Merge tag 'timers-core-2025-11-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

Pull timer core updates from Thomas Gleixner:

 - Prevent a thundering herd problem when the timekeeper CPU is delayed
   and a large number of CPUs compete to acquire jiffies_lock to do the
   update. Limit it to one CPU with a separate "uncontended" atomic
   variable.

 - A set of improvements for the timer migration mechanism:

     - Support imbalanced NUMA trees correctly

     - Support dynamic exclusion of CPUs from the migrator duty to allow
       the cpuset/isolation mechanism to exclude them from handling
       timers of remote idle CPUs

 - The usual small updates, cleanups and enhancements

* tag 'timers-core-2025-11-30' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  timers/migration: Exclude isolated cpus from hierarchy
  cpumask: Add initialiser to use cleanup helpers
  sched/isolation: Force housekeeping if isolcpus and nohz_full don't leave any
  cgroup/cpuset: Rename update_unbound_workqueue_cpumask() to update_isolation_cpumasks()
  timers/migration: Use scoped_guard on available flag set/clear
  timers/migration: Add mask for CPUs available in the hierarchy
  timers/migration: Rename 'online' bit to 'available'
  selftests/timers/nanosleep: Add tests for return of remaining time
  selftests/timers: Clean up kernel version check in posix_timers
  time: Fix a few typos in time[r] related code comments
  time: tick-oneshot: Add missing Return and parameter descriptions to kernel-doc
  hrtimer: Store time as ktime_t in restart block
  timers/migration: Remove dead code handling idle CPU checking for remote timers
  timers/migration: Remove unused "cpu" parameter from tmigr_get_group()
  timers/migration: Assert that hotplug preparing CPU is part of stable active hierarchy
  timers/migration: Fix imbalanced NUMA trees
  timers/migration: Remove locking on group connection
  timers/migration: Convert "while" loops to use "for"
  tick/sched: Limit non-timekeeper CPUs calling jiffies update

2 files changed, 77 insertions, 10 deletions

diff --git a/tools/testing/selftests/timers/nanosleep.c b/tools/testing/selftests/timers/nanosleep.c
index 252c6308c569..10badae13ebe 100644
--- a/tools/testing/selftests/timers/nanosleep.c
+++ b/tools/testing/selftests/timers/nanosleep.c
@@ -116,6 +116,56 @@ int nanosleep_test(int clockid, long long ns)
 	return 0;
 }
 
+static void dummy_event_handler(int val)
+{
+	/* No action needed */
+}
+
+static int nanosleep_test_remaining(int clockid)
+{
+	struct timespec rqtp = {}, rmtp = {};
+	struct itimerspec itimer = {};
+	struct sigaction sa = {};
+	timer_t timer;
+	int ret;
+
+	sa.sa_handler = dummy_event_handler;
+	ret = sigaction(SIGALRM, &sa, NULL);
+	if (ret)
+		return -1;
+
+	ret = timer_create(clockid, NULL, &timer);
+	if (ret)
+		return -1;
+
+	itimer.it_value.tv_nsec = NSEC_PER_SEC / 4;
+	ret = timer_settime(timer, 0, &itimer, NULL);
+	if (ret)
+		return -1;
+
+	rqtp.tv_nsec = NSEC_PER_SEC / 2;
+	ret = clock_nanosleep(clockid, 0, &rqtp, &rmtp);
+	if (ret != EINTR)
+		return -1;
+
+	ret = timer_delete(timer);
+	if (ret)
+		return -1;
+
+	sa.sa_handler = SIG_DFL;
+	ret = sigaction(SIGALRM, &sa, NULL);
+	if (ret)
+		return -1;
+
+	if (!in_order((struct timespec) {}, rmtp))
+		return -1;
+
+	if (!in_order(rmtp, rqtp))
+		return -1;
+
+	return 0;
+}
+
 int main(int argc, char **argv)
 {
 	long long length;
@@ -150,6 +200,11 @@ int main(int argc, char **argv)
 			}
 			length *= 100;
 		}
+		ret = nanosleep_test_remaining(clockid);
+		if (ret < 0) {
+			ksft_test_result_fail("%-31s\n", clockstring(clockid));
+			ksft_exit_fail();
+		}
 		ksft_test_result_pass("%-31s\n", clockstring(clockid));
 next:
 		ret = 0;
diff --git a/tools/testing/selftests/timers/posix_timers.c b/tools/testing/selftests/timers/posix_timers.c
index f0eceb0faf34..a563c438ac79 100644
--- a/tools/testing/selftests/timers/posix_timers.c
+++ b/tools/testing/selftests/timers/posix_timers.c
@@ -18,6 +18,7 @@
 #include <time.h>
 #include <include/vdso/time64.h>
 #include <pthread.h>
+#include <stdbool.h>
 
 #include "../kselftest.h"
 
@@ -670,8 +671,14 @@ static void check_timer_create_exact(void)
 
 int main(int argc, char **argv)
 {
+	bool run_sig_ign_tests = ksft_min_kernel_version(6, 13);
+
 	ksft_print_header();
-	ksft_set_plan(19);
+	if (run_sig_ign_tests) {
+		ksft_set_plan(19);
+	} else {
+		ksft_set_plan(10);
+	}
 
 	ksft_print_msg("Testing posix timers. False negative may happen on CPU execution \n");
 	ksft_print_msg("based timers if other threads run on the CPU...\n");
@@ -695,15 +702,20 @@ int main(int argc, char **argv)
 	check_timer_create(CLOCK_PROCESS_CPUTIME_ID, "CLOCK_PROCESS_CPUTIME_ID");
 	check_timer_distribution();
 
-	check_sig_ign(0);
-	check_sig_ign(1);
-	check_rearm();
-	check_delete();
-	check_sigev_none(CLOCK_MONOTONIC, "CLOCK_MONOTONIC");
-	check_sigev_none(CLOCK_PROCESS_CPUTIME_ID, "CLOCK_PROCESS_CPUTIME_ID");
-	check_gettime(CLOCK_MONOTONIC, "CLOCK_MONOTONIC");
-	check_gettime(CLOCK_PROCESS_CPUTIME_ID, "CLOCK_PROCESS_CPUTIME_ID");
-	check_gettime(CLOCK_THREAD_CPUTIME_ID, "CLOCK_THREAD_CPUTIME_ID");
+	if (run_sig_ign_tests) {
+		check_sig_ign(0);
+		check_sig_ign(1);
+		check_rearm();
+		check_delete();
+		check_sigev_none(CLOCK_MONOTONIC, "CLOCK_MONOTONIC");
+		check_sigev_none(CLOCK_PROCESS_CPUTIME_ID, "CLOCK_PROCESS_CPUTIME_ID");
+		check_gettime(CLOCK_MONOTONIC, "CLOCK_MONOTONIC");
+		check_gettime(CLOCK_PROCESS_CPUTIME_ID, "CLOCK_PROCESS_CPUTIME_ID");
+		check_gettime(CLOCK_THREAD_CPUTIME_ID, "CLOCK_THREAD_CPUTIME_ID");
+	} else {
+		ksft_print_msg("Skipping SIG_IGN tests on kernel < 6.13\n");
+	}
+
 	check_overrun(CLOCK_MONOTONIC, "CLOCK_MONOTONIC");
 	check_overrun(CLOCK_PROCESS_CPUTIME_ID, "CLOCK_PROCESS_CPUTIME_ID");
 	check_overrun(CLOCK_THREAD_CPUTIME_ID, "CLOCK_THREAD_CPUTIME_ID");