On Tue, 8 May 2007, Oliver Neukum wrote:
> Am Dienstag, 8. Mai 2007 20:33 schrieb Alan Stern:
> > > > > +int usb_wait_anchor_empty_timeout(struct usb_anchor *anchor, int
> > > > > timeout)
> > > > > +{
> > > > > + int res;
> > > > > +
> > > > > + res = wait_event_timeout(anchor->wait,
> > > > > list_empty(&anchor->urb_list), timeout);
> > > >
> > > > Maybe make this an interruptible wait?
> > >
> > > For use in disconnect(), suspend() and pre_reset()? Theses can't handle
> > > signals.
> >
> > What do you mean? They don't have to handle signals. They just have to
> > cut the timeout short when a signal arrives and then kill the outstanding
> > URBs.
>
> Who would send a signal? If this is called with pending URBs, aren't
> tasks frozen?
disconnect() can be called as a result of a user doing:
echo -n $device_name >/sys/bus/usb/drivers/$driver_name/unbind
and a signal could occur if the user presses ^C. suspend() can also be
called as a result of writing to sysfs. pre_reset() can be called as
part of a reset initiated through usbfs. None of these things require
tasks to be frozen.
> > Also, you don't want to contribute to the load average while you're
> > waiting.
>
> Why? This is a system function.
To tell the truth, I never understand the reason why interruptible waits
don't add to the load average and uninterruptible waits do. As far as I
can see, a wait should never count as load since the process isn't doing
anything or using CPU time.
> > Is this really correct? You might end up reporting one user's errors
> > to a different user. But maybe that's the standard approach; I don't
> > know...
>
> We are mixing writes anyway.
Yeah. Oh well.
Alan Stern
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