On Thu, 2012-09-06 at 14:29 -0700, Paul E. McKenney wrote:
>
> > Didn't we talk about having the rcu_dereference_raw() not do the check?
> > The function tracer is just too invasive to add work arounds to prevent
> > lockdep from screaming about it.
>
> Actually, rcu_dereference_raw() is already supposed to bypass the
> lockdep checks. And the code looks to me like it does the bypass,
> OR-ing "1" into the asssertion condition.
>
> So what am I missing here?
>From my tree, I see:
#define rcu_dereference_raw(p) rcu_dereference_check(p, 1)
#define rcu_dereference_check(p, c) \
__rcu_dereference_check((p), rcu_read_lock_held() || (c), __rcu)
Note the 'c' comes after rcu_read_lock_held()
static inline int rcu_read_lock_held(void)
{
if (!debug_lockdep_rcu_enabled())
return 1;
if (rcu_is_cpu_idle())
return 0;
if (!rcu_lockdep_current_cpu_online())
return 0;
return lock_is_held(&rcu_lock_map);
}
Then when lock_is_held() is called, we get the false warning message.
-- Steve
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