[Intel-gfx] [PATCH 20/20] drm/i915/selftests: Check that resets are safe from inside the shrinker

[Chris Wilson]

We need to be able to reclaim from any process context, including the
shrinker. We can simulate being inside the shrinker using lockdep and
adjusting the task's reclaim state.

References: https://bugs.freedesktop.org/show_bug.cgi?id=101857
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 drivers/gpu/drm/i915/selftests/intel_hangcheck.c | 39 ++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/drivers/gpu/drm/i915/selftests/intel_hangcheck.c b/drivers/gpu/drm/i915/selftests/intel_hangcheck.c
index 4129d01b67a1..f800bf7a822d 100644
--- a/drivers/gpu/drm/i915/selftests/intel_hangcheck.c
+++ b/drivers/gpu/drm/i915/selftests/intel_hangcheck.c
@@ -359,6 +359,44 @@ static int igt_global_reset(void *arg)
 	return err;
 }
 
+static int igt_reclaim_reset(void *arg)
+{
+	struct drm_i915_private *i915 = arg;
+	unsigned int reset_count;
+	int err = 0;
+
+	/* Check that we can perform a reset from inside the shrinker/kswapd */
+
+	global_reset_lock(i915);
+	set_bit(I915_RESET_HANDOFF, &i915->gpu_error.flags);
+
+	mutex_lock(&i915->drm.struct_mutex);
+	reset_count = i915_reset_count(&i915->gpu_error);
+
+	/* We need to support resets from any process context, including
+	 * from inside the shrinker.
+	 */
+	lockdep_set_current_reclaim_state(GFP_KERNEL);
+
+	i915_reset(i915, I915_RESET_QUIET);
+
+	lockdep_clear_current_reclaim_state();
+
+	if (i915_reset_count(&i915->gpu_error) == reset_count) {
+		pr_err("No GPU reset recorded!\n");
+		err = -EINVAL;
+	}
+	mutex_unlock(&i915->drm.struct_mutex);
+
+	GEM_BUG_ON(test_bit(I915_RESET_HANDOFF, &i915->gpu_error.flags));
+	global_reset_unlock(i915);
+
+	if (i915_terminally_wedged(&i915->gpu_error))
+		err = -EIO;
+
+	return err;
+}
+
 static int igt_reset_engine(void *arg)
 {
 	struct drm_i915_private *i915 = arg;
@@ -840,6 +878,7 @@ int intel_hangcheck_live_selftests(struct drm_i915_private *i915)
 	static const struct i915_subtest tests[] = {
 		SUBTEST(igt_hang_sanitycheck),
 		SUBTEST(igt_global_reset),
+		SUBTEST(igt_reclaim_reset),
 		SUBTEST(igt_reset_engine),
 		SUBTEST(igt_reset_active_engines),
 		SUBTEST(igt_wait_reset),
-- 
2.13.3