# Re: \[patch 09/24\] timekeeping: Add CLOCK\_AUX support for ktime\_get\_snapshot\_id()

- From: Thomas Weißschuh \<hidden\>
- Date: 2026-06-26 08:48:12 
- List: netdev
- Page: https://ratatoskr.run/netdev/2026/06/17179296
- Thread: https://ratatoskr.run/kvmarm/2026/05/17032577/t/2.md

```text
On Tue, May 26, 2026 at 07:14:13PM +0200, Thomas Gleixner wrote:
(...)

>  static inline void tk_update_aux_offs(struct timekeeper *tk, ktime_t offs)
> @@ -1218,6 +1223,12 @@ bool ktime_get_snapshot_id(struct system
>  		tkd = &tk_core;
>  		offs = &tk_core.timekeeper.offs_boot;
>  		break;
> +	case CLOCK_AUX ... CLOCK_AUX_LAST:
> +		tkd = aux_get_tk_data(clock_id);
> +		if (!tkd)
> +			return false;
> +		offs = &tkd->timekeeper.offs_aux;
> +		break;

'tkd' is also used to compute 'monoraw'. However 'tkr_raw' and 'tkr_mono'
are the same for auxilary clocks, so this will compute a wrong 'monoraw'.
Instead 'monoraw' should be computed based on 'tk_core'.
Which then also requires the sequence locking of 'tk_core'.

As you know I have a series which unifies the locking between the
different timekeepers. Maybe we revert this patch for 7.2 and I send
a fixed variant including the prerequisites for 7.3.

(The same goes for get_device_system_crosststamp())

>  	default:
>  		WARN_ON_ONCE(1);
>  		return false;
> @@ -1228,6 +1239,10 @@ bool ktime_get_snapshot_id(struct system
>  	do {
>  		seq = read_seqcount_begin(&tkd->seq);
>  
> +		/* Aux clocks can be invalid */
> +		if (!tk->clock_valid)
> +			return false;
> +
>  		now = tk_clock_read(&tk->tkr_mono);
>  		systime_snapshot->cs_id = tk->tkr_mono.clock->id;
>  		systime_snapshot->cs_was_changed_seq = tk->cs_was_changed_seq;
> 
```