Merge branches 'expcb.2026.07.24a', 'misc.2026.07.30a', 'rcu-tasks.2026.07.30a', 'srcu.2026.08.11a' and 'torture.2026.08.14a' into HEADgrafted

Changes:

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.

1 files changed, 98 insertions, 0 deletions

diff --git a/lib/timerqueue.c b/lib/timerqueue.c
new file mode 100644
index 000000000..e2a1e08cb
--- /dev/null
+++ b/lib/timerqueue.c
@@ -0,0 +1,98 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  Generic Timer-queue
+ *
+ *  Manages a simple queue of timers, ordered by expiration time.
+ *  Uses rbtrees for quick list adds and expiration.
+ *
+ *  NOTE: All of the following functions need to be serialized
+ *  to avoid races. No locking is done by this library code.
+ */
+
+#include <linux/bug.h>
+#include <linux/timerqueue.h>
+#include <linux/rbtree.h>
+#include <linux/export.h>
+
+#define __node_2_tq(_n) \
+	rb_entry((_n), struct timerqueue_node, node)
+
+static inline bool __timerqueue_less(struct rb_node *a, const struct rb_node *b)
+{
+	return __node_2_tq(a)->expires < __node_2_tq(b)->expires;
+}
+
+/**
+ * timerqueue_add - Adds timer to timerqueue.
+ *
+ * @head: head of timerqueue
+ * @node: timer node to be added
+ *
+ * Adds the timer node to the timerqueue, sorted by the node's expires
+ * value. Returns true if the newly added timer is the first expiring timer in
+ * the queue.
+ */
+bool timerqueue_add(struct timerqueue_head *head, struct timerqueue_node *node)
+{
+	/* Make sure we don't add nodes that are already added */
+	WARN_ON_ONCE(!RB_EMPTY_NODE(&node->node));
+
+	return rb_add_cached(&node->node, &head->rb_root, __timerqueue_less);
+}
+EXPORT_SYMBOL_GPL(timerqueue_add);
+
+/**
+ * timerqueue_del - Removes a timer from the timerqueue.
+ *
+ * @head: head of timerqueue
+ * @node: timer node to be removed
+ *
+ * Removes the timer node from the timerqueue. Returns true if the queue is
+ * not empty after the remove.
+ */
+bool timerqueue_del(struct timerqueue_head *head, struct timerqueue_node *node)
+{
+	WARN_ON_ONCE(RB_EMPTY_NODE(&node->node));
+
+	rb_erase_cached(&node->node, &head->rb_root);
+	RB_CLEAR_NODE(&node->node);
+
+	return !RB_EMPTY_ROOT(&head->rb_root.rb_root);
+}
+EXPORT_SYMBOL_GPL(timerqueue_del);
+
+/**
+ * timerqueue_iterate_next - Returns the timer after the provided timer
+ *
+ * @node: Pointer to a timer.
+ *
+ * Provides the timer that is after the given node. This is used, when
+ * necessary, to iterate through the list of timers in a timer list
+ * without modifying the list.
+ */
+struct timerqueue_node *timerqueue_iterate_next(struct timerqueue_node *node)
+{
+	struct rb_node *next;
+
+	if (!node)
+		return NULL;
+	next = rb_next(&node->node);
+	if (!next)
+		return NULL;
+	return container_of(next, struct timerqueue_node, node);
+}
+EXPORT_SYMBOL_GPL(timerqueue_iterate_next);
+
+#define __node_2_tq_linked(_n) \
+	container_of(rb_entry((_n), struct rb_node_linked, node), struct timerqueue_linked_node, node)
+
+static __always_inline bool __tq_linked_less(struct rb_node *a, const struct rb_node *b)
+{
+	return __node_2_tq_linked(a)->expires < __node_2_tq_linked(b)->expires;
+}
+
+bool timerqueue_linked_add(struct timerqueue_linked_head *head, struct timerqueue_linked_node *node)
+{
+	return rb_add_linked(&node->node, &head->rb_root, __tq_linked_less);
+}
+EXPORT_SYMBOL_GPL(timerqueue_linked_add);