On Thu, 8 Oct 2009, Oliver Neukum wrote:
> Am Mittwoch, 7. Oktober 2009 23:34:12 schrieb Alan Stern:
> > I'm losing track of the original point of this thread. IIRC, the
> > problem is how the resume method should know whether or not to submit
> > the receive URB(s). It can't afford to acquire the port mutex because
> > it might be called by open or close, at which time the mutex is already
> > held.
> >
> > Other schemes could work, but to me it seems simplest to rely on a flag
> > protected by a spinlock. The flag would mean "URBs are supposed to be
> > queued unless we are suspended". It would be set by open and
> > unthrottle, and cleared by close and throttle.
>
> 1. Why a spinlock?
Because the amount of work involved seems too small for a mutex. But
you could use a mutex if you wanted, since everything occurs in process
context.
> 2. Can we get by with only one flag?
If all you want to do is answer a single question ("Should URBs be
submitted") then a single flag should be all you need. Why, do you
think more information will be necessary? You can always add more.
Alan Stern
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