On Wed, Sep 26, 2007 at 10:54:46PM +0200, Peter Zijlstra wrote: > > On Wed, 2007-09-26 at 12:55 -0700, Paul E. McKenney wrote: > > > Well, we could make spin_lock_irqsave() invoke rcu_read_lock() and > > spin_lock_irqrestore() invoke rcu_read_unlock(), with similar adjustments > > to the other primitives in this group. Then RCU priority boosting would > > kick in if configured. > > Might be me, but 'hiding' the RCU scope like that makes my skin crawl. > What is wrong with using rcu_read_lock() explicitly where you depend on > it? It even makes the code cleaner in that it documents the usage. > > These blanket locks like lock_kernel(), preempt_disable(), > local_irq_disable() etc. are very hard to get rid of because they don't > document what is protected. > > Please lets not add to this mess and keep all this explicit. > > Yes, -rt changes the preemption model, and that has concequences. But > IMHO the resulting code is cleaner in most cases. I am not going to argue with you on this one!!! But it is not me that needs convincing. > I'd go as far as to depricate synchronize_sched() and replace all its > users with proper RCU. But this might be going too far, though you might well be able to convince me. Reducing RCU API proliferation would be a good thing in general... > The more I think of it, the more I dislike this synchronize_all_irqs() > and the 'magic' property of irq handlers. So I produced a 'magic' patch? Cool!!! ;-) Seriously, I agree that using explicit rcu_read_lock() where needed would be much better from a readability and robustness viewpoint. However, if the goal is to support the existing code unmodified, then this patch is one solution. I would be just as happy to see it become unnecessary as to see it go in, as long as the problem is solved one way or another. Thanx, Paul - To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
