This removes the need to verify for eventless file descriptors and
mitigates risks of bug due to behaviour mismatch.
Signed-off-by: Yannick Lamarre <ylama...@efficios.com>
---
src/common/compat/compat-poll.c | 33 ++++++++++++++++++++++++++++++---
1 file changed, 30 insertions(+), 3 deletions(-)
diff --git a/src/common/compat/compat-poll.c b/src/common/compat/compat-poll.c
index b7c17df7..6aa9414d 100644
--- a/src/common/compat/compat-poll.c
+++ b/src/common/compat/compat-poll.c
@@ -292,6 +292,7 @@ error:
int compat_poll_wait(struct lttng_poll_event *events, int timeout)
{
int ret;
+ int eidx = 0;
if (events == NULL || events->current.events == NULL) {
ERR("poll wait arguments error");
@@ -324,10 +325,36 @@ int compat_poll_wait(struct lttng_poll_event *events, int
timeout)
}
/*
- * poll() should always iterate on all FDs since we handle the pollset
in
- * user space and after poll returns, we have to try every fd for a
match.
+ * Swap all nonzero revents pollfd structs to the beginning of the
array to
+ * emulate compat-epoll behaviour. This algorithm takes advantage of
poll's
+ * returned value and the burst nature of waking events on the file
+ * descriptors. The while loop garantees that idlepfd will always point
to
+ * a pollfd with revents == 0.
*/
- return events->wait.nb_fd;
+ if (ret == events->wait.nb_fd) {
+ goto skip;
+ }
+ while (eidx < ret && events->wait.events[eidx].revents != 0) {
+ eidx += 1;
+ }
+
+ for (int idx = eidx + 1; eidx < ret; idx++) {
+ struct pollfd swapfd;
+ struct pollfd *idlepfd = &events->wait.events[eidx];
+ struct pollfd *ipfd = &events->wait.events[idx];
+
+ assert(idx < events->wait.nb_fd);
+
+ if (ipfd->revents != 0) {
+ swapfd = *ipfd;
+ *ipfd = *idlepfd;
+ *idlepfd = swapfd;
+ eidx += 1;
+ }
+ }
+
+skip:
+ return ret;
error:
return -1;
--
2.11.0
_______________________________________________
lttng-dev mailing list
lttng-dev@lists.lttng.org
https://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev
