netdev - Re: [RFC PATCHv2 1/3] hrtimer: Add notifer for clock_was

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Date:	Wed, 7 Aug 2013 17:31:30 +0800
From:	Fan Du <fan.du@...driver.com>
To:	Daniel Borkmann <dborkman@...hat.com>
CC:	<steffen.klassert@...unet.com>, <davem@...emloft.net>,
	<herbert@...dor.hengli.com.au>, <netdev@...r.kernel.org>
Subject: Re: [RFC PATCHv2 1/3] hrtimer: Add notifer for clock_was_set



On 2013年08月07日 17:20, Daniel Borkmann wrote:
> 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 <fan.du@...driver.com>
>> ---
>> 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.

Thanks for your attention.
After taking a look at netevent_notif_chain, you mean I should do it in below style:

static ATOMIC_NOTIFIER_HEAD(clock_change_notifier_list);

int un/register_clock_change_notifier(struct notifier_block *nb)
{
         int err;

         err = atomic_notifier_chain_un/register(&clock_change_notifier_list, nb);
         return err;
}
EXPORT_SYMBOL_GPL(clock_change_notifier_list);

int call_clock_change_notifiers(unsigned long val, void *v)
{
         return atomic_notifier_call_chain(&clock_change_notifier, val, v);
}
EXPORT_SYMBOL_GPL(call_clock_change_notifiers);

Will do it in next version after others comment rest of patches.

Thanks Daniel.

>> }
>>
>> /*
>>
>

-- 
浮沉随浪只记今朝笑

--fan
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