On Wed, 19 Aug 2009, Rafael J. Wysocki wrote: > On Wednesday 19 August 2009, Alan Stern wrote: > > On Wed, 19 Aug 2009, Rafael J. Wysocki wrote: > > > > > There's a problem that for safety reasons I maintain the ordering of dpm_list > > > and the callbacks are scheduled for async execution in the same order in > > > which they would have been executed synchronously. If were to change this, > > > we'd have to be _very_ careful. > > > > Why? The order in which jobs are scheduled for async execution doesn't > > bear any particular relation to the order in which they get run. > > Yes, it does, if all of the async threads are busy and we add more async jobs > to the queue. We must ensure that none of the jobs being executed will wait > for any jobs in the queue. That's part of the reason for the dependencies: to make sure that where it matters, things don't run in the wrong order. > Also, if any devices are handled synchronously, they must not wait for any > "async" devices that haven't been scheduled yet. I'm not sure what you mean. If a device is handled synchronously, it must wait for all the devices preceding it on the list, regardless of whether those devices are handled asynchronously. > With a master thread that would do all the waiting that wouldn't be a problem > any more, but I'm not sure how to implement such a thread efficiently. The > problem is that each device may depend on multiple other devices, so even > if one callback finishes, there's no guarantee there will be any device with > satisfied dependencies, so it looks like the master thread would have to > browse dpm_list continuously searching it for devices that are ready for > suspending. > > Also I don't think we can change the ordering of dpm_list as a result of > asynchronous execution. Okay, so I'll try to write something. We'll see how it comes out. Alan Stern _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
