From ef9ff354212ff4b038e1a5b6a7ed0ffe1b949663 Mon Sep 17 00:00:00 2001
From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Date: Thu, 12 Jan 2012 13:04:34 -0500
Subject: [PATCH] Close stream and channel file descriptors as soon as passed
 to sessiond

Ensure we don't bust the open FD limit with many sessions.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
---
 include/lttng/ust-abi.h                       | 20 +++++--
 include/lttng/ust-events.h                    | 16 ++---
 liblttng-ust-ctl/ustctl.c                     |  4 +-
 liblttng-ust/ltt-events.c                     |  4 +-
 liblttng-ust/ltt-ring-buffer-client.h         | 12 ++--
 .../ltt-ring-buffer-metadata-client.h         | 12 ++--
 liblttng-ust/lttng-ust-abi.c                  | 59 +++++++++++++------
 liblttng-ust/lttng-ust-comm.c                 | 58 +++++++++++++++---
 libringbuffer/frontend.h                      |  8 +--
 libringbuffer/ring_buffer_frontend.c          |  6 +-
 libringbuffer/shm.c                           | 10 ++--
 libringbuffer/shm.h                           |  8 +--
 tests/ust-basic-tracing/ust-basic-tracing.c   |  4 +-
 tests/ust-multi-test/ust-multi-test.c         |  4 +-
 14 files changed, 151 insertions(+), 74 deletions(-)

diff --git a/include/lttng/ust-abi.h b/include/lttng/ust-abi.h
index 8b819773..6a15e0dd 100644
--- a/include/lttng/ust-abi.h
+++ b/include/lttng/ust-abi.h
@@ -49,10 +49,6 @@ struct lttng_ust_channel {
 	unsigned int switch_timer_interval;	/* usecs */
 	unsigned int read_timer_interval;	/* usecs */
 	enum lttng_ust_output output;		/* output mode */
-	/* The following fields are used internally within UST. */
-	int shm_fd;
-	int wait_fd;
-	uint64_t memory_map_size;
 };
 
 /*
@@ -158,8 +154,22 @@ struct lttng_ust_object_data {
 
 struct lttng_ust_obj;
 
+union ust_args {
+	struct {
+		int *shm_fd;
+		int *wait_fd;
+		uint64_t *memory_map_size;
+	} channel;
+	struct {
+		int *shm_fd;
+		int *wait_fd;
+		uint64_t *memory_map_size;
+	} stream;
+};
+
 struct lttng_ust_objd_ops {
-	long (*cmd)(int objd, unsigned int cmd, unsigned long arg);
+	long (*cmd)(int objd, unsigned int cmd, unsigned long arg,
+		union ust_args *args);
 	int (*release)(int objd);
 };
 
diff --git a/include/lttng/ust-events.h b/include/lttng/ust-events.h
index b74a1767..4d1cace5 100644
--- a/include/lttng/ust-events.h
+++ b/include/lttng/ust-events.h
@@ -304,14 +304,14 @@ struct ltt_channel_ops {
 				size_t subbuf_size, size_t num_subbuf,
 				unsigned int switch_timer_interval,
 				unsigned int read_timer_interval,
-				int *shm_fd, int *wait_fd,
-				uint64_t *memory_map_size,
+				int **shm_fd, int **wait_fd,
+				uint64_t **memory_map_size,
 				struct ltt_channel *chan_priv_init);
 	void (*channel_destroy)(struct ltt_channel *ltt_chan);
 	struct lttng_ust_lib_ring_buffer *(*buffer_read_open)(struct channel *chan,
 				struct lttng_ust_shm_handle *handle,
-				int *shm_fd, int *wait_fd,
-				uint64_t *memory_map_size);
+				int **shm_fd, int **wait_fd,
+				uint64_t **memory_map_size);
 	void (*buffer_read_close)(struct lttng_ust_lib_ring_buffer *buf,
 				struct lttng_ust_shm_handle *handle);
 	int (*event_reserve)(struct lttng_ust_lib_ring_buffer_ctx *ctx,
@@ -392,16 +392,16 @@ struct ltt_channel *ltt_channel_create(struct ltt_session *session,
 				       size_t subbuf_size, size_t num_subbuf,
 				       unsigned int switch_timer_interval,
 				       unsigned int read_timer_interval,
-				       int *shm_fd, int *wait_fd,
-				       uint64_t *memory_map_size,
+				       int **shm_fd, int **wait_fd,
+				       uint64_t **memory_map_size,
 				       struct ltt_channel *chan_priv_init);
 struct ltt_channel *ltt_global_channel_create(struct ltt_session *session,
 				       int overwrite, void *buf_addr,
 				       size_t subbuf_size, size_t num_subbuf,
 				       unsigned int switch_timer_interval,
 				       unsigned int read_timer_interval,
-				       int *shm_fd, int *wait_fd,
-				       uint64_t *memory_map_size);
+				       int **shm_fd, int **wait_fd,
+				       uint64_t **memory_map_size);
 
