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, 82 insertions, 0 deletions

diff --git a/drivers/acpi/reboot.c b/drivers/acpi/reboot.c
new file mode 100644
index 000000000..b79b7c99c
--- /dev/null
+++ b/drivers/acpi/reboot.c
@@ -0,0 +1,82 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#define pr_fmt(fmt) "ACPI: " fmt
+
+#include <linux/pci.h>
+#include <linux/acpi.h>
+#include <acpi/reboot.h>
+#include <linux/delay.h>
+
+#ifdef CONFIG_PCI
+static void acpi_pci_reboot(struct acpi_generic_address *rr, u8 reset_value)
+{
+	unsigned int devfn;
+	struct pci_bus *bus0;
+
+	/* The reset register can only live on bus 0. */
+	bus0 = pci_find_bus(0, 0);
+	if (!bus0)
+		return;
+	/* Form PCI device/function pair. */
+	devfn = PCI_DEVFN((rr->address >> 32) & 0xffff,
+			  (rr->address >> 16) & 0xffff);
+	pr_debug("Resetting with ACPI PCI RESET_REG.\n");
+	/* Write the value that resets us. */
+	pci_bus_write_config_byte(bus0, devfn,
+			(rr->address & 0xffff), reset_value);
+}
+#else
+static inline void acpi_pci_reboot(struct acpi_generic_address *rr,
+				   u8 reset_value)
+{
+	pr_warn_once("PCI configuration space access is not supported\n");
+}
+#endif
+
+void acpi_reboot(void)
+{
+	struct acpi_generic_address *rr;
+	u8 reset_value;
+
+	if (acpi_disabled)
+		return;
+
+	rr = &acpi_gbl_FADT.reset_register;
+
+	/* ACPI reset register was only introduced with v2 of the FADT */
+
+	if (acpi_gbl_FADT.header.revision < 2)
+		return;
+
+	/* Is the reset register supported? The spec says we should be
+	 * checking the bit width and bit offset, but Windows ignores
+	 * these fields */
+	if (!(acpi_gbl_FADT.flags & ACPI_FADT_RESET_REGISTER))
+		return;
+
+	reset_value = acpi_gbl_FADT.reset_value;
+
+	/* The reset register can only exist in I/O, Memory or PCI config space
+	 * on a device on bus 0. */
+	switch (rr->space_id) {
+	case ACPI_ADR_SPACE_PCI_CONFIG:
+		acpi_pci_reboot(rr, reset_value);
+		break;
+
+	case ACPI_ADR_SPACE_SYSTEM_MEMORY:
+	case ACPI_ADR_SPACE_SYSTEM_IO:
+		pr_debug("ACPI MEMORY or I/O RESET_REG.\n");
+		acpi_reset();
+		break;
+	}
+
+	/*
+	 * Some platforms do not shut down immediately after writing to the
+	 * ACPI reset register, and this results in racing with the
+	 * subsequent reboot mechanism.
+	 *
+	 * The 15ms delay has been found to be long enough for the system
+	 * to reboot on the affected platforms.
+	 */
+	mdelay(15);
+}