linux/kernel/time
Thomas Gleixner 13bb06f8dd tick/common: Align tick period during sched_timer setup
The tick period is aligned very early while the first clock_event_device is
registered. At that point the system runs in periodic mode and switches
later to one-shot mode if possible.

The next wake-up event is programmed based on the aligned value
(tick_next_period) but the delta value, that is used to program the
clock_event_device, is computed based on ktime_get().

With the subtracted offset, the device fires earlier than the exact time
frame. With a large enough offset the system programs the timer for the
next wake-up and the remaining time left is too small to make any boot
progress. The system hangs.

Move the alignment later to the setup of tick_sched timer. At this point
the system switches to oneshot mode and a high resolution clocksource is
available. At this point it is safe to align tick_next_period because
ktime_get() will now return accurate (not jiffies based) time.

[bigeasy: Patch description + testing].

Fixes: e9523a0d81 ("tick/common: Align tick period with the HZ tick.")
Reported-by: Mathias Krause <minipli@grsecurity.net>
Reported-by: "Bhatnagar, Rishabh" <risbhat@amazon.com>
Suggested-by: Mathias Krause <minipli@grsecurity.net>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Richard W.M. Jones <rjones@redhat.com>
Tested-by: Mathias Krause <minipli@grsecurity.net>
Acked-by: SeongJae Park <sj@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/5a56290d-806e-b9a5-f37c-f21958b5a8c0@grsecurity.net
Link: https://lore.kernel.org/12c6f9a3-d087-b824-0d05-0d18c9bc1bf3@amazon.com
Link: https://lore.kernel.org/r/20230615091830.RxMV2xf_@linutronix.de
2023-06-16 20:45:28 +02:00
..
alarmtimer.c driver core: class: remove struct class_interface * from callbacks 2023-04-03 21:42:52 +02:00
clockevents.c clockevents: Repair kernel-doc for clockevent_delta2ns() 2022-12-01 13:35:41 +01:00
clocksource-wdtest.c clocksource: Make clocksource watchdog test safe for slow-HZ systems 2021-08-28 17:01:32 +02:00
clocksource.c clocksource: Suspend the watchdog temporarily when high read latency detected 2023-01-24 15:12:48 -08:00
hrtimer.c hrtimer: Ignore slack time for RT tasks in schedule_hrtimeout_range() 2023-01-31 11:23:07 +01:00
itimer.c
jiffies.c clocksource: Make clocksource watchdog test safe for slow-HZ systems 2021-08-28 17:01:32 +02:00
Kconfig clocksource: Loosen clocksource watchdog constraints 2023-01-03 20:43:45 -08:00
Makefile
namespace.c vdso/timens: Refactor copy-pasted find_timens_vvar_page() helper into one copy 2022-12-01 11:35:40 +01:00
ntp_internal.h
ntp.c
posix-clock.c
posix-cpu-timers.c posix-cpu-timers: Implement the missing timer_wait_running callback 2023-04-21 15:34:33 +02:00
posix-stubs.c timers: Prevent union confusion from unexpected restart_syscall() 2023-01-11 19:31:47 +01:00
posix-timers.c posix-cpu-timers: Implement the missing timer_wait_running callback 2023-04-21 15:34:33 +02:00
posix-timers.h
sched_clock.c time/sched_clock: Fix formatting of frequency reporting code 2022-05-02 14:29:04 +02:00
test_udelay.c time/debug: Fix memory leak with using debugfs_lookup() 2023-02-09 20:12:27 +01:00
tick-broadcast-hrtimer.c time/tick-broadcast: Remove RCU_NONIDLE() usage 2023-01-13 11:48:16 +01:00
tick-broadcast.c tick/broadcast: Make broadcast device replacement work correctly 2023-05-08 23:18:16 +02:00
tick-common.c tick/common: Align tick period during sched_timer setup 2023-06-16 20:45:28 +02:00
tick-internal.h clocksource: Make clocksource watchdog test safe for slow-HZ systems 2021-08-28 17:01:32 +02:00
tick-legacy.c
tick-oneshot.c time: Fix various kernel-doc problems 2023-01-03 11:07:58 +01:00
tick-sched.c tick/common: Align tick period during sched_timer setup 2023-06-16 20:45:28 +02:00
tick-sched.h timers/nohz: Protect idle/iowait sleep time under seqcount 2023-04-18 16:35:12 +02:00
time_test.c
time.c time: Fix various kernel-doc problems 2023-01-03 11:07:58 +01:00
timeconst.bc
timeconv.c
timecounter.c
timekeeping_debug.c
timekeeping_internal.h
timekeeping.c timekeeping: Fix references to nonexistent ktime_get_fast_ns() 2023-04-26 23:43:16 +02:00
timekeeping.h
timer_list.c
timer.c timers: Provide timer_shutdown[_sync]() 2022-11-24 15:09:12 +01:00
vsyscall.c