[PATCH 1/2] drm/sched: Fix drm_sched_entity_flush() return val

[Philipp Stanner]

The documentation of drm_sched_entity_flush() states that the function
shall - always - return the remaining timeout time in jiffies.

However, that is not what the function actually does; in one of its if
branches it simply returns the unchanged timeout value.

Furthermore, the used function wait_event_timeout() doesn't always
return the remaining timeout time.

Adjust the function so that it actually does what the documentation
states it shall do.

Cc: Christian König <christian.koe...@amd.com>
Signed-off-by: Philipp Stanner <pstan...@redhat.com>
---
@AMD:
You guys are the only ones who use the function's return code, so I
leave it completely up to you to decide what behavior you want.

But we should at least do something, because right now function
documentation and behavior do not match.

P.
---
 drivers/gpu/drm/scheduler/sched_entity.c | 23 ++++++++++++++++-------
 1 file changed, 16 insertions(+), 7 deletions(-)

diff --git a/drivers/gpu/drm/scheduler/sched_entity.c 
b/drivers/gpu/drm/scheduler/sched_entity.c
index a75eede8bf8d..16b172aee453 100644
--- a/drivers/gpu/drm/scheduler/sched_entity.c
+++ b/drivers/gpu/drm/scheduler/sched_entity.c
@@ -278,7 +278,7 @@ static void drm_sched_entity_kill(struct drm_sched_entity 
*entity)
  * waiting, removes the entity from the runqueue and returns an error when the
  * process was killed.
  *
- * Returns the remaining time in jiffies left from the input timeout
+ * Returns: 0 if the timeout ellapsed, the remaining time otherwise.
  */
 long drm_sched_entity_flush(struct drm_sched_entity *entity, long timeout)
 {
@@ -294,15 +294,24 @@ long drm_sched_entity_flush(struct drm_sched_entity 
*entity, long timeout)
         * The client will not queue more IBs during this fini, consume existing
         * queued IBs or discard them on SIGKILL
         */
-       if (current->flags & PF_EXITING) {
-               if (timeout)
-                       ret = wait_event_timeout(
-                                       sched->job_scheduled,
-                                       drm_sched_entity_is_idle(entity),
-                                       timeout);
+       if (timeout != 0 && (current->flags & PF_EXITING)) {
+               ret = wait_event_timeout(sched->job_scheduled,
+                               drm_sched_entity_is_idle(entity),
+                               timeout);
+               /*
+                * wait_event_timeout() returns 1 if it timed out but the
+                * condition became true on timeout. We only care about whether
+                * it timed out or not.
+                */
+               if (ret == 1)
+                       ret = 0;
        } else {
                wait_event_killable(sched->job_scheduled,
                                    drm_sched_entity_is_idle(entity));
+
+               ret -= (long)get_jiffies_64();
+               if (ret < 0)
+                       ret = 0;
        }
 
        /* For killed process disable any more IBs enqueue right now */
-- 
2.47.0