linux-kernel - Re: [RFC][PATCH v4 -next 1/4] Move kmsg_dump(KMSG_DUMP_PANIC) below smp_send

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Date:	Tue, 10 Jan 2012 11:06:27 +0800
From:	Chen Gong <gong.chen@...ux.intel.com>
To:	Seiji Aguchi <seiji.aguchi@....com>
CC:	Don Zickus <dzickus@...hat.com>,
	"Luck, Tony" <tony.luck@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Matthew Garrett <mjg@...hat.com>,
	Vivek Goyal <vgoyal@...hat.com>,
	"Chen, Gong" <gong.chen@...el.com>,
	"akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
	"Brown, Len" <len.brown@...el.com>,
	"'ying.huang@...el.com'" <'ying.huang@...el.com'>,
	"'ak@...ux.intel.com'" <'ak@...ux.intel.com'>,
	"'hughd@...omium.org'" <'hughd@...omium.org'>,
	"'mingo@...e.hu'" <'mingo@...e.hu'>,
	"jmorris@...ei.org" <jmorris@...ei.org>,
	"a.p.zijlstra@...llo.nl" <a.p.zijlstra@...llo.nl>,
	"namhyung@...il.com" <namhyung@...il.com>,
	"dle-develop@...ts.sourceforge.net" 
	<dle-develop@...ts.sourceforge.net>,
	Satoru Moriya <satoru.moriya@....com>
Subject: Re: [RFC][PATCH v4 -next 1/4] Move kmsg_dump(KMSG_DUMP_PANIC) below
 smp_send_stop()

于 2012/1/10 1:59, Seiji Aguchi 写道:
>>
>> I don't know how to prove something is hardened other than not seeing any
>> hangs or false reboots on in that piece of code.
>>
>
> I don't know how we can prove reliability of smp_send_stop() of all archs as well.
>
> Another possible solution is replacing smp_send_stop() with
> machine_crash_shutdown().
> This is a function call stopping other cpus reliably in panic situation
> so that kdump can work .
> But, I don't know whether it works in all archs.

machine_crash_shutdown is defined in only some Archs so it is obvious that it
can't be used in all platforms, BTW, this function is bracketed by CONFIG_KEXEC,
which means it can't be used without this macro. So it is not suitable for
this scenario.

> We need further discussion with Eric for checking this idea is feasible...
>
>
> I would like to go forward step by step rather than doing tough work at once.
> I think just moving kmsg_dump() below smp_send_stop() is a good start for improving pstore.

I agree with you. How about adding macros or something like WARN_ON(XX_ARCH) or
Kconfig to limit its scope?

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