Messages in this thread | | | Date | Thu, 8 Oct 2009 12:58:08 -0400 (EDT) | From | Alan Stern <> | Subject | Re: [PATCH 4/5] usb_serial: Kill port mutex |
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On Thu, 8 Oct 2009, Oliver Neukum wrote:
> Am Donnerstag, 8. Oktober 2009 16:58:39 schrieb Alan Stern: > > On Thu, 8 Oct 2009, Oliver Neukum wrote: > > > Am Mittwoch, 7. Oktober 2009 23:34:12 schrieb Alan Stern: > > > > > 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. > > We have to submit URBs under that lock.
Yes. What's your point?
> > > 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. > > We have at least three reasons URBs should not be submitted. > - closure > - throttling > - suspension > Resume() should not submit if either closure or throttling are active, > neither should unthrottle() resubmit if closure or suspension are active.
True. Nor should open() submit if throttling is active. Feel free to use three separate flags. :-)
Alan Stern
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