drm/i915: Provide a timeout to i915_gem_wait_for_idle()

Usually we have no idea about the upper bound we need to wait to catch
up with userspace when idling the device, but in a few situations we
know the system was idle beforehand and can provide a short timeout in
order to very quickly catch a failure, long before hangcheck kicks in.

In the following patches, we will use the timeout to curtain two overly
long waits, where we know we can expect the GPU to complete within a
reasonable time or declare it broken.

In particular, with a broken GPU we expect it to fail during the initial
GPU setup where do a couple of context switches to record the defaults.
This is a task that takes a few milliseconds even on the slowest of
devices, but we may have to wait 60s for hangcheck to give in and
declare the machine inoperable. In this a case where any gpu hang is
unacceptable, both from a timeliness and practical standpoint.

The other improvement is that in selftests, we do not need to arm an
independent timer to inject a wedge, as we can just limit the timeout on
the wait directly.

v2: Include the timeout parameter in the trace.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Joonas Lahtinen <joonas.lahtinen@linux.intel.com>
Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Cc: Tvrtko Ursulin <tvrtko.ursulin@intel.com>
Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180709122044.7028-1-chris@chris-wilson.co.uk

1 files changed, 29 insertions, 19 deletions

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 1a9dab302433..91d705a67d38 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -2267,7 +2267,9 @@ static int i915_gem_object_create_mmap_offset(struct drm_i915_gem_object *obj)
 
 	/* Attempt to reap some mmap space from dead objects */
 	do {
-		err = i915_gem_wait_for_idle(dev_priv, I915_WAIT_INTERRUPTIBLE);
+		err = i915_gem_wait_for_idle(dev_priv,
+					     I915_WAIT_INTERRUPTIBLE,
+					     MAX_SCHEDULE_TIMEOUT);
 		if (err)
 			break;
 
@@ -3742,14 +3744,14 @@ i915_gem_wait_ioctl(struct drm_device *dev, void *data, struct drm_file *file)
 	return ret;
 }
 
-static int wait_for_timeline(struct i915_timeline *tl, unsigned int flags)
+static long wait_for_timeline(struct i915_timeline *tl,
+			      unsigned int flags, long timeout)
 {
 	struct i915_request *rq;
-	long ret;
 
 	rq = i915_gem_active_get_unlocked(&tl->last_request);
 	if (!rq)
-		return 0;
+		return timeout;
 
 	/*
 	 * "Race-to-idle".
@@ -3763,10 +3765,10 @@ static int wait_for_timeline(struct i915_timeline *tl, unsigned int flags)
 	if (flags & I915_WAIT_FOR_IDLE_BOOST)
 		gen6_rps_boost(rq, NULL);
 
-	ret = i915_request_wait(rq, flags, MAX_SCHEDULE_TIMEOUT);
+	timeout = i915_request_wait(rq, flags, timeout);
 	i915_request_put(rq);
 
-	return ret < 0 ? ret : 0;
+	return timeout;
 }
 
 static int wait_for_engines(struct drm_i915_private *i915)
@@ -3782,10 +3784,12 @@ static int wait_for_engines(struct drm_i915_private *i915)
 	return 0;
 }
 
-int i915_gem_wait_for_idle(struct drm_i915_private *i915, unsigned int flags)
+int i915_gem_wait_for_idle(struct drm_i915_private *i915,
+			   unsigned int flags, long timeout)
 {
-	GEM_TRACE("flags=%x (%s)\n",
-		  flags, flags & I915_WAIT_LOCKED ? "locked" : "unlocked");
+	GEM_TRACE("flags=%x (%s), timeout=%ld%s\n",
+		  flags, flags & I915_WAIT_LOCKED ? "locked" : "unlocked",
+		  timeout, timeout == MAX_SCHEDULE_TIMEOUT ? " (forever)" : "");
 
 	/* If the device is asleep, we have no requests outstanding */
 	if (!READ_ONCE(i915->gt.awake))
@@ -3798,9 +3802,9 @@ int i915_gem_wait_for_idle(struct drm_i915_private *i915, unsigned int flags)
 		lockdep_assert_held(&i915->drm.struct_mutex);
 
 		list_for_each_entry(tl, &i915->gt.timelines, link) {
-			err = wait_for_timeline(tl, flags);
-			if (err)
-				return err;
+			timeout = wait_for_timeline(tl, flags, timeout);
+			if (timeout < 0)
+				return timeout;
 		}
 
 		err = wait_for_engines(i915);
@@ -3812,12 +3816,13 @@ int i915_gem_wait_for_idle(struct drm_i915_private *i915, unsigned int flags)
 	} else {
 		struct intel_engine_cs *engine;
 		enum intel_engine_id id;
-		int err;
 
 		for_each_engine(engine, i915, id) {
-			err = wait_for_timeline(&engine->timeline, flags);
-			if (err)
-				return err;
+			struct i915_timeline *tl = &engine->timeline;
+
+			timeout = wait_for_timeline(tl, flags, timeout);
+			if (timeout < 0)
+				return timeout;
 		}
 	}
 
@@ -5052,7 +5057,8 @@ int i915_gem_suspend(struct drm_i915_private *dev_priv)
 		ret = i915_gem_wait_for_idle(dev_priv,
 					     I915_WAIT_INTERRUPTIBLE |
 					     I915_WAIT_LOCKED |
-					     I915_WAIT_FOR_IDLE_BOOST);
+					     I915_WAIT_FOR_IDLE_BOOST,
+					     MAX_SCHEDULE_TIMEOUT);
 		if (ret && ret != -EIO)
 			goto err_unlock;
 
@@ -5356,7 +5362,9 @@ static int __intel_engines_record_defaults(struct drm_i915_private *i915)
 	if (err)
 		goto err_active;
 
-	err = i915_gem_wait_for_idle(i915, I915_WAIT_LOCKED);
+	err = i915_gem_wait_for_idle(i915,
+				     I915_WAIT_LOCKED,
+				     MAX_SCHEDULE_TIMEOUT);
 	if (err)
 		goto err_active;
 
@@ -5421,7 +5429,9 @@ err_active:
 	if (WARN_ON(i915_gem_switch_to_kernel_context(i915)))
 		goto out_ctx;
 
-	if (WARN_ON(i915_gem_wait_for_idle(i915, I915_WAIT_LOCKED)))
+	if (WARN_ON(i915_gem_wait_for_idle(i915,
+					   I915_WAIT_LOCKED,
+					   MAX_SCHEDULE_TIMEOUT)))
 		goto out_ctx;
 
 	i915_gem_contexts_lost(i915);