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, 264 insertions, 0 deletions

diff --git a/drivers/clocksource/timer-atmel-pit.c b/drivers/clocksource/timer-atmel-pit.c
new file mode 100644
index 000000000..888b06731
--- /dev/null
+++ b/drivers/clocksource/timer-atmel-pit.c
@@ -0,0 +1,264 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * at91sam926x_time.c - Periodic Interval Timer (PIT) for at91sam926x
+ *
+ * Copyright (C) 2005-2006 M. Amine SAYA, ATMEL Rousset, France
+ * Revision	 2005 M. Nicolas Diremdjian, ATMEL Rousset, France
+ * Converted to ClockSource/ClockEvents by David Brownell.
+ */
+
+#define pr_fmt(fmt)	"AT91: PIT: " fmt
+
+#include <linux/clk.h>
+#include <linux/clockchips.h>
+#include <linux/interrupt.h>
+#include <linux/irq.h>
+#include <linux/kernel.h>
+#include <linux/of.h>
+#include <linux/of_address.h>
+#include <linux/of_irq.h>
+#include <linux/slab.h>
+
+#define AT91_PIT_MR		0x00			/* Mode Register */
+#define AT91_PIT_PITIEN			BIT(25)			/* Timer Interrupt Enable */
+#define AT91_PIT_PITEN			BIT(24)			/* Timer Enabled */
+#define AT91_PIT_PIV			GENMASK(19, 0)		/* Periodic Interval Value */
+
+#define AT91_PIT_SR		0x04			/* Status Register */
+#define AT91_PIT_PITS			BIT(0)			/* Timer Status */
+
+#define AT91_PIT_PIVR		0x08			/* Periodic Interval Value Register */
+#define AT91_PIT_PIIR		0x0c			/* Periodic Interval Image Register */
+#define AT91_PIT_PICNT			GENMASK(31, 20)		/* Interval Counter */
+#define AT91_PIT_CPIV			GENMASK(19, 0)		/* Inverval Value */
+
+#define PIT_CPIV(x)	((x) & AT91_PIT_CPIV)
+#define PIT_PICNT(x)	(((x) & AT91_PIT_PICNT) >> 20)
+
+struct pit_data {
+	struct clock_event_device	clkevt;
+	struct clocksource		clksrc;
+
+	void __iomem	*base;
+	u32		cycle;
+	u32		cnt;
+	unsigned int	irq;
+	struct clk	*mck;
+};
+
+static inline struct pit_data *clksrc_to_pit_data(struct clocksource *clksrc)
+{
+	return container_of(clksrc, struct pit_data, clksrc);
+}
+
+static inline struct pit_data *clkevt_to_pit_data(struct clock_event_device *clkevt)
+{
+	return container_of(clkevt, struct pit_data, clkevt);
+}
+
+static inline unsigned int pit_read(void __iomem *base, unsigned int reg_offset)
+{
+	return readl_relaxed(base + reg_offset);
+}
+
+static inline void pit_write(void __iomem *base, unsigned int reg_offset, unsigned long value)
+{
+	writel_relaxed(value, base + reg_offset);
+}
+
+/*
+ * Clocksource:  just a monotonic counter of MCK/16 cycles.
+ * We don't care whether or not PIT irqs are enabled.
+ */
+static u64 read_pit_clk(struct clocksource *cs)
+{
+	struct pit_data *data = clksrc_to_pit_data(cs);
+	unsigned long flags;
+	u32 elapsed;
+	u32 t;
+
+	raw_local_irq_save(flags);
+	elapsed = data->cnt;
+	t = pit_read(data->base, AT91_PIT_PIIR);
+	raw_local_irq_restore(flags);
+
+	elapsed += PIT_PICNT(t) * data->cycle;
+	elapsed += PIT_CPIV(t);
+	return elapsed;
+}
+
+static int pit_clkevt_shutdown(struct clock_event_device *dev)
+{
+	struct pit_data *data = clkevt_to_pit_data(dev);
+
+	/* disable irq, leaving the clocksource active */
+	pit_write(data->base, AT91_PIT_MR, (data->cycle - 1) | AT91_PIT_PITEN);
+	return 0;
+}
+
+/*
+ * Clockevent device:  interrupts every 1/HZ (== pit_cycles * MCK/16)
+ */
+static int pit_clkevt_set_periodic(struct clock_event_device *dev)
+{
+	struct pit_data *data = clkevt_to_pit_data(dev);
+
+	/* update clocksource counter */
+	data->cnt += data->cycle * PIT_PICNT(pit_read(data->base, AT91_PIT_PIVR));
+	pit_write(data->base, AT91_PIT_MR,
+		  (data->cycle - 1) | AT91_PIT_PITEN | AT91_PIT_PITIEN);
+	return 0;
+}
+
+static void at91sam926x_pit_suspend(struct clock_event_device *cedev)
+{
+	struct pit_data *data = clkevt_to_pit_data(cedev);
+
+	/* Disable timer */
+	pit_write(data->base, AT91_PIT_MR, 0);
+}
+
+static void at91sam926x_pit_reset(struct pit_data *data)
+{
+	/* Disable timer and irqs */
+	pit_write(data->base, AT91_PIT_MR, 0);
+
+	/* Clear any pending interrupts, wait for PIT to stop counting */
+	while (PIT_CPIV(pit_read(data->base, AT91_PIT_PIVR)) != 0)
+		cpu_relax();
+
+	/* Start PIT but don't enable IRQ */
+	pit_write(data->base, AT91_PIT_MR,
+		  (data->cycle - 1) | AT91_PIT_PITEN);
+}
+
+static void at91sam926x_pit_resume(struct clock_event_device *cedev)
+{
+	struct pit_data *data = clkevt_to_pit_data(cedev);
+
+	at91sam926x_pit_reset(data);
+}
+
+/*
+ * IRQ handler for the timer.
