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, 156 insertions, 0 deletions

diff --git a/lib/tests/cpumask_kunit.c b/lib/tests/cpumask_kunit.c
new file mode 100644
index 000000000..6b62a6bdd
--- /dev/null
+++ b/lib/tests/cpumask_kunit.c
@@ -0,0 +1,156 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * KUnit tests for cpumask.
+ *
+ * Author: Sander Vanheule <sander@svanheule.net>
+ */
+
+#include <kunit/test.h>
+#include <linux/cpu.h>
+#include <linux/cpumask.h>
+
+#define MASK_MSG(m) \
+	"%s contains %sCPUs %*pbl", #m, (cpumask_weight(m) ? "" : "no "), \
+	nr_cpumask_bits, cpumask_bits(m)
+
+#define EXPECT_FOR_EACH_CPU_EQ(test, mask)			\
+	do {							\
+		const cpumask_t *m = (mask);			\
+		int mask_weight = cpumask_weight(m);		\
+		int cpu, iter = 0;				\
+		for_each_cpu(cpu, m)				\
+			iter++;					\
+		KUNIT_EXPECT_EQ_MSG((test), mask_weight, iter, MASK_MSG(mask));	\
+	} while (0)
+
+#define EXPECT_FOR_EACH_CPU_OP_EQ(test, op, mask1, mask2)			\
+	do {									\
+		const cpumask_t *m1 = (mask1);					\
+		const cpumask_t *m2 = (mask2);					\
+		int weight;                                                     \
+		int cpu, iter = 0;						\
+		cpumask_##op(&mask_tmp, m1, m2);                                \
+		weight = cpumask_weight(&mask_tmp);				\
+		for_each_cpu_##op(cpu, mask1, mask2)				\
+			iter++;							\
+		KUNIT_EXPECT_EQ((test), weight, iter);				\
+	} while (0)
+
+#define EXPECT_FOR_EACH_CPU_WRAP_EQ(test, mask)			\
+	do {							\
+		const cpumask_t *m = (mask);			\
+		int mask_weight = cpumask_weight(m);		\
+		int cpu, iter = 0;				\
+		for_each_cpu_wrap(cpu, m, nr_cpu_ids / 2)	\
+			iter++;					\
+		KUNIT_EXPECT_EQ_MSG((test), mask_weight, iter, MASK_MSG(mask));	\
+	} while (0)
+
+#define EXPECT_FOR_EACH_CPU_BUILTIN_EQ(test, name)		\
+	do {							\
+		int mask_weight = num_##name##_cpus();		\
+		int cpu, iter = 0;				\
+		for_each_##name##_cpu(cpu)			\
+			iter++;					\
+		KUNIT_EXPECT_EQ_MSG((test), mask_weight, iter, MASK_MSG(cpu_##name##_mask));	\
+	} while (0)
+
+static cpumask_t mask_empty;
+static cpumask_t mask_all;
+static cpumask_t mask_tmp;
+
+static void test_cpumask_weight(struct kunit *test)
+{
+	KUNIT_EXPECT_TRUE_MSG(test, cpumask_empty(&mask_empty), MASK_MSG(&mask_empty));
+	KUNIT_EXPECT_TRUE_MSG(test, cpumask_full(&mask_all), MASK_MSG(&mask_all));
+
+	KUNIT_EXPECT_EQ_MSG(test, 0, cpumask_weight(&mask_empty), MASK_MSG(&mask_empty));
+	KUNIT_EXPECT_EQ_MSG(test, nr_cpu_ids, cpumask_weight(cpu_possible_mask),
+			    MASK_MSG(cpu_possible_mask));
+	KUNIT_EXPECT_EQ_MSG(test, nr_cpu_ids, cpumask_weight(&mask_all), MASK_MSG(&mask_all));
+}
+
+static void test_cpumask_first(struct kunit *test)
+{
+	KUNIT_EXPECT_LE_MSG(test, nr_cpu_ids, cpumask_first(&mask_empty), MASK_MSG(&mask_empty));
