[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>

#include "common/runas.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 = run_as_open(stream->path_name,
				O_WRONLY|O_CREAT|O_TRUNC,
				S_IRWXU|S_IRWXG|S_IRWXO,
				stream->uid, stream->gid);
		if (ret < 0) {
			ERR("Opening %s", stream->path_name);
			perror("open");
			goto error;
		}
		stream->out_fd = ret;
	}

	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>
0857097f DG	36
0857097f DG	37	#include "common/runas.h"
3bd1e081 MD	38
	39	extern struct lttng_consumer_global_data consumer_data;
	40	extern int consumer_poll_timeout;
	41	extern volatile int consumer_quit;
	42
	43	/*
	44	* Mmap the ring buffer, read it and write the data to the tracefile.
	45	*
	46	* Returns the number of bytes written
	47	*/
	48	int lttng_kconsumer_on_read_subbuffer_mmap(
	49	struct lttng_consumer_local_data *ctx,
	50	struct lttng_consumer_stream *stream, unsigned long len)
	51	{
	52	unsigned long mmap_offset;
	53	long ret = 0;
	54	off_t orig_offset = stream->out_fd_offset;
	55	int fd = stream->wait_fd;
	56	int outfd = stream->out_fd;
	57
	58	/* get the offset inside the fd to mmap */
	59	ret = kernctl_get_mmap_read_offset(fd, &mmap_offset);
	60	if (ret != 0) {
	61	ret = -errno;
	62	perror("kernctl_get_mmap_read_offset");
	63	goto end;
	64	}
	65
	66	while (len > 0) {
	67	ret = write(outfd, stream->mmap_base + mmap_offset, len);
	68	if (ret >= len) {
	69	len = 0;
	70	} else if (ret < 0) {
	71	ret = -errno;
	72	perror("Error in file write");
	73	goto end;
	74	}
	75	/* This won't block, but will start writeout asynchronously */
	76	sync_file_range(outfd, stream->out_fd_offset, ret,
	77	SYNC_FILE_RANGE_WRITE);
	78	stream->out_fd_offset += ret;
	79	}
	80
	81	lttng_consumer_sync_trace_file(stream, orig_offset);
	82
	83	goto end;
	84
	85	end:
	86	return ret;
	87	}
	88
	89	/*
	90	* Splice the data from the ring buffer to the tracefile.
	91	*
	92	* Returns the number of bytes spliced.
	93	*/
	94	int lttng_kconsumer_on_read_subbuffer_splice(
	95	struct lttng_consumer_local_data *ctx,
	96	struct lttng_consumer_stream *stream, unsigned long len)
	97	{
	98	long ret = 0;
	99	loff_t offset = 0;
	100	off_t orig_offset = stream->out_fd_offset;
	101	int fd = stream->wait_fd;
102	int outfd = stream->out_fd;
103
104	while (len > 0) {
105	DBG("splice chan to pipe offset %lu (fd : %d)",
106	(unsigned long)offset, fd);
107	ret = splice(fd, &offset, ctx->consumer_thread_pipe[1], NULL, len,
108	SPLICE_F_MOVE \| SPLICE_F_MORE);
109	DBG("splice chan to pipe ret %ld", ret);
110	if (ret < 0) {
111	ret = errno;
112	perror("Error in relay splice");
113	goto splice_error;
114	}
115
116	ret = splice(ctx->consumer_thread_pipe[0], NULL, outfd, NULL, ret,
117	SPLICE_F_MOVE \| SPLICE_F_MORE);
118	DBG("splice pipe to file %ld", ret);
119	if (ret < 0) {
120	ret = errno;
121	perror("Error in file splice");
122	goto splice_error;
123	}
124	len -= ret;
125	/* This won't block, but will start writeout asynchronously */
126	sync_file_range(outfd, stream->out_fd_offset, ret,
127	SYNC_FILE_RANGE_WRITE);
128	stream->out_fd_offset += ret;
129	}
130	lttng_consumer_sync_trace_file(stream, orig_offset);
131
132	goto end;
133
134	splice_error:
135	/* send the appropriate error description to sessiond */
136	switch(ret) {
137	case EBADF:
138	lttng_consumer_send_error(ctx, CONSUMERD_SPLICE_EBADF);
139	break;
