drm/i915: Beware temporary wedging when determining -EIO

At a few points in our uABI, we check to see if the driver is wedged and
report -EIO back to the user in that case. However, as we perform the
check and reset asynchronously (where once before they were both
serialised by the struct_mutex), we may instead see the temporary wedging
used to cancel inflight rendering to avoid a deadlock during reset
(caused by either us timing out in our reset handler,
i915_wedge_on_timeout or with malice aforethought in intel_reset_prepare
for a stuck modeset). If we suspect this is the case, that is we see a
wedged driver *and* reset in progress, then wait until the reset is
resolved before reporting upon the wedged status.

v2: might_sleep() (Mika)

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=109580
Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20190220145637.23503-1-chris@chris-wilson.co.uk

drivers/gpu/drm/i915/i915_debugfs.c

@@ -3833,11 +3833,18 @@ static const struct file_operations i915_cur_wm_latency_fops = {
 static int
 i915_wedged_get(void *data, u64 *val)
 {
-	struct drm_i915_private *dev_priv = data;
+	int ret = i915_terminally_wedged(data);
 
-	*val = i915_terminally_wedged(&dev_priv->gpu_error);
-
-	return 0;
+	switch (ret) {
+	case -EIO:
+		*val = 1;
+		return 0;
+	case 0:
+		*val = 0;
+		return 0;
+	default:
+		return ret;
+	}
 }
 
 static int
@@ -3918,7 +3925,7 @@ i915_drop_caches_set(void *data, u64 val)
 		mutex_unlock(&i915->drm.struct_mutex);
 	}
 
-	if (val & DROP_RESET_ACTIVE && i915_terminally_wedged(&i915->gpu_error))
+	if (val & DROP_RESET_ACTIVE && i915_terminally_wedged(i915))
 		i915_handle_error(i915, ALL_ENGINES, 0, NULL);
 
 	fs_reclaim_acquire(GFP_KERNEL);

drivers/gpu/drm/i915/i915_drv.h

@@ -3020,11 +3020,16 @@ int __must_check i915_gem_set_global_seqno(struct drm_device *dev, u32 seqno);
 struct i915_request *
 i915_gem_find_active_request(struct intel_engine_cs *engine);
 
-static inline bool i915_terminally_wedged(struct i915_gpu_error *error)
+static inline bool __i915_wedged(struct i915_gpu_error *error)
 {
 	return unlikely(test_bit(I915_WEDGED, &error->flags));
 }
 
+static inline bool i915_reset_failed(struct drm_i915_private *i915)
+{
+	return __i915_wedged(&i915->gpu_error);
+}
+
 static inline u32 i915_reset_count(struct i915_gpu_error *error)
 {
 	return READ_ONCE(error->reset_count);

drivers/gpu/drm/i915/i915_gem.c

@@ -1928,7 +1928,7 @@ err:
 		 * fail). But any other -EIO isn't ours (e.g. swap in failure)
 		 * and so needs to be reported.
 		 */
-		if (!i915_terminally_wedged(&dev_priv->gpu_error))
+		if (!i915_terminally_wedged(dev_priv))
 			return VM_FAULT_SIGBUS;
 		/* else: fall through */
 	case -EAGAIN:
@@ -2958,7 +2958,7 @@ static void assert_kernel_context_is_current(struct drm_i915_private *i915)
 	struct intel_engine_cs *engine;
 	enum intel_engine_id id;
 
-	if (i915_terminally_wedged(&i915->gpu_error))
+	if (i915_reset_failed(i915))
 		return;
 
 	GEM_BUG_ON(i915->gt.active_requests);
@@ -3806,8 +3806,9 @@ i915_gem_ring_throttle(struct drm_device *dev, struct drm_file *file)
 	long ret;
 
 	/* ABI: return -EIO if already wedged */
-	if (i915_terminally_wedged(&dev_priv->gpu_error))
-		return -EIO;
+	ret = i915_terminally_wedged(dev_priv);
+	if (ret)
+		return ret;
 
 	spin_lock(&file_priv->mm.lock);
 	list_for_each_entry(request, &file_priv->mm.request_list, client_link) {
@@ -4460,7 +4461,7 @@ void i915_gem_sanitize(struct drm_i915_private *i915)
 	 * back to defaults, recovering from whatever wedged state we left it
 	 * in and so worth trying to use the device once more.
 	 */
-	if (i915_terminally_wedged(&i915->gpu_error))
+	if (i915_terminally_wedged(i915))
 		i915_gem_unset_wedged(i915);
 
