linux.git/kernel/time/alarmtimer.c, branch v6.6.131

alarmtimer: Fix argument order in alarm_timer_forward()

2026-04-02T11:07:26+00:00

commit 5d16467ae56343b9205caedf85e3a131e0914ad8 upstream.

alarm_timer_forward() passes arguments to alarm_forward() in the wrong
order:

  alarm_forward(alarm, timr->it_interval, now);

However, alarm_forward() is defined as:

  u64 alarm_forward(struct alarm *alarm, ktime_t now, ktime_t interval);

and uses the second argument as the current time:

  delta = ktime_sub(now, alarm->node.expires);

Passing the interval as "now" results in incorrect delta computation,
which can lead to missed expirations or incorrect overrun accounting.

This issue has been present since the introduction of
alarm_timer_forward().

Fix this by swapping the arguments.

Fixes: e7561f1633ac ("alarmtimer: Implement forward callback")
Signed-off-by: Zhan Xusheng 
Signed-off-by: Thomas Gleixner 
Cc: stable@vger.kernel.org
Link: https://patch.msgid.link/20260323061130.29991-1-zhanxusheng@xiaomi.com
Signed-off-by: Greg Kroah-Hartman

alarmtimer: Remove unnecessary (void *) cast

2023-06-18T20:41:53+00:00

Pointers of type void * do not require a type cast when they are assigned
to a real pointer.

Signed-off-by: Li zeming 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20230609182059.4509-1-zeming@nfschina.com

alarmtimer: Remove unnecessary initialization of variable 'ret'

2023-06-18T20:41:53+00:00

ret is assigned before checked, so it does not need to initialize the
variable

Signed-off-by: Li zeming 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20230609182856.4660-1-zeming@nfschina.com

driver core: class: remove struct class_interface * from callbacks

2023-04-03T19:42:52+00:00

The add_dev and remove_dev callbacks in struct class_interface currently
pass in a pointer back to the class_interface structure that is calling
them, but none of the callback implementations actually use this pointer
as it is pointless (the structure is known, the driver passed it in in
the first place if it is really needed again.)

So clean this up and just remove the pointer from the callbacks and fix
up all callback functions.

Cc: Jean Delvare 
Cc: Guenter Roeck 
Cc: "David S. Miller" 
Cc: Eric Dumazet 
Cc: Jakub Kicinski 
Cc: Paolo Abeni 
Cc: Kurt Schwemmer 
Cc: Jon Mason 
Cc: Dave Jiang 
Cc: Allen Hubbe 
Cc: Dominik Brodowski 
Cc: Matt Porter 
Cc: Alexandre Bounine 
Cc: "James E.J. Bottomley" 
Cc: "Martin K. Petersen" 
Cc: Doug Gilbert 
Cc: John Stultz 
Cc: Thomas Gleixner 
Cc: Stephen Boyd 
Cc: Hans de Goede 
Cc: Andrew Morton 
Cc: Wang Weiyang 
Cc: Yang Yingliang 
Cc: Jakob Koschel 
Cc: Cai Xinchen 
Acked-by: Rafael J. Wysocki 
Acked-by: Logan Gunthorpe 
Link: https://lore.kernel.org/r/2023040250-pushover-platter-509c@gregkh
Signed-off-by: Greg Kroah-Hartman

alarmtimer: Prevent starvation by small intervals and SIG_IGN

2023-02-14T10:18:35+00:00

syzbot reported a RCU stall which is caused by setting up an alarmtimer
with a very small interval and ignoring the signal. The reproducer arms the
alarm timer with a relative expiry of 8ns and an interval of 9ns. Not a
problem per se, but that's an issue when the signal is ignored because then
the timer is immediately rearmed because there is no way to delay that
rearming to the signal delivery path.  See posix_timer_fn() and commit
58229a189942 ("posix-timers: Prevent softirq starvation by small intervals
and SIG_IGN") for details.

The reproducer does not set SIG_IGN explicitely, but it sets up the timers
signal with SIGCONT. That has the same effect as explicitely setting
SIG_IGN for a signal as SIGCONT is ignored if there is no handler set and
the task is not ptraced.

The log clearly shows that:

   [pid  5102] --- SIGCONT {si_signo=SIGCONT, si_code=SI_TIMER, si_timerid=0, si_overrun=316014, si_int=0, si_ptr=NULL} ---

It works because the tasks are traced and therefore the signal is queued so
the tracer can see it, which delays the restart of the timer to the signal
delivery path. But then the tracer is killed:

   [pid  5087] kill(-5102, SIGKILL 
   ...
   ./strace-static-x86_64: Process 5107 detached

and after it's gone the stall can be observed:

   syzkaller login: [   79.439102][    C0] hrtimer: interrupt took 68471 ns
   [  184.460538][    C1] rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
   ...
   [  184.658237][    C1] rcu: Stack dump where RCU GP kthread last ran:
   [  184.664574][    C1] Sending NMI from CPU 1 to CPUs 0:
   [  184.669821][    C0] NMI backtrace for cpu 0
   [  184.669831][    C0] CPU: 0 PID: 5108 Comm: syz-executor192 Not tainted 6.2.0-rc6-next-20230203-syzkaller #0
   ...
   [  184.670036][    C0] Call Trace:
   [  184.670041][    C0]  
   [  184.670045][    C0]  alarmtimer_fired+0x327/0x670

posix_timer_fn() prevents that by checking whether the interval for
timers which have the signal ignored is smaller than a jiffie and
artifically delay it by shifting the next expiry out by a jiffie. That's
accurate vs. the overrun accounting, but slightly inaccurate
vs. timer_gettimer(2).

