On Tue, Oct 20, 2015 at 12:46:28PM -0400, Steven Rostedt wrote: > 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.
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