 int ltt_event_create(struct ltt_channel *chan,
 		struct lttng_ust_event *event_param,
diff --git a/liblttng-ust-ctl/ustctl.c b/liblttng-ust-ctl/ustctl.c
index 656aeac5..f7e13a1a 100644
--- a/liblttng-ust-ctl/ustctl.c
+++ b/liblttng-ust-ctl/ustctl.c
@@ -600,8 +600,8 @@ struct lttng_ust_lib_ring_buffer *ustctl_open_stream_read(struct lttng_ust_shm_h
 	int cpu)
 {
 	struct channel *chan = handle->shadow_chan;
-	int shm_fd, wait_fd;
-	uint64_t memory_map_size;
+	int *shm_fd, *wait_fd;
+	uint64_t *memory_map_size;
 	struct lttng_ust_lib_ring_buffer *buf;
 	int ret;
 
diff --git a/liblttng-ust/ltt-events.c b/liblttng-ust/ltt-events.c
index 94e06780..ee88b431 100644
--- a/liblttng-ust/ltt-events.c
+++ b/liblttng-ust/ltt-events.c
@@ -401,8 +401,8 @@ struct ltt_channel *ltt_channel_create(struct ltt_session *session,
 				       size_t subbuf_size, size_t num_subbuf,
 				       unsigned int switch_timer_interval,
 				       unsigned int read_timer_interval,
-				       int *shm_fd, int *wait_fd,
-				       uint64_t *memory_map_size,
+				       int **shm_fd, int **wait_fd,
+				       uint64_t **memory_map_size,
 				       struct ltt_channel *chan_priv_init)
 {
 	struct ltt_channel *chan = NULL;
diff --git a/liblttng-ust/ltt-ring-buffer-client.h b/liblttng-ust/ltt-ring-buffer-client.h
index 6f714da5..a2ace400 100644
--- a/liblttng-ust/ltt-ring-buffer-client.h
+++ b/liblttng-ust/ltt-ring-buffer-client.h
@@ -385,8 +385,8 @@ struct ltt_channel *_channel_create(const char *name,
 				size_t subbuf_size, size_t num_subbuf,
 				unsigned int switch_timer_interval,
 				unsigned int read_timer_interval,
-				int *shm_fd, int *wait_fd,
-				uint64_t *memory_map_size,
+				int **shm_fd, int **wait_fd,
+				uint64_t **memory_map_size,
 				struct ltt_channel *chan_priv_init)
 {
 	void *priv;
@@ -416,8 +416,8 @@ void ltt_channel_destroy(struct ltt_channel *ltt_chan)
 static
 struct lttng_ust_lib_ring_buffer *ltt_buffer_read_open(struct channel *chan,
 					     struct lttng_ust_shm_handle *handle,
-					     int *shm_fd, int *wait_fd,
-					     uint64_t *memory_map_size)
+					     int **shm_fd, int **wait_fd,
+					     uint64_t **memory_map_size)
 {
 	struct lttng_ust_lib_ring_buffer *buf;
 	int cpu;
@@ -521,8 +521,8 @@ int ltt_flush_buffer(struct channel *chan, struct lttng_ust_shm_handle *handle)
 	int cpu;
 
 	for_each_channel_cpu(cpu, chan) {
-		int shm_fd, wait_fd;
-		uint64_t memory_map_size;
+		int *shm_fd, *wait_fd;
+		uint64_t *memory_map_size;
 
