linux-kernel - Re: [PATCH] kgdb: more barrier in blank weak function

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Message-Id: <20081227003448.b78b0a6f.akpm@linux-foundation.org>
Date:	Sat, 27 Dec 2008 00:34:48 -0800
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Yinghai Lu <yinghai@...nel.org>, Sam Ravnborg <sam@...nborg.org>,
	David Howells <dhowells@...hat.com>,
	Kamalesh Babulal <kamalesh@...ux.vnet.ibm.com>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	linux-next@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	mel@....ul.ie
Subject: Re: [PATCH] kgdb: more barrier in blank weak function

On Sat, 27 Dec 2008 09:17:37 +0100 Ingo Molnar <mingo@...e.hu> wrote:

> 
> * Yinghai Lu <yinghai@...nel.org> wrote:
> 
> > Impact: fix panic possible panic etc
> > 
> > some compiler seems to inline the weak global function if no line in it
> 
> >  kgdb_post_primary_code(struct pt_regs *regs, int e_vector, int err_code)
> >  {
> > -	return;
> > +	barrier();
> >  }
> 
> >  void __weak kgdb_disable_hw_debug(struct pt_regs *regs)
> >  {
> > +	barrier();
> >  }
> 
> seems like the barrier() is not enough - the only safe sequence seems to 
> be to turn it into a function that returns an integer.
> 

Give up, and ban that gcc version?  Adrian had a patch a while back,
but I don't know how he worked out the affected compiler versions.
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