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, 292 insertions, 0 deletions

diff --git a/drivers/rtc/rtc-rx4581.c b/drivers/rtc/rtc-rx4581.c
new file mode 100644
index 000000000..c092e0452
--- /dev/null
+++ b/drivers/rtc/rtc-rx4581.c
@@ -0,0 +1,292 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/* drivers/rtc/rtc-rx4581.c
+ *
+ * written by Torben Hohn <torbenh@linutronix.de>
+ *
+ * Based on:
+ * drivers/rtc/rtc-max6902.c
+ *
+ * Copyright (C) 2006 8D Technologies inc.
+ * Copyright (C) 2004 Compulab Ltd.
+ *
+ * Driver for MAX6902 spi RTC
+ *
+ * and based on:
+ * drivers/rtc/rtc-rx8581.c
+ *
+ * An I2C driver for the Epson RX8581 RTC
+ *
+ * Author: Martyn Welch <martyn.welch@ge.com>
+ * Copyright 2008 GE Intelligent Platforms Embedded Systems, Inc.
+ *
+ * Based on: rtc-pcf8563.c (An I2C driver for the Philips PCF8563 RTC)
+ * Copyright 2005-06 Tower Technologies
+ */
+
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/platform_device.h>
+#include <linux/init.h>
+#include <linux/rtc.h>
+#include <linux/spi/spi.h>
+#include <linux/bcd.h>
+
+#define RX4581_REG_SC		0x00 /* Second in BCD */
+#define RX4581_REG_MN		0x01 /* Minute in BCD */
+#define RX4581_REG_HR		0x02 /* Hour in BCD */
+#define RX4581_REG_DW		0x03 /* Day of Week */
+#define RX4581_REG_DM		0x04 /* Day of Month in BCD */
+#define RX4581_REG_MO		0x05 /* Month in BCD */
+#define RX4581_REG_YR		0x06 /* Year in BCD */
+#define RX4581_REG_RAM		0x07 /* RAM */
+#define RX4581_REG_AMN		0x08 /* Alarm Min in BCD*/
+#define RX4581_REG_AHR		0x09 /* Alarm Hour in BCD */
+#define RX4581_REG_ADM		0x0A
+#define RX4581_REG_ADW		0x0A
+#define RX4581_REG_TMR0		0x0B
+#define RX4581_REG_TMR1		0x0C
+#define RX4581_REG_EXT		0x0D /* Extension Register */
+#define RX4581_REG_FLAG		0x0E /* Flag Register */
+#define RX4581_REG_CTRL		0x0F /* Control Register */
+
+
+/* Flag Register bit definitions */
+#define RX4581_FLAG_UF		0x20 /* Update */
+#define RX4581_FLAG_TF		0x10 /* Timer */
+#define RX4581_FLAG_AF		0x08 /* Alarm */
+#define RX4581_FLAG_VLF		0x02 /* Voltage Low */
+
+/* Control Register bit definitions */
+#define RX4581_CTRL_UIE		0x20 /* Update Interrupt Enable */
+#define RX4581_CTRL_TIE		0x10 /* Timer Interrupt Enable */
+#define RX4581_CTRL_AIE		0x08 /* Alarm Interrupt Enable */
+#define RX4581_CTRL_STOP	0x02 /* STOP bit */
+#define RX4581_CTRL_RESET	0x01 /* RESET bit */
+
+static int rx4581_set_reg(struct device *dev, unsigned char address,
+				unsigned char data)
+{
+	struct spi_device *spi = to_spi_device(dev);
+	unsigned char buf[2];
+
+	/* high nibble must be '0' to write */
+	buf[0] = address & 0x0f;
+	buf[1] = data;
+
+	return spi_write_then_read(spi, buf, 2, NULL, 0);
+}
+
+static int rx4581_get_reg(struct device *dev, unsigned char address,
+				unsigned char *data)
+{
+	struct spi_device *spi = to_spi_device(dev);
+
+	/* Set MSB to indicate read */
+	*data = address | 0x80;
+
+	return spi_write_then_read(spi, data, 1, data, 1);
+}
+
+/*
+ * In the routines that deal directly with the rx8581 hardware, we use
+ * rtc_time -- month 0-11, hour 0-23, yr = calendar year-epoch.
