[lttng-tools.git] / liblttng-kconsumer / lttng-kconsumer.c

/*
 * Copyright (C) 2011 - Julien Desfossez <julien.desfossez@polymtl.ca>
 *                      Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * as published by the Free Software Foundation; only version 2
 * of the License.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

#define _GNU_SOURCE
#include <assert.h>
#include <fcntl.h>
#include <poll.h>
#include <pthread.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <unistd.h>

#include <lttng-kernel-ctl.h>
#include <lttng-sessiond-comm.h>
#include <lttng/lttng-kconsumer.h>
#include <lttngerr.h>

extern struct lttng_consumer_global_data consumer_data;
extern int consumer_poll_timeout;
extern volatile int consumer_quit;

/*
 * Mmap the ring buffer, read it and write the data to the tracefile.
 *
 * Returns the number of bytes written
 */
int lttng_kconsumer_on_read_subbuffer_mmap(
		struct lttng_consumer_local_data *ctx,
		struct lttng_consumer_stream *stream, unsigned long len)
{
	unsigned long mmap_offset;
	long ret = 0;
	off_t orig_offset = stream->out_fd_offset;
	int fd = stream->wait_fd;
	int outfd = stream->out_fd;

	/* get the offset inside the fd to mmap */
	ret = kernctl_get_mmap_read_offset(fd, &mmap_offset);
	if (ret != 0) {
		ret = -errno;
		perror("kernctl_get_mmap_read_offset");
		goto end;
	}

	while (len > 0) {
		ret = write(outfd, stream->mmap_base + mmap_offset, len);
		if (ret >= len) {
			len = 0;
		} else if (ret < 0) {
			ret = -errno;
			perror("Error in file write");
			goto end;
		}
		/* This won't block, but will start writeout asynchronously */
		sync_file_range(outfd, stream->out_fd_offset, ret,
				SYNC_FILE_RANGE_WRITE);
		stream->out_fd_offset += ret;
	}

	lttng_consumer_sync_trace_file(stream, orig_offset);

	goto end;

end:
	return ret;
}

/*
 * Splice the data from the ring buffer to the tracefile.
 *
 * Returns the number of bytes spliced.
 */
int lttng_kconsumer_on_read_subbuffer_splice(
		struct lttng_consumer_local_data *ctx,
		struct lttng_consumer_stream *stream, unsigned long len)
{
	long ret = 0;
	loff_t offset = 0;
	off_t orig_offset = stream->out_fd_offset;
	int fd = stream->wait_fd;
	int outfd = stream->out_fd;

	while (len > 0) {
		DBG("splice chan to pipe offset %lu (fd : %d)",
				(unsigned long)offset, fd);
		ret = splice(fd, &offset, ctx->consumer_thread_pipe[1], NULL, len,
				SPLICE_F_MOVE | SPLICE_F_MORE);
		DBG("splice chan to pipe ret %ld", ret);
		if (ret < 0) {
			ret = errno;
			perror("Error in relay splice");
			goto splice_error;
		}

		ret = splice(ctx->consumer_thread_pipe[0], NULL, outfd, NULL, ret,
				SPLICE_F_MOVE | SPLICE_F_MORE);
		DBG("splice pipe to file %ld", ret);
		if (ret < 0) {
			ret = errno;
			perror("Error in file splice");
			goto splice_error;
		}
		len -= ret;
		/* This won't block, but will start writeout asynchronously */
		sync_file_range(outfd, stream->out_fd_offset, ret,
				SYNC_FILE_RANGE_WRITE);
		stream->out_fd_offset += ret;
	}
	lttng_consumer_sync_trace_file(stream, orig_offset);

	goto end;

splice_error:
	/* send the appropriate error description to sessiond */
	switch(ret) {
	case EBADF:
		lttng_consumer_send_error(ctx, CONSUMERD_SPLICE_EBADF);
		break;
	case EINVAL:
		lttng_consumer_send_error(ctx, CONSUMERD_SPLICE_EINVAL);
		break;
	case ENOMEM:
		lttng_consumer_send_error(ctx, CONSUMERD_SPLICE_ENOMEM);
		break;
	case ESPIPE:
		lttng_consumer_send_error(ctx, CONSUMERD_SPLICE_ESPIPE);
		break;
	}

