[Intel-gfx] [PATCH i-g-t] lib: Use read() for timerfd timeout detection

[Chris Wilson]

The poll() is proving unreliable, where our tests timeout without the
spinner being terminated. Let's try a blocking read instead!

Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/1676
Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
Cc: "Dixit, Ashutosh" <ashutosh.dixit at intel.com>
---
 lib/igt_dummyload.c | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/lib/igt_dummyload.c b/lib/igt_dummyload.c
index 99ca84ad8..ae0fb9378 100644
--- a/lib/igt_dummyload.c
+++ b/lib/igt_dummyload.c
@@ -399,14 +399,14 @@ igt_spin_factory(int fd, const struct igt_spin_factory *opts)
 static void *timer_thread(void *data)
 {
 	igt_spin_t *spin = data;
-	struct pollfd pfd = {
-		.fd = spin->timerfd,
-		.events = POLLIN,
-	};
+	uint64_t overruns = 0;
 
-	if (poll(&pfd, 1, -1) >= 0)
-		igt_spin_end(spin);
+	/* Wait until we see the timer fire, or we get cancelled */
+	do {
+		read(spin->timerfd, &overruns, sizeof(overruns));
+	} while (!overruns);
 
+	igt_spin_end(spin);
 	return NULL;
 }
 
-- 
2.26.0