Re: [PATCH v2 35/40] tracing: Reverse the order event_mutex/trace_types_lock are taken

[Steven Rostedt]

On Fri, 8 Sep 2017 15:41:36 -0400
Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:

> On Fri, 8 Sep 2017 15:31:35 -0400
> Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
> 
> > On Tue,  5 Sep 2017 16:57:47 -0500
> > Tom Zanussi <tom.zanussi@xxxxxxxxxxxxxxx> wrote:
> >   
> > > Change the order event_mutex and trace_types_lock are taken, to avoid
> > > circular dependencies and lockdep spew.
> > > 
> > > Changing the order shouldn't matter to any current code, but does to
> > > anything that takes the event_mutex first and then trace_types_lock.
> > > This is the case when calling tracing_set_clock from inside an event
> > > command, which already holds the event_mutex.    
> > 
> > This is a very scary patch. I'll apply it and run a bunch of tests with
> > lockdep enabled. Let's see what blows up (or not).  
> 
> Boom!
>


> It appears to be caused by instance creation. I'll look at that.

OK, this may be a simple fix. I'll send you a patch to fold in after I
finish testing it.

-- Steve