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, 164 insertions, 0 deletions

diff --git a/tools/perf/tests/keep-tracking.c b/tools/perf/tests/keep-tracking.c
new file mode 100644
index 000000000..729cc9cc1
--- /dev/null
+++ b/tools/perf/tests/keep-tracking.c
@@ -0,0 +1,164 @@
+// SPDX-License-Identifier: GPL-2.0
+#include <linux/types.h>
+#include <limits.h>
+#include <unistd.h>
+#include <sys/prctl.h>
+#include <perf/cpumap.h>
+#include <perf/evlist.h>
+#include <perf/mmap.h>
+
+#include "debug.h"
+#include "parse-events.h"
+#include "evlist.h"
+#include "evsel.h"
+#include "record.h"
+#include "thread_map.h"
+#include "tests.h"
+#include "util/mmap.h"
+
+#define CHECK__(x) {				\
+	while ((x) < 0) {			\
+		pr_debug(#x " failed!\n");	\
+		goto out_err;			\
+	}					\
+}
+
+#define CHECK_NOT_NULL__(x) {			\
+	while ((x) == NULL) {			\
+		pr_debug(#x " failed!\n");	\
+		goto out_err;			\
+	}					\
+}
+
+static int find_comm(struct evlist *evlist, const char *comm)
+{
+	union perf_event *event;
+	struct mmap *md;
+	int i, found;
+
+	found = 0;
+	for (i = 0; i < evlist->core.nr_mmaps; i++) {
+		md = &evlist->mmap[i];
+		if (perf_mmap__read_init(&md->core) < 0)
+			continue;
+		while ((event = perf_mmap__read_event(&md->core)) != NULL) {
+			if (event->header.type == PERF_RECORD_COMM &&
+			    (pid_t)event->comm.pid == getpid() &&
+			    (pid_t)event->comm.tid == getpid() &&
+			    strcmp(event->comm.comm, comm) == 0)
+				found += 1;
+			perf_mmap__consume(&md->core);
+		}
+		perf_mmap__read_done(&md->core);
+	}
+	return found;
+}
+
+/**
+ * test__keep_tracking - test using a dummy software event to keep tracking.
+ *
+ * This function implements a test that checks that tracking events continue
+ * when an event is disabled but a dummy software event is not disabled.  If the
+ * test passes %0 is returned, otherwise %-1 is returned.
+ */
+static int test__keep_tracking(struct test_suite *test __maybe_unused, int subtest __maybe_unused)
+{
+	struct record_opts opts = {
+		.mmap_pages	     = UINT_MAX,
+		.user_freq	     = UINT_MAX,
+		.user_interval	     = ULLONG_MAX,
+		.target		     = {
+			.uses_mmap   = true,
+		},
+	};
+	struct perf_thread_map *threads = NULL;
+	struct perf_cpu_map *cpus = NULL;
+	struct evlist *evlist = NULL;
+	struct evsel *evsel = NULL;
+	int found, err = -1;
+	const char *comm;
+
+	threads = thread_map__new_by_tid(getpid());
+	CHECK_NOT_NULL__(threads);
+
+	cpus = perf_cpu_map__new_online_cpus();
+	CHECK_NOT_NULL__(cpus);
+
+	evlist = evlist__new();
+	CHECK_NOT_NULL__(evlist);
+
+	perf_evlist__set_maps(&evlist->core, cpus, threads);
+
+	CHECK__(parse_event(evlist, "dummy:u"));
+	CHECK__(parse_event(evlist, "cpu-cycles:u"));
+
+	evlist__config(evlist, &opts, NULL);
+
+	evsel = evlist__first(evlist);
+
+	evsel->core.attr.comm = 1;
+	evsel->core.attr.disabled = 1;
+	evsel->core.attr.enable_on_exec = 0;
+
+	if (evlist__open(evlist) < 0) {
+		pr_debug("Unable to open dummy and cycles event\n");
+		err = TEST_SKIP;
+		goto out_err;
+	}
+
+	CHECK__(evlist__mmap(evlist, UINT_MAX));
+
+	/*
+	 * First, test that a 'comm' event can be found when the event is
+	 * enabled.
+	 */
+
+	evlist__enable(evlist);
+
+	comm = "Test COMM 1";
+	CHECK__(prctl(PR_SET_NAME, (unsigned long)comm, 0, 0, 0));
+
+	evlist__disable(evlist);
+
+	found = find_comm(evlist, comm);
+	if (found != 1) {
+		pr_debug("First time, failed to find tracking event.\n");
+		goto out_err;
+	}
+
+	/*
+	 * Secondly, test that a 'comm' event can be found when the event is
+	 * disabled with the dummy event still enabled.
+	 */
+
+	evlist__enable(evlist);
+
+	evsel = evlist__last(evlist);
+
+	CHECK__(evsel__disable(evsel));
+
+	comm = "Test COMM 2";
+	CHECK__(prctl(PR_SET_NAME, (unsigned long)comm, 0, 0, 0));
+
+	evlist__disable(evlist);
+
+	found = find_comm(evlist, comm);
+	if (found != 1) {
+		pr_debug("Second time, failed to find tracking event.\n");
+		goto out_err;
+	}
+
+	err = 0;
+
+out_err:
+	if (evlist) {
+		evlist__disable(evlist);
+		evlist__delete(evlist);
+	}
+	perf_cpu_map__put(cpus);
+	perf_thread_map__put(threads);
+
+	return err;
+}
+
+DEFINE_SUITE("Use a dummy software event to keep tracking", keep_tracking);