Re: [PATCH v7 3/7] timekeeping: Account for clocksource tick quantisation via NTP

[Marek Szyprowski]

On 09.07.2026 18:08, David Woodhouse wrote:
> On Thu, 2026-07-09 at 14:56 +0200, Marek Szyprowski wrote:
>> This patch landed yesterday in linux-next as commit e8bf3955dc2f
>> ("timekeeping: Account for clocksource tick quantisation via NTP").
>> In my tests I found that it breaks booting Raspberry Pi 3B and Pi 4B
>> boards in ARM 32bit mode with quite old (Debian 10) userspace. Booting
>> freezes just before getting a getty login prompt and no more kernel
>> or userspace messages are observed. If I start with init=/bin/bash in
>> kernel cmdline and then wait a while and do "exec /sbin/init" I get
>> the following additional kernel message:
>>
>> [  186.867605] Adjusting arch_sys_counter more than 11% (12136 vs 344864995)
>>
>> then booting freezes again before getting getty prompt.
>>
>> I can do some more tests, just let me know what will help debugging this
>> issue. Other ARM 32bit machines I have work fine with this patch.
>>
>> Reverting subject together with its dependencies on top of linux-next 
>> fixes the issue.
> Thanks for the report, and the debugging. Does this fix it?

Yes! Feel free to add:

Reported-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>

Tested-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>


> --- a/kernel/time/timekeeping.c
> +++ b/kernel/time/timekeeping.c
> @@ -352,7 +352,7 @@ static void tk_setup_internals(struct timekeeper *tk, struct clocksource *clock)
>         tk->tkr_raw.cycle_last = tk->tkr_mono.cycle_last;
>  
>         /* Do the ns -> cycle conversion first, using original mult */
> -       interval = NTP_INTERVAL_LENGTH << clock->shift;
> +       interval = (u64)NTP_INTERVAL_LENGTH << clock->shift;
>         interval += clock->mult/2;
>         do_div(interval, clock->mult);
>         if (interval == 0)
>
Best regards
-- 
Marek Szyprowski, PhD
Samsung R&D Institute Poland