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From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: David Laight <David.Laight@aculab.com>
Cc: 'Jiri Slaby' <jirislaby@kernel.org>,
	Jari Ruusu <jariruusu@protonmail.com>,
	Sasha Levin <sashal@kernel.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"stable@vger.kernel.org" <stable@vger.kernel.org>,
	"torvalds@linux-foundation.org" <torvalds@linux-foundation.org>,
	"masahiroy@kernel.org" <masahiroy@kernel.org>
Subject: Re: Kernel version numbers after 4.9.255 and 4.4.255
Date: Thu, 4 Feb 2021 17:48:10 +0100	[thread overview]
Message-ID: <YBwlSi85/IA5HytP@kroah.com> (raw)
In-Reply-To: <b17b4c3b2e4b45f9b10206b276b7d831@AcuMS.aculab.com>

On Thu, Feb 04, 2021 at 04:28:19PM +0000, David Laight wrote:
> From: Jiri Slaby
> > Sent: 04 February 2021 11:01
> > 
> > On 04. 02. 21, 9:51, Greg Kroah-Hartman wrote:
> > >> It might work somewhere, but there are a lot of (X * 65536 + Y * 256 + Z)
> > >> assumptions all around the world. So this doesn't look like a good idea.
> > >
> > > Ok, so what happens if we "wrap"?  What will break with that?  At first
> > > glance, I can't see anything as we keep the padding the same, and our
> > > build scripts seem to pick the number up from the Makefile and treat it
> > > like a string.
> > >
> > > It's only the crazy out-of-tree kernel stuff that wants to do minor
> > > version checks that might go boom.  And frankly, I'm not all that
> > > concerned if they have problems :)
> > 
> > Agreed. But currently, sublevel won't "wrap", it will "overflow" to
> > patchlevel. And that might be a problem. So we might need to update the
> > header generation using e.g. "sublevel & 0xff" (wrap around) or
> > "sublevel > 255 : 255 : sublevel" (be monotonic and get stuck at 255).
> > 
> > In both LINUX_VERSION_CODE generation and KERNEL_VERSION proper.
> 
> A full wrap might catch checks for less than (say) 4.4.2 which
> might be present to avoid very early versions.

Who does that?

> So sticking at 255 or wrapping onto (say) 128 to 255 might be better.

Better how?

> I'm actually intrigued about how often you expect people to update
> systems running these LTS kernels.

Whenever they can, and should.

> At a release every week it takes 5 years to run out of sublevels.
> No one is going to reboot a server anywhere near that often.

Why not?

Usually kernels this old are stuck in legacy embedded systems, like last
year's new phone models :)

thanks,

greg k-h

  reply	other threads:[~2021-02-04 16:51 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-02-04  5:59 Jari Ruusu
2021-02-04  6:20 ` Greg Kroah-Hartman
2021-02-04  7:26   ` Jiri Slaby
2021-02-04  8:51     ` Greg Kroah-Hartman
2021-02-04 11:00       ` Jiri Slaby
2021-02-04 16:28         ` David Laight
2021-02-04 16:48           ` Greg Kroah-Hartman [this message]
2021-02-04 20:19           ` Christoph Biedl
2021-02-05  6:52             ` Greg KH
2021-02-05 17:31         ` Tony Battersby
2021-02-05 18:11           ` Mauro Carvalho Chehab
2021-02-06  7:20             ` Greg Kroah-Hartman
2021-02-06  9:24               ` Mauro Carvalho Chehab
2021-02-06  9:29                 ` Greg Kroah-Hartman
2021-02-06  9:48                   ` Mauro Carvalho Chehab
2021-02-06 10:18                     ` Hans Verkuil
2021-02-06 11:18                       ` Mauro Carvalho Chehab
2021-02-06  7:22           ` Greg Kroah-Hartman
2021-02-05  9:06       ` Pavel Machek
2021-02-05  9:33         ` Greg Kroah-Hartman
2021-02-05 18:44           ` Pavel Machek
2021-02-06  7:23             ` Greg Kroah-Hartman

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