Re: [PATCH] ftrace: Remove possible deadlock between register_kprobe() and ftrace_run_update_code()

[Thomas Gleixner]

On Thu, 27 Jun 2019, Josh Poimboeuf wrote:
> On Fri, Jun 28, 2019 at 01:09:08AM +0200, Thomas Gleixner wrote:
> > On Thu, 27 Jun 2019, Steven Rostedt wrote:
> > > I agree with Josh on this. As the original bug was the race between
> > > ftrace and live patching / modules changing the text from ro to rw and
> > > vice versa. Just protecting the update to the text permissions is more
> > > robust, and should be more self documenting when we need to handle
> > > other architectures for this.
> > 
> > How is that supposed to work?
> > 
> >     ftrace  	     	
> > 	prepare()
> > 	 setrw()
> > 			setro()
> > 	patch <- FAIL
> 
> /me dodges frozen shark
> 
> You are right of course.  My brain has apparently already shut off for
> the day.
> 
> Maybe a comment or two would help though.

Agreed. That would indeed be useful.

Thanks,

	tglx