Am Freitag, 15. April 2005 22:59 schrieb Alan Stern:
> On Fri, 15 Apr 2005, Oliver Neukum wrote:
>
> > Am Freitag, 15. April 2005 19:38 schrieb David Brownell:
> > > > IMHO the best way to reduce times is to move all memory
> > > > allocations into urb allocation.
> > >
> > > That's an approach I've thought about. Unfortunately it's costs an
> > > invasive
> > > API change: passing the device (or better yet, usb_host_endpoint) into
> > > the URB allocation. Though to clarify: that would affect allocation of
> > > TDs and any urb-private data, not the data buffers. Something like
> > >
> > > usb_urb_alloc(usb_host_endpoint *ep, // hook to HCD
> > > size_t maxbuf, // ... for prealloc of N TDs
> > > unsigned n_iso,
> > > unsigned gfp_flags);
> > >
> >
> > It is pretty straightforward a change. Auditing locking in all drivers is
> > not.
> > Switching to tasklets would result in revisting locking in drivers.
>
> Why would switching uhci-hcd over to a tasklet require any change in other
> drivers?
You have to audit all drivers to check them for synchronization between
the callback and other hard irqs. In addition to reap the full benefit from
a switch to tasklets, you'd have to change the drivers to use spin_lock_bh().
Regards
Oliver
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