On Die, 2013-06-11 at 16:23 -0700, Andy Lutomirski wrote: > If the device is idle for over ten seconds, then the next attempt to do > anything can race with the lockup detector and cause a bogus lockup > to be detected. > > Oddly, the situation is well-described in the lockup detector's comments > and a fix is even described. This patch implements that fix (and corrects > some typos in the description). > > My system has been stable for about a week running this code. Without this, > my screen would go blank every now and then and, when it came back, everything > would be remarkably slow (the latter is a separate bug). > > Signed-off-by: Andy Lutomirski <luto@xxxxxxxxxxxxxx> [...] > diff --git a/drivers/gpu/drm/radeon/radeon_ring.c b/drivers/gpu/drm/radeon/radeon_ring.c > index 1ef5eaa..fb7b3ea 100644 > --- a/drivers/gpu/drm/radeon/radeon_ring.c > +++ b/drivers/gpu/drm/radeon/radeon_ring.c > @@ -547,12 +547,12 @@ void radeon_ring_lockup_update(struct radeon_ring *ring) > * have CP rptr to a different value of jiffies wrap around which will force > * initialization of the lockup tracking informations. > * > - * A possible false positivie is if we get call after while and last_cp_rptr == > - * the current CP rptr, even if it's unlikely it might happen. To avoid this > - * if the elapsed time since last call is bigger than 2 second than we return > - * false and update the tracking information. Due to this the caller must call > - * radeon_ring_test_lockup several time in less than 2sec for lockup to be reported > - * the fencing code should be cautious about that. > + * A possible false positive is if we get called after a while and > + * last_cp_rptr == the current CP rptr, even if it's unlikely it might > + * happen. To avoid this if the elapsed time since the last call is bigger > + * than 2 second then we return false and update the tracking > + * information. Due to this the caller must call radeon_ring_test_lockup > + * more frequently than once every 2s when waiting. Is it guaranteed that radeon_ring_test_lockup will be called more often than every 2s when waiting? If not, this change might prevent a real lockup from being detected? Either way, I wonder if there might not be a simpler solution to the problem, e.g. by updating last_activity when submitting commands to a previously empty ring. -- Earthling Michel Dänzer | http://www.amd.com Libre software enthusiast | Debian, X and DRI developer _______________________________________________ dri-devel mailing list dri-devel@xxxxxxxxxxxxxxxxxxxxx http://lists.freedesktop.org/mailman/listinfo/dri-devel
