X-Git-Url: https://git.lttng.org/?a=blobdiff_plain;f=src%2Fcommon%2Fcompat%2Fcompat-epoll.c;h=6a781c7ae04034f321f974c244df6e43e01e58b3;hb=18710679a8ac57fda5dbd26cf16bb180dce9e286;hp=9c2688d33e09c3c774b914b366226424504324e7;hpb=22dad56815ce0201c5ae7d5ef5d79cc0c6a42c5e;p=lttng-tools.git

diff --git a/src/common/compat/compat-epoll.c b/src/common/compat/compat-epoll.c
index 9c2688d33..6a781c7ae 100644
--- a/src/common/compat/compat-epoll.c
+++ b/src/common/compat/compat-epoll.c
@@ -197,6 +197,47 @@ error:
 	return -1;
 }
 
+/*
+ * Set an fd's events.
+ */
+int compat_epoll_mod(struct lttng_poll_event *events, int fd, uint32_t req_events)
+{
+	int ret;
+	struct epoll_event ev;
+
+	if (events == NULL || fd < 0 || events->nb_fd == 0) {
+		goto error;
+	}
+
+	/*
+	 * Zero struct epoll_event to ensure all representations of its
+	 * union are zeroed.
+	 */
+	memset(&ev, 0, sizeof(ev));
+	ev.events = req_events;
+	ev.data.fd = fd;
+
+	ret = epoll_ctl(events->epfd, EPOLL_CTL_MOD, fd, &ev);
+	if (ret < 0) {
+		switch (errno) {
+		case ENOENT:
+		case EPERM:
+			/* Print PERROR and goto end not failing. Show must go on. */
+			PERROR("epoll_ctl MOD");
+			goto end;
+		default:
+			PERROR("epoll_ctl MOD fatal");
+			goto error;
+		}
+	}
+
+end:
+	return 0;
+
+error:
+	return -1;
+}
+
 /*
  * Wait on epoll set. This is a blocking call of timeout value.
  */
@@ -260,7 +301,15 @@ int compat_epoll_set_max_size(void)
 
 	fd = open(COMPAT_EPOLL_PROC_PATH, O_RDONLY);
 	if (fd < 0) {
-		retval = -1;
+		/*
+		 * Failing on opening [1] is not an error per see. [1] was
+		 * introduced in Linux 2.6.28 but epoll is available since
+		 * 2.5.44. Hence, goto end and set a default value without
+		 * setting an error return value.
+		 *
+		 * [1] /proc/sys/fs/epoll/max_user_watches
+		 */
+		retval = 0;
 		goto end;
 	}