 	/*
@@ -4504,7 +4505,7 @@ int i915_gem_suspend(struct drm_i915_private *i915)
 	 * state. Fortunately, the kernel_context is disposable and we do
 	 * not rely on its state.
 	 */
-	if (!i915_terminally_wedged(&i915->gpu_error)) {
+	if (!i915_reset_failed(i915)) {
 		ret = i915_gem_switch_to_kernel_context(i915);
 		if (ret)
 			goto err_unlock;
@@ -4625,8 +4626,9 @@ out_unlock:
 	return;
 
 err_wedged:
-	if (!i915_terminally_wedged(&i915->gpu_error)) {
-		DRM_ERROR("failed to re-initialize GPU, declaring wedged!\n");
+	if (!i915_reset_failed(i915)) {
+		dev_err(i915->drm.dev,
+			"Failed to re-initialize GPU, declaring it wedged!\n");
 		i915_gem_set_wedged(i915);
 	}
 	goto out_unlock;
@@ -4731,10 +4733,9 @@ int i915_gem_init_hw(struct drm_i915_private *dev_priv)
 	init_unused_rings(dev_priv);
 
 	BUG_ON(!dev_priv->kernel_context);
-	if (i915_terminally_wedged(&dev_priv->gpu_error)) {
-		ret = -EIO;
+	ret = i915_terminally_wedged(dev_priv);
+	if (ret)
 		goto out;
-	}
 
 	ret = i915_ppgtt_init_hw(dev_priv);
 	if (ret) {
@@ -5107,7 +5108,7 @@ err_uc_misc:
 		 * wedged. But we only want to do this where the GPU is angry,
 		 * for all other failure, such as an allocation failure, bail.
 		 */
-		if (!i915_terminally_wedged(&dev_priv->gpu_error)) {
+		if (!i915_reset_failed(dev_priv)) {
 			i915_load_error(dev_priv,
 					"Failed to initialize GPU, declaring it wedged!\n");
 			i915_gem_set_wedged(dev_priv);

drivers/gpu/drm/i915/i915_request.c

@@ -559,8 +559,9 @@ i915_request_alloc(struct intel_engine_cs *engine, struct i915_gem_context *ctx)
 	 * ABI: Before userspace accesses the GPU (e.g. execbuffer), report
 	 * EIO if the GPU is already wedged.
 	 */
-	if (i915_terminally_wedged(&i915->gpu_error))
-		return ERR_PTR(-EIO);
+	ret = i915_terminally_wedged(i915);
+	if (ret)
+		return ERR_PTR(ret);
 
 	/*
 	 * Pinning the contexts may generate requests in order to acquire

drivers/gpu/drm/i915/i915_reset.c

@@ -1032,7 +1032,7 @@ void i915_reset(struct drm_i915_private *i915,
 
 finish:
 	reset_finish(i915);
-	if (!i915_terminally_wedged(error))
+	if (!__i915_wedged(error))
 		reset_restart(i915);
 	return;
 
@@ -1253,7 +1253,7 @@ void i915_handle_error(struct drm_i915_private *i915,
 	 * Try engine reset when available. We fall back to full reset if
 	 * single reset fails.
 	 */
-	if (intel_has_reset_engine(i915) && !i915_terminally_wedged(error)) {
+	if (intel_has_reset_engine(i915) && !__i915_wedged(error)) {
 		for_each_engine_masked(engine, i915, engine_mask, tmp) {
 			BUILD_BUG_ON(I915_RESET_MODESET >= I915_RESET_ENGINE);
 			if (test_and_set_bit(I915_RESET_ENGINE + engine->id,
@@ -1339,6 +1339,31 @@ __releases(&i915->gpu_error.reset_backoff_srcu)
 	srcu_read_unlock(&error->reset_backoff_srcu, tag);
 }
 
