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, 99 insertions, 0 deletions

diff --git a/lib/notifier-error-inject.c b/lib/notifier-error-inject.c
new file mode 100644
index 000000000..954c3412d
--- /dev/null
+++ b/lib/notifier-error-inject.c
@@ -0,0 +1,99 @@
+// SPDX-License-Identifier: GPL-2.0-only
+#include <linux/module.h>
+
+#include "notifier-error-inject.h"
+
+static int debugfs_errno_set(void *data, u64 val)
+{
+	*(int *)data = clamp_t(int, val, -MAX_ERRNO, 0);
+	return 0;
+}
+
+static int debugfs_errno_get(void *data, u64 *val)
+{
+	*val = *(int *)data;
+	return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE_SIGNED(fops_errno, debugfs_errno_get, debugfs_errno_set,
+			"%lld\n");
+
+static struct dentry *debugfs_create_errno(const char *name, umode_t mode,
+				struct dentry *parent, int *value)
+{
+	return debugfs_create_file(name, mode, parent, value, &fops_errno);
+}
+
+static int notifier_err_inject_callback(struct notifier_block *nb,
+				unsigned long val, void *p)
+{
+	int err = 0;
+	struct notifier_err_inject *err_inject =
+		container_of(nb, struct notifier_err_inject, nb);
+	struct notifier_err_inject_action *action;
+
+	for (action = err_inject->actions; action->name; action++) {
+		if (action->val == val) {
+			err = action->error;
+			break;
+		}
+	}
+	if (err)
+		pr_info("Injecting error (%d) to %s\n", err, action->name);
+
+	return notifier_from_errno(err);
+}
+
+struct dentry *notifier_err_inject_dir;
+EXPORT_SYMBOL_GPL(notifier_err_inject_dir);
+
+struct dentry *notifier_err_inject_init(const char *name, struct dentry *parent,
+			struct notifier_err_inject *err_inject, int priority)
+{
+	struct notifier_err_inject_action *action;
+	umode_t mode = S_IFREG | S_IRUSR | S_IWUSR;
+	struct dentry *dir;
+	struct dentry *actions_dir;
+
+	err_inject->nb.notifier_call = notifier_err_inject_callback;
+	err_inject->nb.priority = priority;
+
+	dir = debugfs_create_dir(name, parent);
+
+	actions_dir = debugfs_create_dir("actions", dir);
+
+	for (action = err_inject->actions; action->name; action++) {
+		struct dentry *action_dir;
+
+		action_dir = debugfs_create_dir(action->name, actions_dir);
+
+		/*
+		 * Create debugfs r/w file containing action->error. If
+		 * notifier call chain is called with action->val, it will
+		 * fail with the error code
+		 */
+		debugfs_create_errno("error", mode, action_dir, &action->error);
+	}
+	return dir;
+}
+EXPORT_SYMBOL_GPL(notifier_err_inject_init);
+
+static int __init err_inject_init(void)
+{
+	notifier_err_inject_dir =
+		debugfs_create_dir("notifier-error-inject", NULL);
+
+	return 0;
+}
+
+static void __exit err_inject_exit(void)
+{
+	debugfs_remove_recursive(notifier_err_inject_dir);
+}
+
+module_init(err_inject_init);
+module_exit(err_inject_exit);
+
+MODULE_DESCRIPTION("Notifier error injection module");
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("Akinobu Mita <akinobu.mita@gmail.com>");