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Bug#820567: kexec on mipsel partially broken between ckt20 and ckt25

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On Sun, 2016-04-10 at 11:09 -0700, Elliott Mitchell wrote:
> On Sun, Apr 10, 2016 at 10:09:38AM +0100, Ben Hutchings wrote:
> > 
> > On Sat, 2016-04-09 at 18:31 -0700, Elliott Mitchell wrote:
> > > 
> > > Between 3.16.7-ctk20 and 3.16.7-ctk25 the kexec functionality of the
> > > Linux kernel was damaged.????The system I'm looking at uses a 3.3 kernel
> > > to load the "real" kernel off a filesystem and kexec into that.????The 3.3
> > > kernel was able to successfully kexec into a 3.16.7-ctk20 kernel, but
> > > is unable to kexec into a 3.16.7-ctk25 kernel.????However I found the
> > > 3.16.7-ctk20 IS able to successfully kexec the 3.16.7-ctk25 kernel.
> > Surely this is a bug in the built-in (3.3) kernel, not the new one? ??If
> > there's something simple that can be done in the Debian kernel to work
> > around this, we should do that, but otherwise you're stuck with this.
> This is certainly a reasonable theory.  Alas, I cannot speak to which of
> these theories is correct.  All I can say for certain is that something
> changed between ctk20 and ctk25 which made the 3.3 kernel unable to kexec
> ctk25.  I'm under the impression as of 3.3 the kexec functionality was
> supposed to be stable on MIPS, but that could be incorrect.
> 
> I should also note, during the failed kexecs I would see the messages
> from the 3.3 kernel saying the kexec was starting, but never see any
> messages from the ctk25 kernel.  Unless someone wants to send me a JTAG
> decoder that is all I can say.

One of the MIPS porters may be able to help you, but I have no idea
what to suggest.

Are you using one of the linux-image packages or building from source
with your own configuration?  In the latter case, are you sure you used
the same configuration for old and new kernels?

> > > Doing a double-kexec does work around the issue, but it means I need to
> > > hold onto that one magic kernel for the moment...
> > > 
> > > In other news, it appears sometime between 3.3 and 3.10 there started
> > > being a requirement for GCC 4.8 on mipsel.
> > Packages in jessie must be buildable using compiler versions in jessie.
> > That means either gcc-4.8 or gcc-4.9.
> linux-source-3.16 is available as a backport to wheezy, which does not
> feature gcc-4.8.

That in no way contradicts what I said. :-)  When I backport the linux
source package from jessie to wheezy I change it to use gcc-4.6.

But the linux-source-X.Y packages (which are a different thing to the
linux source package!) don't specify any particular compiler version.
You can choose that with the CC variable; otherwise the default
compiler (specified by the gcc package) will be used.

Ben.

-- 
Ben Hutchings
I'm always amazed by the number of people who take up solipsism because
they heard someone else explain it. - E*Borg on alt.fan.pratchett

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Bug#820567: kexec on mipsel partially broken between ckt20 and ckt25 Elliott Mitchell <ehem+debian@m5p.com> - 2016-04-10 03:40 +0200
  Bug#820567: kexec on mipsel partially broken between ckt20 and ckt25 Ben Hutchings <ben@decadent.org.uk> - 2016-04-10 11:20 +0200
    Bug#820567: kexec on mipsel partially broken between ckt20 and ckt25 Elliott Mitchell <ehem+debian@m5p.com> - 2016-04-10 20:20 +0200
      Bug#820567: kexec on mipsel partially broken between ckt20 and ckt25 Ben Hutchings <ben@decadent.org.uk> - 2016-04-10 21:00 +0200
        Bug#820567: kexec on mipsel partially broken between ckt20 and ckt25 Elliott Mitchell <ehem+debian@m5p.com> - 2016-04-10 23:40 +0200
          Bug#820567: kexec on mipsel partially broken between ckt20 and ckt25 Ben Hutchings <ben@decadent.org.uk> - 2016-04-11 02:40 +0200
            Bug#820567: kexec on mipsel partially broken between ckt20 and ckt25 Elliott Mitchell <ehem+debian@m5p.com> - 2016-04-11 08:00 +0200
  Processed: Re: Bug#820567: kexec on mipsel partially broken  between ckt20 and ckt25 owner@bugs.debian.org (Debian Bug Tracking System) - 2016-04-10 11:20 +0200
  Processed: Re: Bug#820567: kexec on mipsel partially broken  between ckt20 and ckt25 owner@bugs.debian.org (Debian Bug Tracking System) - 2016-04-10 21:00 +0200
  Bug#820567: marked as done (kexec on mipsel partially broken  between ckt20 and ckt25) owner@bugs.debian.org (Debian Bug Tracking System) - 2016-04-11 13:40 +0200

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