Re: bug: ftrace & lockdep badness

[Steven Rostedt]

On Wed, 5 Nov 2008, Ingo Molnar wrote:

> 
> * Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> 
> > This is the type of problems we deal with when we have the tracer 
> > tracing lockdep code at the same time the lockdep code is checking 
> > the tracer.
> 
> ok ... you are right, i guess we need to go back to raw locks after 
> all?

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.

This way we can still test the integrity of the ring_buffer for other 
tracers. We just need to be careful when we are using function tracing or 
irqs/preempt off tracing. But we need to be careful with those anyway.

-- Steve

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