On Tue, 2009-11-17 at 14:23 +0900, Tejun Heo wrote: > Hello, > > 11/17/2009 09:47 AM, Andy Walls wrote: > > An important property of the single threaded workqueue, upon which the > > cx18 driver relies, is that work objects will be processed strictly in > > the order in which they were queued. The cx18 driver has a pool of > > "work orders" and multiple active work orders can be queued up on the > > workqueue especially if multiple streams are active. If these work > > orders were to be processed out of order, video artifacts would result > > in video display applications. > > That's an interesting use of single thread workqueue. Most of single > thread workqueues seem to be made single thread just to save number of > threads. Some seem to depend on single thread of execution but I > never knew there are ones which depend on the exact execution order. > Do you think that usage is wide-spread? I doubt it. Most that I have seen use the singlethreaded workqueue object with a queue depth of essentially 1 for syncronization - as you have noted. > Implementing strict ordering > shouldn't be too difficult but I can't help but feeling that such > assumption is abuse of implementation detail. Hmmm, does not the "queue" in workqueue mean "FIFO"? If not for strict ordering, why else would a driver absolutely need a singlethreaded workqueue object? It seems to me the strict ording is the driving requirement for a singlethreaded workqueue at all. Your patch series indicates to me that the performance and synchronization use cases are not driving requirements for a singlethreaded workqueue. Thanks for your consideration. Regards, Andy > Thanks. -- To unsubscribe from this list: send the line "unsubscribe linux-media" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
