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, 122 insertions, 0 deletions

diff --git a/drivers/usb/serial/empeg.c b/drivers/usb/serial/empeg.c
new file mode 100644
index 000000000..4937575ca
--- /dev/null
+++ b/drivers/usb/serial/empeg.c
@@ -0,0 +1,122 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * USB Empeg empeg-car player driver
+ *
+ *	Copyright (C) 2000, 2001
+ *	    Gary Brubaker (xavyer@ix.netcom.com)
+ *
+ *	Copyright (C) 1999 - 2001
+ *	    Greg Kroah-Hartman (greg@kroah.com)
+ *
+ * See Documentation/usb/usb-serial.rst for more information on using this
+ * driver
+ */
+
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/slab.h>
+#include <linux/tty.h>
+#include <linux/module.h>
+#include <linux/spinlock.h>
+#include <linux/usb.h>
+#include <linux/usb/serial.h>
+
+#define DRIVER_AUTHOR "Greg Kroah-Hartman <greg@kroah.com>, Gary Brubaker <xavyer@ix.netcom.com>"
+#define DRIVER_DESC "USB Empeg Mark I/II Driver"
+
+#define EMPEG_VENDOR_ID			0x084f
+#define EMPEG_PRODUCT_ID		0x0001
+
+/* function prototypes for an empeg-car player */
+static int  empeg_startup(struct usb_serial *serial);
+static void empeg_init_termios(struct tty_struct *tty);
+
+static const struct usb_device_id id_table[] = {
+	{ USB_DEVICE(EMPEG_VENDOR_ID, EMPEG_PRODUCT_ID) },
+	{ }					/* Terminating entry */
+};
+
+MODULE_DEVICE_TABLE(usb, id_table);
+
+static struct usb_serial_driver empeg_device = {
+	.driver = {
+		.name =		"empeg",
+	},
+	.id_table =		id_table,
+	.num_ports =		1,
+	.bulk_out_size =	256,
+	.throttle =		usb_serial_generic_throttle,
+	.unthrottle =		usb_serial_generic_unthrottle,
+	.attach =		empeg_startup,
+	.init_termios =		empeg_init_termios,
+};
+
+static struct usb_serial_driver * const serial_drivers[] = {
+	&empeg_device, NULL
+};
+
+static int empeg_startup(struct usb_serial *serial)
+{
+	int r;
+
+	if (serial->dev->actconfig->desc.bConfigurationValue != 1) {
+		dev_err(&serial->dev->dev, "active config #%d != 1 ??\n",
+			serial->dev->actconfig->desc.bConfigurationValue);
+		return -ENODEV;
+	}
+
+	r = usb_reset_configuration(serial->dev);
+
+	/* continue on with initialization */
+	return r;
+}
+
+static void empeg_init_termios(struct tty_struct *tty)
+{
+	struct ktermios *termios = &tty->termios;
+
+	/*
+	 * The empeg-car player wants these particular tty settings.
+	 * You could, for example, change the baud rate, however the
+	 * player only supports 115200 (currently), so there is really
+	 * no point in support for changes to the tty settings.
+	 * (at least for now)
+	 *
+	 * The default requirements for this device are:
+	 */
+	termios->c_iflag
+		&= ~(IGNBRK	/* disable ignore break */
+		| BRKINT	/* disable break causes interrupt */
+		| PARMRK	/* disable mark parity errors */
+		| ISTRIP	/* disable clear high bit of input characters */
+		| INLCR		/* disable translate NL to CR */
+		| IGNCR		/* disable ignore CR */
+		| ICRNL		/* disable translate CR to NL */
+		| IXON);	/* disable enable XON/XOFF flow control */
+
+	termios->c_oflag
+		&= ~OPOST;	/* disable postprocess output characters */
+
+	termios->c_lflag
+		&= ~(ECHO	/* disable echo input characters */
+		| ECHONL	/* disable echo new line */
+		| ICANON	/* disable erase, kill, werase, and rprnt special characters */
+		| ISIG		/* disable interrupt, quit, and suspend special characters */
+		| IEXTEN);	/* disable non-POSIX special characters */
+
+	termios->c_cflag
+		&= ~(CSIZE	/* no size */
+		| PARENB	/* disable parity bit */
+		| CBAUD);	/* clear current baud rate */
+
+	termios->c_cflag
+		|= CS8;		/* character size 8 bits */
+
+	tty_encode_baud_rate(tty, 115200, 115200);
+}
+
+module_usb_serial_driver(serial_drivers, id_table);
+
+MODULE_AUTHOR(DRIVER_AUTHOR);
+MODULE_DESCRIPTION(DRIVER_DESC);
+MODULE_LICENSE("GPL v2");