/* Reader flavor for srcu_struct structure? */
+						/* Values: SRCU_READ_FLAVOR_.*  */
 
 	/* Update-side state. */
 	spinlock_t __private lock ____cacheline_internodealigned_in_smp;
@@ -43,11 +44,6 @@ struct srcu_data {
 	struct srcu_struct *ssp;
 };
 
-/* Values for ->srcu_reader_flavor. */
-#define SRCU_READ_FLAVOR_NORMAL	0x1		// srcu_read_lock().
-#define SRCU_READ_FLAVOR_NMI	0x2		// srcu_read_lock_nmisafe().
-#define SRCU_READ_FLAVOR_LITE	0x4		// srcu_read_lock_lite().
-
 /*
  * Node in SRCU combining tree, similar in function to rcu_data.
  */
@@ -258,7 +254,7 @@ static inline void srcu_check_read_flavor_lite(struct srcu_struct *ssp)
 	if (likely(READ_ONCE(sdp->srcu_reader_flavor) & SRCU_READ_FLAVOR_LITE))
 		return;
 
-	// Note that the cmpxchg() in srcu_check_read_flavor() is fully ordered.
+	// Note that the cmpxchg() in __srcu_check_read_flavor() is fully ordered.
 	__srcu_check_read_flavor(ssp, SRCU_READ_FLAVOR_LITE);
 }
 
diff --git a/include/linux/torture.h b/include/linux/torture.h
index c2e979f82f8d..0134e7221cae 100644
--- a/include/linux/torture.h
+++ b/include/linux/torture.h
@@ -130,7 +130,7 @@ void _torture_stop_kthread(char *m, struct task_struct **tp);
 #endif
 
 #if IS_ENABLED(CONFIG_RCU_TORTURE_TEST) || IS_MODULE(CONFIG_RCU_TORTURE_TEST) || IS_ENABLED(CONFIG_LOCK_TORTURE_TEST) || IS_MODULE(CONFIG_LOCK_TORTURE_TEST)
-long torture_sched_setaffinity(pid_t pid, const struct cpumask *in_mask);
+long torture_sched_setaffinity(pid_t pid, const struct cpumask *in_mask, bool dowarn);
 #endif
 
 #endif /* __LINUX_TORTURE_H */