linux-kernel - Re: (Resend) 2038 Kernel Summit Discussion Fodder

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Message-ID: <20140823222640.GA1382@xo-6d-61-c0.localdomain>
Date:	Sun, 24 Aug 2014 00:26:40 +0200
From:	Pavel Machek <pavel@....cz>
To:	John Stultz <john.stultz@...aro.org>
Cc:	ksummit-discuss@...ts.linuxfoundation.org,
	lkml <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Arnd Bergmann <arnd@...db.de>,
	"Joseph S. Myers" <joseph@...esourcery.com>,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: (Resend) 2038 Kernel Summit Discussion Fodder

Hi!

> There was also some pre-discussion before the sessions started around
> why we don't just change time_t to be unsigned. From the kernel's
> point of view this would be mostly fine, since dates before 1970 are
> not considered valid for any internal uses (with the exception of some
> filesystem timestamps). However, the problem with this approach is
> that userspace may want to handle dates prior to 1970, so this would
> eliminate that possibility. And removing the sign could cause problems
> with existing comparison logic. There is also the fact that having the
> same time unit range on 32bit and 64bit systems avoids complicating
> how timestamps are interpreted between architectures, where as having
> it be unsigned on 32bit but signed on 64bit would likely cause
> confusion. It is quite likely that using unsigned timestamps will be a
> useful solution for cases where timestamps cannot be converted to
> 64bits, but from the kernel perspective if we are going to change the
> abi, we should probably go all the way to 64bits. There seemed to be
> no disagreement here.
> 
> For the rest of the session, I opened it up for further thoughts or
> ideas. While there wasn't any new proposals, there was a question as
> to if anyone will really be running 32bit hardware in 2038, which made
> some folks point out that as systems get smaller there are likely to
> be tiny embedded platforms using Linux. The point that these systems

I'm pretty sure people will run 32bit hardware in 2038... that is not even
a question.

Today, there's good chance there's linux somewhere in your car. (Dashboard,
entertainment system). People like to keep cars from 1910 working, and I suspect
that is not going to change.

So yes, in 2038 people will be running 32bit linux.

Whether there will be people putting 32bit linux into new devices is a question,
but I suspect answer is still yes.
										Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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