 		buf = channel_get_ring_buffer(&client_config, chan,
 				cpu, handle, &shm_fd, &wait_fd,
diff --git a/liblttng-ust/ltt-ring-buffer-metadata-client.h b/liblttng-ust/ltt-ring-buffer-metadata-client.h
index a9c2f641..7e79b116 100644
--- a/liblttng-ust/ltt-ring-buffer-metadata-client.h
+++ b/liblttng-ust/ltt-ring-buffer-metadata-client.h
@@ -167,8 +167,8 @@ struct ltt_channel *_channel_create(const char *name,
 				size_t subbuf_size, size_t num_subbuf,
 				unsigned int switch_timer_interval,
 				unsigned int read_timer_interval,
-				int *shm_fd, int *wait_fd,
-				uint64_t *memory_map_size,
+				int **shm_fd, int **wait_fd,
+				uint64_t **memory_map_size,
 				struct ltt_channel *chan_priv_init)
 {
 	void *priv;
@@ -198,8 +198,8 @@ void ltt_channel_destroy(struct ltt_channel *ltt_chan)
 static
 struct lttng_ust_lib_ring_buffer *ltt_buffer_read_open(struct channel *chan,
 					     struct lttng_ust_shm_handle *handle,
-					     int *shm_fd, int *wait_fd,
-					     uint64_t *memory_map_size)
+					     int **shm_fd, int **wait_fd,
+					     uint64_t **memory_map_size)
 {
 	struct lttng_ust_lib_ring_buffer *buf;
 
@@ -283,8 +283,8 @@ static
 int ltt_flush_buffer(struct channel *chan, struct lttng_ust_shm_handle *handle)
 {
 	struct lttng_ust_lib_ring_buffer *buf;
-	int shm_fd, wait_fd;
-	uint64_t memory_map_size;
+	int *shm_fd, *wait_fd;
+	uint64_t *memory_map_size;
 
 	buf = channel_get_ring_buffer(&client_config, chan,
 			0, handle, &shm_fd, &wait_fd,
diff --git a/liblttng-ust/lttng-ust-abi.c b/liblttng-ust/lttng-ust-abi.c
index 716a2cc9..b3db6fd7 100644
--- a/liblttng-ust/lttng-ust-abi.c
+++ b/liblttng-ust/lttng-ust-abi.c
@@ -281,6 +281,7 @@ long lttng_abi_add_context(int objd,
  *	@objd: the object descriptor
  *	@cmd: the command
  *	@arg: command arg
+ *	@uargs: UST arguments (internal)
  *
  *	This descriptor implements lttng commands:
  *	LTTNG_UST_SESSION
@@ -295,7 +296,8 @@ long lttng_abi_add_context(int objd,
  * The returned session will be deleted when its file descriptor is closed.
  */
 static
-long lttng_cmd(int objd, unsigned int cmd, unsigned long arg)
+long lttng_cmd(int objd, unsigned int cmd, unsigned long arg,
+	union ust_args *uargs)
 {
 	switch (cmd) {
 	case LTTNG_UST_SESSION:
@@ -350,7 +352,8 @@ create_error:
 
 int lttng_abi_create_channel(int session_objd,
 			     struct lttng_ust_channel *chan_param,
-			     enum channel_type channel_type)
+			     enum channel_type channel_type,
+			     union ust_args *uargs)
 {
 	struct ltt_session *session = objd_private(session_objd);
 	const struct lttng_ust_objd_ops *ops;
@@ -399,9 +402,9 @@ int lttng_abi_create_channel(int session_objd,
 				  chan_param->num_subbuf,
 				  chan_param->switch_timer_interval,
 				  chan_param->read_timer_interval,
-				  &chan_param->shm_fd,
-				  &chan_param->wait_fd,
-				  &chan_param->memory_map_size,
+				  &uargs->channel.shm_fd,
+				  &uargs->channel.wait_fd,
+				  &uargs->channel.memory_map_size,
 				  &chan_priv_init);
 	if (!chan) {
 		ret = -EINVAL;
@@ -435,6 +438,7 @@ objd_error:
  *	@obj: the object
  *	@cmd: the command
  *	@arg: command arg
+ *	@uargs: UST arguments (internal)
  *
  *	This descriptor implements lttng commands:
  *	LTTNG_UST_CHANNEL
@@ -449,7 +453,8 @@ objd_error:
  * The returned channel will be deleted when its file descriptor is closed.
  */
 static
-long lttng_session_cmd(int objd, unsigned int cmd, unsigned long arg)
+long lttng_session_cmd(int objd, unsigned int cmd, unsigned long arg,
+	union ust_args *uargs)
 {
 	struct ltt_session *session = objd_private(objd);
 