+int i915_terminally_wedged(struct drm_i915_private *i915)
+{
+	struct i915_gpu_error *error = &i915->gpu_error;
+
+	might_sleep();
+
+	if (!__i915_wedged(error))
+		return 0;
+
+	/* Reset still in progress? Maybe we will recover? */
+	if (!test_bit(I915_RESET_BACKOFF, &error->flags))
+		return -EIO;
+
+	/* XXX intel_reset_finish() still takes struct_mutex!!! */
+	if (mutex_is_locked(&i915->drm.struct_mutex))
+		return -EAGAIN;
+
+	if (wait_event_interruptible(error->reset_queue,
+				     !test_bit(I915_RESET_BACKOFF,
+					       &error->flags)))
+		return -EINTR;
+
+	return __i915_wedged(error) ? -EIO : 0;
+}
+
 bool i915_reset_flush(struct drm_i915_private *i915)
 {
 	int err;

drivers/gpu/drm/i915/i915_reset.h

@@ -36,6 +36,8 @@ bool i915_reset_flush(struct drm_i915_private *i915);
 int __must_check i915_reset_trylock(struct drm_i915_private *i915);
 void i915_reset_unlock(struct drm_i915_private *i915, int tag);
 
+int i915_terminally_wedged(struct drm_i915_private *i915);
+
 bool intel_has_gpu_reset(struct drm_i915_private *i915);
 bool intel_has_reset_engine(struct drm_i915_private *i915);
 

drivers/gpu/drm/i915/intel_engine_cs.c

@@ -1007,10 +1007,8 @@ static bool ring_is_idle(struct intel_engine_cs *engine)
  */
 bool intel_engine_is_idle(struct intel_engine_cs *engine)
 {
-	struct drm_i915_private *dev_priv = engine->i915;
-
 	/* More white lies, if wedged, hw state is inconsistent */
-	if (i915_terminally_wedged(&dev_priv->gpu_error))
+	if (i915_reset_failed(engine->i915))
 		return true;
 
 	/* Any inflight/incomplete requests? */
@@ -1054,7 +1052,7 @@ bool intel_engines_are_idle(struct drm_i915_private *dev_priv)
 	 * If the driver is wedged, HW state may be very inconsistent and
 	 * report that it is still busy, even though we have stopped using it.
 	 */
-	if (i915_terminally_wedged(&dev_priv->gpu_error))
+	if (i915_reset_failed(dev_priv))
 		return true;
 
 	for_each_engine(engine, dev_priv, id) {
@@ -1496,7 +1494,7 @@ void intel_engine_dump(struct intel_engine_cs *engine,
 		va_end(ap);
 	}
 
-	if (i915_terminally_wedged(&engine->i915->gpu_error))
+	if (i915_reset_failed(engine->i915))
 		drm_printf(m, "*** WEDGED ***\n");
 
 	drm_printf(m, "\tcurrent seqno %x, last %x, hangcheck %x [%d ms]\n",

drivers/gpu/drm/i915/intel_hangcheck.c

@@ -263,7 +263,7 @@ static void i915_hangcheck_elapsed(struct work_struct *work)
 	if (!READ_ONCE(dev_priv->gt.awake))
 		return;
 
-	if (i915_terminally_wedged(&dev_priv->gpu_error))
+	if (i915_terminally_wedged(dev_priv))
 		return;
 
 	/* As enabling the GPU requires fairly extensive mmio access,

drivers/gpu/drm/i915/selftests/huge_pages.c

@@ -1764,7 +1764,7 @@ int i915_gem_huge_page_live_selftests(struct drm_i915_private *dev_priv)
 		return 0;
 	}
 
-	if (i915_terminally_wedged(&dev_priv->gpu_error))
+	if (i915_terminally_wedged(dev_priv))
 		return 0;
 
 	file = mock_file(dev_priv);

drivers/gpu/drm/i915/selftests/i915_active.c

@@ -150,7 +150,7 @@ int i915_active_live_selftests(struct drm_i915_private *i915)
 		SUBTEST(live_active_retire),
 	};
 
