linux-kernel - Re: [GIT PULL] tracing: use raw spinlocks for trace

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Date:	Wed, 11 Mar 2009 20:45:11 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL] tracing: use raw spinlocks for trace_vprintk

On Wed, 2009-03-11 at 14:32 -0400, Steven Rostedt wrote:
> On Wed, 11 Mar 2009, Ingo Molnar wrote:
> 
> > 
> > * Peter Zijlstra <peterz@...radead.org> wrote:
> > 
> > > On Tue, 2009-03-10 at 21:26 -0400, Steven Rostedt wrote:
> > > 
> > > > commit 80370cb758e7ca2692cd9fb5e413d970b1f4b2b2
> > > > Author: Steven Rostedt <srostedt@...hat.com>
> > > > Date:   Tue Mar 10 17:16:35 2009 -0400
> > > > 
> > > >     tracing: use raw spinlocks for trace_vprintk
> > > >     
> > > >     Impact: prevent locking up by lockdep tracer
> > > >     
> > > >     The lockdep tracer uses trace_vprintk and thus trace_vprintk can not
> > > >     call back into lockdep without locking up.
> > > 
> > > Hmm, I did this when I posted the lockdep tracepoints, so someone then
> > > did a bad copy/paste job when renaming ftrace_printk or something?
> > > 
> > > See efed792d6738964f399a508ef9e831cd60fa4657
> > 
> > What's the conclusion in this thread? I'm holding the pull 
> > until there's agreement.
> 
> I believe the conclusion is that Peter's changes got removed when Frederic 
> removed the old printk version. But his new version did not have the 
> changes.
> 
> My changes are basically the same as Peter's except that I did not do 
> anything with the local_irq_save, since I do not think those are needed.
> 
> Peter,
> 
> Are you fine with the change? I guess it's up to you now.

Yeah, although I'd rather see the raw_local_irq_save() there too, but
the patch as it stands solves the problem.

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