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, 97 insertions, 0 deletions

diff --git a/arch/powerpc/boot/opal.c b/arch/powerpc/boot/opal.c
new file mode 100644
index 000000000..b69818ce5
--- /dev/null
+++ b/arch/powerpc/boot/opal.c
@@ -0,0 +1,97 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (c) 2016 IBM Corporation.
+ */
+
+#include "ops.h"
+#include "stdio.h"
+#include "io.h"
+#include <libfdt.h>
+#include "../include/asm/opal-api.h"
+
+/* Global OPAL struct used by opal-call.S */
+struct opal {
+	u64 base;
+	u64 entry;
+} opal;
+
+static u32 opal_con_id;
+
+/* see opal-wrappers.S */
+int64_t opal_console_write(int64_t term_number, u64 *length, const u8 *buffer);
+int64_t opal_console_read(int64_t term_number, uint64_t *length, u8 *buffer);
+int64_t opal_console_write_buffer_space(uint64_t term_number, uint64_t *length);
+int64_t opal_console_flush(uint64_t term_number);
+int64_t opal_poll_events(uint64_t *outstanding_event_mask);
+
+void opal_kentry(unsigned long fdt_addr, void *vmlinux_addr);
+
+static int opal_con_open(void)
+{
+	/*
+	 * When OPAL loads the boot kernel it stashes the OPAL base and entry
+	 * address in r8 and r9 so the kernel can use the OPAL console
+	 * before unflattening the devicetree. While executing the wrapper will
+	 * probably trash r8 and r9 so this kentry hook restores them before
+	 * entering the decompressed kernel.
+	 */
+	platform_ops.kentry = opal_kentry;
+	return 0;
+}
+
+static void opal_con_putc(unsigned char c)
+{
+	int64_t rc;
+	uint64_t olen, len;
+
+	do {
+		rc = opal_console_write_buffer_space(opal_con_id, &olen);
+		len = be64_to_cpu(olen);
+		if (rc)
+			return;
+		opal_poll_events(NULL);
+	} while (len < 1);
+
+
+	olen = cpu_to_be64(1);
+	opal_console_write(opal_con_id, &olen, &c);
+}
+
+static void opal_con_close(void)
+{
+	opal_console_flush(opal_con_id);
+}
+
+static void opal_init(void)
+{
+	void *opal_node;
+
+	opal_node = finddevice("/ibm,opal");
+	if (!opal_node)
+		return;
+	if (getprop(opal_node, "opal-base-address", &opal.base, sizeof(u64)) < 0)
+		return;
+	opal.base = be64_to_cpu(opal.base);
+	if (getprop(opal_node, "opal-entry-address", &opal.entry, sizeof(u64)) < 0)
+		return;
+	opal.entry = be64_to_cpu(opal.entry);
+}
+
+int opal_console_init(void *devp, struct serial_console_data *scdp)
+{
+	opal_init();
+
+	if (devp) {
+		int n = getprop(devp, "reg", &opal_con_id, sizeof(u32));
+		if (n != sizeof(u32))
+			return -1;
+		opal_con_id = be32_to_cpu(opal_con_id);
+	} else
+		opal_con_id = 0;
+
+	scdp->open = opal_con_open;
+	scdp->putc = opal_con_putc;
+	scdp->close = opal_con_close;
+
+	return 0;
+}