Re: [PATCH 0/6] [git pull] updates for tip/tracing/ftrace

[Ingo Molnar <mingo@elte.hu>]

* Frederic Weisbecker <fweisbec@gmail.com> wrote:

> > the function-graph-tracer started locking up since the last 
> > batch of changes:
> > 
> >  Testing tracer sysprof: .. no entries found ..FAILED!
> >  initcall 0xffffffff812e91d1 returned -1 after 101562 usecs
> >  initcall 0xffffffff812e91d1 returned with error code -1 
> >  calling  0xffffffff812e91e3 @ 1
> >  Testing tracer function: PASSED
> >  Testing dynamic ftrace: 
> >  [hard lockup]
> 
> I've successfully reproduced it with your config.
> Note that I didn't built the function graph tracer.
> 
> I also tried to set ftrace=nop as a parameter to avoid the selftests and then
> enabled the function tracer after the boot. And then I had no problem.
> 
> Looks like it happens during dynamic ftrace initialization.
> Perhaps a problem with the recent mutex conversion and kstopmachine, which
> could result in a hardlockup in case of a deadlock.
> 
> But lockdep didn't say anything.
> I'm reverting some of the last patches and will see.

Frederic, Steve, any progress on this bug? It's blocking all new 
tracing patches.

	Ingo