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, 90 insertions, 0 deletions

diff --git a/io_uring/nop.c b/io_uring/nop.c
new file mode 100644
index 000000000..60ab19604
--- /dev/null
+++ b/io_uring/nop.c
@@ -0,0 +1,90 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/fs.h>
+#include <linux/file.h>
+#include <linux/io_uring.h>
+
+#include <uapi/linux/io_uring.h>
+
+#include "io_uring.h"
+#include "rsrc.h"
+#include "nop.h"
+
+struct io_nop {
+	struct file     *file;
+	int             result;
+	int		fd;
+	unsigned int	flags;
+	__u64		extra1;
+	__u64		extra2;
+};
+
+#define NOP_FLAGS	(IORING_NOP_INJECT_RESULT | IORING_NOP_FIXED_FILE | \
+			 IORING_NOP_FIXED_BUFFER | IORING_NOP_FILE | \
+			 IORING_NOP_TW | IORING_NOP_CQE32)
+
+int io_nop_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)
+{
+	struct io_nop *nop = io_kiocb_to_cmd(req, struct io_nop);
+
+	nop->flags = READ_ONCE(sqe->nop_flags);
+	if (nop->flags & ~NOP_FLAGS)
+		return -EINVAL;
+
+	if (nop->flags & IORING_NOP_INJECT_RESULT)
+		nop->result = READ_ONCE(sqe->len);
+	else
+		nop->result = 0;
+	if (nop->flags & IORING_NOP_FILE)
+		nop->fd = READ_ONCE(sqe->fd);
+	else
+		nop->fd = -1;
+	if (nop->flags & IORING_NOP_FIXED_FILE)
+		req->flags |= REQ_F_FIXED_FILE;
+	if (nop->flags & IORING_NOP_FIXED_BUFFER)
+		req->buf_index = READ_ONCE(sqe->buf_index);
+	if (nop->flags & IORING_NOP_CQE32) {
+		struct io_ring_ctx *ctx = req->ctx;
+
+		if (!(ctx->flags & (IORING_SETUP_CQE32|IORING_SETUP_CQE_MIXED)))
+			return -EINVAL;
+		nop->extra1 = READ_ONCE(sqe->off);
+		nop->extra2 = READ_ONCE(sqe->addr);
+	}
+	return 0;
+}
+
+int io_nop(struct io_kiocb *req, unsigned int issue_flags)
+{
+	struct io_nop *nop = io_kiocb_to_cmd(req, struct io_nop);
+	int ret = nop->result;
+
+	if (nop->flags & IORING_NOP_FILE) {
+		if (req->flags & REQ_F_FIXED_FILE)
+			req->file = io_file_get_fixed(req, nop->fd, issue_flags);
+		else
+			req->file = io_file_get_normal(req, nop->fd);
+		if (!req->file) {
+			ret = -EBADF;
+			goto done;
+		}
+	}
+	if (nop->flags & IORING_NOP_FIXED_BUFFER) {
+		if (!io_find_buf_node(req, issue_flags))
+			ret = -EFAULT;
+	}
+done:
+	if (ret < 0)
+		req_set_fail(req);
+	if (nop->flags & IORING_NOP_CQE32)
+		io_req_set_res32(req, ret, 0, nop->extra1, nop->extra2);
+	else
+		io_req_set_res(req, ret, 0);
+	if (nop->flags & IORING_NOP_TW) {
+		req->io_task_work.func = io_req_task_complete;
+		io_req_task_work_add(req);
+		return IOU_ISSUE_SKIP_COMPLETE;
+	}
+	return IOU_COMPLETE;
+}