linux-kernel - Re: [ntpwg] Bug: Status/Summary of slashdot leap-second crash on new years 2008-2009

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Message-Id: <20090107.102434.-1980908153.imp@bsdimp.com>
Date:	Wed, 07 Jan 2009 10:24:34 -0700 (MST)
From:	"M. Warner Losh" <imp@...imp.com>
To:	davidn@...idnewall.com
Cc:	linasvepstas@...il.com, david@...g.hm, hancockr@...w.ca,
	kyle@...fetthome.net, slashdot@...eshallam.info,
	goodgerster@...il.com, mayer@....isc.org,
	linux-kernel@...r.kernel.org, ntpwg@...ts.ntp.isc.org,
	pretzalz@...hhouse.org, burdell@...ntheinter.net,
	nick@...k-andrew.net, jeff@...owsky.org
Subject: Re: [ntpwg] Bug: Status/Summary of slashdot leap-second crash on
 new years 2008-2009

In message: <49647E0F.9030008@...idnewall.com>
            David Newall <davidn@...idnewall.com> writes:
: Linas Vepstas wrote:
: > Currently, the Linux kernel keeps time in UTC. This means
: > that it must take special actions to tick twice when a leap
: > second comes by.
: 
: Except it doesn't have to tick twice.  Refer to
: http://lkml.org/lkml/2009/1/7/78 in which I show that a time_t (what
: time() returns) counts leap seconds (According to Bernstein this is what
: UTC means), and using zoneinfo, the library processes leap seconds
: correctly.

This is *NOT* POSIX time_t.  In order to be posix compliant, you can't
do what Bernstein suggests.  You can be non-complaint and deal it with
zoneinfo.

: I just realised that the Notes in man 2 time are confusing and probably
: unnecessary.  Suffice to say that (assuming correctly configured
: zoneinfo) time() returns the number of seconds elapsed since start 1970.

That's not POSIX complaint.

Warner
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