On Wed, Jun 12, 2013 at 6:56 AM, Jerome Glisse j.glisse@gmail.com wrote:
On Wed, Jun 12, 2013 at 6:26 AM, Michel Dänzer michel@daenzer.net wrote:
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@amacapital.net
[...]
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?
Yes it will if you wait for a fence, because the fence timeout wait is way smaller than 2sec so radeon_ring_is_lockup get call several time, which call radeon_ring_force_activity and then radeon_ring_test_lockup.
This also means it very very very unlikely (see below for the likely case) to have a wrap around that give last rptr same as current one.
The likely case is when you have something like a long compute, then nothing is lockup but you keep filling ring with radeon_ring_force_activity but the cp is still stuck on the ib of the compute stuff so rptr does not progress.
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.
Maybe but i still don't think it should matter.
Andy can you test (without your patch) and see if it helps with your issue : http://people.freedesktop.org/~glisse/0001-drm-radeon-update-lockup-tracking...
Testing now. I'll report back in a couple of days.
I don't think that long computes have anything to do with it. The bogus lockups happen when I look away from my computer for a while and then click something. I thing the graphics are usually completely idle when this happens.
AFAIK I've never run an OpenCL or similar application on this system.
--Andy