With the gpu reset no longer using a trylock we've the chances of
userspace getting stuck quite a bit. To make that (hopefully) rare
case more paletable time out when waiting for the gpu reset code to
complete and signal this little issue to the caller by returning -EIO.

This should help userspace to somewhat gracefully fall back and
hopefully allow the user to grab some logs and reboot the machine
(instead of staring at a frozen X screen in agony).

Suggested by Chris Wilson because I've been stubborn about allowing
the gpu reset code to fail.

Signed-Off-by: Daniel Vetter <daniel.vet...@ffwll.ch>
---
 drivers/gpu/drm/i915/i915_gem.c |   13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index af6a510..7d28555 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -96,9 +96,18 @@ i915_gem_wait_for_error(struct drm_device *dev)
        if (!atomic_read(&dev_priv->mm.wedged))
                return 0;
 
-       ret = wait_for_completion_interruptible(x);
-       if (ret)
+       /*
+        * Only wait 10 seconds for the gpu reset to complete to avoid hanging
+        * userspace. If it takes that long something really bad is going on and
+        * we should simply try to bail out and fail as gracefully as possible.
+        */
+       ret = wait_for_completion_interruptible_timeout(x, 10*HZ);
+       if (ret == 0) {
+               DRM_ERROR("Timed out waiting for the gpu reset to complete\n");
+               return -EIO;
+       } else if (ret < 0) {
                return ret;
+       }
 
        if (atomic_read(&dev_priv->mm.wedged)) {
                /* GPU is hung, bump the completion count to account for
-- 
1.7.10

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