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

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Date:	Thu,  3 Feb 2011 14:20:53 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
Cc:	kosaki.motohiro@...fujitsu.com, Vivek Goyal <vgoyal@...hat.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()

> AFAIK, kexec is used sneak rebooting way when the system face unexpected
> scenario on some devices. (Some embedded is running very long time, then 
> it can't avoid memory bit corruption. all of reset is a last resort. 
> and a vendor gather logs at periodically checkback).
> 
> The main purpose of to introduce KMSG_DUMP_KEXEC is to be separate it
> from KMSG_DUMP_PANIC. At kmsg_dump() initial patch, KMSG_DUMP_PANIC 
> is always called both kdump is configured or not. But it's no good idea
> the same log is to be appeared when both kexec was successed and failured.
> Moreover someone don't want any log at kexec phase. They only want logs
> when real panic (ie kexec failure) route. Then, I've separated it to two.
> Two separated argument can solve above both requreiment.

A bit additional explanation, An original patch have kmsg_dump(KMSG_DUMP_PANIC)
callsite at following point. I didn't think it makes either embedded or 
kdump folks happiness. Thus I moved it after crash_kexec().


---------------------------------------------------------------------
@@ -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);
---------------------------------------------------------------------



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