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, 174 insertions, 0 deletions

diff --git a/lib/test_ubsan.c b/lib/test_ubsan.c
new file mode 100644
index 000000000..a4b6f52b9
--- /dev/null
+++ b/lib/test_ubsan.c
@@ -0,0 +1,174 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/init.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+typedef void(*test_ubsan_fp)(void);
+
+#define UBSAN_TEST(config, ...)	do {					\
+		pr_info("%s " __VA_ARGS__ "%s(%s=%s)\n", __func__,	\
+			sizeof(" " __VA_ARGS__) > 2 ? " " : "",		\
+			#config, IS_ENABLED(config) ? "y" : "n");	\
+	} while (0)
+
+static void test_ubsan_add_overflow(void)
+{
+	volatile int val = INT_MAX;
+
+	UBSAN_TEST(CONFIG_UBSAN_INTEGER_WRAP);
+	val += 2;
+}
+
+static void test_ubsan_sub_overflow(void)
+{
+	volatile int val = INT_MIN;
+	volatile int val2 = 2;
+
+	UBSAN_TEST(CONFIG_UBSAN_INTEGER_WRAP);
+	val -= val2;
+}
+
+static void test_ubsan_mul_overflow(void)
+{
+	volatile int val = INT_MAX / 2;
+
+	UBSAN_TEST(CONFIG_UBSAN_INTEGER_WRAP);
+	val *= 3;
+}
+
+static void test_ubsan_negate_overflow(void)
+{
+	volatile int val = INT_MIN;
+
+	UBSAN_TEST(CONFIG_UBSAN_INTEGER_WRAP);
+	val = -val;
+}
+
+static void test_ubsan_divrem_overflow(void)
+{
+	volatile int val = 16;
+	volatile int val2 = 0;
+
+	UBSAN_TEST(CONFIG_UBSAN_DIV_ZERO);
+	val /= val2;
+}
+
+static void test_ubsan_truncate_signed(void)
+{
+	volatile long val = LONG_MAX;
+	volatile int val2 = 0;
+
+	UBSAN_TEST(CONFIG_UBSAN_INTEGER_WRAP);
+	val2 = val;
+}
+
+static void test_ubsan_shift_out_of_bounds(void)
+{
+	volatile int neg = -1, wrap = 4;
+	volatile int val1 = 10;
+	volatile int val2 = INT_MAX;
+
+	UBSAN_TEST(CONFIG_UBSAN_SHIFT, "negative exponent");
+	val1 <<= neg;
+
+	UBSAN_TEST(CONFIG_UBSAN_SHIFT, "left overflow");
+	val2 <<= wrap;
+}
+
+static void test_ubsan_out_of_bounds(void)
+{
+	int i = 4, j = 4, k = -1;
+	volatile struct {
+		char above[4]; /* Protect surrounding memory. */
+		int arr[4];
+		char below[4]; /* Protect surrounding memory. */
+	} data;
+
+	OPTIMIZER_HIDE_VAR(i);
+	OPTIMIZER_HIDE_VAR(j);
+	OPTIMIZER_HIDE_VAR(k);
+
+	UBSAN_TEST(CONFIG_UBSAN_BOUNDS, "above");
+	data.arr[j] = i;
+
+	UBSAN_TEST(CONFIG_UBSAN_BOUNDS, "below");
+	data.arr[k] = i;
+}
+
+enum ubsan_test_enum {
+	UBSAN_TEST_ZERO = 0,
+	UBSAN_TEST_ONE,
+	UBSAN_TEST_MAX,
+};
+
+static void test_ubsan_load_invalid_value(void)
+{
+	volatile char *dst, *src;
+	bool val, val2, *ptr;
+	enum ubsan_test_enum eval, eval2, *eptr;
+	unsigned char c = 0xff;
+
+	UBSAN_TEST(CONFIG_UBSAN_BOOL, "bool");
+	dst = (char *)&val;
+	src = &c;
+	*dst = *src;
+
+	ptr = &val2;
+	val2 = val;
+
+	UBSAN_TEST(CONFIG_UBSAN_ENUM, "enum");
+	dst = (char *)&eval;
+	src = &c;
+	*dst = *src;
+
+	eptr = &eval2;
+	eval2 = eval;
+}
+
+static void test_ubsan_misaligned_access(void)
+{
+	volatile char arr[5] __aligned(4) = {1, 2, 3, 4, 5};
+	volatile int *ptr, val = 6;
+
+	UBSAN_TEST(CONFIG_UBSAN_ALIGNMENT);
+	ptr = (int *)(arr + 1);
+	*ptr = val;
+}
+
+static const test_ubsan_fp test_ubsan_array[] = {
+	test_ubsan_add_overflow,
+	test_ubsan_sub_overflow,
+	test_ubsan_mul_overflow,
+	test_ubsan_negate_overflow,
+	test_ubsan_truncate_signed,
+	test_ubsan_shift_out_of_bounds,
+	test_ubsan_out_of_bounds,
+	test_ubsan_load_invalid_value,
+	test_ubsan_misaligned_access,
+};
+
+/* Excluded because they Oops the module. */
+static __used const test_ubsan_fp skip_ubsan_array[] = {
+	test_ubsan_divrem_overflow,
+};
+
+static int __init test_ubsan_init(void)
+{
+	unsigned int i;
+
+	for (i = 0; i < ARRAY_SIZE(test_ubsan_array); i++)
+		test_ubsan_array[i]();
+
+	return 0;
+}
+module_init(test_ubsan_init);
+
+static void __exit test_ubsan_exit(void)
+{
+	/* do nothing */
+}
+module_exit(test_ubsan_exit);
+
+MODULE_AUTHOR("Jinbum Park <jinb.park7@gmail.com>");
+MODULE_DESCRIPTION("UBSAN unit test");
+MODULE_LICENSE("GPL v2");