sna: Avoid recursing whilst waiting for events within TearFree

Occasionally TearFree likes to flushing pending event to try and avoid a
stall or a reallocation of a buffer. When it does so, we must avoid
processing vblanks as they may cause an update to the frontbuffer
re-entering the TearFree handler. Instead of deferring the obvious
recursions until the next vblank, buffer the events temporarily whilst
we wait inside TearFree.

Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>

3 files changed, 61 insertions, 24 deletions

diff --git a/src/sna/sna.h b/src/sna/sna.h
index eb3489d4..c4978cbc 100644
--- a/src/sna/sna.h
+++ b/src/sna/sna.h
@@ -312,6 +312,10 @@ struct sna {
 		bool shadow_wait;
 		bool dirty;
 
+		struct drm_event_vblank *shadow_events;
+		int shadow_nevent;
+		int shadow_size;
+
 		int max_crtc_width, max_crtc_height;
 		RegionRec shadow_region;
 		RegionRec shadow_cancel;
diff --git a/src/sna/sna_display.c b/src/sna/sna_display.c
index aa8b4fb5..96793281 100644
--- a/src/sna/sna_display.c
+++ b/src/sna/sna_display.c
@@ -1523,6 +1523,48 @@ static bool overlap(const BoxRec *a, const BoxRec *b)
 	return true;
 }
 
+static void defer_event(struct sna *sna, struct drm_event *base)
+{
+	if (sna->mode.shadow_nevent == sna->mode.shadow_size) {
+		int size = sna->mode.shadow_size * 2;
+		void *ptr;
+
+		ptr = realloc(sna->mode.shadow_events,
+			      sizeof(struct drm_event_vblank)*size);
+		if (!ptr)
+			return;
+
+		sna->mode.shadow_events = ptr;
+		sna->mode.shadow_size = size;
+	}
+
+	memcpy(&sna->mode.shadow_events[sna->mode.shadow_nevent++],
+	       base, sizeof(struct drm_event_vblank));
+	DBG(("%s: deferring event count=%d\n", sna->mode.shadow_nevent));
+}
+
+static void flush_events(struct sna *sna)
+{
+	int n;
+
+	if (!sna->mode.shadow_nevent)
+		return;
+
+	DBG(("%s: flushing %d events=%d\n", sna->mode.shadow_nevent));
+
+	for (n = 0; n < sna->mode.shadow_nevent; n++) {
+		struct drm_event_vblank *vb = &sna->mode.shadow_events[n];
+
+		if ((uintptr_t)(vb->user_data) & 2)
+			sna_present_vblank_handler(vb);
+		else
+			sna_dri2_vblank_handler(vb);
+	}
+
+	sna->mode.shadow_nevent = 0;
+}
+
+
 static bool wait_for_shadow(struct sna *sna,
 			    struct sna_pixmap *priv,
 			    unsigned flags)
@@ -1545,8 +1587,7 @@ static bool wait_for_shadow(struct sna *sna,
 		goto done;
 
 	assert(sna->mode.shadow_damage);
-	if (sna->mode.shadow_wait)
-		return ret;
+	assert(!sna->mode.shadow_wait);
 
 	if ((flags & MOVE_WRITE) == 0) {
 		if ((flags & __MOVE_SCANOUT) == 0) {
@@ -1748,6 +1789,7 @@ done:
 	priv->move_to_gpu = NULL;
 
 	assert(!sna->mode.shadow_wait);
+	flush_events(sna);
 
 	return ret;
 }
@@ -7308,6 +7350,11 @@ bool sna_mode_pre_init(ScrnInfoPtr scrn, struct sna *sna)
 	if (!sna_mode_fake_init(sna, num_fake))
 		return false;
 
+	sna->mode.shadow_size = 256;
+	sna->mode.shadow_events = malloc(sna->mode.shadow_size * sizeof(struct drm_event_vblank));
+	if (!sna->mode.shadow_events)
+		return false;
+
 	if (!sna_probe_initial_configuration(sna)) {
 		xf86CrtcConfigPtr config = XF86_CRTC_CONFIG_PTR(scrn);
 
