On Wed, Jun 11, 2014 at 07:07:05PM +0200, Oleg Nesterov wrote: > On 06/11, Paul E. McKenney wrote: > > > > @@ -1202,10 +1204,14 @@ static int rcu_boost(struct rcu_node *rnp) > > t = container_of(tb, struct task_struct, rcu_node_entry); > > rt_mutex_init_proxy_locked(&mtx, t); > > t->rcu_boost_mutex = &mtx; > > + init_completion(&rnp->boost_completion); > > can't rcu_init_one() do this? but this is minor,
It could, but I would have to define yet another init-time function under CONFIG_RCU_BOOST and not. Yeah, lazy... > > raw_spin_unlock_irqrestore(&rnp->lock, flags); > > rt_mutex_lock(&mtx); /* Side effect: boosts task t's priority. */ > > rt_mutex_unlock(&mtx); /* Keep lockdep happy. */ > > > > + /* Wait until boostee is done accessing mtx before reinitializing. */ > > + wait_for_completion(&rnp->boost_completion); > > + > > I must have missed something, I dont understand why we need > ->boost_completion. Because rt_mutex_init_proxy_locked() stomps on mtx periodically. Which might happen to be work at the moment, but doesn't seem like a particularly good thing. > What if you simply move that rt_mutex into rcu_node ? > > Or. Given that rcu_boost_kthread() never exits, it can declare this mutex > on stack and pass the pointer to rcu_boost() ? It is true that moving mtx to either the rcu_node structure or to rcu_boost_kthread()'s stack frame would preserve type safety, but not initialization safety. Or maybe I am being too paranoid? Thanx, Paul -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/