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, 124 insertions, 0 deletions

diff --git a/tools/perf/util/parse-regs-options.c b/tools/perf/util/parse-regs-options.c
new file mode 100644
index 000000000..c93c2f0c8
--- /dev/null
+++ b/tools/perf/util/parse-regs-options.c
@@ -0,0 +1,124 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <stdbool.h>
+#include <stdlib.h>
+#include <stdint.h>
+#include <string.h>
+#include <stdio.h>
+#include "util/debug.h"
+#include <dwarf-regs.h>
+#include <subcmd/parse-options.h>
+#include "util/perf_regs.h"
+#include "util/parse-regs-options.h"
+
+static void list_perf_regs(FILE *fp, uint64_t mask)
+{
+	const char *last_name = NULL;
+
+	fprintf(fp, "available registers: ");
+	for (int reg = 0; reg < 64; reg++) {
+		const char *name;
+
+		if (((1ULL << reg) & mask) == 0)
+			continue;
+
+		name = perf_reg_name(reg, EM_HOST, EF_HOST);
+		if (name && (!last_name || strcmp(last_name, name)))
+			fprintf(fp, "%s%s", reg > 0 ? " " : "", name);
+		last_name = name;
+	}
+	fputc('\n', fp);
+}
+
+static uint64_t name_to_perf_reg_mask(const char *to_match, uint64_t mask)
+{
+	uint64_t reg_mask = 0;
+
+	for (int reg = 0; reg < 64; reg++) {
+		const char *name;
+
+		if (((1ULL << reg) & mask) == 0)
+			continue;
+
+		name = perf_reg_name(reg, EM_HOST, EF_HOST);
+		if (!name)
+			continue;
+
+		if (!strcasecmp(to_match, name))
+			reg_mask |= 1ULL << reg;
+	}
+	return reg_mask;
+}
+
+static int
+__parse_regs(const struct option *opt, const char *str, int unset, bool intr)
+{
+	uint64_t *mode = (uint64_t *)opt->value;
+	char *s, *os = NULL, *p;
+	int ret = -1;
+	uint64_t mask;
+
+	if (unset)
+		return 0;
+
+	/*
+	 * cannot set it twice
+	 */
+	if (*mode)
+		return -1;
+
+	mask = intr ? perf_intr_reg_mask(EM_HOST) : perf_user_reg_mask(EM_HOST);
+
+	/* str may be NULL in case no arg is passed to -I */
+	if (!str) {
+		*mode = mask;
+		return 0;
+	}
+
+	/* because str is read-only */
+	s = os = strdup(str);
+	if (!s)
+		return -1;
+
+	for (;;) {
+		uint64_t reg_mask;
+
+		p = strchr(s, ',');
+		if (p)
+			*p = '\0';
+
+		if (!strcmp(s, "?")) {
+			list_perf_regs(stderr, mask);
+			goto error;
+		}
+
+		reg_mask = name_to_perf_reg_mask(s, mask);
+		if (reg_mask == 0) {
+			ui__warning("Unknown register \"%s\", check man page or run \"perf record %s?\"\n",
+				s, intr ? "-I" : "--user-regs=");
+			goto error;
+		}
+		*mode |= reg_mask;
+
+		if (!p)
+			break;
+
+		s = p + 1;
+	}
+	ret = 0;
+
+error:
+	free(os);
+	return ret;
+}
+
+int
+parse_user_regs(const struct option *opt, const char *str, int unset)
+{
+	return __parse_regs(opt, str, unset, false);
+}
+
+int
+parse_intr_regs(const struct option *opt, const char *str, int unset)
+{
+	return __parse_regs(opt, str, unset, true);
+}