@@ -8504,7 +8551,10 @@ sna_crtc_redisplay(xf86CrtcPtr crtc, RegionPtr region, struct kgem_bo *bo)
 static void shadow_flip_handler(struct drm_event_vblank *e,
 				void *data)
 {
-	sna_mode_redisplay(data);
+	struct sna *sna = data;
+
+	if (!sna->mode.shadow_wait)
+		sna_mode_redisplay(sna);
 }
 
 void sna_shadow_set_crtc(struct sna *sna,
@@ -9098,7 +9148,9 @@ again:
 		struct drm_event *e = (struct drm_event *)&buffer[i];
 		switch (e->type) {
 		case DRM_EVENT_VBLANK:
-			if (((uintptr_t)((struct drm_event_vblank *)e)->user_data) & 2)
+			if (sna->mode.shadow_wait)
+				defer_event(sna, e);
+			else if (((uintptr_t)((struct drm_event_vblank *)e)->user_data) & 2)
 				sna_present_vblank_handler((struct drm_event_vblank *)e);
 			else
 				sna_dri2_vblank_handler((struct drm_event_vblank *)e);
diff --git a/src/sna/sna_dri2.c b/src/sna/sna_dri2.c
index 2c3a3ed7..876a9095 100644
--- a/src/sna/sna_dri2.c
+++ b/src/sna/sna_dri2.c
@@ -2514,15 +2514,6 @@ static void chain_swap(struct sna_dri2_event *chain)
 	switch (chain->type) {
 	case SWAP_COMPLETE:
 		DBG(("%s: emitting chained vsync'ed blit\n", __FUNCTION__));
-		if (chain->sna->mode.shadow_wait) {
-			/* recursed from wait_for_shadow(), simply requeue */
-			DBG(("%s -- recursed from wait_for_shadow(), requeuing\n", __FUNCTION__));
-			if (sna_next_vblank(chain))
-				return;
-
-			DBG(("%s -- requeue failed, errno=%d\n", __FUNCTION__, errno));
-		}
-
 		if (can_xchg(chain->sna, chain->draw, chain->front, chain->back)) {
 			sna_dri2_xchg(chain->draw, chain->front, chain->back);
 		} else if (can_xchg_crtc(chain->sna, chain->draw, chain->crtc,
@@ -2609,10 +2600,7 @@ void sna_dri2_vblank_handler(struct drm_event_vblank *event)
 		/* else fall through to blit */
 	case SWAP:
 		assert(info->signal);
-		if (sna->mode.shadow_wait) {
-			/* recursed from wait_for_shadow(), simply requeue */
-			DBG(("%s -- recursed from wait_for_shadow(), requeuing\n", __FUNCTION__));
-		} else if (can_xchg(info->sna, draw, info->front, info->back)) {
+		if (can_xchg(info->sna, draw, info->front, info->back)) {
 			sna_dri2_xchg(draw, info->front, info->back);
 			info->type = SWAP_COMPLETE;
 		} else if (can_xchg_crtc(sna, draw, info->crtc,
@@ -2655,13 +2643,6 @@ void sna_dri2_vblank_handler(struct drm_event_vblank *event)
 			     info->pending.bo->handle, info->pending.name, info->pending.bo->active_scanout,
 			     get_private(info->front)->bo->handle, info->front->name, get_private(info->front)->bo->active_scanout));
 
-			if (sna->mode.shadow_wait) {
-				/* recursed from wait_for_shadow(), simply requeue */
-				DBG(("%s -- recursed from wait_for_shadow(), requeuing\n", __FUNCTION__));
-				if (sna_next_vblank(info))
-					return;
-			}
-
 			assert(info->pending.bo->active_scanout > 0);
 			info->pending.bo->active_scanout--;