@@ -457,7 +462,7 @@ long lttng_session_cmd(int objd, unsigned int cmd, unsigned long arg)
 	case LTTNG_UST_CHANNEL:
 		return lttng_abi_create_channel(objd,
 				(struct lttng_ust_channel *) arg,
-				PER_CPU_CHANNEL);
+				PER_CPU_CHANNEL, uargs);
 	case LTTNG_UST_SESSION_START:
 	case LTTNG_UST_ENABLE:
 		return ltt_session_enable(session);
@@ -467,7 +472,7 @@ long lttng_session_cmd(int objd, unsigned int cmd, unsigned long arg)
 	case LTTNG_UST_METADATA:
 		return lttng_abi_create_channel(objd,
 				(struct lttng_ust_channel *) arg,
-				METADATA_CHANNEL);
+				METADATA_CHANNEL, uargs);
 	default:
 		return -EINVAL;
 	}
@@ -500,7 +505,8 @@ static const struct lttng_ust_objd_ops lttng_session_ops = {
 };
 
 static
-long lttng_tracepoint_list_cmd(int objd, unsigned int cmd, unsigned long arg)
+long lttng_tracepoint_list_cmd(int objd, unsigned int cmd, unsigned long arg,
+	union ust_args *uargs)
 {
 	struct lttng_ust_tracepoint_list *list = objd_private(objd);
 	struct lttng_ust_tracepoint_iter *tp =
@@ -587,7 +593,8 @@ struct stream_priv_data {
 };
 
 static
-int lttng_abi_open_stream(int channel_objd, struct lttng_ust_stream *info)
+int lttng_abi_open_stream(int channel_objd, struct lttng_ust_stream *info,
+		union ust_args *uargs)
 {
 	struct ltt_channel *channel = objd_private(channel_objd);
 	struct lttng_ust_lib_ring_buffer *buf;
@@ -595,7 +602,9 @@ int lttng_abi_open_stream(int channel_objd, struct lttng_ust_stream *info)
 	int stream_objd, ret;
 
 	buf = channel->ops->buffer_read_open(channel->chan, channel->handle,
-			&info->shm_fd, &info->wait_fd, &info->memory_map_size);
+			&uargs->stream.shm_fd,
+			&uargs->stream.wait_fd,
+			&uargs->stream.memory_map_size);
 	if (!buf)
 		return -ENOENT;
 
@@ -742,6 +751,7 @@ objd_error:
  *	@objd: the object descriptor
  *	@cmd: the command
  *	@arg: command arg
+ *	@uargs: UST arguments (internal)
  *
  *	This object descriptor implements lttng commands:
  *      LTTNG_UST_STREAM
@@ -759,7 +769,8 @@ objd_error:
  * Channel and event file descriptors also hold a reference on the session.
  */
 static
-long lttng_channel_cmd(int objd, unsigned int cmd, unsigned long arg)
+long lttng_channel_cmd(int objd, unsigned int cmd, unsigned long arg,
+	union ust_args *uargs)
 {
 	struct ltt_channel *channel = objd_private(objd);
 
@@ -770,7 +781,7 @@ long lttng_channel_cmd(int objd, unsigned int cmd, unsigned long arg)
 
 		stream = (struct lttng_ust_stream *) arg;
 		/* stream used as output */
-		return lttng_abi_open_stream(objd, stream);
+		return lttng_abi_open_stream(objd, stream, uargs);
 	}
 	case LTTNG_UST_EVENT:
 	{
@@ -808,6 +819,7 @@ long lttng_channel_cmd(int objd, unsigned int cmd, unsigned long arg)
  *	@objd: the object descriptor
  *	@cmd: the command
  *	@arg: command arg
+ *	@uargs: UST arguments (internal)
  *
  *	This object descriptor implements lttng commands:
  *      LTTNG_UST_STREAM
@@ -816,7 +828,8 @@ long lttng_channel_cmd(int objd, unsigned int cmd, unsigned long arg)
  * Channel and event file descriptors also hold a reference on the session.
  */
 static
-long lttng_metadata_cmd(int objd, unsigned int cmd, unsigned long arg)
+long lttng_metadata_cmd(int objd, unsigned int cmd, unsigned long arg,
+	union ust_args *uargs)
 {
 	struct ltt_channel *channel = objd_private(objd);
 
