linux-kernel - Re: Query about kdump_msg hook into crash

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Message-Id: <20110308102741.7E9C.A69D9226@jp.fujitsu.com>
Date:	Tue,  8 Mar 2011 10:31:33 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Vivek Goyal <vgoyal@...hat.com>
Cc:	kosaki.motohiro@...fujitsu.com,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux kernel mailing list <linux-kernel@...r.kernel.org>,
	Jarod Wilson <jwilson@...hat.com>
Subject: Re: Query about kdump_msg hook into crash_kexec()

I'm sorry I've missed this mail long time.

> > ---------------------------------------------------------------------
> > @@ -74,6 +75,7 @@ NORET_TYPE void panic(const char * fmt, ...)
> >         dump_stack();
> >  #endif
> > 
> > +       kmsg_dump(KMSG_DUMP_PANIC);
> >         /*
> >          * If we have crashed and we have a crash kernel loaded let it handle
> >          * everything else.
> >          * Do we want to call this before we try to display a message?
> >          */
> >         crash_kexec(NULL);
> > ---------------------------------------------------------------------
> 
> And I think to compensate for that somebody introduced additional
> kmsg_dump(KEXEC) call inside crash_kexec() and put it under CONFIG
> option so that one can change the behavior based on config options.
> 
> I think this makes the logic somewhat twisted and an unnecessary call
> inside crash_kexec(). So until and unless there is a strong reason we
> can get rid of KEXEC event and move kmsg_dump call before crash_kexec()
> for now and see how does it go, IMHO.

I think I can agree your proposal. But could you please explain why do
you think kmsg _before_ kdump and kmsg _in_ kdump are so different?
I think it is only C level difference. CPU don't care C function and
anyway the kernel call kmsg_dump() because invoke second kernel even 
if you proposal applied.

It is only curious. I'm not against your proposal.

Thanks.



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