Merge tag 'timers-core-2026-06-13' of gitolite.kernel.org:pub/scm/linux/kernel/git/tip/tip

Pull timer core updates from Thomas Gleixner:
 "Updates for the time/timer core subsystem:

   - Harden the user space controllable hrtimer interfaces further to
     protect against unpriviledged DoS attempts by arming timers in the
     past.

   - Add per-capacity hierarchies to the timer migration code to prevent
     timer migration accross different capacity domains. This code has
     been disabled last minute as there is a pathological problem with
     SoCs which advertise a larger number of capacity domains. The
     problem is under investigation and the code won't be active before
     v7.3, but that turned out to be less intrusive than a full revert
     as it preserves the preparatory steps and allows people to work on
     the final resolution

   - Export time namespace functionality as a recent user can be built
     as a module.

   - Initialize the jiffies clocksource before using it. The recent
     hardening against time moving backward requires that the related
     members of struct clocksource have been initialized, otherwise it
     clamps the readout to 0, which makes time stand sill and causes
     boot delays.

   - Fix a more than twenty year old PID reference count leak in an
     error path of the POSIX CPU timer code.

   - The usual small fixes, improvements and cleanups all over the
     place"

* tag 'timers-core-2026-06-13' of gitolite.kernel.org:pub/scm/linux/kernel/git/tip/tip: (31 commits)
  posix-cpu-timers: Fix pid refcount leak in do_cpu_nanosleep() error path
  time/jiffies: Register jiffies clocksource before usage
  timers/migration: Temporarily disable per capacity hierarchies
  timers/migration: Turn tmigr_hierarchy level_list into a flexible array
  timers/migration: Deactivate per-capacity hierarchies under nohz_full
  timers/migration: Fix hotplug migrator selection target on asymetric capacity machines
  ntsync: Honour caller's time namespace for absolute MONOTONIC timeouts
  time/namespace: Export init_time_ns and do_timens_ktime_to_host()
  timers/migration: Update stale @online doc to @available
  timers: Fix flseep() typo in kernel-doc comment
  hrtimer: Fix the bogus return type of __hrtimer_start_range_ns()
  hrtimer: Return ktime_t from hrtimer_get_next_event()/hrtimer_next_event_without()
  clocksource: Clean up clocksource_update_freq() functions
  alarmtimer: Remove stale return description from alarm_handle_timer()
  selftests/posix_timers: Use CLOCK_THREAD_CPUTIME_ID for ITIMER_PROF measurements
  scripts/timers: Add timer_migration_tree.py
  timers/migration: Handle capacity in connect tracepoints
  timers/migration: Split per-capacity hierarchies
  timers/migration: Track CPUs in a hierarchy
  timers/migration: Abstract out hierarchy to prepare for CPU capacity awareness
  ...

1 files changed, 28 insertions, 8 deletions

diff --git a/kernel/time/timer_migration.h b/kernel/time/timer_migration.h
index 70879cde6fdd..31735dd52327 100644
--- a/kernel/time/timer_migration.h
+++ b/kernel/time/timer_migration.h
@@ -6,6 +6,24 @@
 #define TMIGR_CHILDREN_PER_GROUP 8
 
 /**
+ * struct tmigr_hierarchy - a hierarchy associated to a given CPU capacity.
+ *                          Homogeneous systems have only one hierarchy.
+ *                          Heterogenous have one hierarchy per CPU capacity.
+ * @cpumask:	CPUs belonging to this hierarchy
+ * @root:	The current root of the hierarchy
+ * @capacity:	CPU capacity associated to this hierarchy
+ * @node:	Node in the global hierarchy list
+ * @level_list:	Per level lists of tmigr groups
+ */
+struct tmigr_hierarchy {
+	struct cpumask		*cpumask;
+	struct tmigr_group	*root;
+	unsigned long		capacity;
+	struct list_head	node;
+	struct list_head	level_list[];
+};
+
+/**
  * struct tmigr_event - a timer event associated to a CPU
  * @nextevt:	The node to enqueue an event in the parent group queue
  * @cpu:	The CPU to which this event belongs
@@ -75,15 +93,17 @@ struct tmigr_group {
 /**
  * struct tmigr_cpu - timer migration per CPU group
  * @lock:		Lock protecting the tmigr_cpu group information
- * @online:		Indicates whether the CPU is online; In deactivate path
- *			it is required to know whether the migrator in the top
- *			level group is to be set offline, while a timer is
- *			pending. Then another online CPU needs to be notified to
- *			take over the migrator role. Furthermore the information
- *			is required in CPU hotplug path as the CPU is able to go
- *			idle before the timer migration hierarchy hotplug AP is
- *			reached. During this phase, the CPU has to handle the
+ * @available:		Indicates whether the CPU is available for handling
+ *			global timers. In the deactivate path it is required to
+ *			know whether the migrator in the top level group is to
+ *			be set offline, while a timer is pending. Then another
+ *			available CPU needs to be notified to take over the
+ *			migrator role. Furthermore the information is required
+ *			in the CPU hotplug path as the CPU is able to go idle
+ *			before the timer migration hierarchy hotplug callback is
+ *			reached.  During this phase, the CPU has to handle the
  *			global timers on its own and must not act as a migrator.
+
  * @idle:		Indicates whether the CPU is idle in the timer migration
  *			hierarchy
  * @remote:		Is set when timers of the CPU are expired remotely