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Date: Mon, 26 Jan 2015 16:03:19 +0100
From: Heiko Carstens <heiko.carstens@de.ibm.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Masami Hiramatsu <maasami.hiramatsu.pt@hitachi.com>,
        Vojtech Pavlik <vojtech@suse.cz>, Jiri Kosina <jkosina@suse.cz>,
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        Dominik Vogt <vogt@linux.vnet.ibm.com>,
        Martin Schwidefsky <schwidefsky@de.ibm.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH/RFC 2/3] ftrace: introduce nohotpatch function attribute
Message-ID: <20150126150319.GF4968@osiris>
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On Mon, Jan 26, 2015 at 09:37:01AM -0500, Steven Rostedt wrote:
> On Mon, 26 Jan 2015 13:54:53 +0100
> Heiko Carstens <heiko.carstens@de.ibm.com> wrote:
> 
> > gcc supports an s390 specific function attribute called "hotpatch".
> > It can be used to specify the number of halfwords that shall be added before
> > and after a function that shall be filled with nops for runtime patching.
> > 
> > s390 will use the hotpatch attribute for function tracing, therefore
> > introduce a nohotpatch define, depending on CC_USING_HOTPATCH, and add it
> > to the existing notrace define.
> 
> Are the two mutually exclusive? That is, can you have -pg and hotpatch
> together? Reason why I ask is, if you have either -pg or hotpatch, then
> we only need "no_instrument_function" or "hotpatch" in the notrace
> define, not both. But I could be wrong.

Actually they should be mutually exclusive. I just merged them "just in case".

So something like this

#ifdef CC_USING_HOTPATCH
#define notrace __attribute__((hotpatch(0,0)))
#else
#define notrace __attribute__((no_instrument_function))
#endif

will work as well (just tested).