The comment in that function says what needs to be done and there was a fix
available for the regular userspace induced SIG_IGN mechanism, but that did
not work due to the implicit ignore for SIGCONT and similar signals. This
needs to be worked on, but for now the only available workaround is to do
exactly what posix_timer_fn() does:

Increase the interval of self-rearming timers, which have their signal
ignored, to at least a jiffie.

Interestingly this has been fixed before via commit ff86bf0c65f1
("alarmtimer: Rate limit periodic intervals") already, but that fix got
lost in a later rework.

Reported-by: syzbot+b9564ba6e8e00694511b@syzkaller.appspotmail.com
Fixes: f2c45807d399 ("alarmtimer: Switch over to generic set/get/rearm routine")
Signed-off-by: Thomas Gleixner 
Acked-by: John Stultz 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/87k00q1no2.ffs@tglx

alarmtimer: Check RTC features instead of ops

2021-05-11T19:28:04+00:00

RTC drivers used to leave .set_alarm() NULL in order to signal the RTC
device doesn't support alarms. The drivers are now clearing the
RTC_FEATURE_ALARM bit for that purpose in order to keep the rtc_class_ops
structure const. So now, .set_alarm() is set unconditionally and this
possibly causes the alarmtimer code to select an RTC device that doesn't
support alarms.

Test RTC_FEATURE_ALARM instead of relying on ops->set_alarm to determine
whether alarms are available.

Fixes: 7ae41220ef58 ("rtc: introduce features bitfield")
Signed-off-by: Alexandre Belloni 
Signed-off-by: Thomas Gleixner 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20210511014516.563031-1-alexandre.belloni@bootlin.com

Merge tag 'timers-core-2021-04-26' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip

2021-04-26T16:54:03+00:00

Pull timer updates from Thomas Gleixner:
 "The time and timers updates contain:

  Core changes:

   - Allow runtime power management when the clocksource is changed.

   - A correctness fix for clock_adjtime32() so that the return value on
     success is not overwritten by the result of the copy to user.

   - Allow late installment of broadcast clockevent devices which was
     broken because nothing switched them over to oneshot mode. This
     went unnoticed so far because clockevent devices used to be built
     in, but now people started to make them modular.

   - Debugfs related simplifications

   - Small cleanups and improvements here and there

  Driver changes:

   - The usual set of device tree binding updates for a wide range of
     drivers/devices.

   - The usual updates and improvements for drivers all over the place
     but nothing outstanding.

   - No new clocksource/event drivers. They'll come back next time"

* tag 'timers-core-2021-04-26' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (24 commits)
  posix-timers: Preserve return value in clock_adjtime32()
  tick/broadcast: Allow late registered device to enter oneshot mode
  tick: Use tick_check_replacement() instead of open coding it
  time/timecounter: Mark 1st argument of timecounter_cyc2time() as const
  dt-bindings: timer: nuvoton,npcm7xx: Add wpcm450-timer
  clocksource/drivers/arm_arch_timer: Add __ro_after_init and __init
  clocksource/drivers/timer-ti-dm: Handle dra7 timer wrap errata i940
  clocksource/drivers/timer-ti-dm: Prepare to handle dra7 timer wrap issue
  clocksource/drivers/dw_apb_timer_of: Add handling for potential memory leak
  clocksource/drivers/npcm: Add support for WPCM450
  clocksource/drivers/sh_cmt: Don't use CMTOUT_IE with R-Car Gen2/3
  clocksource/drivers/pistachio: Fix trivial typo
  clocksource/drivers/ingenic_ost: Fix return value check in ingenic_ost_probe()
  clocksource/drivers/timer-ti-dm: Add missing set_state_oneshot_stopped
  clocksource/drivers/timer-ti-dm: Fix posted mode status check order
  dt-bindings: timer: renesas,cmt: Document R8A77961
  dt-bindings: timer: renesas,cmt: Add r8a779a0 CMT support
  clocksource/drivers/ingenic-ost: Add support for the JZ4760B
  clocksource/drivers/ingenic: Add support for the JZ4760
  dt-bindings: timer: ingenic: Add compatible strings for JZ4760(B)
  ...

timekeeping, clocksource: Fix various typos in comments

2021-03-22T22:06:48+00:00

Fix ~56 single-word typos in timekeeping & clocksource code comments.

Signed-off-by: Ingo Molnar 
Cc: Thomas Gleixner 
Cc: John Stultz 
Cc: Stephen Boyd 
Cc: Daniel Lezcano 
Cc: linux-kernel@vger.kernel.org

kernel, fs: Introduce and use set_restart_fn() and arch_set_restart_data()

2021-03-16T21:13:10+00:00

Preparation for fixing get_nr_restart_syscall() on X86 for COMPAT.

Add a new helper which sets restart_block->fn and calls a dummy
arch_set_restart_data() helper.

Fixes: 609c19a385c8 ("x86/ptrace: Stop setting TS_COMPAT in ptrace code")
Signed-off-by: Oleg Nesterov 
Signed-off-by: Thomas Gleixner 
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/20210201174641.GA17871@redhat.com

alarmtimer: Update kerneldoc

2021-02-05T18:26:41+00:00

Update kerneldoc comments to reflect the actual arguments and return values
of the documented functions.

Signed-off-by: Alexandre Belloni 
Signed-off-by: Thomas Gleixner 
Link: https://lore.kernel.org/r/20210202013457.3482388-1-alexandre.belloni@bootlin.com