end:
	return ret;
}

/*
 * Take a snapshot for a specific fd
 *
 * Returns 0 on success, < 0 on error
 */
int lttng_kconsumer_take_snapshot(struct lttng_consumer_local_data *ctx,
		struct lttng_consumer_stream *stream)
{
	int ret = 0;
	int infd = stream->wait_fd;

	ret = kernctl_snapshot(infd);
	if (ret != 0) {
		ret = errno;
		perror("Getting sub-buffer snapshot.");
	}

	return ret;
}

/*
 * Get the produced position
 *
 * Returns 0 on success, < 0 on error
 */
int lttng_kconsumer_get_produced_snapshot(
		struct lttng_consumer_local_data *ctx,
		struct lttng_consumer_stream *stream,
		unsigned long *pos)
{
	int ret;
	int infd = stream->wait_fd;

	ret = kernctl_snapshot_get_produced(infd, pos);
	if (ret != 0) {
		ret = errno;
		perror("kernctl_snapshot_get_produced");
	}

	return ret;
}

int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
		int sock, struct pollfd *consumer_sockpoll)
{
	ssize_t ret;
	struct lttcomm_consumer_msg msg;

	ret = lttcomm_recv_unix_sock(sock, &msg, sizeof(msg));
	if (ret != sizeof(msg)) {
		lttng_consumer_send_error(ctx, CONSUMERD_ERROR_RECV_CMD);
		return ret;
	}
	if (msg.cmd_type == LTTNG_CONSUMER_STOP) {
		return -ENOENT;
	}

	switch (msg.cmd_type) {
	case LTTNG_CONSUMER_ADD_CHANNEL:
	{
		struct lttng_consumer_channel *new_channel;

		DBG("consumer_add_channel %d", msg.u.channel.channel_key);
		new_channel = consumer_allocate_channel(msg.u.channel.channel_key,
				-1, -1,
				msg.u.channel.mmap_len,
				msg.u.channel.max_sb_size);
		if (new_channel == NULL) {
			lttng_consumer_send_error(ctx, CONSUMERD_OUTFD_ERROR);
			goto end_nosignal;
		}
		if (ctx->on_recv_channel != NULL) {
			ret = ctx->on_recv_channel(new_channel);
			if (ret == 0) {
				consumer_add_channel(new_channel);
			} else if (ret < 0) {
				goto end_nosignal;
			}
		} else {
			consumer_add_channel(new_channel);
		}
		goto end_nosignal;
	}
	case LTTNG_CONSUMER_ADD_STREAM:
	{
		struct lttng_consumer_stream *new_stream;
		int fd;

		/* block */
		if (lttng_consumer_poll_socket(consumer_sockpoll) < 0) {
			return -EINTR;
		}
		ret = lttcomm_recv_fds_unix_sock(sock, &fd, 1);
		if (ret != sizeof(fd)) {
			lttng_consumer_send_error(ctx, CONSUMERD_ERROR_RECV_FD);
			return ret;
		}

		DBG("consumer_add_stream %s (%d)", msg.u.stream.path_name,
			fd);
		new_stream = consumer_allocate_stream(msg.u.stream.channel_key,
				msg.u.stream.stream_key,
				fd, fd,
				msg.u.stream.state,
				msg.u.stream.mmap_len,
				msg.u.stream.output,
				msg.u.stream.path_name,
				msg.u.stream.uid,
				msg.u.stream.gid);
		if (new_stream == NULL) {
			lttng_consumer_send_error(ctx, CONSUMERD_OUTFD_ERROR);
			goto end;
		}
		if (ctx->on_recv_stream != NULL) {
			ret = ctx->on_recv_stream(new_stream);
			if (ret == 0) {
				consumer_add_stream(new_stream);
			} else if (ret < 0) {
				goto end;
			}
		} else {
			consumer_add_stream(new_stream);
		}
		break;
	}
	case LTTNG_CONSUMER_UPDATE_STREAM:
	{
		if (ctx->on_update_stream != NULL) {
			ret = ctx->on_update_stream(msg.u.stream.stream_key, msg.u.stream.state);
			if (ret == 0) {
				consumer_change_stream_state(msg.u.stream.stream_key, msg.u.stream.state);
			} else if (ret < 0) {
				goto end;
			}
		} else {
			consumer_change_stream_state(msg.u.stream.stream_key,
				msg.u.stream.state);
		}
		break;
	}
	default:
		break;
	}
end:
	/* signal the poll thread */
	ret = write(ctx->consumer_poll_pipe[1], "4", 1);
	if (ret < 0) {
		perror("write consumer poll");
	}
end_nosignal:
	return 0;
}