-	if (i915_terminally_wedged(&i915->gpu_error))
+	if (i915_terminally_wedged(i915))
 		return 0;
 
 	return i915_subtests(tests, i915);

drivers/gpu/drm/i915/selftests/i915_gem_coherency.c

@@ -248,12 +248,12 @@ static bool always_valid(struct drm_i915_private *i915)
 
 static bool needs_fence_registers(struct drm_i915_private *i915)
 {
-	return !i915_terminally_wedged(&i915->gpu_error);
+	return !i915_terminally_wedged(i915);
 }
 
 static bool needs_mi_store_dword(struct drm_i915_private *i915)
 {
-	if (i915_terminally_wedged(&i915->gpu_error))
+	if (i915_terminally_wedged(i915))
 		return false;
 
 	return intel_engine_can_store_dword(i915->engine[RCS]);

drivers/gpu/drm/i915/selftests/i915_gem_context.c

@@ -1632,7 +1632,7 @@ int i915_gem_context_live_selftests(struct drm_i915_private *dev_priv)
 		SUBTEST(igt_vm_isolation),
 	};
 
-	if (i915_terminally_wedged(&dev_priv->gpu_error))
+	if (i915_terminally_wedged(dev_priv))
 		return 0;
 
 	return i915_subtests(tests, dev_priv);

drivers/gpu/drm/i915/selftests/i915_gem_evict.c

@@ -547,7 +547,7 @@ int i915_gem_evict_live_selftests(struct drm_i915_private *i915)
 		SUBTEST(igt_evict_contexts),
 	};
 
-	if (i915_terminally_wedged(&i915->gpu_error))
+	if (i915_terminally_wedged(i915))
 		return 0;
 
 	return i915_subtests(tests, i915);

drivers/gpu/drm/i915/selftests/i915_gem_object.c

@@ -583,7 +583,7 @@ static int igt_mmap_offset_exhaustion(void *arg)
 	for (loop = 0; loop < 3; loop++) {
 		intel_wakeref_t wakeref;
 
-		if (i915_terminally_wedged(&i915->gpu_error))
+		if (i915_terminally_wedged(i915))
 			break;
 
 		obj = i915_gem_object_create_internal(i915, PAGE_SIZE);

drivers/gpu/drm/i915/selftests/i915_request.c

@@ -1246,7 +1246,7 @@ int i915_request_live_selftests(struct drm_i915_private *i915)
 		SUBTEST(live_breadcrumbs_smoketest),
 	};
 
-	if (i915_terminally_wedged(&i915->gpu_error))
+	if (i915_terminally_wedged(i915))
 		return 0;
 
 	return i915_subtests(tests, i915);

drivers/gpu/drm/i915/selftests/igt_flush_test.c

@@ -29,5 +29,5 @@ int igt_flush_test(struct drm_i915_private *i915, unsigned int flags)
 		i915_gem_set_wedged(i915);
 	}
 
-	return i915_terminally_wedged(&i915->gpu_error) ? -EIO : 0;
+	return i915_terminally_wedged(i915);
 }

drivers/gpu/drm/i915/selftests/intel_hangcheck.c

@@ -342,7 +342,7 @@ static int igt_hang_sanitycheck(void *arg)
 			timeout = i915_request_wait(rq,
 						    I915_WAIT_LOCKED,
 						    MAX_SCHEDULE_TIMEOUT);
-		if (i915_terminally_wedged(&i915->gpu_error))
+		if (i915_reset_failed(i915))
 			timeout = -EIO;
 
 		i915_request_put(rq);
@@ -383,7 +383,7 @@ static int igt_global_reset(void *arg)
 
 	igt_global_reset_unlock(i915);
 
-	if (i915_terminally_wedged(&i915->gpu_error))
+	if (i915_reset_failed(i915))
 		err = -EIO;
 
 	return err;
@@ -401,13 +401,13 @@ static int igt_wedged_reset(void *arg)
 
 	i915_gem_set_wedged(i915);
 
-	GEM_BUG_ON(!i915_terminally_wedged(&i915->gpu_error));
+	GEM_BUG_ON(!i915_reset_failed(i915));
 	i915_reset(i915, ALL_ENGINES, NULL);
 
 	intel_runtime_pm_put(i915, wakeref);
 	igt_global_reset_unlock(i915);
 
