Re: [Kgdb-bugreport] 2.6.23-rc3-mm1: kgdb build failure on powerpc

[Randy Dunlap]

On Wed, 29 Aug 2007 18:19:29 -0700 Pete/Piet Delaney wrote:

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> Pete/Piet Delaney wrote:
> > Jason Wessel wrote:
> >> Andrew Morton wrote:
> >>> On Wed, 22 Aug 2007 17:44:12 -0500
> >>> Jason Wessel <jason.wessel@xxxxxxxxxxxxx> wrote:
> >>>
> >>>  
> >>>> +    while (!atomic_read(&debugger_active));
> >>>>     
> >>> eek.  We're in the process of hunting down and eliminating exactly this
> >>> construct.  There have been cases where the compiler cached the
> >>> atomic_read() result in a register, turning the above into an infinite
> >>> loop.
> >>>
> >>> Plus we should never add power-burners like that into the kernel
> >>> anyway. That loop should have a cpu_relax() in it.  Which will also
> >>> fix the
> >>> compiler problem described above.
> >>>
> >>>   
> >> Agreed, and fixed with a cpu_relax.
> > 
> >>> Thirdly, please always add a newline when coding statements like that:
> >>>
> >>>     while (expr())
> >>>         ;
> >>>   
> >> The other instances I found of the same problem in the kgdb core are
> >> fixed too.
> > 
> >> I merged all the changes into the for_mm branch in the kgdb git tree.
> > 
> > Where is the kgdb git tree?
> 
> Why am I getting this when I do:
> 
> git clone
> http://master.kernel.org/pub/scm/linux/kernel/git/jwessel/linux-2.6-kgdb.git
> 
> -
> ----------------------------------------------------------------------------
> error: Couldn't get
> http://master.kernel.org/pub/scm/linux/kernel/git/jwessel/linux-2.6-kgdb.git/refs/tags/v2.6.11
> for tags/v2.6.11
> The requested URL returned error: 404
> error: Could not interpret tags/v2.6.11 as something to pull
> rm: cannot remove directory
> `/nethome/piet/Src/linux/git/jwessel/linux-2.6-kgdb/.git/clone-tmp':
> Directory not empty
> /nethome/piet/Src/linux/git/jwessel$
> -
> ----------------------------------------------------------------------------

See the URLs at the top of
http://git.kernel.org/?p=linux/kernel/git/jwessel/linux-2.6-kgdb.git;a=summary
and try one of those (the git one preferably).


> We are getting a problem with VMware where kernel text is the schedler
> is getting wacked with four null bytes into the code. Thought I'd use
> the current linux-2.6-kgdb.git tree and possible the CONFIG_DEBUG_RODATA
> patch to make kernel text readonly:
> 
>  https://www.x86-64.org/pipermail/patches/2007-March/003666.html
> 
> I thought the kernel text was RO and gdb had to disable it to
> insert a breakpoint.
> 
> - -piet
> 
> > 
> > -piet
> > 
> >> Thanks,
> >> Jason.
> >> -
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> > 
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---
~Randy
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