/*
 * Consume data on a file descriptor and write it on a trace file.
 */
int lttng_kconsumer_read_subbuffer(struct lttng_consumer_stream *stream,
		struct lttng_consumer_local_data *ctx)
{
	unsigned long len;
	int err;
	long ret = 0;
	int infd = stream->wait_fd;

	DBG("In read_subbuffer (infd : %d)", infd);
	/* Get the next subbuffer */
	err = kernctl_get_next_subbuf(infd);
	if (err != 0) {
		ret = errno;
		/*
		 * This is a debug message even for single-threaded consumer,
		 * because poll() have more relaxed criterions than get subbuf,
		 * so get_subbuf may fail for short race windows where poll()
		 * would issue wakeups.
		 */
		DBG("Reserving sub buffer failed (everything is normal, "
				"it is due to concurrency)");
		goto end;
	}

	switch (stream->output) {
		case LTTNG_EVENT_SPLICE:
			/* read the whole subbuffer */
			err = kernctl_get_padded_subbuf_size(infd, &len);
			if (err != 0) {
				ret = errno;
				perror("Getting sub-buffer len failed.");
				goto end;
			}

			/* splice the subbuffer to the tracefile */
			ret = lttng_consumer_on_read_subbuffer_splice(ctx, stream, len);
			if (ret < 0) {
				/*
				 * display the error but continue processing to try
				 * to release the subbuffer
				 */
				ERR("Error splicing to tracefile");
			}
			break;
		case LTTNG_EVENT_MMAP:
			/* read the used subbuffer size */
			err = kernctl_get_padded_subbuf_size(infd, &len);
			if (err != 0) {
				ret = errno;
				perror("Getting sub-buffer len failed.");
				goto end;
			}
			/* write the subbuffer to the tracefile */
			ret = lttng_consumer_on_read_subbuffer_mmap(ctx, stream, len);
			if (ret < 0) {
				/*
				 * display the error but continue processing to try
				 * to release the subbuffer
				 */
				ERR("Error writing to tracefile");
			}
			break;
		default:
			ERR("Unknown output method");
			ret = -1;
	}

	err = kernctl_put_next_subbuf(infd);
	if (err != 0) {
		ret = errno;
		if (errno == EFAULT) {
			perror("Error in unreserving sub buffer\n");
		} else if (errno == EIO) {
			/* Should never happen with newer LTTng versions */
			perror("Reader has been pushed by the writer, last sub-buffer corrupted.");
		}
		goto end;
	}

end:
	return ret;
}

int lttng_kconsumer_on_recv_stream(struct lttng_consumer_stream *stream)
{
	int ret;

	/* Opening the tracefile in write mode */
	if (stream->path_name != NULL) {
		ret = open(stream->path_name,
				O_WRONLY|O_CREAT|O_TRUNC, S_IRWXU|S_IRWXG|S_IRWXO);
		if (ret < 0) {
			ERR("Opening %s", stream->path_name);
			perror("open");
			goto error;
		}
		stream->out_fd = ret;
		ret = chown(stream->path_name, stream->uid, stream->gid);
		if (ret < 0) {
			ERR("Changing ownership of %s", stream->path_name);
			perror("chown");
		}
	}

	if (stream->output == LTTNG_EVENT_MMAP) {
		/* get the len of the mmap region */
		unsigned long mmap_len;

		ret = kernctl_get_mmap_len(stream->wait_fd, &mmap_len);
		if (ret != 0) {
			ret = errno;
			perror("kernctl_get_mmap_len");
			goto error_close_fd;
		}
		stream->mmap_len = (size_t) mmap_len;

		stream->mmap_base = mmap(NULL, stream->mmap_len,
				PROT_READ, MAP_PRIVATE, stream->wait_fd, 0);
		if (stream->mmap_base == MAP_FAILED) {
			perror("Error mmaping");
			ret = -1;
			goto error_close_fd;
		}
	}