+ */
+static int rx4581_get_datetime(struct device *dev, struct rtc_time *tm)
+{
+	struct spi_device *spi = to_spi_device(dev);
+	unsigned char date[7];
+	unsigned char data;
+	int err;
+
+	/* First we ensure that the "update flag" is not set, we read the
+	 * time and date then re-read the "update flag". If the update flag
+	 * has been set, we know that the time has changed during the read so
+	 * we repeat the whole process again.
+	 */
+	err = rx4581_get_reg(dev, RX4581_REG_FLAG, &data);
+	if (err != 0) {
+		dev_err(dev, "Unable to read device flags\n");
+		return -EIO;
+	}
+
+	do {
+		/* If update flag set, clear it */
+		if (data & RX4581_FLAG_UF) {
+			err = rx4581_set_reg(dev,
+				RX4581_REG_FLAG, (data & ~RX4581_FLAG_UF));
+			if (err != 0) {
+				dev_err(dev, "Unable to write device "
+					"flags\n");
+				return -EIO;
+			}
+		}
+
+		/* Now read time and date */
+		date[0] = 0x80;
+		err = spi_write_then_read(spi, date, 1, date, 7);
+		if (err < 0) {
+			dev_err(dev, "Unable to read date\n");
+			return -EIO;
+		}
+
+		/* Check flag register */
+		err = rx4581_get_reg(dev, RX4581_REG_FLAG, &data);
+		if (err != 0) {
+			dev_err(dev, "Unable to read device flags\n");
+			return -EIO;
+		}
+	} while (data & RX4581_FLAG_UF);
+
+	if (data & RX4581_FLAG_VLF)
+		dev_info(dev,
+			"low voltage detected, date/time is not reliable.\n");
+
+	dev_dbg(dev,
+		"%s: raw data is sec=%02x, min=%02x, hr=%02x, "
+		"wday=%02x, mday=%02x, mon=%02x, year=%02x\n",
+		__func__,
+		date[0], date[1], date[2], date[3], date[4], date[5], date[6]);
+
+	tm->tm_sec = bcd2bin(date[RX4581_REG_SC] & 0x7F);
+	tm->tm_min = bcd2bin(date[RX4581_REG_MN] & 0x7F);
+	tm->tm_hour = bcd2bin(date[RX4581_REG_HR] & 0x3F); /* rtc hr 0-23 */
+	tm->tm_wday = ilog2(date[RX4581_REG_DW] & 0x7F);
+	tm->tm_mday = bcd2bin(date[RX4581_REG_DM] & 0x3F);
+	tm->tm_mon = bcd2bin(date[RX4581_REG_MO] & 0x1F) - 1; /* rtc mn 1-12 */
+	tm->tm_year = bcd2bin(date[RX4581_REG_YR]);
+	if (tm->tm_year < 70)
+		tm->tm_year += 100;	/* assume we are in 1970...2069 */
+
+
+	dev_dbg(dev, "%s: tm is secs=%d, mins=%d, hours=%d, "
+		"mday=%d, mon=%d, year=%d, wday=%d\n",
+		__func__,
+		tm->tm_sec, tm->tm_min, tm->tm_hour,
+		tm->tm_mday, tm->tm_mon, tm->tm_year, tm->tm_wday);
+
+	return 0;
+}
+
+static int rx4581_set_datetime(struct device *dev, struct rtc_time *tm)
+{
+	struct spi_device *spi = to_spi_device(dev);
+	int err;
+	unsigned char buf[8], data;
+
+	dev_dbg(dev, "%s: secs=%d, mins=%d, hours=%d, "
+		"mday=%d, mon=%d, year=%d, wday=%d\n",
+		__func__,
+		tm->tm_sec, tm->tm_min, tm->tm_hour,
+		tm->tm_mday, tm->tm_mon, tm->tm_year, tm->tm_wday);
