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, 186 insertions, 0 deletions

diff --git a/include/drm/drm_writeback.h b/include/drm/drm_writeback.h
new file mode 100644
index 000000000..c380a7b8f
--- /dev/null
+++ b/include/drm/drm_writeback.h
@@ -0,0 +1,186 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * (C) COPYRIGHT 2016 ARM Limited. All rights reserved.
+ * Author: Brian Starkey <brian.starkey@arm.com>
+ *
+ * This program is free software and is provided to you under the terms of the
+ * GNU General Public License version 2 as published by the Free Software
+ * Foundation, and any use by you of this program is subject to the terms
+ * of such GNU licence.
+ */
+
+#ifndef __DRM_WRITEBACK_H__
+#define __DRM_WRITEBACK_H__
+#include <drm/drm_connector.h>
+#include <drm/drm_encoder.h>
+#include <linux/workqueue.h>
+
+/**
+ * struct drm_writeback_connector - DRM writeback connector
+ */
+struct drm_writeback_connector {
+	/**
+	 * @base: base drm_connector object
+	 */
+	struct drm_connector base;
+
+	/**
+	 * @encoder: Internal encoder used by the connector to fulfill
+	 * the DRM framework requirements. The users of the
+	 * @drm_writeback_connector control the behaviour of the @encoder
+	 * by passing the @enc_funcs parameter to drm_writeback_connector_init()
+	 * function.
+	 * For users of drm_writeback_connector_init_with_encoder(), this field
+	 * is not valid as the encoder is managed within their drivers.
+	 */
+	struct drm_encoder encoder;
+
+	/**
+	 * @pixel_formats_blob_ptr:
+	 *
+	 * DRM blob property data for the pixel formats list on writeback
+	 * connectors
+	 * See also drm_writeback_connector_init()
+	 */
+	struct drm_property_blob *pixel_formats_blob_ptr;
+
+	/** @job_lock: Protects job_queue */
+	spinlock_t job_lock;
+
+	/**
+	 * @job_queue:
+	 *
+	 * Holds a list of a connector's writeback jobs; the last item is the
+	 * most recent. The first item may be either waiting for the hardware
+	 * to begin writing, or currently being written.
+	 *
+	 * See also: drm_writeback_queue_job() and
+	 * drm_writeback_signal_completion()
+	 */
+	struct list_head job_queue;
+
+	/**
+	 * @fence_context:
+	 *
+	 * timeline context used for fence operations.
+	 */
+	unsigned int fence_context;
+	/**
+	 * @fence_lock:
+	 *
+	 * spinlock to protect the fences in the fence_context.
+	 */
+	spinlock_t fence_lock;
+	/**
+	 * @fence_seqno:
+	 *
+	 * Seqno variable used as monotonic counter for the fences
+	 * created on the connector's timeline.
+	 */
+	unsigned long fence_seqno;
+	/**
+	 * @timeline_name:
+	 *
+	 * The name of the connector's fence timeline.
+	 */
+	char timeline_name[32];
+};
+
+/**
+ * struct drm_writeback_job - DRM writeback job
+ */
+struct drm_writeback_job {
+	/**
+	 * @connector:
+	 *
+	 * Back-pointer to the writeback connector associated with the job
+	 */
+	struct drm_writeback_connector *connector;
+
+	/**
+	 * @prepared:
+	 *
+	 * Set when the job has been prepared with drm_writeback_prepare_job()
+	 */
+	bool prepared;
+
+	/**
+	 * @cleanup_work:
+	 *
+	 * Used to allow drm_writeback_signal_completion to defer dropping the
+	 * framebuffer reference to a workqueue
+	 */
+	struct work_struct cleanup_work;
+
+	/**
+	 * @list_entry:
+	 *
+	 * List item for the writeback connector's @job_queue
+	 */
+	struct list_head list_entry;
+
+	/**
+	 * @fb:
+	 *
+	 * Framebuffer to be written to by the writeback connector. Do not set
+	 * directly, use drm_writeback_set_fb()
+	 */
+	struct drm_framebuffer *fb;
+
+	/**
+	 * @out_fence:
+	 *
+	 * Fence which will signal once the writeback has completed
+	 */
+	struct dma_fence *out_fence;
+
+	/**
+	 * @priv:
+	 *
+	 * Driver-private data
+	 */
+	void *priv;
+};
+
+static inline struct drm_writeback_connector *
+drm_connector_to_writeback(struct drm_connector *connector)
+{
+	return container_of(connector, struct drm_writeback_connector, base);
+}
+
+int drm_writeback_connector_init(struct drm_device *dev,
+				 struct drm_writeback_connector *wb_connector,
+				 const struct drm_connector_funcs *con_funcs,
+				 const struct drm_encoder_helper_funcs *enc_helper_funcs,
+				 const u32 *formats, int n_formats,
+				 u32 possible_crtcs);
+
+int drm_writeback_connector_init_with_encoder(struct drm_device *dev,
+				struct drm_writeback_connector *wb_connector,
+				struct drm_encoder *enc,
+				const struct drm_connector_funcs *con_funcs, const u32 *formats,
+				int n_formats);
+
+int drmm_writeback_connector_init(struct drm_device *dev,
+				  struct drm_writeback_connector *wb_connector,
+				  const struct drm_connector_funcs *con_funcs,
+				  struct drm_encoder *enc,
+				  const u32 *formats, int n_formats);
+
+int drm_writeback_set_fb(struct drm_connector_state *conn_state,
+			 struct drm_framebuffer *fb);
+
+int drm_writeback_prepare_job(struct drm_writeback_job *job);
+
+void drm_writeback_queue_job(struct drm_writeback_connector *wb_connector,
+			     struct drm_connector_state *conn_state);
+
+void drm_writeback_cleanup_job(struct drm_writeback_job *job);
+
+void
+drm_writeback_signal_completion(struct drm_writeback_connector *wb_connector,
+				int status);
+
+struct dma_fence *
+drm_writeback_get_out_fence(struct drm_writeback_connector *wb_connector);
+#endif