Re: [PATCH v5 1/2] sched/clock: interface to allow timestamps early in boot

From	Pasha Tatashin <pasha.tatashin@oracle.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH v5 1/2] sched/clock: interface to allow timestamps early in boot
Date	2017-08-28 20:10 +0200
Message-ID	<ujwE2-pb-27@gated-at.bofh.it> (permalink)
References	<uhKL9-5jQ-29@gated-at.bofh.it> <uhKL9-5jQ-27@gated-at.bofh.it> <uivK2-1z1-9@gated-at.bofh.it> <ujt3s-6CP-11@gated-at.bofh.it> <ujtZy-7cf-77@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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>> void __init timekeeping_init(void)
>> {
>> 	/*
>> 	 * We must determine boot timestamp before getting current  	
>> 	 * persistent clock value, because implementation of
>> 	 * read_boot_clock64() might also call the persistent
>> 	 * clock, and a leap second may occur.
>> 	 */
>>
>> 	read_boot_clock64(&boot);
>> 	...
>> 	read_persistent_clock64(&now);
> 
> No. That's the same crap just the other way round.
> 
> s390 can do that, because the boot timestamp is correlated with the
> persistent clock. Your's not so much.
> 

OK, how about reading the persistent clock only once, and send it's 
value to use for calculation of boot stamp to read_boot_clock64() via a 
new argument:

read_boot_clock64(&now, &boot);

Does this sound alright or is there a better way?

I would need to update read_boot_clock64() everywhere it is declared to 
add the __init macro, so this extra argument is not going to increase 
number of line changes.

Thank you,
Pasha

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Re: [PATCH v5 1/2] sched/clock: interface to allow timestamps early  in boot Thomas Gleixner <tglx@linutronix.de> - 2017-08-26 01:00 +0200
  Re: [PATCH v5 1/2] sched/clock: interface to allow timestamps early  in boot Pasha Tatashin <pasha.tatashin@oracle.com> - 2017-08-28 16:20 +0200
    Re: [PATCH v5 1/2] sched/clock: interface to allow timestamps early  in boot Thomas Gleixner <tglx@linutronix.de> - 2017-08-28 17:20 +0200
      Re: [PATCH v5 1/2] sched/clock: interface to allow timestamps early  in boot Pasha Tatashin <pasha.tatashin@oracle.com> - 2017-08-28 19:50 +0200
    Re: [PATCH v5 1/2] sched/clock: interface to allow timestamps early  in boot Thomas Gleixner <tglx@linutronix.de> - 2017-08-28 17:20 +0200
      Re: [PATCH v5 1/2] sched/clock: interface to allow timestamps early  in boot Pasha Tatashin <pasha.tatashin@oracle.com> - 2017-08-28 20:10 +0200

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