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Date: Fri, 28 Feb 2014 21:58:28 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>, Vince Weaver <vincent.weaver@maine.edu>,
        Linux Kernel <linux-kernel@vger.kernel.org>,
        Ingo Molnar <mingo@redhat.com>, Jiri Olsa <jolsa@redhat.com>,
        Arnaldo Carvalho de Melo <acme@ghostprotocols.net>
Subject: Re: [PATCH] x86: Rename copy_from_user_nmi() to
 copy_from_user_trace()
Message-ID: <20140228205828.GE14089@laptop.programming.kicks-ass.net>
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On Fri, Feb 28, 2014 at 03:51:30PM -0500, Steven Rostedt wrote:
> On Fri, 28 Feb 2014 21:46:21 +0100
> Peter Zijlstra <peterz@infradead.org> wrote:
> 
> > On Fri, Feb 28, 2014 at 02:33:16PM -0500, Steven Rostedt wrote:
> > > [ H. Peter, Here's the rename patch. I did not include your update. You
> > > can add that first and then massage this patch on top. But this isn't
> > > critical for mainline or stable, where as I believe your patch is. ]
> > > 
> > > The tracing utilities sometimes need to read from userspace (stack tracing),
> > > and to do this it has as special copy_from_user function called
> > > copy_from_user_nmi(). Well, as tracers can call this from outside of
> > > nmi context, the "_nmi" part is a misnomer and "_trace" is a better
> > > name.
> > 
> > NAK, spin_lock_irq() is very much an IRQ safe lock. Similarly
> > copy_from_user_nmi() is an NMI safe copy from user.
> > 
> > Furthermore, there's exactly 0 trace users, so the proposed name is
> > actively worse.
> 
> Heh, I consider perf and oprofile special tracers ;-)

They're first and foremost profilers; which is an entirely different
thing. But other people seem to get confused on this distinction too.