Messages in this thread | | | Date | Thu, 29 Oct 2020 10:37:44 -0400 | From | Steven Rostedt <> | Subject | Re: [PATCH 6/9] livepatch/ftrace: Add recursion protection to the ftrace callback |
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On Thu, 29 Oct 2020 14:51:06 +0100 (CET) Miroslav Benes <mbenes@suse.cz> wrote:
> > index b552cf2d85f8..6c0164d24bbd 100644 > > --- a/kernel/livepatch/patch.c > > +++ b/kernel/livepatch/patch.c > > @@ -45,9 +45,13 @@ static void notrace klp_ftrace_handler(unsigned long ip, > > struct klp_ops *ops; > > struct klp_func *func; > > int patch_state; > > + int bit; > > > > ops = container_of(fops, struct klp_ops, fops); > > > > + bit = ftrace_test_recursion_trylock(); > > + if (bit < 0) > > + return; > > This means that the original function will be called in case of recursion. > That's probably fair, but I'm wondering if we should at least WARN about > it.
It's probably what happens today. But if you add a WARN_ON_ONCE() it may not hurt.
I also plan on adding code that reports when recursion has happened, because even if it's not a problem, recursion adds extra overhead.
-- Steve
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