-	return i915_terminally_wedged(&i915->gpu_error) ? -EIO : 0;
+	return i915_reset_failed(i915) ? -EIO : 0;
 }
 
 static bool wait_for_idle(struct intel_engine_cs *engine)
@@ -529,7 +529,7 @@ static int __igt_reset_engine(struct drm_i915_private *i915, bool active)
 			break;
 	}
 
-	if (i915_terminally_wedged(&i915->gpu_error))
+	if (i915_reset_failed(i915))
 		err = -EIO;
 
 	if (active) {
@@ -843,7 +843,7 @@ unwind:
 			break;
 	}
 
-	if (i915_terminally_wedged(&i915->gpu_error))
+	if (i915_reset_failed(i915))
 		err = -EIO;
 
 	if (flags & TEST_ACTIVE) {
@@ -969,7 +969,7 @@ unlock:
 	mutex_unlock(&i915->drm.struct_mutex);
 	igt_global_reset_unlock(i915);
 
-	if (i915_terminally_wedged(&i915->gpu_error))
+	if (i915_reset_failed(i915))
 		return -EIO;
 
 	return err;
@@ -1166,7 +1166,7 @@ fini:
 unlock:
 	mutex_unlock(&i915->drm.struct_mutex);
 
-	if (i915_terminally_wedged(&i915->gpu_error))
+	if (i915_reset_failed(i915))
 		return -EIO;
 
 	return err;
@@ -1372,7 +1372,7 @@ unlock:
 	mutex_unlock(&i915->drm.struct_mutex);
 	igt_global_reset_unlock(i915);
 
-	if (i915_terminally_wedged(&i915->gpu_error))
+	if (i915_reset_failed(i915))
 		return -EIO;
 
 	return err;
@@ -1552,7 +1552,7 @@ static int igt_atomic_reset_engine(struct intel_engine_cs *engine,
 			i915_request_wait(rq,
 					  I915_WAIT_LOCKED,
 					  MAX_SCHEDULE_TIMEOUT);
-		if (i915_terminally_wedged(&i915->gpu_error))
+		if (i915_reset_failed(i915))
 			err = -EIO;
 	}
 
@@ -1591,7 +1591,7 @@ static int igt_atomic_reset(void *arg)
 
 	/* Flush any requests before we get started and check basics */
 	force_reset(i915);
-	if (i915_terminally_wedged(&i915->gpu_error))
+	if (i915_reset_failed(i915))
 		goto unlock;
 
 	if (intel_has_gpu_reset(i915)) {
@@ -1665,7 +1665,7 @@ int intel_hangcheck_live_selftests(struct drm_i915_private *i915)
 	if (!intel_has_gpu_reset(i915))
 		return 0;
 
-	if (i915_terminally_wedged(&i915->gpu_error))
+	if (i915_terminally_wedged(i915))
 		return -EIO; /* we're long past hope of a successful reset */
 
 	wakeref = intel_runtime_pm_get(i915);

drivers/gpu/drm/i915/selftests/intel_lrc.c

@@ -895,7 +895,7 @@ int intel_execlists_live_selftests(struct drm_i915_private *i915)
 	if (!HAS_EXECLISTS(i915))
 		return 0;
 
-	if (i915_terminally_wedged(&i915->gpu_error))
+	if (i915_terminally_wedged(i915))
 		return 0;
 
 	return i915_subtests(tests, i915);

drivers/gpu/drm/i915/selftests/intel_workarounds.c

@@ -181,7 +181,7 @@ static int check_whitelist(struct i915_gem_context *ctx,
 	err = 0;
 	igt_wedge_on_timeout(&wedge, ctx->i915, HZ / 5) /* a safety net! */
 		err = i915_gem_object_set_to_cpu_domain(results, false);
-	if (i915_terminally_wedged(&ctx->i915->gpu_error))
+	if (i915_terminally_wedged(ctx->i915))
 		err = -EIO;
 	if (err)
 		goto out_put;
@@ -510,7 +510,7 @@ int intel_workarounds_live_selftests(struct drm_i915_private *i915)
 	};
 	int err;
 
-	if (i915_terminally_wedged(&i915->gpu_error))
+	if (i915_terminally_wedged(i915))
 		return 0;
 
 	mutex_lock(&i915->drm.struct_mutex);