	/* we return 0 to let the library handle the FD internally */
	return 0;

error_close_fd:
	{
		int err;

		err = close(stream->out_fd);
		assert(!err);
	}
error:
	return ret;
}
Commit	Line	Data
3bd1e081 MD	1	/*
	2	* Copyright (C) 2011 - Julien Desfossez <julien.desfossez@polymtl.ca>
	3	* Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
	4	*
	5	* This program is free software; you can redistribute it and/or
	6	* modify it under the terms of the GNU General Public License
	7	* as published by the Free Software Foundation; only version 2
	8	* of the License.
	9	*
	10	* This program is distributed in the hope that it will be useful,
	11	* but WITHOUT ANY WARRANTY; without even the implied warranty of
	12	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	13	* GNU General Public License for more details.
	14	*
	15	* You should have received a copy of the GNU General Public License
	16	* along with this program; if not, write to the Free Software
	17	* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
	18	*/
	19
	20	#define _GNU_SOURCE
	21	#include <assert.h>
	22	#include <fcntl.h>
	23	#include <poll.h>
	24	#include <pthread.h>
	25	#include <stdlib.h>
	26	#include <string.h>
	27	#include <sys/mman.h>
	28	#include <sys/socket.h>
	29	#include <sys/types.h>
	30	#include <unistd.h>
	31
	32	#include <lttng-kernel-ctl.h>
	33	#include <lttng-sessiond-comm.h>
	34	#include <lttng/lttng-kconsumer.h>
	35	#include <lttngerr.h>
	36
	37	extern struct lttng_consumer_global_data consumer_data;
	38	extern int consumer_poll_timeout;
	39	extern volatile int consumer_quit;
	40
	41	/*
	42	* Mmap the ring buffer, read it and write the data to the tracefile.
	43	*
	44	* Returns the number of bytes written
	45	*/
	46	int lttng_kconsumer_on_read_subbuffer_mmap(
	47	struct lttng_consumer_local_data *ctx,
	48	struct lttng_consumer_stream *stream, unsigned long len)
	49	{
	50	unsigned long mmap_offset;
	51	long ret = 0;
	52	off_t orig_offset = stream->out_fd_offset;
	53	int fd = stream->wait_fd;
	54	int outfd = stream->out_fd;
	55
	56	/* get the offset inside the fd to mmap */
	57	ret = kernctl_get_mmap_read_offset(fd, &mmap_offset);
	58	if (ret != 0) {
	59	ret = -errno;
	60	perror("kernctl_get_mmap_read_offset");
	61	goto end;
	62	}
	63
	64	while (len > 0) {
65	ret = write(outfd, stream->mmap_base + mmap_offset, len);
66	if (ret >= len) {
67	len = 0;
68	} else if (ret < 0) {
69	ret = -errno;
70	perror("Error in file write");
71	goto end;
72	}
73	/* This won't block, but will start writeout asynchronously */
74	sync_file_range(outfd, stream->out_fd_offset, ret,
75	SYNC_FILE_RANGE_WRITE);
76	stream->out_fd_offset += ret;
77	}
78
79	lttng_consumer_sync_trace_file(stream, orig_offset);
80
81	goto end;
82
83	end:
84	return ret;
85	}
86
87	/*
88	* Splice the data from the ring buffer to the tracefile.
89	*
90	* Returns the number of bytes spliced.
91	*/
92	int lttng_kconsumer_on_read_subbuffer_splice(
93	struct lttng_consumer_local_data *ctx,
94	struct lttng_consumer_stream *stream, unsigned long len)
95	{
96	long ret = 0;
97	loff_t offset = 0;
98	off_t orig_offset = stream->out_fd_offset;
