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.

2 files changed, 86 insertions, 0 deletions

diff --git a/samples/hw_breakpoint/Makefile b/samples/hw_breakpoint/Makefile
new file mode 100644
index 000000000..ef4b6fdd7
--- /dev/null
+++ b/samples/hw_breakpoint/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-$(CONFIG_SAMPLE_HW_BREAKPOINT) += data_breakpoint.o
diff --git a/samples/hw_breakpoint/data_breakpoint.c b/samples/hw_breakpoint/data_breakpoint.c
new file mode 100644
index 000000000..fbb03b66d
--- /dev/null
+++ b/samples/hw_breakpoint/data_breakpoint.c
@@ -0,0 +1,84 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * data_breakpoint.c - Sample HW Breakpoint file to watch kernel data address
+ *
+ * usage: insmod data_breakpoint.ko ksym=<ksym_name>
+ *
+ * This file is a kernel module that places a breakpoint over ksym_name kernel
+ * variable using Hardware Breakpoint register. The corresponding handler which
+ * prints a backtrace is invoked every time a write operation is performed on
+ * that variable.
+ *
+ * Copyright (C) IBM Corporation, 2009
+ *
+ * Author: K.Prasad <prasad@linux.vnet.ibm.com>
+ */
+#include <linux/module.h>	/* Needed by all modules */
+#include <linux/kernel.h>	/* Needed for KERN_INFO */
+#include <linux/init.h>		/* Needed for the macros */
+#include <linux/kallsyms.h>
+
+#include <linux/perf_event.h>
+#include <linux/hw_breakpoint.h>
+
+static struct perf_event * __percpu *sample_hbp;
+
+static char ksym_name[KSYM_NAME_LEN] = "jiffies";
+module_param_string(ksym, ksym_name, KSYM_NAME_LEN, S_IRUGO);
+MODULE_PARM_DESC(ksym, "Kernel symbol to monitor; this module will report any"
+			" write operations on the kernel symbol");
+
+static void sample_hbp_handler(struct perf_event *bp,
+			       struct perf_sample_data *data,
+			       struct pt_regs *regs)
+{
+	printk(KERN_INFO "%s value is changed\n", ksym_name);
+	dump_stack();
+	printk(KERN_INFO "Dump stack from sample_hbp_handler\n");
+}
+
+static int __init hw_break_module_init(void)
+{
+	int ret;
+	struct perf_event_attr attr;
+	void *addr = __symbol_get(ksym_name);
+
+	if (!addr)
+		return -ENXIO;
+
+	hw_breakpoint_init(&attr);
+	attr.bp_addr = (unsigned long)addr;
+	attr.bp_len = HW_BREAKPOINT_LEN_4;
+	attr.bp_type = HW_BREAKPOINT_W;
+
+	sample_hbp = register_wide_hw_breakpoint(&attr, sample_hbp_handler, NULL);
+	if (IS_ERR_PCPU(sample_hbp)) {
+		ret = PTR_ERR_PCPU(sample_hbp);
+		goto fail;
+	}
+
+	printk(KERN_INFO "HW Breakpoint for %s write installed\n", ksym_name);
+
+	return 0;
+
+fail:
+	printk(KERN_INFO "Breakpoint registration failed\n");
+
+	return ret;
+}
+
+static void __exit hw_break_module_exit(void)
+{
+	unregister_wide_hw_breakpoint(sample_hbp);
+#ifdef CONFIG_MODULE_UNLOAD
+	__symbol_put(ksym_name);
+#endif
+	printk(KERN_INFO "HW Breakpoint for %s write uninstalled\n", ksym_name);
+}
+
+module_init(hw_break_module_init);
+module_exit(hw_break_module_exit);
+
+MODULE_LICENSE("GPL");
+MODULE_AUTHOR("K.Prasad");
+MODULE_DESCRIPTION("ksym breakpoint");