@@ -827,7 +840,7 @@ long lttng_metadata_cmd(int objd, unsigned int cmd, unsigned long arg)
 
 		stream = (struct lttng_ust_stream *) arg;
 		/* stream used as output */
-		return lttng_abi_open_stream(objd, stream);
+		return lttng_abi_open_stream(objd, stream, uargs);
 	}
 	case LTTNG_UST_FLUSH_BUFFER:
 		return channel->ops->flush_buffer(channel->chan, channel->handle);
@@ -893,12 +906,14 @@ static const struct lttng_ust_objd_ops lttng_metadata_ops = {
  *	@objd: the object descriptor
  *	@cmd: the command
  *	@arg: command arg
+ *	@uargs: UST arguments (internal)
  *
  *	This object descriptor implements lttng commands:
  *		(None for now. Access is done directly though shm.)
  */
 static
-long lttng_rb_cmd(int objd, unsigned int cmd, unsigned long arg)
+long lttng_rb_cmd(int objd, unsigned int cmd, unsigned long arg,
+	union ust_args *uargs)
 {
 	switch (cmd) {
 	default:
@@ -949,6 +964,7 @@ static const struct lttng_ust_objd_ops lib_ring_buffer_objd_ops = {
  *	@objd: the object descriptor
  *	@cmd: the command
  *	@arg: command arg
+ *	@uargs: UST arguments (internal)
  *
  *	This object descriptor implements lttng commands:
  *	LTTNG_UST_CONTEXT
@@ -959,7 +975,8 @@ static const struct lttng_ust_objd_ops lib_ring_buffer_objd_ops = {
  *		Disable recording for this event (strong disable)
  */
 static
-long lttng_event_cmd(int objd, unsigned int cmd, unsigned long arg)
+long lttng_event_cmd(int objd, unsigned int cmd, unsigned long arg,
+	union ust_args *uargs)
 {
 	struct ltt_event *event = objd_private(objd);
 
@@ -999,6 +1016,7 @@ static const struct lttng_ust_objd_ops lttng_event_ops = {
  *	@objd: the object descriptor
  *	@cmd: the command
  *	@arg: command arg
+ *	@uargs: UST arguments (internal)
  *
  *	This object descriptor implements lttng commands:
  *	LTTNG_UST_CONTEXT
@@ -1010,7 +1028,8 @@ static const struct lttng_ust_objd_ops lttng_event_ops = {
  *		Disable recording for these loglevel events (strong disable)
  */
 static
-long lttng_loglevel_cmd(int objd, unsigned int cmd, unsigned long arg)
+long lttng_loglevel_cmd(int objd, unsigned int cmd, unsigned long arg,
+	union ust_args *uargs)
 {
 	struct session_loglevel *loglevel = objd_private(objd);
 
@@ -1053,6 +1072,7 @@ static const struct lttng_ust_objd_ops lttng_loglevel_ops = {
  *	@objd: the object descriptor
  *	@cmd: the command
  *	@arg: command arg
+ *	@uargs: UST arguments (internal)
  *
  *	This object descriptor implements lttng commands:
  *	LTTNG_UST_CONTEXT
@@ -1064,7 +1084,8 @@ static const struct lttng_ust_objd_ops lttng_loglevel_ops = {
  *		Disable recording for these wildcard events (strong disable)
  */
 static
-long lttng_wildcard_cmd(int objd, unsigned int cmd, unsigned long arg)
+long lttng_wildcard_cmd(int objd, unsigned int cmd, unsigned long arg,
+	union ust_args *uargs)
 {
 	struct session_wildcard *wildcard = objd_private(objd);
 
diff --git a/liblttng-ust/lttng-ust-comm.c b/liblttng-ust/lttng-ust-comm.c
index b968b498..516e39d2 100644
--- a/liblttng-ust/lttng-ust-comm.c
+++ b/liblttng-ust/lttng-ust-comm.c
@@ -239,6 +239,7 @@ int handle_message(struct sock_info *sock_info,
 	const struct lttng_ust_objd_ops *ops;
 	struct ustcomm_ust_reply lur;
 	int shm_fd, wait_fd;
+	union ust_args args;
 
 	ust_lock();
 
