linux-kernel - Re: [RFC Patch 1/2][slimdump] Append CRASH

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Date:	Tue, 29 Nov 2011 20:07:52 +0530
From:	"K.Prasad" <prasad@...ux.vnet.ibm.com>
To:	Dave Anderson <anderson@...hat.com>
Cc:	Vivek Goyal <vgoyal@...hat.com>, Borislav Petkov <bp@...en8.de>,
	Tony Luck <tony.luck@...el.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	tachibana@....nes.nec.co.jp, oomichi@....nes.nec.co.jp,
	Valdis Kletnieks <Valdis.Kletnieks@...edu>,
	Nick Bowler <nbowler@...iptictech.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [RFC Patch 1/2][slimdump] Append CRASH_REASON to VMCOREINFO
 elf-note

On Wed, Nov 23, 2011 at 02:45:23PM -0500, Dave Anderson wrote:
> 
> 
> ----- Original Message -----
> > On Mon, Nov 21, 2011 at 10:19:31AM -0500, Dave Anderson wrote:
> > > 
> > > 
> > > ----- Original Message -----
> > > > Allow various crash paths to append the reason of crash into the
> > > > VMCOREINFO elf-note through the field CRASH_REASON. We also make the
> > > > fatal machine check exceptions append "PANIC_MCE" as the crash
> > > > reason.  This string will be recognised by upstream tools like
> > > > makedumpfile and crash to generate slimdump.
> > > 
> > > I don't understand -- how could "various paths" append a reason?
> > > The patch below seems to return "PANIC_MCE" for every x86 crash.
> > > What am I missing?
> > > 
> > > Dave
> > >
> > 
> > Yes, presently it can only be "PANIC_MCE" for MCE crashes in x86 (not
> > for every crash though).
> 
> Why only MCE crashes?  If your arch/x86/kernel/cpu/mcheck/mce.c is 
> compiled into any x86 kernel, then its arch_add_crash_reason() will 
> always override the weak version in kernel/kexec.c, right? 
>

(Sorry for the delayed reply...there was a multiple-day outage in my
email server).

Yes, I think it should be better by using a variable to allow
various crash paths of each architecture populate the reason (the
function approach doesn't work, we can use a function pointer
that just returns a pointer to a char array, but that's less
preferable and convoluted).

I'll change the code to contain a char pointer in a generic file, say
arch/x86/kernel/crash.c which will be populated by the MCE crash path.
The code in kernel/kexec.c can just use this.

Thanks for your comments.

--K.Prasad
 

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