linux-stable.git/kernel/time/hrtimer.c, branch linux-5.15.y

hrtimer: Fix trace oddity

2026-03-04T12:19:24+00:00

[ Upstream commit 5d6446f409da00e5a389125ddb5ce09f5bc404c9 ]

It turns out that __run_hrtimer() will trace like:

          -0     [032] d.h2. 20705.474563: hrtimer_cancel:       hrtimer=0xff2db8f77f8226e8
          -0     [032] d.h1. 20705.474563: hrtimer_expire_entry: hrtimer=0xff2db8f77f8226e8 now=20699452001850 function=tick_nohz_handler/0x0

Which is a bit nonsensical, the timer doesn't get canceled on
expiration. The cause is the use of the incorrect debug helper.

Fixes: c6a2a1770245 ("hrtimer: Add tracepoint for hrtimers")
Reported-by: Peter Zijlstra (Intel) 
Signed-off-by: Thomas Gleixner 
Signed-off-by: Peter Zijlstra (Intel) 
Link: https://patch.msgid.link/20260121143208.219595606@infradead.org
Signed-off-by: Sasha Levin

hrtimer: Fix softirq base check in update_needs_ipi()

2026-02-06T15:41:48+00:00

commit 05dc4a9fc8b36d4c99d76bbc02aa9ec0132de4c2 upstream.

The 'clockid' field is not the correct way to check for a softirq base.

Fix the check to correctly compare the base type instead of the clockid.

Fixes: 1e7f7fbcd40c ("hrtimer: Avoid more SMP function calls in clock_was_set()")
Signed-off-by: Thomas Weißschuh 
Signed-off-by: Thomas Gleixner 
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260107-hrtimer-clock-base-check-v1-1-afb5dbce94a1@linutronix.de
Signed-off-by: Greg Kroah-Hartman

hrtimers: Unconditionally update target CPU base after offline timer migration

2025-10-02T11:39:04+00:00

[ Upstream commit e895f8e29119c8c966ea794af9e9100b10becb88 ]

When testing softirq based hrtimers on an ARM32 board, with high resolution
mode and NOHZ inactive, softirq based hrtimers fail to expire after being
moved away from an offline CPU:

CPU0				CPU1
				hrtimer_start(..., HRTIMER_MODE_SOFT);
cpu_down(CPU1)			...
				hrtimers_cpu_dying()
				  // Migrate timers to CPU0
				  smp_call_function_single(CPU0, returgger_next_event);
  retrigger_next_event()
    if (!highres && !nohz)
        return;

As retrigger_next_event() is a NOOP when both high resolution timers and
NOHZ are inactive CPU0's hrtimer_cpu_base::softirq_expires_next is not
updated and the migrated softirq timers never expire unless there is a
softirq based hrtimer queued on CPU0 later.

Fix this by removing the hrtimer_hres_active() and tick_nohz_active() check
in retrigger_next_event(), which enforces a full update of the CPU base.
As this is not a fast path the extra cost does not matter.

[ tglx: Massaged change log ]

Fixes: 5c0930ccaad5 ("hrtimers: Push pending hrtimers away from outgoing CPU earlier")
Co-developed-by: Frederic Weisbecker 
Signed-off-by: Frederic Weisbecker 
Signed-off-by: Xiongfeng Wang 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/all/20250805081025.54235-1-wangxiongfeng2@huawei.com
Signed-off-by: Sasha Levin

hrtimer: Rename __hrtimer_hres_active() to hrtimer_hres_active()

2025-10-02T11:39:04+00:00

[ Upstream commit b7c8e1f8a7b4352c1d0b4310686385e3cf6c104a ]

The function hrtimer_hres_active() are defined in the hrtimer.c file, but
not called elsewhere, so rename __hrtimer_hres_active() to
hrtimer_hres_active() and remove the old hrtimer_hres_active() function.

kernel/time/hrtimer.c:653:19: warning: unused function 'hrtimer_hres_active'.

Fixes: 82ccdf062a64 ("hrtimer: Remove unused function")
Reported-by: Abaci Robot 
Signed-off-by: Jiapeng Chong 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Anna-Maria Behnsen 
Link: https://lore.kernel.org/r/20240418023000.130324-1-jiapeng.chong@linux.alibaba.com
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=8778
Stable-dep-of: e895f8e29119 ("hrtimers: Unconditionally update target CPU base after offline timer migration")
Signed-off-by: Sasha Levin

hrtimer: Remove unused function

2025-10-02T11:39:04+00:00

[ Upstream commit 82ccdf062a64f3c4ac575c16179ce68edbbbe8e4 ]

The function is defined, but not called anywhere:

  kernel/time/hrtimer.c:1880:20: warning: unused function '__hrtimer_peek_ahead_timers'.

Remove it.