@@ -271,7 +272,8 @@ int handle_message(struct sock_info *sock_info,
 	default:
 		if (ops->cmd)
 			ret = ops->cmd(lum->handle, lum->cmd,
-					(unsigned long) &lum->u);
+					(unsigned long) &lum->u,
+					&args);
 		else
 			ret = -ENOSYS;
 		break;
@@ -293,15 +295,15 @@ end:
 		 * Special-case reply to send stream info.
 		 * Use lum.u output.
 		 */
-		lur.u.stream.memory_map_size = lum->u.stream.memory_map_size;
-		shm_fd = lum->u.stream.shm_fd;
-		wait_fd = lum->u.stream.wait_fd;
+		lur.u.stream.memory_map_size = *args.stream.memory_map_size;
+		shm_fd = *args.stream.shm_fd;
+		wait_fd = *args.stream.wait_fd;
 		break;
 	case LTTNG_UST_METADATA:
 	case LTTNG_UST_CHANNEL:
-		lur.u.channel.memory_map_size = lum->u.channel.memory_map_size;
-		shm_fd = lum->u.channel.shm_fd;
-		wait_fd = lum->u.channel.wait_fd;
+		lur.u.channel.memory_map_size = *args.channel.memory_map_size;
+		shm_fd = *args.channel.shm_fd;
+		wait_fd = *args.channel.wait_fd;
 		break;
 	case LTTNG_UST_TRACER_VERSION:
 		lur.u.version = lum->u.version;
@@ -336,6 +338,48 @@ end:
 			goto error;
 		}
 	}
+	/*
+	 * We still have the memory map reference, and the fds have been
+	 * sent to the sessiond. We can therefore close those fds.
+	 */
+	if (lur.ret_code == USTCOMM_OK) {
+		switch (lum->cmd) {
+		case LTTNG_UST_STREAM:
+			if (shm_fd >= 0) {
+				ret = close(shm_fd);
+				if (ret) {
+					PERROR("Error closing stream shm_fd");
+				}
+				*args.stream.shm_fd = -1;
+			}
+			if (wait_fd >= 0) {
+				ret = close(wait_fd);
+				if (ret) {
+					PERROR("Error closing stream wait_fd");
+				}
+				*args.stream.wait_fd = -1;
+			}
+			break;
+		case LTTNG_UST_METADATA:
+		case LTTNG_UST_CHANNEL:
+			if (shm_fd >= 0) {
+				ret = close(shm_fd);
+				if (ret) {
+					PERROR("Error closing channel shm_fd");
+				}
+				*args.channel.shm_fd = -1;
+			}
+			if (wait_fd >= 0) {
+				ret = close(wait_fd);
+				if (ret) {
+					PERROR("Error closing channel wait_fd");
+				}
+				*args.channel.wait_fd = -1;
+			}
+			break;
+		}
+	}
+
 error:
 	ust_unlock();
 	return ret;
diff --git a/libringbuffer/frontend.h b/libringbuffer/frontend.h
index eb95e622..ce79cdee 100644
--- a/libringbuffer/frontend.h
+++ b/libringbuffer/frontend.h
@@ -52,8 +52,8 @@ struct lttng_ust_shm_handle *channel_create(const struct lttng_ust_lib_ring_buff
 				size_t subbuf_size, size_t num_subbuf,
 				unsigned int switch_timer_interval,
 				unsigned int read_timer_interval,
-				int *shm_fd, int *wait_fd,
-				uint64_t *memory_map_size);
+				int **shm_fd, int **wait_fd,
+				uint64_t **memory_map_size);
 
 /* channel_handle_create - for consumer. */
 extern
@@ -89,8 +89,8 @@ extern struct lttng_ust_lib_ring_buffer *channel_get_ring_buffer(
 				const struct lttng_ust_lib_ring_buffer_config *config,
 				struct channel *chan, int cpu,
 				struct lttng_ust_shm_handle *handle,
-				int *shm_fd, int *wait_fd,
-				uint64_t *memory_map_size);
+				int **shm_fd, int **wait_fd,
+				uint64_t **memory_map_size);
 extern int lib_ring_buffer_open_read(struct lttng_ust_lib_ring_buffer *buf,
 				     struct lttng_ust_shm_handle *handle,
 				     int shadow);
diff --git a/libringbuffer/ring_buffer_frontend.c b/libringbuffer/ring_buffer_frontend.c
index f558793a..d0649f3e 100644
--- a/libringbuffer/ring_buffer_frontend.c
+++ b/libringbuffer/ring_buffer_frontend.c
@@ -420,7 +420,7 @@ struct lttng_ust_shm_handle *channel_create(const struct lttng_ust_lib_ring_buff
 		   void *buf_addr, size_t subbuf_size,
 		   size_t num_subbuf, unsigned int switch_timer_interval,
 		   unsigned int read_timer_interval,
-		   int *shm_fd, int *wait_fd, uint64_t *memory_map_size)
+		   int **shm_fd, int **wait_fd, uint64_t **memory_map_size)
 {
 	int ret, cpu;
 	size_t shmsize, chansize;
@@ -610,8 +610,8 @@ struct lttng_ust_lib_ring_buffer *channel_get_ring_buffer(
 					const struct lttng_ust_lib_ring_buffer_config *config,
 					struct channel *chan, int cpu,
 					struct lttng_ust_shm_handle *handle,
-					int *shm_fd, int *wait_fd,
-					uint64_t *memory_map_size)
+					int **shm_fd, int **wait_fd,
+					uint64_t **memory_map_size)
 {
 	struct shm_ref *ref;
 
