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, 117 insertions, 0 deletions

diff --git a/drivers/virtio/virtio_debug.c b/drivers/virtio/virtio_debug.c
new file mode 100644
index 000000000..ccf1955a1
--- /dev/null
+++ b/drivers/virtio/virtio_debug.c
@@ -0,0 +1,117 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <linux/virtio.h>
+#include <linux/virtio_config.h>
+#include <linux/debugfs.h>
+
+static struct dentry *virtio_debugfs_dir;
+
+static int virtio_debug_device_features_show(struct seq_file *s, void *data)
+{
+	u64 device_features[VIRTIO_FEATURES_U64S];
+	struct virtio_device *dev = s->private;
+	unsigned int i;
+
+	virtio_get_features(dev, device_features);
+	for (i = 0; i < VIRTIO_FEATURES_BITS; i++) {
+		if (virtio_features_test_bit(device_features, i))
+			seq_printf(s, "%u\n", i);
+	}
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(virtio_debug_device_features);
+
+static int virtio_debug_filter_features_show(struct seq_file *s, void *data)
+{
+	struct virtio_device *dev = s->private;
+	unsigned int i;
+
+	for (i = 0; i < VIRTIO_FEATURES_BITS; i++) {
+		if (virtio_features_test_bit(dev->debugfs_filter_features, i))
+			seq_printf(s, "%u\n", i);
+	}
+	return 0;
+}
+DEFINE_SHOW_ATTRIBUTE(virtio_debug_filter_features);
+
+static int virtio_debug_filter_features_clear(void *data, u64 val)
+{
+	struct virtio_device *dev = data;
+
+	if (val == 1)
+		virtio_features_zero(dev->debugfs_filter_features);
+	return 0;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(virtio_debug_filter_features_clear_fops, NULL,
+			 virtio_debug_filter_features_clear, "%llu\n");
+
+static int virtio_debug_filter_feature_add(void *data, u64 val)
+{
+	struct virtio_device *dev = data;
+
+	if (val >= VIRTIO_FEATURES_BITS)
+		return -EINVAL;
+
+	virtio_features_set_bit(dev->debugfs_filter_features, val);
+	return 0;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(virtio_debug_filter_feature_add_fops, NULL,
+			 virtio_debug_filter_feature_add, "%llu\n");
+
+static int virtio_debug_filter_feature_del(void *data, u64 val)
+{
+	struct virtio_device *dev = data;
+
+	if (val >= VIRTIO_FEATURES_BITS)
+		return -EINVAL;
+
+	virtio_features_clear_bit(dev->debugfs_filter_features, val);
+	return 0;
+}
+
+DEFINE_DEBUGFS_ATTRIBUTE(virtio_debug_filter_feature_del_fops, NULL,
+			 virtio_debug_filter_feature_del, "%llu\n");
+
+void virtio_debug_device_init(struct virtio_device *dev)
+{
+	dev->debugfs_dir = debugfs_create_dir(dev_name(&dev->dev),
+					      virtio_debugfs_dir);
+	debugfs_create_file("device_features", 0400, dev->debugfs_dir, dev,
+			    &virtio_debug_device_features_fops);
+	debugfs_create_file("filter_features", 0400, dev->debugfs_dir, dev,
+			    &virtio_debug_filter_features_fops);
+	debugfs_create_file("filter_features_clear", 0200, dev->debugfs_dir, dev,
+			    &virtio_debug_filter_features_clear_fops);
+	debugfs_create_file("filter_feature_add", 0200, dev->debugfs_dir, dev,
+			    &virtio_debug_filter_feature_add_fops);
+	debugfs_create_file("filter_feature_del", 0200, dev->debugfs_dir, dev,
+			    &virtio_debug_filter_feature_del_fops);
+}
+EXPORT_SYMBOL_GPL(virtio_debug_device_init);
+
+void virtio_debug_device_filter_features(struct virtio_device *dev)
+{
+	virtio_features_andnot(dev->features_array, dev->features_array,
+			       dev->debugfs_filter_features);
+}
+EXPORT_SYMBOL_GPL(virtio_debug_device_filter_features);
+
+void virtio_debug_device_exit(struct virtio_device *dev)
+{
+	debugfs_remove_recursive(dev->debugfs_dir);
+}
+EXPORT_SYMBOL_GPL(virtio_debug_device_exit);
+
+void virtio_debug_init(void)
+{
+	virtio_debugfs_dir = debugfs_create_dir("virtio", NULL);
+}
+EXPORT_SYMBOL_GPL(virtio_debug_init);
+
+void virtio_debug_exit(void)
+{
+	debugfs_remove_recursive(virtio_debugfs_dir);
+}
+EXPORT_SYMBOL_GPL(virtio_debug_exit);