From f057dfc322670467e14c661d625cec0747ce8a31 Mon Sep 17 00:00:00 2001
From: =?utf8?q?J=C3=A9r=C3=A9mie=20Galarneau?=
 <jeremie.galarneau@efficios.com>
Date: Thu, 4 May 2017 22:58:25 -0400
Subject: [PATCH] Implement poll mask modification support in poll wrappers
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Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
---
 src/common/compat/compat-epoll.c | 41 ++++++++++++++++++++++++++++++++
 src/common/compat/compat-poll.c  | 37 ++++++++++++++++++++++++++++
 src/common/compat/poll.h         | 16 +++++++++++++
 3 files changed, 94 insertions(+)

diff --git a/src/common/compat/compat-epoll.c b/src/common/compat/compat-epoll.c
index 9c2688d33..dbaf68233 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.
  */
diff --git a/src/common/compat/compat-poll.c b/src/common/compat/compat-poll.c
index 7d4d0e133..2b459e42f 100644
--- a/src/common/compat/compat-poll.c
+++ b/src/common/compat/compat-poll.c
@@ -20,6 +20,7 @@
 #include <stdlib.h>
 #include <sys/resource.h>
 #include <sys/time.h>
+#include <stdbool.h>
 
 #include <common/defaults.h>
 #include <common/error.h>
@@ -196,6 +197,42 @@ error:
 	return -1;
 }
 
+/*
+ * Modify an fd's events..
+ */
+int compat_poll_mod(struct lttng_poll_event *events, int fd,
+		uint32_t req_events)
+{
+	int ret, i;
+	bool fd_found = false;
+	struct compat_poll_event_array *current;
+
+	if (events == NULL || events->current.events == NULL || fd < 0) {
+		ERR("Bad compat poll mod arguments");
+		goto error;
+	}
+
+	current = &events->current;
+
+	for (i = 0; i < current->nb_fd; i++) {
+		if (current->events[i].fd == fd) {
+			fd_found = true;
+			current->events[i].events = req_events;
+			events->need_update = 1;
+			break;
+		}
+	}
+
+	if (!fd_found) {
+		goto error;
+	}
+
+	return 0;
+
+error:
+	return -1;
+}
+
 /*
  * Remove a fd from the pollfd structure.
  */
diff --git a/src/common/compat/poll.h b/src/common/compat/poll.h
index 77c46a1d0..d4bd87f58 100644
--- a/src/common/compat/poll.h
+++ b/src/common/compat/poll.h
@@ -171,6 +171,14 @@ extern int compat_epoll_del(struct lttng_poll_event *events, int fd);
 #define lttng_poll_del(events, fd) \
 	compat_epoll_del(events, fd)
 
+/*
+ * Modify an fd's events in the epoll set.
+ */
+extern int compat_epoll_mod(struct lttng_poll_event *events,
+		int fd, uint32_t req_events);
+#define lttng_poll_mod(events, fd, req_events) \
+	compat_epoll_add(events, fd, req_events)
+
 /*
  * Set up the poll set limits variable poll_max_size
  */
@@ -347,6 +355,14 @@ extern int compat_poll_del(struct lttng_poll_event *events, int fd);
 #define lttng_poll_del(events, fd) \
 	compat_poll_del(events, fd)
 
+/*
+ * Modify an fd's events in the epoll set.
+ */
+extern int compat_poll_mod(struct lttng_poll_event *events,
+		int fd, uint32_t req_events);
+#define lttng_poll_mod(events, fd, req_events) \
+	compat_poll_add(events, fd, req_events)
+
 /*
  * Set up the poll set limits variable poll_max_size
  */
-- 
2.34.1