Re: 2.6.39-rc6-mmotm0506 - lockdep splat in RCU code on page fault

Ingo Molnar
2011-05-10T08:58:08Z

* Paul E. McKenney <paulmck@linux.vnet.ibm.com> wrote:

> - raw_spin_lock_irqsave(&rnp->lock, flags);
> - rnp->wakemask |= rdp->grpmask;
> - raw_spin_unlock_irqrestore(&rnp->lock, flags);
> + do {
> + old = rnp->wakemask;
> + new = old | rdp->grpmask;
> + } while (cmpxchg(&rnp->wakemask, old, new) != old);

Hm, isnt this an inferior version of atomic_or_long() in essence?

Note that atomic_or_long() is x86 only, so a generic one would have to be
offered too i suspect, atomic_cmpxchg() driven or so - which would look like
the above loop.

Most architectures could offer atomic_or_long() i suspect.

Thanks,

Ingo