Reported-by: Abaci Robot 
Signed-off-by: Jiapeng Chong 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20240322070441.29646-1-jiapeng.chong@linux.alibaba.com
Closes: https://bugzilla.openanolis.cn/show_bug.cgi?id=8611
Stable-dep-of: e895f8e29119 ("hrtimers: Unconditionally update target CPU base after offline timer migration")
Signed-off-by: Sasha Levin

hrtimers: Mark is_migration_base() with __always_inline

2025-04-10T12:31:50+00:00

[ Upstream commit 27af31e44949fa85550176520ef7086a0d00fd7b ]

When is_migration_base() is unused, it prevents kernel builds
with clang, `make W=1` and CONFIG_WERROR=y:

kernel/time/hrtimer.c:156:20: error: unused function 'is_migration_base' [-Werror,-Wunused-function]
  156 | static inline bool is_migration_base(struct hrtimer_clock_base *base)
      |                    ^~~~~~~~~~~~~~~~~

Fix this by marking it with __always_inline.

[ tglx: Use __always_inline instead of __maybe_unused and move it into the
  	usage sites conditional ]

Signed-off-by: Andy Shevchenko 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/all/20250116160745.243358-1-andriy.shevchenko@linux.intel.com
Signed-off-by: Sasha Levin

hrtimers: Handle CPU state correctly on hotplug

2025-01-23T16:16:02+00:00

commit 2f8dea1692eef2b7ba6a256246ed82c365fdc686 upstream.

Consider a scenario where a CPU transitions from CPUHP_ONLINE to halfway
through a CPU hotunplug down to CPUHP_HRTIMERS_PREPARE, and then back to
CPUHP_ONLINE:

Since hrtimers_prepare_cpu() does not run, cpu_base.hres_active remains set
to 1 throughout. However, during a CPU unplug operation, the tick and the
clockevents are shut down at CPUHP_AP_TICK_DYING. On return to the online
state, for instance CFS incorrectly assumes that the hrtick is already
active, and the chance of the clockevent device to transition to oneshot
mode is also lost forever for the CPU, unless it goes back to a lower state
than CPUHP_HRTIMERS_PREPARE once.

This round-trip reveals another issue; cpu_base.online is not set to 1
after the transition, which appears as a WARN_ON_ONCE in enqueue_hrtimer().

Aside of that, the bulk of the per CPU state is not reset either, which
means there are dangling pointers in the worst case.

Address this by adding a corresponding startup() callback, which resets the
stale per CPU state and sets the online flag.

[ tglx: Make the new callback unconditionally available, remove the online
  	modification in the prepare() callback and clear the remaining
  	state in the starting callback instead of the prepare callback ]

Fixes: 5c0930ccaad5 ("hrtimers: Push pending hrtimers away from outgoing CPU earlier")
Signed-off-by: Koichiro Den 
Signed-off-by: Thomas Gleixner 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/all/20241220134421.3809834-1-koichiro.den@canonical.com
Signed-off-by: Greg Kroah-Hartman

hrtimer: Prevent queuing of hrtimer without a function callback

2024-09-04T11:23:28+00:00

[ Upstream commit 5a830bbce3af16833fe0092dec47b6dd30279825 ]

The hrtimer function callback must not be NULL. It has to be specified by
the call side but it is not validated by the hrtimer code. When a hrtimer
is queued without a function callback, the kernel crashes with a null
pointer dereference when trying to execute the callback in __run_hrtimer().

Introduce a validation before queuing the hrtimer in
hrtimer_start_range_ns().

[anna-maria: Rephrase commit message]

Signed-off-by: Phil Chang 
Signed-off-by: Anna-Maria Behnsen 
Signed-off-by: Thomas Gleixner 
Reviewed-by: Anna-Maria Behnsen 
Signed-off-by: Sasha Levin

hrtimer: Ignore slack time for RT tasks in schedule_hrtimeout_range()

2024-02-23T07:55:14+00:00

commit 0c52310f260014d95c1310364379772cb74cf82d upstream.

While in theory the timer can be triggered before expires + delta, for the
cases of RT tasks they really have no business giving any lenience for
extra slack time, so override any passed value by the user and always use
zero for schedule_hrtimeout_range() calls. Furthermore, this is similar to
what the nanosleep(2) family already does with current->timer_slack_ns.

Signed-off-by: Davidlohr Bueso 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20230123173206.6764-3-dave@stgolabs.net
Signed-off-by: Felix Moessbauer 
Signed-off-by: Greg Kroah-Hartman

hrtimer: Report offline hrtimer enqueue

2024-02-23T07:55:00+00:00

commit dad6a09f3148257ac1773cd90934d721d68ab595 upstream.

The hrtimers migration on CPU-down hotplug process has been moved
earlier, before the CPU actually goes to die. This leaves a small window
of opportunity to queue an hrtimer in a blind spot, leaving it ignored.

For example a practical case has been reported with RCU waking up a
SCHED_FIFO task right before the CPUHP_AP_IDLE_DEAD stage, queuing that
way a sched/rt timer to the local offline CPU.

Make sure such situations never go unnoticed and warn when that happens.

Fixes: 5c0930ccaad5 ("hrtimers: Push pending hrtimers away from outgoing CPU earlier")
Reported-by: Paul E. McKenney 
Signed-off-by: Frederic Weisbecker 
Signed-off-by: Paul E. McKenney 
Signed-off-by: Thomas Gleixner 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20240129235646.3171983-4-boqun.feng@gmail.com
Signed-off-by: Greg Kroah-Hartman