X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;f=src%2Fcommon%2Fcompat%2Fcompat-poll.c;h=4ea23c17318e1439f36a94b134194d13b070e4de;hb=9f32e9bf43a6438c55f35d3c5ed1c378d0c715c4;hp=2318920aed84a7c9dcdb5c1668035913ecb0ff10;hpb=a1de8fcc86468f9ae88786634face3e327e2f3b3;p=lttng-tools.git

diff --git a/src/common/compat/compat-poll.c b/src/common/compat/compat-poll.c
index 2318920ae..4ea23c173 100644
--- a/src/common/compat/compat-poll.c
+++ b/src/common/compat/compat-poll.c
@@ -291,9 +291,12 @@ error:
 /*
  * Wait on poll() with timeout. Blocking call.
  */
-int compat_poll_wait(struct lttng_poll_event *events, int timeout)
+int compat_poll_wait(struct lttng_poll_event *events, int timeout,
+		bool interruptible)
 {
-	int ret;
+	int ret, active_fd_count;
+	int idle_pfd_index = 0;
+	size_t i;
 
 	if (events == NULL || events->current.events == NULL) {
 		ERR("poll wait arguments error");
@@ -318,18 +321,47 @@ int compat_poll_wait(struct lttng_poll_event *events, int timeout)
 
 	do {
 		ret = poll(events->wait.events, events->wait.nb_fd, timeout);
-	} while (ret == -1 && errno == EINTR);
+	} while (!interruptible && ret == -1 && errno == EINTR);
 	if (ret < 0) {
-		/* At this point, every error is fatal */
-		PERROR("poll wait");
+		if (errno != EINTR) {
+			PERROR("poll wait");
+		}
 		goto error;
 	}
 
+	active_fd_count = ret;
+
 	/*
-	 * 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 active 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 active
+	 * events on the file descriptors. The while loop guarantees that
+	 * idle_pfd will always point to an idle fd.
 	 */
-	return events->wait.nb_fd;
+	if (active_fd_count == events->wait.nb_fd) {
+		goto end;
+	}
+	while (idle_pfd_index < active_fd_count &&
+			events->wait.events[idle_pfd_index].revents != 0) {
+		idle_pfd_index++;
+	}
+
+	for (i = idle_pfd_index + 1; idle_pfd_index < active_fd_count;
+			i++) {
+		struct pollfd swap_pfd;
+		struct pollfd *idle_pfd = &events->wait.events[idle_pfd_index];
+		struct pollfd *current_pfd = &events->wait.events[i];
+
+		if (idle_pfd->revents != 0) {
+			swap_pfd = *current_pfd;
+			*current_pfd = *idle_pfd;
+			*idle_pfd = swap_pfd;
+			idle_pfd_index++;
+		}
+	}
+
+end:
+	return ret;
 
 error:
 	return -1;