Nouveau - Aug 2020 - [PATCH 1/2] drmmode: make event handler leave a note that there are stuck events

We don't really expect to have too many events in the queue. If there
are, then the algorithm we use isn't appropriate. Add a warning when the
queue gets very long, as it's an indication of something having gone
wrong.

Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
---
 src/drmmode_display.c | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/src/drmmode_display.c b/src/drmmode_display.c
index 2d3229c..45292c4 100644
--- a/src/drmmode_display.c
+++ b/src/drmmode_display.c
@@ -159,6 +159,8 @@ drmmode_events = {
 	.prev = &drmmode_events,
 };
 
+static bool warned = false;
+
 static void
 drmmode_event_handler(int fd, unsigned int frame, unsigned int tv_sec,
 		      unsigned int tv_usec, void *event_data)
@@ -166,7 +168,10 @@ drmmode_event_handler(int fd, unsigned int frame, unsigned
int tv_sec,
 	const uint64_t ust = (uint64_t)tv_sec * 1000000 + tv_usec;
 	struct drmmode_event *e = event_data;
 
+	int counter = 0;
+
 	xorg_list_for_each_entry(e, &drmmode_events, head) {
+		counter++;
 		if (e == event_data) {
 			xorg_list_del(&e->head);
 			e->func((void *)(e + 1), e->name, ust, frame);
@@ -174,6 +179,12 @@ drmmode_event_handler(int fd, unsigned int frame, unsigned
int tv_sec,
 			break;
 		}
 	}
+
+	if (counter > 100 && !warned) {
+		xf86DrvMsg(0, X_WARNING,
+			   "Event handler iterated %d times\n", counter);
+		warned = true;
+	}
 }
 
 void
-- 
2.26.2

When drmWaitVBlank fails, make sure to remove the event from the queue.

Signed-off-by: Ilia Mirkin <imirkin at alum.mit.edu>
---

Note this needs a bit more testing, and also double-checking what the
"correct" way of dealing with these errors is. I was able to trigger
errors with "xset dpms force off", but perhaps there are also other
conditions.

 src/nouveau_present.c | 13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

diff --git a/src/nouveau_present.c b/src/nouveau_present.c
index 8167fd8..15516d6 100644
--- a/src/nouveau_present.c
+++ b/src/nouveau_present.c
@@ -113,8 +113,19 @@ nouveau_present_vblank_queue(RRCrtcPtr rrcrtc, uint64_t
event_id, uint64_t msc)
 	args.request.signal = (unsigned long)token;
 
 	while ((ret = drmWaitVBlank(pNv->dev->fd, &args)) != 0) {
-		if (errno != EBUSY || drmmode_event_flush(crtc->scrn) < 0)
+		if (errno != EBUSY) {
+			xf86DrvMsg(crtc->scrn->scrnIndex, X_DEBUG,
+				   "PRESENT: Wait for VBlank failed: %s\n", strerror(errno));
+			drmmode_event_abort(crtc->scrn, event_id, false);
 			return BadAlloc;
+		}
+		ret = drmmode_event_flush(crtc->scrn);
+		if (ret < 0) {
+			xf86DrvMsg(crtc->scrn->scrnIndex, X_DEBUG,
+				   "PRESENT: Event flush failed\n");
+			drmmode_event_abort(crtc->scrn, event_id, false);
+			return BadAlloc;
+		}
 	}
 
 	return Success;
-- 
2.26.2