On Wed, 2010-06-09 at 12:20 +0200, Florian Mickler wrote: > On Wed, 09 Jun 2010 11:38:07 +0200 > Johannes Berg <johannes@xxxxxxxxxxxxxxxx> wrote: > > > On Wed, 2010-06-09 at 11:15 +0200, florian@xxxxxxxxxxx wrote: > > > In order to have the pm_qos framework be callable from interrupt > > > context, all listeners have to also be callable in that context. > > > > That makes no sense at all. Why add work structs _everywhere_ in the > > callees and make the API harder to use and easy to get wrong completely, > > instead of just adding a single work struct that will be queued from the > > caller and dealing with the locking complexity etc. just once. > There are only two listeners at the moment. I suspect that most future > uses of the framework need to be atomic, as the driver that > requests a specific quality of service probably doesn't want to get into > races with the provider of that service(listener). So i suspected the > network listener to be the special case. Well even if it doesn't _want_ to race with it, a lot of drivers like USB drivers etc. can't really do anything without deferring to a workqueue. And what's the race anyway? You get one update, defer the work, and if another update happens inbetween you just read the new value when the work finally runs -- and you end up doing it only once instead of twice. That doesn't seem like a problem. > The race between service-provider and qos-requester for non-atomic > contextes is already there, isn't it? so, locking complexity shouldn't > be worse than before. I have no idea how it works now? I thought you can't request an update from an atomic context. However, if you request a QoS value, it is fundamentally that -- a request. There's no guarantee as to when or how it will be honoured. > But my first approach to this is seen here: > https://lists.linux-foundation.org/pipermail/linux-pm/2010-June/026902.html Icky too. > A third possibility would be to make it dependent on the > type of the constraint, if blocking notifiers are allowed or not. > But that would sacrifice API consistency (update_request for one > constraint is allowed to be called in interrupt context and > update_request for another would be not). I don't see what's wrong with the fourth possibility: Allow calling pm_qos_update_request() from atomic context, but change _it_ to schedule off a work that calls the blocking notifier chain. That avoids the complexity in notify-API users since they have process context, and also in request-API users since they can call it from any context. johannes -- To unsubscribe from this list: send the line "unsubscribe linux-wireless" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
