On Wed, 26 Jun 2019 16:44:45 +0200 (CEST)
Thomas Gleixner [off-list ref] wrote:

quoted

It should be enough to fix the original problem because
x86 is the only architecture that calls set_all_modules_text_rw()
in ftrace path and supports livepatching at the same time.  

Looks correct, but I've paged out all the gory details vs. lock ordering in
that area.

I don't believe ftrace_lock and text_mutex had an order before Petr's
initial patches. Reversing them shouldn't be an issue here. They were
basically both "leaf" mutexes (not grabbing any mutexes when they are
held).

-- Steve