linux-kernel - Re: [PATCH v2] printk: ignore recursion

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Date:	Fri, 25 May 2012 08:30:11 +0800
From:	Yanmin Zhang <yanmin_zhang@...ux.intel.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Borislav Petkov <bp@...en8.de>, ShuoX Liu <shuox.liu@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	andi@...stfloor.org, Tony Luck <tony.luck@...el.com>,
	Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH v2] printk: ignore recursion_bug flag in HW error handle
 process

On Thu, 2012-05-24 at 15:56 -0700, Andrew Morton wrote:
> On Thu, 24 May 2012 08:11:45 +0200
> Borislav Petkov <bp@...en8.de> wrote:
> 
> > > +/* HW error handle status helpers */
> > > +extern atomic_t hw_error;
> > > +static inline void hw_error_enter(void)
> > > +{
> > > +	atomic_inc(&hw_error);
> > > +}
> > > +
> > > +static inline void hw_error_exit(void)
> > > +{
> > > +	atomic_dec(&hw_error);
> > > +}
> > > +
> > > +static inline int in_hw_error(void)
> > > +{
> > > +	return atomic_read(&hw_error);
> > > +}
> > 
> > Shouldn't those be generic empty functions and each arch implement their
> > own with the stuff they want to do on the respective architecture when
> > they get a hardware error?
> 
> This code needs documentation.
> 
> Specifically, it should clearly explain (and hence define) what a
> "hardware error" *is*, and for what purpose this code exists.
> 
> Because as it stands, this interface is hopelessly vague.  Once one
> sees that it is *specifically* used for handling mce within a printk,
> it all makes sense.
> 
> And with that understanding comes the realisation that the interface is
> poorly named.  It will not be used for any purpose other than adjusting
> printk() behavior so it should mention printk() in its name and in its
> comments and probably it should all be moved into printk.h.
> 
> Futhermore, this code is not really related to MCE or hardware or
> anything else.  It is simply a way in which callers can suppress
> printk()'s recursion check.  Callers are free to use it for reasons
> other than "hardware errors".
> 
> And once all that is done, and this interface becomes part of printk()
> then no, there is no need to add per-arch hooks.  An arch can call into
> printk_recursion_check_disable() and printk_recursion_chack_enable() -
> nice and simple.
> 
> 
> IOW, the title of this patch should be
> 
> 	[patch 1/2] printk: add interface for disabling recursion check
> 	[patch 2/2] x86 mce: use new printk recursion disabling interface
Andrew,

Thanks for the detailed comment. It's more reasonable to bind it to printk.
We would follow it to create new patches.

Yanmin


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