Re: [PATCH] tracing/markers: make markers select tracepoints

From: Steven Rostedt <rostedt@goodmis.org>
To: "Frank Ch. Eigler" <fche@redhat.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@elte.hu>,
	Randy Dunlap <randy.dunlap@oracle.com>,
	Frederic Weisbecker <fweisbec@gmail.com>,
	linux-kernel@vger.kernel.org, zippel@linux-m68k.org,
	linux-kbuild@vger.kernel.org
Subject: Re: [PATCH] tracing/markers: make markers select tracepoints
Date: Mon, 23 Feb 2009 12:31:31 -0500 (EST)	[thread overview]
Message-ID: <alpine.DEB.2.00.0902231228420.18221@gandalf.stny.rr.com> (raw)
In-Reply-To: <20090223171032.GA2566@redhat.com>

On Mon, 23 Feb 2009, Frank Ch. Eigler wrote:
> 
> > Furthermore, trace_mark() exposes that crap like an ABI, now suppose
> > some distro goes and declares that stable for some daft reason,
> > imagine the poor sod having to fix something littered with
> > trace_mark().
> 
> The impression that this is somehow different with tracepoints is
> mistaken.  Tracepoints are *exactly* as "ABI-like" as markers.
> 

I disagree with this point. markers are text strings that will eventually 
appear to userspace. trace points need translation. A trace point can be 
modified at any time and should never mess up user apps.

You may have a hook to a trace point that provides user apps a text based 
output. If the trace point changes, this hook may break. But the tracer 
maintainer of that hook will be responsible for that change, not the 
maintainer of the code the tracepoint existed in.

-- Steve