99	int fd = stream->wait_fd;
100	int outfd = stream->out_fd;
101
102	while (len > 0) {
103	DBG("splice chan to pipe offset %lu (fd : %d)",
104	(unsigned long)offset, fd);
105	ret = splice(fd, &offset, ctx->consumer_thread_pipe[1], NULL, len,
106	SPLICE_F_MOVE \| SPLICE_F_MORE);
107	DBG("splice chan to pipe ret %ld", ret);
108	if (ret < 0) {
109	ret = errno;
110	perror("Error in relay splice");
111	goto splice_error;
112	}
113
114	ret = splice(ctx->consumer_thread_pipe[0], NULL, outfd, NULL, ret,
115	SPLICE_F_MOVE \| SPLICE_F_MORE);
116	DBG("splice pipe to file %ld", ret);
117	if (ret < 0) {
118	ret = errno;
119	perror("Error in file splice");
120	goto splice_error;
121	}
122	len -= ret;
123	/* This won't block, but will start writeout asynchronously */
124	sync_file_range(outfd, stream->out_fd_offset, ret,
125	SYNC_FILE_RANGE_WRITE);
126	stream->out_fd_offset += ret;
127	}
128	lttng_consumer_sync_trace_file(stream, orig_offset);
129
130	goto end;
131
132	splice_error:
133	/* send the appropriate error description to sessiond */
134	switch(ret) {
135	case EBADF:
136	lttng_consumer_send_error(ctx, CONSUMERD_SPLICE_EBADF);
137	break;
138	case EINVAL:
139	lttng_consumer_send_error(ctx, CONSUMERD_SPLICE_EINVAL);
140	break;
141	case ENOMEM:
142	lttng_consumer_send_error(ctx, CONSUMERD_SPLICE_ENOMEM);
143	break;
144	case ESPIPE:
145	lttng_consumer_send_error(ctx, CONSUMERD_SPLICE_ESPIPE);
146	break;
147	}
148
149	end:
150	return ret;
151	}
152
153	/*
154	* Take a snapshot for a specific fd
155	*
156	* Returns 0 on success, < 0 on error
157	*/
158	int lttng_kconsumer_take_snapshot(struct lttng_consumer_local_data *ctx,
159	struct lttng_consumer_stream *stream)
160	{
161	int ret = 0;
162	int infd = stream->wait_fd;
163
164	ret = kernctl_snapshot(infd);
165	if (ret != 0) {
166	ret = errno;
167	perror("Getting sub-buffer snapshot.");
168	}
169
170	return ret;
171	}
172
173	/*
174	* Get the produced position
175	*
176	* Returns 0 on success, < 0 on error
177	*/
178	int lttng_kconsumer_get_produced_snapshot(
179	struct lttng_consumer_local_data *ctx,
180	struct lttng_consumer_stream *stream,
181	unsigned long *pos)
182	{
183	int ret;
184	int infd = stream->wait_fd;
185
186	ret = kernctl_snapshot_get_produced(infd, pos);
187	if (ret != 0) {
188	ret = errno;
189	perror("kernctl_snapshot_get_produced");
190	}
191
192	return ret;
193	}
194
195	int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
196	int sock, struct pollfd *consumer_sockpoll)
197	{
198	ssize_t ret;
199	struct lttcomm_consumer_msg msg;
200
201	ret = lttcomm_recv_unix_sock(sock, &msg, sizeof(msg));
202	if (ret != sizeof(msg)) {
f2fc6720	203	lttng_consumer_send_error(ctx, CONSUMERD_ERROR_RECV_CMD);
3bd1e081 MD	204	return ret;
	205	}
	206	if (msg.cmd_type == LTTNG_CONSUMER_STOP) {
	207	return -ENOENT;
	208	}
	209
	210	switch (msg.cmd_type) {
	211	case LTTNG_CONSUMER_ADD_CHANNEL:
	212	{
	213	struct lttng_consumer_channel *new_channel;
	214
	215	DBG("consumer_add_channel %d", msg.u.channel.channel_key);
	216	new_channel = consumer_allocate_channel(msg.u.channel.channel_key,
	217	-1, -1,
	218	msg.u.channel.mmap_len,
