linux-kernel - Re: [PATCH 09/10] perf: Remove more fastpath code

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Date:	Fri, 21 May 2010 13:18:06 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	rostedt@...dmis.org
Cc:	Ingo Molnar <mingo@...e.hu>, Paul Mackerras <paulus@...ba.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Frederic Weisbecker <fweisbec@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 09/10] perf: Remove more fastpath code

On Fri, 2010-05-21 at 07:15 -0400, Steven Rostedt wrote:
> > -     if (WARN_ON_ONCE(((long)(handle->head - handle->offset)) < 0))
> > -             return;
> 
> Are you sure you want to remove this? I mean, sanity checks are a small
> cost (I have several in the ftrace ring buffer) and can catch bugs in
> case something happens during development. Especially when the code is
> under a lot of flux.

Yeah, I pondered adding a CONFIG_PERF_DEBUG for that.. thing is I was
tracking 2 variables just for this, and that seemed a bit excessive.

> I even have a sanity check that Ingo asked me to add, which would detect
> if a tracer (not the ring buffer, but the user of the ring buffer)
> recursed on itself. I think that check detected one bug in the function
> tracer in the begging, but hasn't caught anything since.

I still have recursion checks.

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