From: Arnd Bergmann <arnd@arndb.de>
To: eranian@gmail.com
Subject: Re: I.1 - System calls - ioctl
Date: Thu, 30 Jul 2009 19:20:52 +0200
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Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>,
       Christoph Hellwig <hch@infradead.org>, Ingo Molnar <mingo@elte.hu>,
       LKML <linux-kernel@vger.kernel.org>,
       Andrew Morton <akpm@linux-foundation.org>,
       Thomas Gleixner <tglx@linutronix.de>,
       Robert Richter <robert.richter@amd.com>,
       Paul Mackerras <paulus@samba.org>, Andi Kleen <andi@firstfloor.org>,
       Maynard Johnson <mpjohn@us.ibm.com>, Carl Love <cel@us.ibm.com>,
       Corey J Ashford <cjashfor@us.ibm.com>,
       Philip Mucci <mucci@eecs.utk.edu>, Dan Terpstra <terpstra@eecs.utk.edu>,
       "perfmon2-devel" <perfmon2-devel@lists.sourceforge.net>
References: <7c86c4470906161042p7fefdb59y10f8ef4275793f0e@mail.gmail.com> <200907301840.50894.arnd@arndb.de> <7c86c4470907300953g255c6088t7caaa1188be164e3@mail.gmail.com>
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On Thursday 30 July 2009, stephane eranian wrote:
> But that won't always work in the case of a 32-bit monitoring tool
> running on top of
> a 64-bit OS. Imagine the target id is indeed 64-bit, e.g., inode
> number (as suggested
> by Peter). It's not because you are a 32-bit tool than you cannot name
> a monitoring
> resource in a 64-bit OS.

Right, there are obviously things that you cannot address with 
a 'long', but there are potentially other things that you could
that you cannot address with an 'int', e.g. an opaque user
token (representing a user pointer) that you can get back in
the sample data.

In the worst case, you could still redefine the argument as a
transparent union to a long and pointer in the future if you
use a 'long' now. AFAICT, there are no advantages of using
an 'int' instead of a 'long', but there are disadvantages of
using a 'long long'.

	Arnd <><
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