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, 178 insertions, 0 deletions

diff --git a/drivers/gpu/host1x/context.c b/drivers/gpu/host1x/context.c
new file mode 100644
index 000000000..512f3d189
--- /dev/null
+++ b/drivers/gpu/host1x/context.c
@@ -0,0 +1,178 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (c) 2021, NVIDIA Corporation.
+ */
+
+#include <linux/device.h>
+#include <linux/host1x_context_bus.h>
+#include <linux/kref.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
+#include <linux/pid.h>
+#include <linux/slab.h>
+
+#include "context.h"
+#include "dev.h"
+
+static void host1x_memory_context_release(struct device *dev)
+{
+	/* context device is freed in host1x_memory_context_list_free() */
+}
+
+int host1x_memory_context_list_init(struct host1x *host1x)
+{
+	struct host1x_memory_context_list *cdl = &host1x->context_list;
+	struct device_node *node = host1x->dev->of_node;
+	struct host1x_memory_context *ctx;
+	unsigned int i;
+	int err;
+
+	cdl->devs = NULL;
+	cdl->len = 0;
+	mutex_init(&cdl->lock);
+
+	err = of_property_count_u32_elems(node, "iommu-map");
+	if (err < 0)
+		return 0;
+
+	cdl->len = err / 4;
+	cdl->devs = kzalloc_objs(*cdl->devs, cdl->len);
+	if (!cdl->devs)
+		return -ENOMEM;
+
+	for (i = 0; i < cdl->len; i++) {
+		ctx = &cdl->devs[i];
+
+		ctx->host = host1x;
+
+		device_initialize(&ctx->dev);
+
+		/*
+		 * Due to an issue with T194 NVENC, only 38 bits can be used.
+		 * Anyway, 256GiB of IOVA ought to be enough for anyone.
+		 */
+		ctx->dma_mask = DMA_BIT_MASK(38);
+		ctx->dev.dma_mask = &ctx->dma_mask;
+		ctx->dev.coherent_dma_mask = ctx->dma_mask;
+		dev_set_name(&ctx->dev, "host1x-ctx.%d", i);
+		ctx->dev.bus = &host1x_context_device_bus_type;
+		ctx->dev.parent = host1x->dev;
+		ctx->dev.release = host1x_memory_context_release;
+
+		ctx->dev.dma_parms = &ctx->dma_parms;
+		dma_set_max_seg_size(&ctx->dev, UINT_MAX);
+
+		err = device_add(&ctx->dev);
+		if (err) {
+			dev_err(host1x->dev, "could not add context device %d: %d\n", i, err);
+			put_device(&ctx->dev);
+			goto unreg_devices;
+		}
+
+		err = of_dma_configure_id(&ctx->dev, node, true, &i);
+		if (err) {
+			dev_err(host1x->dev, "IOMMU configuration failed for context device %d: %d\n",
+				i, err);
+			device_unregister(&ctx->dev);
+			goto unreg_devices;
+		}
+
+		if (!tegra_dev_iommu_get_stream_id(&ctx->dev, &ctx->stream_id) ||
+		    !device_iommu_mapped(&ctx->dev)) {
+			dev_err(host1x->dev, "Context device %d has no IOMMU!\n", i);
+			device_unregister(&ctx->dev);
+
+			/*
+			 * This means that if IOMMU is disabled but context devices
+			 * are defined in the device tree, Host1x will fail to probe.
+			 * That's probably OK in this time and age.
+			 */
+			err = -EINVAL;
+
+			goto unreg_devices;
+		}
+	}
+
+	return 0;
+
+unreg_devices:
+	while (i--)
+		device_unregister(&cdl->devs[i].dev);
+
+	kfree(cdl->devs);
+	cdl->devs = NULL;
+	cdl->len = 0;
+
+	return err;
+}
+
+void host1x_memory_context_list_free(struct host1x_memory_context_list *cdl)
+{
+	unsigned int i;
+
+	for (i = 0; i < cdl->len; i++)
+		device_unregister(&cdl->devs[i].dev);
+
+	kfree(cdl->devs);
+	cdl->len = 0;
+}
+
+struct host1x_memory_context *host1x_memory_context_alloc(struct host1x *host1x,
+							  struct device *dev,
+							  struct pid *pid)
+{
+	struct host1x_memory_context_list *cdl = &host1x->context_list;
+	struct host1x_memory_context *free = NULL;
+	int i;
+
+	if (!cdl->len)
+		return ERR_PTR(-EOPNOTSUPP);
+
+	mutex_lock(&cdl->lock);
+
+	for (i = 0; i < cdl->len; i++) {
+		struct host1x_memory_context *cd = &cdl->devs[i];
+
+		if (cd->dev.iommu->iommu_dev != dev->iommu->iommu_dev)
+			continue;
+
+		if (cd->owner == pid) {
+			refcount_inc(&cd->ref);
+			mutex_unlock(&cdl->lock);
+			return cd;
+		} else if (!cd->owner && !free) {
+			free = cd;
+		}
+	}
+
+	if (!free) {
+		mutex_unlock(&cdl->lock);
+		return ERR_PTR(-EBUSY);
+	}
+
+	refcount_set(&free->ref, 1);
+	free->owner = get_pid(pid);
+
+	mutex_unlock(&cdl->lock);
+
+	return free;
+}
+EXPORT_SYMBOL_GPL(host1x_memory_context_alloc);
+
+void host1x_memory_context_get(struct host1x_memory_context *cd)
+{
+	refcount_inc(&cd->ref);
+}
+EXPORT_SYMBOL_GPL(host1x_memory_context_get);
+
+void host1x_memory_context_put(struct host1x_memory_context *cd)
+{
+	struct host1x_memory_context_list *cdl = &cd->host->context_list;
+
+	if (refcount_dec_and_mutex_lock(&cd->ref, &cdl->lock)) {
+		put_pid(cd->owner);
+		cd->owner = NULL;
+		mutex_unlock(&cdl->lock);
+	}
+}
+EXPORT_SYMBOL_GPL(host1x_memory_context_put);