Bug 30073

I forgot to mention both trees were from git://anongit.freedesktop.org/~ickle/drm-intel .

The obvious question is whether hangcheck is doing its job properly and preventing a machine hang?


diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 59457e8..294361b 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -1353,8 +1353,8 @@ void i915_hangcheck_elapsed(unsigned long data)
                dev_priv->hangcheck_count = 0;
 
                /* Issue a wake-up to catch stuck h/w. */
-               if (dev_priv->render_ring.waiting_gem_seqno |
-                   dev_priv->bsd_ring.waiting_gem_seqno) {
+               if (0&&(dev_priv->render_ring.waiting_gem_seqno |
+                       dev_priv->bsd_ring.waiting_gem_seqno)) {
                        DRM_ERROR("Hangcheck timer elapsed... GPU idle, missed I
                        if (dev_priv->render_ring.waiting_gem_seqno)
                                DRM_WAKEUP(&dev_priv->render_ring.irq_queue);

With the patch in comment #3 the pauses every 10 seconds still occur in the latest drm-intel-fixes (2.6.36-rc3-00028-gc3add4b) but no message about the pause is logged in dmesg. Perhaps each pause is ever so slightly smaller than previously.

So the periodic stall is due to "hotplug" polling: https://bugs.freedesktop.org/show_bug.cgi?id=29536

The fact that this now causes an error to be displayed is obviously ++bad.

As mentioned in the previous comment, using
echo n >  /sys/module/drm_kms_helper/parameters/poll
resolves the problem seen in drm-intel-fixes. However, the regular half second stutters of drm-intel-next are not resolved by doing this.

Created attachment 38571 [details] [review]
check the wait request is still pending before generating an error.

This should prevent the "missed irq" error when under heavy load (such as the load-detect polling on i8xx/i915).

[It's in -staging as well.]

With the latest -staging (which has the patch mentioned in comment #6 in it) the 10 second jerkiness when drm_kms_helper's poll is y is still there but the hangcheck messages no longer appear in dmesg.

Perfect testing, just the result I was hoping for.

* moves to -fixes.

Marking this bug as fixed. Sitsofe, please can you file a new bug for the -next stutter.