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, 58 insertions, 0 deletions

diff --git a/drivers/misc/ibmasm/uart.c b/drivers/misc/ibmasm/uart.c
new file mode 100644
index 000000000..a5d4c8e01
--- /dev/null
+++ b/drivers/misc/ibmasm/uart.c
@@ -0,0 +1,58 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+/*
+ * IBM ASM Service Processor Device Driver
+ *
+ * Copyright (C) IBM Corporation, 2004
+ *
+ * Author: Max Asböck <amax@us.ibm.com>
+ */
+
+#include <linux/termios.h>
+#include <linux/tty.h>
+#include <linux/serial_core.h>
+#include <linux/serial_reg.h>
+#include <linux/serial_8250.h>
+#include "ibmasm.h"
+#include "lowlevel.h"
+
+
+void ibmasm_register_uart(struct service_processor *sp)
+{
+	struct uart_8250_port uart;
+	void __iomem *iomem_base;
+
+	iomem_base = sp->base_address + SCOUT_COM_B_BASE;
+
+	/* read the uart scratch register to determine if the UART
+	 * is dedicated to the service processor or if the OS can use it
+	 */
+	if (0 == readl(iomem_base + UART_SCR)) {
+		dev_info(sp->dev, "IBM SP UART not registered, owned by service processor\n");
+		sp->serial_line = -1;
+		return;
+	}
+
+	memset(&uart, 0, sizeof(uart));
+	uart.port.irq		= sp->irq;
+	uart.port.uartclk	= 3686400;
+	uart.port.flags		= UPF_SHARE_IRQ;
+	uart.port.iotype	= UPIO_MEM;
+	uart.port.membase	= iomem_base;
+
+	sp->serial_line = serial8250_register_8250_port(&uart);
+	if (sp->serial_line < 0) {
+		dev_err(sp->dev, "Failed to register serial port\n");
+		return;
+	}
+	enable_uart_interrupts(sp->base_address);
+}
+
+void ibmasm_unregister_uart(struct service_processor *sp)
+{
+	if (sp->serial_line < 0)
+		return;
+
+	disable_uart_interrupts(sp->base_address);
+	serial8250_unregister_port(sp->serial_line);
+}