[lttng-dev] [PATCH lttng-tools 8/9] lttng-ctl: notifications: use epoll()/poll() instead of select()
Mathieu Desnoyers
mathieu.desnoyers at efficios.com
Fri May 3 09:55:46 EDT 2019
The select(2) system call is an ancient ABI limited to processes
containing at most FD_SETSIZE file descriptors overall (typically
1024).
Those notification APIs will fail if the target file descriptor
is above FD_SETSIZE in a process containing many file descriptors.
Never use select, use the lttng epoll/poll wrapper instead.
This patch depends on "Change lttng_poll_wait behaviour of compat-poll
to match compat-epoll" posted by Yannick Lamarre.
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
CC: Yannick Lamarre <ylamarre at efficios.com>
---
src/lib/lttng-ctl/channel.c | 76 +++++++++++++++++++++++++++------------------
1 file changed, 45 insertions(+), 31 deletions(-)
diff --git a/src/lib/lttng-ctl/channel.c b/src/lib/lttng-ctl/channel.c
index 5271aa13..bcecc65f 100644
--- a/src/lib/lttng-ctl/channel.c
+++ b/src/lib/lttng-ctl/channel.c
@@ -26,8 +26,7 @@
#include <common/defaults.h>
#include <assert.h>
#include "lttng-ctl-helper.h"
-#include <sys/select.h>
-#include <sys/time.h>
+#include <common/compat/poll.h>
static
int handshake(struct lttng_notification_channel *channel);
@@ -211,7 +210,7 @@ lttng_notification_channel_get_next_notification(
struct lttng_notification *notification = NULL;
enum lttng_notification_channel_status status =
LTTNG_NOTIFICATION_CHANNEL_STATUS_OK;
- fd_set read_fds;
+ struct lttng_poll_event events;
if (!channel || !_notification) {
status = LTTNG_NOTIFICATION_CHANNEL_STATUS_INVALID;
@@ -241,9 +240,9 @@ lttng_notification_channel_get_next_notification(
}
/*
- * Block on select() instead of the message reception itself as the
- * recvmsg() wrappers always restard on EINTR. We choose to wait
- * using select() in order to:
+ * Block on interruptible epoll/poll() instead of the message reception
+ * itself as the recvmsg() wrappers always restart on EINTR. We choose
+ * to wait using interruptible epoll/poll() in order to:
* 1) Return if a signal occurs,
* 2) Not deal with partially received messages.
*
@@ -252,20 +251,28 @@ lttng_notification_channel_get_next_notification(
* announced length, receive_message() will block on recvmsg()
* and never return (even if a signal is received).
*/
- FD_ZERO(&read_fds);
- FD_SET(channel->socket, &read_fds);
- ret = select(channel->socket + 1, &read_fds, NULL, NULL, NULL);
- if (ret == -1) {
- status = errno == EINTR ?
+ ret = lttng_poll_create(&events, 1, LTTNG_CLOEXEC);
+ if (ret < 0) {
+ status = LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
+ goto end_unlock;
+ }
+ ret = lttng_poll_add(&events, channel->socket, LPOLLIN | LPOLLERR);
+ if (ret < 0) {
+ status = LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
+ goto end_clean_poll;
+ }
+ ret = lttng_poll_wait_interruptible(&events, -1);
+ if (ret <= 0) {
+ status = (ret == -1 && errno == EINTR) ?
LTTNG_NOTIFICATION_CHANNEL_STATUS_INTERRUPTED :
LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
- goto end_unlock;
+ goto end_clean_poll;
}
ret = receive_message(channel);
if (ret) {
status = LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
- goto end_unlock;
+ goto end_clean_poll;
}
switch (get_current_message_type(channel)) {
@@ -274,7 +281,7 @@ lttng_notification_channel_get_next_notification(
channel);
if (!notification) {
status = LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
- goto end_unlock;
+ goto end_clean_poll;
}
break;
case LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_NOTIFICATION_DROPPED:
@@ -284,9 +291,11 @@ lttng_notification_channel_get_next_notification(
default:
/* Protocol error. */
status = LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
- goto end_unlock;
+ goto end_clean_poll;
}
+end_clean_poll:
+ lttng_poll_clean(&events);
end_unlock:
pthread_mutex_unlock(&channel->lock);
*_notification = notification;
@@ -387,11 +396,7 @@ lttng_notification_channel_has_pending_notification(
int ret;
enum lttng_notification_channel_status status =
LTTNG_NOTIFICATION_CHANNEL_STATUS_OK;
- fd_set read_fds;
- struct timeval timeout;
-
- FD_ZERO(&read_fds);
- memset(&timeout, 0, sizeof(timeout));
+ struct lttng_poll_event events;
if (!channel || !_notification_pending) {
status = LTTNG_NOTIFICATION_CHANNEL_STATUS_INVALID;
@@ -426,48 +431,57 @@ lttng_notification_channel_has_pending_notification(
* message if we see data available on the socket. If the peer does
* not respect the protocol, this may block indefinitely.
*/
- FD_SET(channel->socket, &read_fds);
- do {
- ret = select(channel->socket + 1, &read_fds, NULL, NULL, &timeout);
- } while (ret < 0 && errno == EINTR);
-
+ ret = lttng_poll_create(&events, 1, LTTNG_CLOEXEC);
+ if (ret < 0) {
+ status = LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
+ goto end_unlock;
+ }
+ ret = lttng_poll_add(&events, channel->socket, LPOLLIN | LPOLLERR);
+ if (ret < 0) {
+ status = LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
+ goto end_clean_poll;
+ }
+ /* timeout = 0: return immediately. */
+ ret = lttng_poll_wait_interruptible(&events, 0);
if (ret == 0) {
/* No data available. */
*_notification_pending = false;
- goto end_unlock;
+ goto end_clean_poll;
} else if (ret < 0) {
status = LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
- goto end_unlock;
+ goto end_clean_poll;
}
/* Data available on socket. */
ret = receive_message(channel);
if (ret) {
status = LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
- goto end_unlock;
+ goto end_clean_poll;
}
switch (get_current_message_type(channel)) {
case LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_NOTIFICATION:
ret = enqueue_notification_from_current_message(channel);
if (ret) {
- goto end_unlock;
+ goto end_clean_poll;
}
*_notification_pending = true;
break;
case LTTNG_NOTIFICATION_CHANNEL_MESSAGE_TYPE_NOTIFICATION_DROPPED:
ret = enqueue_dropped_notification(channel);
if (ret) {
- goto end_unlock;
+ goto end_clean_poll;
}
*_notification_pending = true;
break;
default:
/* Protocol error. */
status = LTTNG_NOTIFICATION_CHANNEL_STATUS_ERROR;
- goto end_unlock;
+ goto end_clean_poll;
}
+end_clean_poll:
+ lttng_poll_clean(&events);
end_unlock:
pthread_mutex_unlock(&channel->lock);
end:
--
2.11.0
More information about the lttng-dev
mailing list