Re: [RFC][PATCH 2/6] lockdep: validate rcu_dereference() vs rcu_read_lock()

Peter Zijlstra
2007-09-19T19:42:51Z

On Wed, 19 Sep 2007 14:49:56 -0400 "Dmitry Torokhov"
<dmitry.torokhov@gmail.com> wrote:

> On 9/19/07, Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote:

> > PS to previous -- any problem with inserting rcu_read_lock() and
> > rcu_read_unlock() around the portion of the IRQ handler that has
> > these accesses?
> >
>
> I guess I could but it is an extra lock that needs to be managed and
> given the fact that it is not really needed (other to make a newly
> developed tool happy) I am hestsant to do that.

As is, these sites are a bug in -rt and we'll need to fix them anyway.

As for the code you pointed me to, the i8042 driver, it seems to play
way to funny tricks for a simple 'slow' driver.

If you replace the spin_lock() + sync_sched(), with rcu_read_lock() +
rcu_call() it should work again without adding an extra lock.