drm/i915: Adjust hangcheck EIO semantics

Owain Ainsworth reported an issue between the interaction of the
hangcheck and userspace immediately (and permanently) falling back to
s/w rasterisation. In order to break the mutex and begin resetting the
GPU, we must abort the current operation (usually within the wait) and
climb sufficiently far back up the call chain to drop the mutex. In his
implementation, Owain has a loop within the ioctl handler to detect the
hang and then sleep until the error handler has run. I've chosen to
return to userspace and report an EAGAIN which should trigger the
userspace ioctl handler to repeat the call (simply because it felt less
invasive...). Before hitting a wedged GPU, we then wait upon completion
of the error handler.

Reported-by: Owain G. Ainsworth <zerooa@googlemail.com>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

1 files changed, 2 insertions, 0 deletions

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 2611e85bdd3d..f2ff258cdfd5 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -363,6 +363,7 @@ typedef struct drm_i915_private {
         spinlock_t error_lock;
         struct drm_i915_error_state *first_error;
         struct work_struct error_work;
+        struct completion error_completion;
         struct workqueue_struct *wq;
 
         /* Display functions */
@@ -957,6 +958,7 @@ extern void i915_mem_takedown(struct mem_block **heap);
 extern void i915_mem_release(struct drm_device * dev,
                              struct drm_file *file_priv, struct mem_block *heap);
 /* i915_gem.c */
+int i915_gem_check_is_wedged(struct drm_device *dev);
 int i915_gem_init_ioctl(struct drm_device *dev, void *data,
                         struct drm_file *file_priv);
 int i915_gem_create_ioctl(struct drm_device *dev, void *data,