linux-kernel - Re: [RFC V2 PATCH 0/1] kexec: crash_kexec_post

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Message-ID: <55BF4B1F.9000602@hitachi.com>
Date:	Mon, 03 Aug 2015 20:06:07 +0900
From:	Hidehiro Kawai <hidehiro.kawai.ez@...achi.com>
To:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Vivek Goyal <vgoyal@...hat.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-mips@...ux-mips.org, Baoquan He <bhe@...hat.com>,
	kexec@...ts.infradead.org, linux-kernel@...r.kernel.org,
	HATAYAMA Daisuke <d.hatayama@...fujitsu.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Daniel Walker <dwalker@...o99.com>,
	Ingo Molnar <mingo@...nel.org>
Subject: Re: [RFC V2 PATCH 0/1] kexec: crash_kexec_post_notifiers boot
 option related fixes

Hello Eric and Vivek,

Do you have any comments?

(2015/07/24 10:16), Hidehiro Kawai wrote:
> This is a bugfix patch for crash_kexec_post_notifiers boot option
> which allows users to call panic notifiers and kmsg dumpers before
> kdump.
> 
> This fixes one of the problems reported by Daniel Walker
> (https://lkml.org/lkml/2015/6/24/44). 
> 
>  Problem 1:
>  If crash_kexec_post_notifiers boot option is specified, some
>  shutting down process which assume other cpus are still alive
>  don't work properly.
> 
>  Problem 2 (addressed by this patch):
>  If crash_kexec_post_notifiers boot option is specified, register
>  information of other cpus are not saved to crash dumps.
> 
> Following Vivek's opinion, this patch replaces smp_send_stop()
> in panic() with suitable version for crash_kexec which saves
> cpu states and other things like cleaning up VMX/SVM.  Since this
> needs architecture specific implementation and it's not so trivial,
> this version only support for x86.  So the problem 1, known to
> happen on MIPS/OCTEON, is not addressed now.
> 
> To keep the modification impact low, this patch doesn't change
> the logic basically if crash_kexec_post_notifiers is not specified.
> 
> Please note that crash_kexec() can be called directly without
> entering panic().  Stopping other cpus functionality is still
> needed in crash_kexec().
> 
> Changes in V2:
> - Replace smp_send_stop() call with crash_kexec version which
>   saves cpu states and does cleanups instead of changing execution
>   flow
> - Drop a fix for Problem 1
> - Drop other patches because they aren't needed anymore
> 
> V1: https://lkml.org/lkml/2015/7/10/316
> 
> ---
> 
> Hidehiro Kawai (1):
>       panic/x86: Replace smp_send_stop() with crash_kexec version
> 
> 
>  arch/x86/kernel/crash.c |   16 +++++++++++-----
>  kernel/panic.c          |   29 +++++++++++++++++++++++------
>  2 files changed, 34 insertions(+), 11 deletions(-)
> 
> 


-- 
Hidehiro Kawai
Hitachi, Ltd. Research & Development Group


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