On Tue, 20 Oct 2015 18:39:52 +0200
Peter Zijlstra <[email protected]> wrote:
> On Tue, Oct 20, 2015 at 12:21:03PM -0400, Steven Rostedt wrote:
> > +++ b/kernel/module.c
> > @@ -284,11 +284,25 @@ static void module_assert_mutex(void)
> > static void module_assert_mutex_or_preempt(void)
> > {
> > #ifdef CONFIG_LOCKDEP
> > + static int once;
> > +
> > if (unlikely(!debug_locks))
> > return;
> >
> > - WARN_ON(!rcu_read_lock_sched_held() &&
> > - !lockdep_is_held(&module_mutex));
> > + /*
> > + * Would be nice to use WARN_ON_ONCE(), but the warning
> > + * that causes a stack trace may call __module_address()
> > + * which may call here, and we trigger the warning again,
> > + * before the WARN_ON_ONCE() updates its flag.
> > + * To prevent the recursion, we need to open code the
> > + * once logic.
> > + */
> > + if (!once &&
> > + unlikely(!rcu_read_lock_sched_held() &&
> > + !lockdep_is_held(&module_mutex))) {
> > + once++;
>
> once = 1;
>
> is more 'once' :-) Otherwise its once every 4-odd billion.
Once it's not 0, it never gets incremented again.
-- Steve
>
> > + WARN_ON(1);
> > + }
> > #endif
> > }
> >
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