	219	msg.u.channel.max_sb_size);
	220	if (new_channel == NULL) {
	221	lttng_consumer_send_error(ctx, CONSUMERD_OUTFD_ERROR);
	222	goto end_nosignal;
	223	}
	224	if (ctx->on_recv_channel != NULL) {
	225	ret = ctx->on_recv_channel(new_channel);
	226	if (ret == 0) {
	227	consumer_add_channel(new_channel);
	228	} else if (ret < 0) {
	229	goto end_nosignal;
	230	}
	231	} else {
	232	consumer_add_channel(new_channel);
	233	}
	234	goto end_nosignal;
	235	}
	236	case LTTNG_CONSUMER_ADD_STREAM:
	237	{
	238	struct lttng_consumer_stream *new_stream;
f2fc6720	239	int fd;
3bd1e081 MD	240
	241	/* block */
	242	if (lttng_consumer_poll_socket(consumer_sockpoll) < 0) {
	243	return -EINTR;
	244	}
f2fc6720 MD	245	ret = lttcomm_recv_fds_unix_sock(sock, &fd, 1);
f2fc6720 MD	246	if (ret != sizeof(fd)) {
3bd1e081 MD	247	lttng_consumer_send_error(ctx, CONSUMERD_ERROR_RECV_FD);
	248	return ret;
	249	}
3bd1e081	250
f2fc6720 MD	251	DBG("consumer_add_stream %s (%d)", msg.u.stream.path_name,
f2fc6720 MD	252	fd);
3bd1e081 MD	253	new_stream = consumer_allocate_stream(msg.u.stream.channel_key,
3bd1e081 MD	254	msg.u.stream.stream_key,
f2fc6720	255	fd, fd,
3bd1e081 MD	256	msg.u.stream.state,
	257	msg.u.stream.mmap_len,
	258	msg.u.stream.output,
6df2e2c9 MD	259	msg.u.stream.path_name,
	260	msg.u.stream.uid,
	261	msg.u.stream.gid);
3bd1e081 MD	262	if (new_stream == NULL) {
	263	lttng_consumer_send_error(ctx, CONSUMERD_OUTFD_ERROR);
	264	goto end;
	265	}
	266	if (ctx->on_recv_stream != NULL) {
	267	ret = ctx->on_recv_stream(new_stream);
	268	if (ret == 0) {
	269	consumer_add_stream(new_stream);
	270	} else if (ret < 0) {
	271	goto end;
	272	}
	273	} else {
	274	consumer_add_stream(new_stream);
	275	}
	276	break;
	277	}
	278	case LTTNG_CONSUMER_UPDATE_STREAM:
	279	{
	280	if (ctx->on_update_stream != NULL) {
	281	ret = ctx->on_update_stream(msg.u.stream.stream_key, msg.u.stream.state);
	282	if (ret == 0) {
	283	consumer_change_stream_state(msg.u.stream.stream_key, msg.u.stream.state);
	284	} else if (ret < 0) {
	285	goto end;
	286	}
	287	} else {
	288	consumer_change_stream_state(msg.u.stream.stream_key,
	289	msg.u.stream.state);
	290	}
	291	break;
	292	}
	293	default:
	294	break;
	295	}
	296	end:
	297	/* signal the poll thread */
	298	ret = write(ctx->consumer_poll_pipe[1], "4", 1);
	299	if (ret < 0) {
	300	perror("write consumer poll");
	301	}
	302	end_nosignal:
	303	return 0;
	304	}
d41f73b7 MD	305
	306	/*
	307	* Consume data on a file descriptor and write it on a trace file.
	308	*/
	309	int lttng_kconsumer_read_subbuffer(struct lttng_consumer_stream *stream,
	310	struct lttng_consumer_local_data *ctx)
	311	{
	312	unsigned long len;
	313	int err;
	314	long ret = 0;
	315	int infd = stream->wait_fd;
	316
	317	DBG("In read_subbuffer (infd : %d)", infd);
	318	/* Get the next subbuffer */
	319	err = kernctl_get_next_subbuf(infd);
	320	if (err != 0) {
	321	ret = errno;
	322	/*
	323	* This is a debug message even for single-threaded consumer,
	324	* because poll() have more relaxed criterions than get subbuf,
	325	* so get_subbuf may fail for short race windows where poll()
	326	* would issue wakeups.
