Subject: Re: [RFC PATCHv2 1/3] hrtimer: Add notifer for clock_was_set

From: Daniel Borkmann <[email-masked]>
Date: Wed, 07 Aug 2013 11:20:55 +0200

On 08/07/2013 11:04 AM, Fan Du wrote:
> When clock_was_set is called in case of system wall time change
> or host resume from suspend state, use this notifier for places
> where interested in this action.

(Only minor commenting on this one ...)

> Signed-off-by: Fan Du <[email-masked]>
> ---
>   kernel/hrtimer.c |    4 ++++
>   1 file changed, 4 insertions(+)
>
> diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
> index 383319b..b7c62a9 100644
> --- a/kernel/hrtimer.c
> +++ b/kernel/hrtimer.c
> @@ -755,6 +755,9 @@ static inline void retrigger_next_event(void *arg) { }
>
>   #endif /* CONFIG_HIGH_RES_TIMERS */
>
> +ATOMIC_NOTIFIER_HEAD(clock_change_notifier_list);
> +EXPORT_SYMBOL(clock_change_notifier_list);

This should be static and hidden from other modules, e.g. have a look at
netevent_notif_chain (net/core/netevent.c).

Instead, this should be accessed via registration/un-registration handlers
for notifier blocks, and those can then be exported as EXPORT_SYMBOL_GPL
as this is core area.

> +
>   /*
>    * Clock realtime was set
>    *
> @@ -773,6 +776,7 @@ void clock_was_set(void)
>   	on_each_cpu(retrigger_next_event, NULL, 1);
>   #endif
>   	timerfd_clock_was_set();
> +	atomic_notifier_call_chain(&clock_change_notifier_list, 0, 0);

Also here a small one-line handler call_clock_change_notifiers() would be
better.

>   }
>   /*