drm/i915: Convert hangcheck from a timer into a delayed work item

When run as a timer, i915_hangcheck_elapsed() must adhere to all the
rules of running in a softirq context. This is advantageous to us as we
want to minimise the risk that a driver bug will prevent us from
detecting a hung GPU. However, that is irrelevant if the driver bug
prevents us from resetting and recovering. Still it is prudent not to
rely on mutexes inside the checker, but given the coarseness of
dev->struct_mutex doing so is extremely hard.

Give in and run from a work queue, i.e. outside of softirq.

v2: Use own workqueue to avoid deadlocks (Daniel)
    Cleanup commit msg and add comment to i915_queue_hangcheck() (Chris)

Cc: Jani Nikula <jani.nikula@intel.com>
Cc: Daniel Vetter <dnaiel.vetter@ffwll.chm>
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk> (v1)
Signed-off-by: Mika Kuoppala <mika.kuoppala@intel.com>
[danvet: Remove accidental kerneldoc comment starter, to appease the 0
day builder.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 12 insertions, 1 deletions

diff --git a/drivers/gpu/drm/i915/i915_dma.c b/drivers/gpu/drm/i915/i915_dma.c
index 51e8fe5f1813..6eaf79504b58 100644
--- a/drivers/gpu/drm/i915/i915_dma.c
+++ b/drivers/gpu/drm/i915/i915_dma.c
@@ -790,6 +790,14 @@ int i915_driver_load(struct drm_device *dev, unsigned long flags)
 		goto out_freewq;
 	}
 
+	dev_priv->gpu_error.hangcheck_wq =
+		alloc_ordered_workqueue("i915-hangcheck", 0);
+	if (dev_priv->gpu_error.hangcheck_wq == NULL) {
+		DRM_ERROR("Failed to create our hangcheck workqueue.\n");
+		ret = -ENOMEM;
+		goto out_freedpwq;
+	}
+
 	intel_irq_init(dev_priv);
 	intel_uncore_sanitize(dev);
 
@@ -864,6 +872,8 @@ out_gem_unload:
 	intel_teardown_gmbus(dev);
 	intel_teardown_mchbar(dev);
 	pm_qos_remove_request(&dev_priv->pm_qos);
+	destroy_workqueue(dev_priv->gpu_error.hangcheck_wq);
+out_freedpwq:
 	destroy_workqueue(dev_priv->dp_wq);
 out_freewq:
 	destroy_workqueue(dev_priv->wq);
@@ -934,7 +944,7 @@ int i915_driver_unload(struct drm_device *dev)
 	}
 
 	/* Free error state after interrupts are fully disabled. */
-	del_timer_sync(&dev_priv->gpu_error.hangcheck_timer);
+	cancel_delayed_work_sync(&dev_priv->gpu_error.hangcheck_work);
 	cancel_work_sync(&dev_priv->gpu_error.work);
 	i915_destroy_error_state(dev);
 
@@ -960,6 +970,7 @@ int i915_driver_unload(struct drm_device *dev)
 
 	destroy_workqueue(dev_priv->dp_wq);
 	destroy_workqueue(dev_priv->wq);
+	destroy_workqueue(dev_priv->gpu_error.hangcheck_wq);
 	pm_qos_remove_request(&dev_priv->pm_qos);
 
 	i915_global_gtt_cleanup(dev);