On Saturday, February 7, 2009 6:54 am Michel Dänzer wrote:
> On Fri, 2009-02-06 at 13:04 -0800, Jesse Barnes wrote:
> > In dc1336ff4fe08ae7cfe8301bfd7f0b2cfd31d20a (set vblank enable flag
> > correctly across IRQ uninstall), we made sure drivers that uninstall
> > their interrupt handler set the vblank enabled flag correctly, so that
> > when interrupts are re-enabled, vblank interrupts & counts work as
> > expected. However I missed the last_vblank field: it needs to be
> > updated as well, otherwise, at the next drm_update_vblank_count we'll end
> > up comparing a current count to a stale one (the last one captured by the
> > disable function), which may trigger the wraparound handling, leading to
> > a jumpy counter and hangs in drm_wait_vblank.
> >
> > The jumpy counter can prevent the DRM_WAIT_ON from returning success if
> > the difference between the current count and the requested count is
> > greater than 2^23, leading to timeouts or hangs, if the ioctl is
> > restarted in a loop (as is the case in libdrm < 2.4.4).
> >
> > Signed-off-by: Jesse Barnes <jbar...@virtuousgeek.org>
> >
> > diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
> > index 69aa0ab..3795dbc 100644
> > --- a/drivers/gpu/drm/drm_irq.c
> > +++ b/drivers/gpu/drm/drm_irq.c
> > @@ -276,6 +276,7 @@ int drm_irq_uninstall(struct drm_device * dev)
> > for (i = 0; i < dev->num_crtcs; i++) {
> > DRM_WAKEUP(&dev->vbl_queue[i]);
> > dev->vblank_enabled[i] = 0;
> > + dev->last_vblank[i] = dev->driver->get_vblank_counter(dev, i);
> > }
> > spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
>
> It probably comes as no surprise to you that I like this much better
> than the workarounds proposed previously. :)
I guess we can take that as an ack then :)
I really wish we didn't uninstall our IRQ handler in the xf86-video-intel
driver; hope you don't make the same mistake on radeon.
--
Jesse Barnes, Intel Open Source Technology Center
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