From mboxrd@z Thu Jan  1 00:00:00 1970
From: Andrew Cooper <andrew.cooper3@citrix.com>
Subject: Re: [PATCH v3 5/5] xen/console: Traditional console
 timestamps including milliseconds
Date: Fri, 7 Mar 2014 00:41:40 +0000
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To: Don Slutz <dslutz@verizon.com>, Xen-devel <xen-devel@lists.xen.org>
Cc: Tim Deegan <tim@xen.org>, Jan Beulich <JBeulich@suse.com>, Keir Fraser <keir@xen.org>, Ian Campbell <ian.campbell@citrix.com>, Stefano Stabellini <stefano.stabellini@citrix.com>
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On 06/03/2014 23:54, Don Slutz wrote:
> On 03/06/14 14:28, Andrew Cooper wrote:
>>
>>   }
>>   -struct tm wallclock_time(void)
>> +struct tm wallclock_time(uint64_t *ns)
>>   {
>
> Adding:
>
>    if ( ns )
>       *ns = 0;
>
> Makes sense here.
>
>>       return (struct tm) { 0 };
>>   }
>> diff --git a/xen/arch/x86/time.c b/xen/arch/x86/time.c
>> index 4f4de22..1156ccc 100644
>> --- a/xen/arch/x86/time.c
>> +++ b/xen/arch/x86/time.c
>> @@ -1646,15 +1646,19 @@ int dom0_pit_access(struct ioreq *ioreq)
>>       return 0;
>>   }
>>   -struct tm wallclock_time(void)
>> +struct tm wallclock_time(uint64_t *ns)
>>   {
>> -    uint64_t seconds;
>> +    uint64_t seconds, nsec;
>>         if ( !wc_sec )
>
> And here.
>
>>           return (struct tm) { 0 };
>>         seconds = NOW() + SECONDS(wc_sec) + wc_nsec;
>> -    do_div(seconds, 1000000000);
>> +    nsec = do_div(seconds, 1000000000);
>> +
>> +    if ( *ns )
>
> This should be just
>
>    if ( ns )

Oops - so it should.

As for the other changes, I am a bit ambivalent.  printk_start_of_line()
is the sole caller of wallclock_time(), which means that tm.tm_day being
0 means *ns will never get looked at.

While it is not exactly a hot codepath, unconditionally clearing it
seems silly, especially as it is not exactly the most likely candidate
to get a new caller in the near future.

~Andrew