Re: [PATCH 2/6] PM: Asynchronous resume of devices

Alan Stern
2009-08-30T00:53:03Z

On Sat, 29 Aug 2009, Rafael J. Wysocki wrote:

> On Saturday 29 August 2009, Rafael J. Wysocki wrote:
> > On Saturday 29 August 2009, Alan Stern wrote:
> ...
> > > Strictly speaking, a new thread should be started only when needed.
> > > That is, only when all the existing threads are busy running a
> > > callback. It shouldn't be too hard to keep track of when that happens.
> >
> > The async framework does that for us. :-)
>
> So, when I said "async threads", I should have rather said "async functions",
> because one async thread can execute multiple functions scheduled with
> async_schedule().
>
> Taking that into consideration, it all works like this. When there's a new
> async device to handle and there are no async threads available, a new thread
> is started and it runs the async function that handles the device and
> "opportunistically" searches dpm_list (once) for other device that are ready
> for handling. After this function has returned, the thread goes to sleep and
> it only exits after being idle for 1 s. In turn, when there's a new async
> device to handle and there are async threads available, on of them gets the
> async function to run.
>
> I don't really think we can do much better than this in any other approach.

Since it obviously works and is relatively simple, I guess we ought to
adopt it.

Alan Stern