David Brownell wrote:
>
> Worked for me too, though I don't think I've seen that failure.
>
> - Dave
>
The patch is mainly for the MPC850 kind of USB hosts.
Without the patch the USB subsystem often hangs during
bootup (with an USB-ethernet dongle connected).
With the patch it does not hang anymore.
You probably will not see this with OHCI and UHCI very
often but I think there is a minimal chance that this
happens at OHCI too.
(The callback has a higher handicap.
Therefore it depends on how high this handicap is
so that the right one always wins the race)
The MPC850 generates interrupts at the end of a transfer
and not just at the end of a frame. So for short transfers
this can be about ~20 microseconds after the submition of
an urb. And if there is another interrupt pending the
done-interrupt will follow immediately after and so the
submission thread will lose the race and the callback
will be called earlier.
- Roman
> ----- Original Message -----
> From: "Roman Weissgaerber" <[EMAIL PROTECTED]>
> To: <[EMAIL PROTECTED]>
> Cc: <[EMAIL PROTECTED]>
> Sent: Tuesday, March 13, 2001 3:37 AM
> Subject: [linux-usb-devel] pegasus driver
>
> > Hi Petkan,
> >
> > there are some races in the pegasus driver.
> >
> > When you submit an URB please keep in mind that the
> > callback of the URB can be called earlier than
> > the URB-submition returns. In this case you wake up the
> > thread first and than put it to sleep.
> > This **really** happens on
> > a CPU time eating HC architecture.
> >
> > The attached patch against kernel 2.4.2ac20 solves
> > this.
> >
> >
> > - Roman
>
> --------------------------------------------------------------------------------
>
> > --- linux-2.4.2ac20/drivers/usb/pegasus.c Tue Mar 13 12:18:21 2001
> > +++ usb/pegasus.c Tue Mar 13 12:23:09 2001
> > @@ -124,7 +124,8 @@
> > static int get_registers(pegasus_t *pegasus, __u16 indx, __u16 size, void *data)
> > {
> > int ret;
> > -
> > + DECLARE_WAITQUEUE (wait, current);
> > +
> > while ( pegasus->flags & ETH_REGS_CHANGED ) {
> > pegasus->flags |= CTRL_URB_SLEEP;
> > interruptible_sleep_on( &pegasus->ctrl_wait );
> > @@ -140,13 +141,18 @@
> > usb_rcvctrlpipe(pegasus->usb,0),
> > (char *)&pegasus->dr,
> > data, size, ctrl_callback, pegasus );
> > -
> > +
> > + add_wait_queue (&pegasus->ctrl_wait, &wait);
> > + set_current_state(TASK_INTERRUPTIBLE);
> > + pegasus->flags |= CTRL_URB_SLEEP;
> > +
> > if ( (ret = usb_submit_urb( &pegasus->ctrl_urb )) ) {
> > err( __FUNCTION__ " BAD CTRLs %d", ret);
> > goto out;
> > }
> > - pegasus->flags |= CTRL_URB_SLEEP;
> > - interruptible_sleep_on( &pegasus->ctrl_wait );
> > +
> > + schedule();
> > + remove_wait_queue (&pegasus->ctrl_wait, &wait);
> > out:
> > return ret;
> > }
> > @@ -155,7 +161,8 @@
> > static int set_registers(pegasus_t *pegasus, __u16 indx, __u16 size, void *data)
> > {
> > int ret;
> > -
> > + DECLARE_WAITQUEUE (wait, current);
> > +
> > while ( pegasus->flags & ETH_REGS_CHANGED ) {
> > pegasus->flags |= CTRL_URB_SLEEP ;
> > interruptible_sleep_on( &pegasus->ctrl_wait );
> > @@ -171,14 +178,18 @@
> > usb_sndctrlpipe(pegasus->usb,0),
> > (char *)&pegasus->dr,
> > data, size, ctrl_callback, pegasus );
> > -
> > +
> > + add_wait_queue (&pegasus->ctrl_wait, &wait);
> > + set_current_state(TASK_INTERRUPTIBLE);
> > + pegasus->flags |= CTRL_URB_SLEEP;
> > +
> > if ( (ret = usb_submit_urb( &pegasus->ctrl_urb )) ) {
> > err( __FUNCTION__ " BAD CTRL %d", ret);
> > return ret;
> > }
> > - pegasus->flags |= CTRL_URB_SLEEP;
> > - interruptible_sleep_on( &pegasus->ctrl_wait );
> > -
> > +
> > + schedule();
> > + remove_wait_queue (&pegasus->ctrl_wait, &wait);
> > return ret;
> > }
> >
> > @@ -187,7 +198,8 @@
> > {
> > int ret;
> > __u16 dat = data;
> > -
> > + DECLARE_WAITQUEUE (wait, current);
> > +
> > while ( pegasus->flags & ETH_REGS_CHANGED ) {
> > pegasus->flags |= CTRL_URB_SLEEP;
> > interruptible_sleep_on( &pegasus->ctrl_wait );
> > @@ -204,13 +216,18 @@
> > (char *)&pegasus->dr,
> > &data, 1, ctrl_callback, pegasus );
> >
> > + add_wait_queue (&pegasus->ctrl_wait, &wait);
> > + set_current_state(TASK_INTERRUPTIBLE);
> > + pegasus->flags |= CTRL_URB_SLEEP;
> > +
> > if ( (ret = usb_submit_urb( &pegasus->ctrl_urb )) ) {
> > err( __FUNCTION__ " BAD CTRL %d", ret);
> > return ret;
> > }
> > - pegasus->flags |= CTRL_URB_SLEEP;
> > - interruptible_sleep_on( &pegasus->ctrl_wait );
> >
> > + schedule();
> > + remove_wait_queue (&pegasus->ctrl_wait, &wait);
> > +
> > return ret;
> > }
> >
> >
>
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