+ */
+static irqreturn_t at91sam926x_pit_interrupt(int irq, void *dev_id)
+{
+	struct pit_data *data = dev_id;
+
+	/* The PIT interrupt may be disabled, and is shared */
+	if (clockevent_state_periodic(&data->clkevt) &&
+	    (pit_read(data->base, AT91_PIT_SR) & AT91_PIT_PITS)) {
+		/* Get number of ticks performed before irq, and ack it */
+		data->cnt += data->cycle * PIT_PICNT(pit_read(data->base,
+							      AT91_PIT_PIVR));
+		data->clkevt.event_handler(&data->clkevt);
+
+		return IRQ_HANDLED;
+	}
+
+	return IRQ_NONE;
+}
+
+/*
+ * Set up both clocksource and clockevent support.
+ */
+static int __init at91sam926x_pit_dt_init(struct device_node *node)
+{
+	unsigned long   pit_rate;
+	unsigned        bits;
+	int             ret;
+	struct pit_data *data;
+
+	data = kzalloc_obj(*data);
+	if (!data)
+		return -ENOMEM;
+
+	data->base = of_iomap(node, 0);
+	if (!data->base) {
+		pr_err("Could not map PIT address\n");
+		ret = -ENXIO;
+		goto exit;
+	}
+
+	data->mck = of_clk_get(node, 0);
+	if (IS_ERR(data->mck)) {
+		pr_err("Unable to get mck clk\n");
+		ret = PTR_ERR(data->mck);
+		goto exit;
+	}
+
+	ret = clk_prepare_enable(data->mck);
+	if (ret) {
+		pr_err("Unable to enable mck\n");
+		goto exit;
+	}
+
+	/* Get the interrupts property */
+	data->irq = irq_of_parse_and_map(node, 0);
+	if (!data->irq) {
+		pr_err("Unable to get IRQ from DT\n");
+		ret = -EINVAL;
+		goto exit;
+	}
+
+	/*
+	 * Use our actual MCK to figure out how many MCK/16 ticks per
+	 * 1/HZ period (instead of a compile-time constant LATCH).
+	 */
+	pit_rate = clk_get_rate(data->mck) / 16;
+	data->cycle = DIV_ROUND_CLOSEST(pit_rate, HZ);
+	WARN_ON(((data->cycle - 1) & ~AT91_PIT_PIV) != 0);
+
+	/* Initialize and enable the timer */
+	at91sam926x_pit_reset(data);
+
+	/*
+	 * Register clocksource.  The high order bits of PIV are unused,
+	 * so this isn't a 32-bit counter unless we get clockevent irqs.
+	 */
+	bits = 12 /* PICNT */ + ilog2(data->cycle) /* PIV */;
+	data->clksrc.mask = CLOCKSOURCE_MASK(bits);
+	data->clksrc.name = "pit";
+	data->clksrc.rating = 175;
+	data->clksrc.read = read_pit_clk;
+	data->clksrc.flags = CLOCK_SOURCE_IS_CONTINUOUS;
+	
+	ret = clocksource_register_hz(&data->clksrc, pit_rate);
+	if (ret) {
+		pr_err("Failed to register clocksource\n");
+		goto exit;
+	}
+
+	/* Set up irq handler */
+	ret = request_irq(data->irq, at91sam926x_pit_interrupt,
+			  IRQF_SHARED | IRQF_TIMER | IRQF_IRQPOLL,
+			  "at91_tick", data);
+	if (ret) {
+		pr_err("Unable to setup IRQ\n");
+		clocksource_unregister(&data->clksrc);
+		goto exit;
+	}
+
+	/* Set up and register clockevents */
+	data->clkevt.name = "pit";
+	data->clkevt.features = CLOCK_EVT_FEAT_PERIODIC;
+	data->clkevt.shift = 32;
+	data->clkevt.mult = div_sc(pit_rate, NSEC_PER_SEC, data->clkevt.shift);
+	data->clkevt.rating = 100;
+	data->clkevt.cpumask = cpumask_of(0);
+
+	data->clkevt.set_state_shutdown = pit_clkevt_shutdown;
+	data->clkevt.set_state_periodic = pit_clkevt_set_periodic;
+	data->clkevt.resume = at91sam926x_pit_resume;
+	data->clkevt.suspend = at91sam926x_pit_suspend;
+	clockevents_register_device(&data->clkevt);
+
+	return 0;
+
+exit:
+	kfree(data);
+	return ret;
+}
+TIMER_OF_DECLARE(at91sam926x_pit, "atmel,at91sam9260-pit",
+		       at91sam926x_pit_dt_init);