Messages in this thread | | | Subject | Re: [PATCH 17/21] workqueue: simple reimplementation of SINGLE_THREAD workqueue | From | Andy Walls <> | Date | Tue, 17 Nov 2009 07:05:25 -0500 |
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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.
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