[PATCH] drm/i915: Fix __wait_seqno to use true infinite timeouts

[Chris Wilson <chris@chris-wilson.co.uk>]

Rather than continue to fix up the timeouts to work around the interface
impedence in wait_event_*(), open code the combination of
wait_event[_interruptible][_timeout]. And note the code size reduction,
and dare say readability?, in doing so..

Food for thought.
---
 drivers/gpu/drm/i915/i915_gem.c | 82 ++++++++++++++++++++---------------------
 1 file changed, 39 insertions(+), 43 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index 99ba622..8adbce9 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1088,23 +1088,18 @@ static int __wait_seqno(struct intel_ring_buffer *ring, u32 seqno,
 			bool interruptible, struct timespec *timeout)
 {
 	drm_i915_private_t *dev_priv = ring->dev->dev_private;
-	struct timespec before, now, wait_time={1,0};
-	unsigned long timeout_jiffies;
-	long end;
-	bool wait_forever = true;
+	struct timespec before, now;
+	DEFINE_WAIT(__wait);
+	long timeout_jiffies;
 	int ret;
 
 	if (i915_seqno_passed(ring->get_seqno(ring, true), seqno))
 		return 0;
 
-	trace_i915_gem_request_wait_begin(ring, seqno);
-
-	if (timeout != NULL) {
-		wait_time = *timeout;
-		wait_forever = false;
-	}
+	if (timeout)
+		timeout_jiffies = timespec_to_jiffies_timeout(timeout);
 
-	timeout_jiffies = timespec_to_jiffies_timeout(&wait_time);
+	trace_i915_gem_request_wait_begin(ring, seqno);
 
 	if (WARN_ON(!ring->irq_get(ring)))
 		return -ENODEV;
@@ -1112,36 +1107,47 @@ static int __wait_seqno(struct intel_ring_buffer *ring, u32 seqno,
 	/* Record current time in case interrupted by signal, or wedged * */
 	getrawmonotonic(&before);
 
-#define EXIT_COND \
-	(i915_seqno_passed(ring->get_seqno(ring, false), seqno) || \
-	 i915_reset_in_progress(&dev_priv->gpu_error) || \
-	 reset_counter != atomic_read(&dev_priv->gpu_error.reset_counter))
-	do {
-		if (interruptible)
-			end = wait_event_interruptible_timeout(ring->irq_queue,
-							       EXIT_COND,
-							       timeout_jiffies);
-		else
-			end = wait_event_timeout(ring->irq_queue, EXIT_COND,
-						 timeout_jiffies);
+	for (;;) {
+		prepare_to_wait(&ring->irq_queue, &__wait,
+				interruptible ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
 
 		/* We need to check whether any gpu reset happened in between
 		 * the caller grabbing the seqno and now ... */
-		if (reset_counter != atomic_read(&dev_priv->gpu_error.reset_counter))
-			end = -EAGAIN;
+		if (reset_counter != atomic_read(&dev_priv->gpu_error.reset_counter)) {
+			/* ... but upgrade the -EGAIN to an -EIO if the gpu
+			 * is truely gone. */
+			ret = i915_gem_check_wedge(&dev_priv->gpu_error, interruptible);
+			if (ret == 0)
+				ret = -EAGAIN;
+			break;
+		}
 
-		/* ... but upgrade the -EGAIN to an -EIO if the gpu is truely
-		 * gone. */
-		ret = i915_gem_check_wedge(&dev_priv->gpu_error, interruptible);
-		if (ret)
-			end = ret;
-	} while (end == 0 && wait_forever);
+		if (i915_seqno_passed(ring->get_seqno(ring, false), seqno)) {
+			ret = 0;
+			break;
+		}
+
+		if (interruptible && signal_pending(current)) {
+			ret = -ERESTARTSYS;
+			break;
+		}
+
+		if (timeout) {
+			if (timeout_jiffies == 0) {
+				ret = -ETIME;
+				break;
+			}
+
+			timeout_jiffies = schedule_timeout(timeout_jiffies);
+		} else
+			schedule();
+	}
+	finish_wait(&ring->irq_queue, &__wait);
 
 	getrawmonotonic(&now);
 
 	ring->irq_put(ring);
 	trace_i915_gem_request_wait_end(ring, seqno);
-#undef EXIT_COND
 
 	if (timeout) {
 		struct timespec sleep_time = timespec_sub(now, before);
@@ -1150,17 +1156,7 @@ static int __wait_seqno(struct intel_ring_buffer *ring, u32 seqno,
 			set_normalized_timespec(timeout, 0, 0);
 	}
 
-	switch (end) {
-	case -EIO:
-	case -EAGAIN: /* Wedged */
-	case -ERESTARTSYS: /* Signal */
-		return (int)end;
-	case 0: /* Timeout */
-		return -ETIME;
-	default: /* Completed */
-		WARN_ON(end < 0); /* We're not aware of other errors */
-		return 0;
-	}
+	return ret;
 }
 
 /**
-- 
1.8.4.rc1