linux-kernel - Re: [PATCH -v2 6/8] kexec jump: fix for lockdep

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Date:	Mon, 11 Aug 2008 08:59:56 +0800
From:	Huang Ying <ying.huang@...el.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Pavel Machek <pavel@....cz>, nigel@...el.suspend2.net,
	"Rafael J. Wysocki" <rjw@...k.pl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Vivek Goyal <vgoyal@...hat.com>, mingo@...e.hu,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org,
	Kexec Mailing List <kexec@...ts.infradead.org>
Subject: Re: [PATCH -v2 6/8] kexec jump: fix for lockdep

On Fri, 2008-08-08 at 12:13 +0200, Peter Zijlstra wrote:
> On Fri, 2008-08-08 at 14:52 +0800, Huang Ying wrote:
> > Replace local_irq_disable() with raw_local_irq_disable() to prevent
> > lockdep complain.
> Uhhm, please provide more information - just using raw_* to silence
> lockdep is generally the wrong thing to do.

In traditional kexec, the new kernel will replace current one, so the
irq is simply disabled. But now jumping back from kexeced kernel is
supported, so the irq should be enabled again.

The code sequence of irq during kexec jump is as follow:

local_irq_disable(); /* in kernel_kexec() */
local_irq_disable(); /* in machine_kexec() */
local_irq_enable(); /* in kernel_kexec() */

The disable and enable is not match. Maybe another method is to use
local_irq_save(), local_irq_restore() pair in machine_kexec(), so the
disable and enable is matched.

Best Regrards,
Huang Ying


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