From: Mathieu Desnoyers Date: Thu, 16 May 2019 19:08:51 +0000 (-0400) Subject: lttng-ctl: notifications: use epoll()/poll() instead of select() X-Git-Tag: v2.12.0-rc1~453 X-Git-Url: https://git.lttng.org/?p=lttng-tools.git;a=commitdiff_plain;h=d977a743144ea108584e328c32eb217d8162c137 lttng-ctl: notifications: use epoll()/poll() instead of select() 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. Signed-off-by: Mathieu Desnoyers Signed-off-by: Jérémie Galarneau --- diff --git a/src/lib/lttng-ctl/channel.c b/src/lib/lttng-ctl/channel.c index 5271aa13f..bcecc65fb 100644 --- a/src/lib/lttng-ctl/channel.c +++ b/src/lib/lttng-ctl/channel.c @@ -26,8 +26,7 @@ #include #include #include "lttng-ctl-helper.h" -#include -#include +#include 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: