Date: Thu, 27 Nov 2008 13:41:16 +0100
From: Andi Kleen <andi@firstfloor.org>
To: eranian@gmail.com
Cc: Oleg Nesterov <oleg@redhat.com>, Ingo Molnar <mingo@elte.hu>,
       linux-kernel@vger.kernel.org, akpm@linux-foundation.org, x86@kernel.org,
       andi@firstfloor.org, sfr@canb.auug.org.au,
       Roland McGrath <roland@redhat.com>
Subject: Re: [patch 20/24] perfmon: system calls interface
Message-ID: <20081127124116.GK6703@one.firstfloor.org>
References: <492d0c0b.170e660a.15ba.ffffdabf@mx.google.com> <20081126140027.GC6562@elte.hu> <20081126165948.GA15755@redhat.com> <7c86c4470811270425i435a2adcq565d674070fd44db@mail.gmail.com>
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>  int pfm_create(int flags, pfarg_sinfo_t *sif, char *fmt_name, void
> *fmt_arg, size_t arg_sz);
> 
> The kernel would look at the last 3 arguments ONLY if it saw the
> PFM_FL_SMPL_FMT bit
>  set in flags. We follow the model used by open(2).

Normally it's a better model to enforce 0 (or whatever appropiate)
in unused argument. That can be done by checking and returning EINVAL.

> 
> I want to double-check that you are fine with this approach.

My recommendation would be to go with the full format 
from the beginning, because otherwise there is a versioning problem 
with glibc.


-Andi

-- 
ak@linux.intel.com
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