+
+	buf[0] = 0x00;
+	/* hours, minutes and seconds */
+	buf[RX4581_REG_SC+1] = bin2bcd(tm->tm_sec);
+	buf[RX4581_REG_MN+1] = bin2bcd(tm->tm_min);
+	buf[RX4581_REG_HR+1] = bin2bcd(tm->tm_hour);
+
+	buf[RX4581_REG_DM+1] = bin2bcd(tm->tm_mday);
+
+	/* month, 1 - 12 */
+	buf[RX4581_REG_MO+1] = bin2bcd(tm->tm_mon + 1);
+
+	/* year and century */
+	buf[RX4581_REG_YR+1] = bin2bcd(tm->tm_year % 100);
+	buf[RX4581_REG_DW+1] = (0x1 << tm->tm_wday);
+
+	/* Stop the clock */
+	err = rx4581_get_reg(dev, RX4581_REG_CTRL, &data);
+	if (err != 0) {
+		dev_err(dev, "Unable to read control register\n");
+		return -EIO;
+	}
+
+	err = rx4581_set_reg(dev, RX4581_REG_CTRL,
+		(data | RX4581_CTRL_STOP));
+	if (err != 0) {
+		dev_err(dev, "Unable to write control register\n");
+		return -EIO;
+	}
+
+	/* write register's data */
+	err = spi_write_then_read(spi, buf, 8, NULL, 0);
+	if (err != 0) {
+		dev_err(dev, "Unable to write to date registers\n");
+		return -EIO;
+	}
+
+	/* get VLF and clear it */
+	err = rx4581_get_reg(dev, RX4581_REG_FLAG, &data);
+	if (err != 0) {
+		dev_err(dev, "Unable to read flag register\n");
+		return -EIO;
+	}
+
+	err = rx4581_set_reg(dev, RX4581_REG_FLAG,
+		(data & ~(RX4581_FLAG_VLF)));
+	if (err != 0) {
+		dev_err(dev, "Unable to write flag register\n");
+		return -EIO;
+	}
+
+	/* Restart the clock */
+	err = rx4581_get_reg(dev, RX4581_REG_CTRL, &data);
+	if (err != 0) {
+		dev_err(dev, "Unable to read control register\n");
+		return -EIO;
+	}
+
+	err = rx4581_set_reg(dev, RX4581_REG_CTRL,
+		(data & ~(RX4581_CTRL_STOP)));
+	if (err != 0) {
+		dev_err(dev, "Unable to write control register\n");
+		return -EIO;
+	}
+
+	return 0;
+}
+
+static const struct rtc_class_ops rx4581_rtc_ops = {
+	.read_time	= rx4581_get_datetime,
+	.set_time	= rx4581_set_datetime,
+};
+
+static int rx4581_probe(struct spi_device *spi)
+{
+	struct rtc_device *rtc;
+	unsigned char tmp;
+	int res;
+
+	res = rx4581_get_reg(&spi->dev, RX4581_REG_SC, &tmp);
+	if (res != 0)
+		return res;
+
+	rtc = devm_rtc_device_register(&spi->dev, "rx4581",
+				&rx4581_rtc_ops, THIS_MODULE);
+	if (IS_ERR(rtc))
+		return PTR_ERR(rtc);
+
+	spi_set_drvdata(spi, rtc);
+	return 0;
+}
+
+static const struct spi_device_id rx4581_id[] = {
+	{ "rx4581", 0 },
+	{ }
+};
+MODULE_DEVICE_TABLE(spi, rx4581_id);
+
+static struct spi_driver rx4581_driver = {
+	.driver = {
+		.name	= "rtc-rx4581",
+	},
+	.probe	= rx4581_probe,
+	.id_table = rx4581_id,
+};
+
+module_spi_driver(rx4581_driver);
+
+MODULE_DESCRIPTION("rx4581 spi RTC driver");
+MODULE_AUTHOR("Torben Hohn");
+MODULE_LICENSE("GPL");
+MODULE_ALIAS("spi:rtc-rx4581");