diff --git a/libringbuffer/shm.c b/libringbuffer/shm.c
index 994204d1..69e4b1a7 100644
--- a/libringbuffer/shm.c
+++ b/libringbuffer/shm.c
@@ -211,10 +211,12 @@ void shmp_object_destroy(struct shm_object *obj)
 			assert(0);
 		}
 	}
-	ret = close(obj->shm_fd);
-	if (ret) {
-		PERROR("close");
-		assert(0);
+	if (obj->shm_fd >= 0) {
+		ret = close(obj->shm_fd);
+		if (ret) {
+			PERROR("close");
+			assert(0);
+		}
 	}
 	for (i = 0; i < 2; i++) {
 		if (obj->wait_fd[i] < 0)
diff --git a/libringbuffer/shm.h b/libringbuffer/shm.h
index 41111447..104eece6 100644
--- a/libringbuffer/shm.h
+++ b/libringbuffer/shm.h
@@ -107,7 +107,7 @@ int shm_get_wait_fd(struct lttng_ust_shm_handle *handle, struct shm_ref *ref)
 
 static inline
 int shm_get_object_data(struct lttng_ust_shm_handle *handle, struct shm_ref *ref,
-		int *shm_fd, int *wait_fd, uint64_t *memory_map_size)
+		int **shm_fd, int **wait_fd, uint64_t **memory_map_size)
 {
 	struct shm_object_table *table = handle->table;
 	struct shm_object *obj;
@@ -117,9 +117,9 @@ int shm_get_object_data(struct lttng_ust_shm_handle *handle, struct shm_ref *ref
 	if (caa_unlikely(index >= table->allocated_len))
 		return -EPERM;
 	obj = &table->objects[index];
-	*shm_fd = obj->shm_fd;
-	*wait_fd = obj->wait_fd[0];
-	*memory_map_size = obj->allocated_len;
+	*shm_fd = &obj->shm_fd;
+	*wait_fd = &obj->wait_fd[0];
+	*memory_map_size = &obj->allocated_len;
 	return 0;
 }
 
diff --git a/tests/ust-basic-tracing/ust-basic-tracing.c b/tests/ust-basic-tracing/ust-basic-tracing.c
index d11b587b..da2852f8 100644
--- a/tests/ust-basic-tracing/ust-basic-tracing.c
+++ b/tests/ust-basic-tracing/ust-basic-tracing.c
@@ -203,8 +203,8 @@ int consume_stream(struct lttng_ust_shm_handle *handle, int cpu, char *outfile)
 	struct channel *chan;
 	struct lttng_ust_lib_ring_buffer *buf;
 	int outfd, ret;
-	int shm_fd, wait_fd;
-	uint64_t memory_map_size;
+	int *shm_fd, *wait_fd;
+	uint64_t *memory_map_size;
 
 	chan = shmp(handle, handle->chan);
 
diff --git a/tests/ust-multi-test/ust-multi-test.c b/tests/ust-multi-test/ust-multi-test.c
index cfd6d355..b3c97ea1 100644
--- a/tests/ust-multi-test/ust-multi-test.c
+++ b/tests/ust-multi-test/ust-multi-test.c
@@ -210,8 +210,8 @@ int consume_stream(struct lttng_ust_shm_handle *handle, int cpu, char *outfile)
 	struct channel *chan;
 	struct lttng_ust_lib_ring_buffer *buf;
 	int outfd, ret;
-	int shm_fd, wait_fd;
-	uint64_t memory_map_size;
+	int *shm_fd, *wait_fd;
+	uint64_t *memory_map_size;
 
 	chan = shmp(handle, handle->chan);
 
-- 
2.34.1