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Thomas Gleixner
13bb06f8dd
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 <[email protected]>
Reported-by: "Bhatnagar, Rishabh" <[email protected]>
Suggested-by: Mathias Krause <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Signed-off-by: Sebastian Andrzej Siewior <[email protected]>
Signed-off-by: Thomas Gleixner <[email protected]>
Tested-by: Richard W.M. Jones <[email protected]>
Tested-by: Mathias Krause <[email protected]>
Acked-by: SeongJae Park <[email protected]>
Cc: [email protected]
Link: https://lore.kernel.org/[email protected]
Link: https://lore.kernel.org/[email protected]
Link: https://lore.kernel.org/r/[email protected]