[PATCH 2/2] drm/i915: Proclaim the driver as wedged if oom-locking fails

[Chris Wilson]

If we cannot make forward progress in acquiring the BKL-struct_mutex for
oom, mark the driver as wedged in order to allow the system to recover -
albeit without the GPU until the next resume.

References: https://bugs.freedesktop.org/show_bug.cgi?id=104327
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/i915_gem_shrinker.c | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_gem_shrinker.c b/drivers/gpu/drm/i915/i915_gem_shrinker.c
index 9029ed04879c..8b6aac713deb 100644
--- a/drivers/gpu/drm/i915/i915_gem_shrinker.c
+++ b/drivers/gpu/drm/i915/i915_gem_shrinker.c
@@ -416,8 +416,21 @@ i915_gem_shrinker_oom(struct notifier_block *nb, unsigned long event, void *ptr)
 		container_of(nb, struct drm_i915_private, mm.oom_notifier);
 	struct drm_i915_gem_object *obj;
 	unsigned long unevictable, bound, unbound, freed_pages;
+	bool unlock;
+
+	if (!shrinker_lock_uninterruptible(i915, &unlock, 5000)) {
+		dev_err(i915->drm.dev,
+			"Unable to acquire device lock for oom; marking wedged\n");
+
+		i915_gem_set_wedged(i915);
+		yield();
+
+		*(unsigned long *)ptr += 1; /* try again */
+		return NOTIFY_DONE;
+	}
 
 	freed_pages = i915_gem_shrink_all(i915);
+	shrinker_unlock(i915, unlock);
 
 	/* Because we may be allocating inside our own driver, we cannot
 	 * assert that there are no objects with pinned pages that are not
-- 
2.15.1