linux-kernel - Re: gcc-4.6.0 generates no code for sub_preempt

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Message-Id: <201104141552.42213.richard@nod.at>
Date:	Thu, 14 Apr 2011 15:52:41 +0200
From:	Richard Weinberger <richard@....at>
To:	Mikael Pettersson <mikpe@...uu.se>
Cc:	linux-kernel@...r.kernel.org,
	user-mode-linux-devel@...ts.sourceforge.net
Subject: Re: gcc-4.6.0 generates no code for sub_preempt_count()

Am Donnerstag 14 April 2011, 09:49:14 schrieb Mikael Pettersson:
> Richard Weinberger writes:
>  > Hi,
>  > 
>  > I'm facing a very strange issue with gcc-4.6.0 and UML.
>  > Within __local_bh_enable() gcc generates no code for
>  > sub_preempt_count().
>  > 
>  > See:
>  > http://userweb.kernel.org/~rw/uml-gcc460/__local_bh_enable-gcc460.txt
>  > vs.
>  > http://userweb.kernel.org/~rw/uml-gcc460/__local_bh_enable-gcc431.txt
>  > 
>  > Interestingly it generates code for add_preempt_count().
>  > I can reproduce this on x86 and x86_64.
>  > 
>  > The problem has to do with UML's current_thread_info() function.
>  > When I replace it with arch/x86's (unportable) variant gcc generates
>  > code.
>  > 
>  > Any ideas whether this is a gcc or a kernel issue?
> 
> Please provide a standalone test case.

There you go!
http://userweb.kernel.org/~rw/uml-gcc460/testcase.c

Thanks,
//richard
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