linux-kernel - Re: Regression :-) Re: [GIT PULL RESEND] x86/jumpmplabel changes for v3.12-rc1

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Date:	Wed, 11 Sep 2013 11:47:08 -0400
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
Cc:	"H. Peter Anvin" <hpa@...ux.intel.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Jason Baron <jbaron@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	boris.ostrovsky@...cle.com, david.vrabel@...rix.com
Subject: Re: Regression :-) Re: [GIT PULL RESEND] x86/jumpmplabel changes
 for v3.12-rc1

On Wed, 11 Sep 2013 11:21:49 -0400
Konrad Rzeszutek Wilk <konrad.wilk@...cle.com> wrote:
> > 
> > I'm trying to understand how this will fix it for you. Are you sure you
> > removed 'xen_nopvspin'?
> 
> Yes.
> > 
> > If you are calling static_key_slow_inc() before jump_label_init(), then
> > it should still fail. The static_key_slow_inc() eventually calls
> > arch_jump_label_transform(), which calls __jump_label_transform() with
> > init == 0.
> 
> Perhaps I am misreading the code, but I believe init is set to one.
> That is due to us calling:
> 
> arch_jump_label_transform (.., JUMP_LABEL_ENABLE)
> 
> which calls __jump_label_transform(.., 1)
> ?

>From what I'm looking at, only arch_jump_label_transform_static() calls
__jump_label_transform() with a 1 for init. arch_jump_label_transform()
calls it with 0 for init, which is what eventually gets called by
xen_init_spinlocks().

> 
> Perhaps the 'init' and 'enable' parameters have different meanings?

Yes they do.

-- Steve

> 
> > 
> > The below code looks to me that it would still compare the contents
> > with the ideal_nop, which hasn't been set yet.
> 
> In the !init case - sure. 
> 
> In the init case - just with default_nop.
> 
--
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