linux-kernel - Re: [PATCH -v2 7/8] kexec jump: ftrace_enabled

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Date:	Mon, 11 Aug 2008 09:22:21 +0800
From:	Huang Ying <ying.huang@...el.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Vivek Goyal <vgoyal@...hat.com>,
	"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>, 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 7/8] kexec jump: ftrace_enabled_save/restore

Hi, Steven,

On Fri, 2008-08-08 at 10:30 -0400, Steven Rostedt wrote:
[...]
> The only problem with this approach is what happens if the user changes 
> the enabled in between these two calls. This would make ftrace 
> inconsistent.
> 
> I have a patch from the -rt tree that handles what you want. It is 
> attached below. Not sure how well it will apply to mainline.
> 
> I really need to go through the rt patch set and start submitting a bunch 
> of clean-up/fixes to mainline. We've been meaning to do it, just have been 
> distracted :-(

Your version is better in general sense. Thank you very much!

But in this specific situation of kexec/kjump. The execution environment
is that other CPUs are disabled, local irq is disabled, and it is not
permitted to switch to other process. But it is safe and sufficient to
use non-locked version here.

So to satisfy both demands, I think it is better to provide both
version, locked and non-locked. What do you think about that?

Best Regards,
Huang Ying


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