linux-kernel - Re: bug: ftrace & lockdep badness

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Date:	Wed, 5 Nov 2008 18:01:18 +0100
From:	"Frédéric Weisbecker" <fweisbec@...il.com>
To:	"Steven Rostedt" <rostedt@...dmis.org>
Cc:	"Ingo Molnar" <mingo@...e.hu>,
	"Heiko Carstens" <heiko.carstens@...ibm.com>,
	"Peter Zijlstra" <a.p.zijlstra@...llo.nl>,
	linux-kernel@...r.kernel.org
Subject: Re: bug: ftrace & lockdep badness

2008/11/5 Steven Rostedt <rostedt@...dmis.org>:
> I do like the fact that lockdep checks it too. But there's times that we
> can not do that.
>
> Perhaps we can do something in between.
>
> Make a rb_spin_lock macro inside ring_buffer.c that can be either a
> spin_lock or a raw_spin_lock.  There are some tracers that must have this
> as a raw (function trace, irqsoff and preemptoff), but the rest should be
> fine. We can make it where the rb_spin_lock is a raw lock when any of
> those three tracers are configured, and make it into a normal lock when
> they are not.


But this way we won't be able to have lockdep checks when only one of
those "raw-need" tracers are
configured. Wouldn't it better to set it as a function pointer? It
would dynamically reference spin_lock or
raw_spin_lock functions depending on what tracer is currently
selected. I think that wouldn't hardly impact
the performances....
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