2.6.24 vs. 2.6.27/29 (was RE: [Linux-Xtensa] shmat and sigpausefailed using LTP on Linux 2.6.24)

Piet Delaney piet.delaney at gmail.com
Wed Apr 22 12:37:45 PDT 2009

Shimon Edelhaus wrote:
> Greg told me you guys will port down to 2.6.24. We have no time to mess with new kernels. We have a chip coming tomorrow. Literally tomorrow...
> I am going to talk to Edy and Greg. This is completely unacceptable.
  I think someone's misunderstood something. We are moving forward from 
2.6.24 to 2.6.27 and 2.6.29 right now.
I was thinking of back porting just well know bug fixes now well tested 
in 2.6.24-smp, 2.6.27-smp, and 2.6.28-smp
back to a new 2.6.24-stable as we pass these changes up stream to 
kernel.org. The advantage is that would increase 2.6.24 stability
and we could use it as a reference to detect bugs getting into the smp 
upgrade. I was thinking of also pulling in bug
fixes from the kernel.org 2.6.24-stable repo. The final kernel would be 
called 2.6.24-stable and wouldn't effect 2.6.24
but might be recommended once LTP test show it's noticeable more stable.

  So the 2.6.24 repo won't be changed and if you want to try the newer 
2.6.24-stable you would have that option.
I haven't decided to do this yet. Just thought it might be low hanging 
fruit will checking into kernel.org. The
bug fixes I thinking of back porting are very localized changes.

    1. Ehternet driver is missing a spinlock and gets a race with 
interrupt hander.

    2. Register spill messes up stack during switch. I suspect this is 
an important bug fix that you want to assimilate.

I'd likely run LTP and demonstrate greater stability with the new 
2.6.24-stable repo. Even
with these obvious bug fixes I don't know if it will be as stable as our 
newer kernels.

> ttfn,
> Simon Edelhaus
> Centillium 2008
> ----- Original Message -----
> From: linux-xtensa-bounces at linux-xtensa.org <linux-xtensa-bounces at linux-xtensa.org>
> To: Piet Delaney <Piet.Delaney at mail.tensilica.com>; hitheshm at tataelxsi.co.in <hitheshm at tataelxsi.co.in>
> Cc: linux-xtensa at linux-xtensa.org <linux-xtensa at linux-xtensa.org>; Piet at linux-xtensa.org <Piet at linux-xtensa.org>; Delaney <piet.delaney at gmail.com>
> Sent: Wed Apr 22 10:51:46 2009
> Subject: 2.6.24 vs. 2.6.27/29 (was RE: [Linux-Xtensa] shmat and sigpausefailed using LTP on Linux 2.6.24)
> Hi,
> Just a note to provide some background on 2.6.24 vs. 2.6.27+
> kernels for Xtensa cores.  You have probably noticed that most
> Wiki pages on linux-xtensa.org still refer to the 2.6.24 kernel
> as being the latest stable one.  It is also the latest for which
> we've created a "snapshot" tarball.
> At some point early last year, work began in earnest on adding
> SMP support for Xtensa.  This development would completely
> destabilize the kernel for a while, so was done in a completely
> separate tree.  SMP also required much more extensive testing to
> find and debug subtle (and not so subtle) issues, and stabilize
> to a point where we have reasonable confidence in the port.
> Piet recently got it to that point, where it runs for days under
> constant LTP testing, without problems.  However, the code base
> for it has moved beyond 2.6.24, and is still progressing quickly
> as the focus is now on merging all these changes with the latest
> kernel and submitting them to kernel.org .  Once this is done and
> more testing has been done, we expect to create another 'snapshot'.
> Which is why, officially, the latest stable tree may still be
> considered to be the 2.6.24 one.  Meanwhile you can get to the
> latest 2.6.27 or 2.6.29 SMP trees using git.  If you look at the
> home page on www.linux-xtensa.org and follow the GIT link, you'll
> see these two trees listed (xtensa-2.6.27-smp and xtensa-2.6.29-smp).
> You should be able to clone and pull these trees in the usual
> manner with git, using these names instead of xtensa-2.6.24 .
> Note that the existing buildroot build instructions might not
> match exactly with it.  For example, currently the default kernel
> config might be setup for SMP instead of single-processor,
> requiring you to change that parameter when doing make menuconfig
> on the kernel (hopefully the default gets fixed soon).
> There might other differences.  You'll have to try and find out.
> Step-by-step instructions will only get updated when things
> stabilize a bit more and we create a new snapshot.
> Hope that helps,
> -Marc
> P.S.  Anything opinions expressed by a Tensilica employee mailing to
> linux-xtensa.org is their own, not necessarily that of Tensilica.
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