On 19.06.23 08:18, Greg KH wrote:
On Thu, Jun 15, 2023 at 11:18:30AM +0200, Sebastian Andrzej Siewior wrote:
From: Thomas Gleixner tglx@linutronix.de
The tick period is aligned very early while the first clock_event_device is registered. The system runs in periodic mode and switches later to one-shot mode if possible.
The next wake-up event is programmed based on 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 devices fires in less than the exacted time frame. With a large enough offset the system programs the timer for the next wake-up and the remaining time left is too little 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 highres clocksource is available. It safe to update tick_next_period ktime_get() will now return accurate (not jiffies based) time.
[bigeasy: Patch description + testing].
Reported-by: Mathias Krause minipli@grsecurity.net Reported-by: "Bhatnagar, Rishabh" risbhat@amazon.com Fixes: e9523a0d81899 ("tick/common: Align tick period with the HZ tick.") Signed-off-by: Thomas Gleixner tglx@linutronix.de Signed-off-by: Sebastian Andrzej Siewior bigeasy@linutronix.de Link: https://lore.kernel.org/5a56290d-806e-b9a5-f37c-f21958b5a8c0@grsecurity.net Link: https://lore.kernel.org/12c6f9a3-d087-b824-0d05-0d18c9bc1bf3@amazon.com
kernel/time/tick-common.c | 11 +---------- kernel/time/tick-sched.c | 13 ++++++++++++- 2 files changed, 13 insertions(+), 11 deletions(-)
What's the status of this fix, I didn't see it in -rc7, am I looking in the wrong place?
It's in the tip tree since Friday, but yeah, no pull request yet:
https://git.kernel.org/tip/13bb06f8dd42
Thanks, Mathias