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, 148 insertions, 0 deletions

diff --git a/rust/proc-macro2/rcvec.rs b/rust/proc-macro2/rcvec.rs
new file mode 100644
index 000000000..e224ebe27
--- /dev/null
+++ b/rust/proc-macro2/rcvec.rs
@@ -0,0 +1,148 @@
+// SPDX-License-Identifier: Apache-2.0 OR MIT
+
+use alloc::rc::Rc;
+use alloc::vec;
+use core::mem;
+use core::panic::RefUnwindSafe;
+use core::slice;
+
+pub(crate) struct RcVec<T> {
+    inner: Rc<Vec<T>>,
+}
+
+pub(crate) struct RcVecBuilder<T> {
+    inner: Vec<T>,
+}
+
+pub(crate) struct RcVecMut<'a, T> {
+    inner: &'a mut Vec<T>,
+}
+
+#[derive(Clone)]
+pub(crate) struct RcVecIntoIter<T> {
+    inner: vec::IntoIter<T>,
+}
+
+impl<T> RcVec<T> {
+    pub(crate) fn is_empty(&self) -> bool {
+        self.inner.is_empty()
+    }
+
+    pub(crate) fn len(&self) -> usize {
+        self.inner.len()
+    }
+
+    pub(crate) fn iter(&self) -> slice::Iter<T> {
+        self.inner.iter()
+    }
+
+    pub(crate) fn make_mut(&mut self) -> RcVecMut<T>
+    where
+        T: Clone,
+    {
+        RcVecMut {
+            inner: Rc::make_mut(&mut self.inner),
+        }
+    }
+
+    pub(crate) fn get_mut(&mut self) -> Option<RcVecMut<T>> {
+        let inner = Rc::get_mut(&mut self.inner)?;
+        Some(RcVecMut { inner })
+    }
+
+    pub(crate) fn make_owned(mut self) -> RcVecBuilder<T>
+    where
+        T: Clone,
+    {
+        let vec = if let Some(owned) = Rc::get_mut(&mut self.inner) {
+            mem::take(owned)
+        } else {
+            Vec::clone(&self.inner)
+        };
+        RcVecBuilder { inner: vec }
+    }
+}
+
+impl<T> RcVecBuilder<T> {
+    pub(crate) fn new() -> Self {
+        RcVecBuilder { inner: Vec::new() }
+    }
+
+    pub(crate) fn with_capacity(cap: usize) -> Self {
+        RcVecBuilder {
+            inner: Vec::with_capacity(cap),
+        }
+    }
+
+    pub(crate) fn push(&mut self, element: T) {
+        self.inner.push(element);
+    }
+
+    pub(crate) fn extend(&mut self, iter: impl IntoIterator<Item = T>) {
+        self.inner.extend(iter);
+    }
+
+    pub(crate) fn as_mut(&mut self) -> RcVecMut<T> {
+        RcVecMut {
+            inner: &mut self.inner,
+        }
+    }
+
+    pub(crate) fn build(self) -> RcVec<T> {
+        RcVec {
+            inner: Rc::new(self.inner),
+        }
+    }
+}
+
+impl<'a, T> RcVecMut<'a, T> {
+    pub(crate) fn push(&mut self, element: T) {
+        self.inner.push(element);
+    }
+
+    pub(crate) fn extend(&mut self, iter: impl IntoIterator<Item = T>) {
+        self.inner.extend(iter);
+    }
+
+    pub(crate) fn as_mut(&mut self) -> RcVecMut<T> {
+        RcVecMut { inner: self.inner }
+    }
+
+    pub(crate) fn take(self) -> RcVecBuilder<T> {
+        let vec = mem::take(self.inner);
+        RcVecBuilder { inner: vec }
+    }
+}
+
+impl<T> Clone for RcVec<T> {
+    fn clone(&self) -> Self {
+        RcVec {
+            inner: Rc::clone(&self.inner),
+        }
+    }
+}
+
+impl<T> IntoIterator for RcVecBuilder<T> {
+    type Item = T;
+    type IntoIter = RcVecIntoIter<T>;
+
+    fn into_iter(self) -> Self::IntoIter {
+        RcVecIntoIter {
+            inner: self.inner.into_iter(),
+        }
+    }
+}
+
+impl<T> Iterator for RcVecIntoIter<T> {
+    type Item = T;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        self.inner.next()
+    }
+
+    fn size_hint(&self) -> (usize, Option<usize>) {
+        self.inner.size_hint()
+    }
+}
+
+impl<T> RefUnwindSafe for RcVec<T> where T: RefUnwindSafe {}