+	KUNIT_EXPECT_EQ_MSG(test, 0, cpumask_first(cpu_possible_mask), MASK_MSG(cpu_possible_mask));
+
+	KUNIT_EXPECT_EQ_MSG(test, 0, cpumask_first_zero(&mask_empty), MASK_MSG(&mask_empty));
+	KUNIT_EXPECT_LE_MSG(test, nr_cpu_ids, cpumask_first_zero(cpu_possible_mask),
+			    MASK_MSG(cpu_possible_mask));
+}
+
+static void test_cpumask_last(struct kunit *test)
+{
+	KUNIT_EXPECT_LE_MSG(test, nr_cpumask_bits, cpumask_last(&mask_empty),
+			    MASK_MSG(&mask_empty));
+	KUNIT_EXPECT_EQ_MSG(test, nr_cpu_ids - 1, cpumask_last(cpu_possible_mask),
+			    MASK_MSG(cpu_possible_mask));
+}
+
+static void test_cpumask_next(struct kunit *test)
+{
+	KUNIT_EXPECT_EQ_MSG(test, 0, cpumask_next_zero(-1, &mask_empty), MASK_MSG(&mask_empty));
+	KUNIT_EXPECT_LE_MSG(test, nr_cpu_ids, cpumask_next_zero(-1, cpu_possible_mask),
+			    MASK_MSG(cpu_possible_mask));
+
+	KUNIT_EXPECT_LE_MSG(test, nr_cpu_ids, cpumask_next(-1, &mask_empty),
+			    MASK_MSG(&mask_empty));
+	KUNIT_EXPECT_EQ_MSG(test, 0, cpumask_next(-1, cpu_possible_mask),
+			    MASK_MSG(cpu_possible_mask));
+}
+
+static void test_cpumask_iterators(struct kunit *test)
+{
+	EXPECT_FOR_EACH_CPU_EQ(test, &mask_empty);
+	EXPECT_FOR_EACH_CPU_WRAP_EQ(test, &mask_empty);
+	EXPECT_FOR_EACH_CPU_OP_EQ(test, and, &mask_empty, &mask_empty);
+	EXPECT_FOR_EACH_CPU_OP_EQ(test, and, cpu_possible_mask, &mask_empty);
+	EXPECT_FOR_EACH_CPU_OP_EQ(test, andnot, &mask_empty, &mask_empty);
+
+	EXPECT_FOR_EACH_CPU_EQ(test, cpu_possible_mask);
+	EXPECT_FOR_EACH_CPU_WRAP_EQ(test, cpu_possible_mask);
+	EXPECT_FOR_EACH_CPU_OP_EQ(test, and, cpu_possible_mask, cpu_possible_mask);
+	EXPECT_FOR_EACH_CPU_OP_EQ(test, andnot, cpu_possible_mask, &mask_empty);
+}
+
+static void test_cpumask_iterators_builtin(struct kunit *test)
+{
+	EXPECT_FOR_EACH_CPU_BUILTIN_EQ(test, possible);
+
+	/* Ensure the dynamic masks are stable while running the tests */
+	cpu_hotplug_disable();
+
+	EXPECT_FOR_EACH_CPU_BUILTIN_EQ(test, online);
+	EXPECT_FOR_EACH_CPU_BUILTIN_EQ(test, present);
+
+	cpu_hotplug_enable();
+}
+
+static int test_cpumask_init(struct kunit *test)
+{
+	cpumask_clear(&mask_empty);
+	cpumask_setall(&mask_all);
+
+	return 0;
+}
+
+static struct kunit_case test_cpumask_cases[] = {
+	KUNIT_CASE(test_cpumask_weight),
+	KUNIT_CASE(test_cpumask_first),
+	KUNIT_CASE(test_cpumask_last),
+	KUNIT_CASE(test_cpumask_next),
+	KUNIT_CASE(test_cpumask_iterators),
+	KUNIT_CASE(test_cpumask_iterators_builtin),
+	{}
+};
+
+static struct kunit_suite test_cpumask_suite = {
+	.name = "cpumask",
+	.init = test_cpumask_init,
+	.test_cases = test_cpumask_cases,
+};
+kunit_test_suite(test_cpumask_suite);
+
+MODULE_DESCRIPTION("KUnit tests for cpumask");
+MODULE_LICENSE("GPL");