Date: Wed, 17 Jun 2009 15:28:39 +0200
From: Ingo Molnar <mingo@elte.hu>
To: Paul Mackerras <paulus@samba.org>
Cc: benh@kernel.crashing.org, Peter Zijlstra <a.p.zijlstra@chello.nl>,
       linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org
Subject: Re: [PATCH 6/6] perf_counter: tools: Makefile tweaks for 64-bit
	powerpc
Message-ID: <20090617132839.GA15428@elte.hu>
References: <19000.55404.103840.393470@cargo.ozlabs.ibm.com> <19000.55666.866148.559620@cargo.ozlabs.ibm.com> <20090617120831.GB26454@elte.hu> <19000.57673.618229.523229@cargo.ozlabs.ibm.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <19000.57673.618229.523229@cargo.ozlabs.ibm.com>
User-Agent: Mutt/1.5.18 (2008-05-17)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 1790
Lines: 48


* Paul Mackerras <paulus@samba.org> wrote:

> Ingo Molnar writes:
> 
> > ah, it does this:
> > 
> > /*
> >  * This is here because we used to use l64 for 64bit powerpc
> >  * and we don't want to impact user mode with our change to ll64
> >  * in the kernel.
> >  */
> > #if defined(__powerpc64__) && !defined(__KERNEL__)
> > # include <asm-generic/int-l64.h>
> > #else
> > # include <asm-generic/int-ll64.h>
> > #endif
> > 
> > That's crappy really.
> 
> We were concerned that changing the userland-visible type of __u64 
> from unsigned long to unsigned long long, etc., would be breaking 
> the ABI, even if only in a small way - I thought it could possibly 
> change C++ mangled function names, for instance, and it would 
> cause fresh compile warnings on existing user code that prints 
> __u64 with %lx, which has always been the correct thing to do on 
> ppc64.
> 
> A counter-argument would be, I guess, that __u64 et al. are purely 
> for use in describing the kernel/user interface, so we have a 
> little more latitude than with the type of e.g. u_int64_t.  I 
> dunno.  I don't recall getting much of an answer from the glibc 
> guys about what they thought of the idea of changing it.
> 
> Anyway, of the 64-bit architectures, alpha, ia64, and mips64 also 
> have __u64 as unsigned long in userspace, so this issue will still 
> crop up even if we change it on powerpc.

Having crap elsewhere is no reason to spread it further really. We 
need consistent types. Can we define __KERNEL__ perhaps to get to 
the real types?

	Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/