	327	*/
	328	DBG("Reserving sub buffer failed (everything is normal, "
	329	"it is due to concurrency)");
	330	goto end;
	331	}
	332
	333	switch (stream->output) {
	334	case LTTNG_EVENT_SPLICE:
	335	/* read the whole subbuffer */
	336	err = kernctl_get_padded_subbuf_size(infd, &len);
	337	if (err != 0) {
	338	ret = errno;
	339	perror("Getting sub-buffer len failed.");
	340	goto end;
	341	}
	342
	343	/* splice the subbuffer to the tracefile */
	344	ret = lttng_consumer_on_read_subbuffer_splice(ctx, stream, len);
	345	if (ret < 0) {
	346	/*
	347	* display the error but continue processing to try
	348	* to release the subbuffer
	349	*/
	350	ERR("Error splicing to tracefile");
	351	}
	352	break;
	353	case LTTNG_EVENT_MMAP:
	354	/* read the used subbuffer size */
	355	err = kernctl_get_padded_subbuf_size(infd, &len);
	356	if (err != 0) {
	357	ret = errno;
	358	perror("Getting sub-buffer len failed.");
	359	goto end;
	360	}
	361	/* write the subbuffer to the tracefile */
	362	ret = lttng_consumer_on_read_subbuffer_mmap(ctx, stream, len);
	363	if (ret < 0) {
	364	/*
	365	* display the error but continue processing to try
	366	* to release the subbuffer
	367	*/
	368	ERR("Error writing to tracefile");
369	}
370	break;
371	default:
372	ERR("Unknown output method");
373	ret = -1;
374	}
375
376	err = kernctl_put_next_subbuf(infd);
377	if (err != 0) {
378	ret = errno;
379	if (errno == EFAULT) {
380	perror("Error in unreserving sub buffer\n");
381	} else if (errno == EIO) {
382	/* Should never happen with newer LTTng versions */
383	perror("Reader has been pushed by the writer, last sub-buffer corrupted.");
384	}
385	goto end;
386	}
387
388	end:
389	return ret;
390	}
391
392	int lttng_kconsumer_on_recv_stream(struct lttng_consumer_stream *stream)
393	{
394	int ret;
395
396	/* Opening the tracefile in write mode */
397	if (stream->path_name != NULL) {
398	ret = open(stream->path_name,
399	O_WRONLY\|O_CREAT\|O_TRUNC, S_IRWXU\|S_IRWXG\|S_IRWXO);
400	if (ret < 0) {
401	ERR("Opening %s", stream->path_name);
402	perror("open");
403	goto error;
404	}
405	stream->out_fd = ret;
6df2e2c9 MD	406	ret = chown(stream->path_name, stream->uid, stream->gid);
	407	if (ret < 0) {
	408	ERR("Changing ownership of %s", stream->path_name);
	409	perror("chown");
	410	}
d41f73b7 MD	411	}
	412
	413	if (stream->output == LTTNG_EVENT_MMAP) {
	414	/* get the len of the mmap region */
	415	unsigned long mmap_len;
	416
	417	ret = kernctl_get_mmap_len(stream->wait_fd, &mmap_len);
	418	if (ret != 0) {
	419	ret = errno;
	420	perror("kernctl_get_mmap_len");
	421	goto error_close_fd;
	422	}
	423	stream->mmap_len = (size_t) mmap_len;
	424
	425	stream->mmap_base = mmap(NULL, stream->mmap_len,
	426	PROT_READ, MAP_PRIVATE, stream->wait_fd, 0);
	427	if (stream->mmap_base == MAP_FAILED) {
	428	perror("Error mmaping");
	429	ret = -1;
	430	goto error_close_fd;
	431	}
	432	}
	433
	434	/* we return 0 to let the library handle the FD internally */
	435	return 0;
	436
	437	error_close_fd:
	438	{
	439	int err;
	440
	441	err = close(stream->out_fd);
	442	assert(!err);
	443	}
	444	error:
	445	return ret;
	446	}
	447