Only 3.19 will have O_NONBLOCK for drm_read(), so the
current ddx will still "stutter" in ZaphodHead mode on
current kernels. Fix the problem by adding a poll() on
the drm fd before potentially blocking on read().
The logic is directly transplanted from the uxa backend
intel_mode_read_drm_events() function.
Fixes fdo bug #84744 on older kernels.
Signed-off-by: Mario Kleiner <mario.kleiner.de@xxxxxxxxx>
---
src/sna/sna_display.c | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)
diff --git a/src/sna/sna_display.c b/src/sna/sna_display.c
index 1633333..a7ad6cc 100644
--- a/src/sna/sna_display.c
+++ b/src/sna/sna_display.c
@@ -7390,7 +7390,16 @@ fixup_flip:
void sna_mode_wakeup(struct sna *sna)
{
char buffer[1024];
- int len, i;
+ int len, i, r;
+ struct pollfd p = { .fd = sna->kgem.fd, .events = POLLIN };
+
+ /* DRM read is blocking on old kernels, so poll first to avoid it. */
+ do {
+ r = poll(&p, 1, 0);
+ } while (r == -1 && (errno == EINTR || errno == EAGAIN));
+
+ if (r <= 0)
+ return;
/* The DRM read semantics guarantees that we always get only
* complete events.
--
1.9.1
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