drm/i915: Improve fallback ring waiting

A few improvements to the fallback method for waiting upon ring space:

1. Fix the start/end wait tracepoints to always be paired.
2. Increase responsiveness of checking
3. Mark the process as waiting upon io
4. Check for signal interruptions

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
Reviewed-by: Brad Volkin <bradley.d.volkin@intel.com>
[danvet: Drop the s/msleep/io_schedule_timeout/ change again since the
latter isn't exported.]
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

1 files changed, 16 insertions, 6 deletions

diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 40a7aa4db589..e6c7a4dfea51 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -1546,7 +1546,6 @@ static int ring_wait_for_space(struct intel_ring_buffer *ring, int n)
         /* force the tail write in case we have been skipping them */
         __intel_ring_advance(ring);
 
-        trace_i915_ring_wait_begin(ring);
         /* With GEM the hangcheck timer should kick us out of the loop,
          * leaving it early runs the risk of corrupting GEM state (due
          * to running on almost untested codepaths). But on resume
@@ -1554,12 +1553,13 @@ static int ring_wait_for_space(struct intel_ring_buffer *ring, int n)
          * case by choosing an insanely large timeout. */
         end = jiffies + 60 * HZ;
 
+        trace_i915_ring_wait_begin(ring);
         do {
                 ring->head = I915_READ_HEAD(ring);
                 ring->space = ring_space(ring);
                 if (ring->space >= n) {
-                        trace_i915_ring_wait_end(ring);
-                        return 0;
+                        ret = 0;
+                        break;
                 }
 
                 if (!drm_core_check_feature(dev, DRIVER_MODESET) &&
@@ -1571,13 +1571,23 @@ static int ring_wait_for_space(struct intel_ring_buffer *ring, int n)
 
                 msleep(1);
 
+                if (dev_priv->mm.interruptible && signal_pending(current)) {
+                        ret = -ERESTARTSYS;
+                        break;
+                }
+
                 ret = i915_gem_check_wedge(&dev_priv->gpu_error,
                                            dev_priv->mm.interruptible);
                 if (ret)
-                        return ret;
-        } while (!time_after(jiffies, end));
+                        break;
+
+                if (time_after(jiffies, end)) {
+                        ret = -EBUSY;
+                        break;
+                }
+        } while (1);
         trace_i915_ring_wait_end(ring);
-        return -EBUSY;
+        return ret;
 }
 
 static int intel_wrap_ring_buffer(struct intel_ring_buffer *ring)