140	case EINVAL:
141	lttng_consumer_send_error(ctx, CONSUMERD_SPLICE_EINVAL);
142	break;
143	case ENOMEM:
144	lttng_consumer_send_error(ctx, CONSUMERD_SPLICE_ENOMEM);
145	break;
146	case ESPIPE:
147	lttng_consumer_send_error(ctx, CONSUMERD_SPLICE_ESPIPE);
148	break;
149	}
150
151	end:
152	return ret;
153	}
154
155	/*
156	* Take a snapshot for a specific fd
157	*
158	* Returns 0 on success, < 0 on error
159	*/
160	int lttng_kconsumer_take_snapshot(struct lttng_consumer_local_data *ctx,
161	struct lttng_consumer_stream *stream)
162	{
163	int ret = 0;
164	int infd = stream->wait_fd;
165
166	ret = kernctl_snapshot(infd);
167	if (ret != 0) {
168	ret = errno;
169	perror("Getting sub-buffer snapshot.");
170	}
171
172	return ret;
173	}
174
175	/*
176	* Get the produced position
177	*
178	* Returns 0 on success, < 0 on error
179	*/
180	int lttng_kconsumer_get_produced_snapshot(
181	struct lttng_consumer_local_data *ctx,
182	struct lttng_consumer_stream *stream,
183	unsigned long *pos)
184	{
185	int ret;
186	int infd = stream->wait_fd;
187
188	ret = kernctl_snapshot_get_produced(infd, pos);
189	if (ret != 0) {
190	ret = errno;
191	perror("kernctl_snapshot_get_produced");
192	}
193
194	return ret;
195	}
196
197	int lttng_kconsumer_recv_cmd(struct lttng_consumer_local_data *ctx,
198	int sock, struct pollfd *consumer_sockpoll)
199	{
200	ssize_t ret;
201	struct lttcomm_consumer_msg msg;
202
203	ret = lttcomm_recv_unix_sock(sock, &msg, sizeof(msg));
204	if (ret != sizeof(msg)) {
f2fc6720	205	lttng_consumer_send_error(ctx, CONSUMERD_ERROR_RECV_CMD);
3bd1e081 MD	206	return ret;
	207	}
	208	if (msg.cmd_type == LTTNG_CONSUMER_STOP) {
	209	return -ENOENT;
	210	}
	211
	212	switch (msg.cmd_type) {
	213	case LTTNG_CONSUMER_ADD_CHANNEL:
	214	{
	215	struct lttng_consumer_channel *new_channel;
	216
	217	DBG("consumer_add_channel %d", msg.u.channel.channel_key);
	218	new_channel = consumer_allocate_channel(msg.u.channel.channel_key,
	219	-1, -1,
	220	msg.u.channel.mmap_len,
	221	msg.u.channel.max_sb_size);
	222	if (new_channel == NULL) {
	223	lttng_consumer_send_error(ctx, CONSUMERD_OUTFD_ERROR);
	224	goto end_nosignal;
	225	}
	226	if (ctx->on_recv_channel != NULL) {
	227	ret = ctx->on_recv_channel(new_channel);
	228	if (ret == 0) {
	229	consumer_add_channel(new_channel);
	230	} else if (ret < 0) {
	231	goto end_nosignal;
	232	}
	233	} else {
	234	consumer_add_channel(new_channel);
	235	}
	236	goto end_nosignal;
	237	}
	238	case LTTNG_CONSUMER_ADD_STREAM:
	239	{
	240	struct lttng_consumer_stream *new_stream;
f2fc6720	241	int fd;
3bd1e081 MD	242
	243	/* block */
	244	if (lttng_consumer_poll_socket(consumer_sockpoll) < 0) {
	245	return -EINTR;
	246	}
f2fc6720 MD	247	ret = lttcomm_recv_fds_unix_sock(sock, &fd, 1);
f2fc6720 MD	248	if (ret != sizeof(fd)) {
3bd1e081 MD	249	lttng_consumer_send_error(ctx, CONSUMERD_ERROR_RECV_FD);
	250	return ret;
	251	}
3bd1e081	252
f2fc6720 MD	253	DBG("consumer_add_stream %s (%d)", msg.u.stream.path_name,
f2fc6720 MD	254	fd);
3bd1e081 MD	255	new_stream = consumer_allocate_stream(msg.u.stream.channel_key,
3bd1e081 MD	256	msg.u.stream.stream_key,
f2fc6720	257	fd, fd,
3bd1e081 MD	258	msg.u.stream.state,
	259	msg.u.stream.mmap_len,
	260	msg.u.stream.output,
6df2e2c9 MD	261	msg.u.stream.path_name,
	262	msg.u.stream.uid,
	263	msg.u.stream.gid);
3bd1e081 MD	264	if (new_stream == NULL) {
	265	lttng_consumer_send_error(ctx, CONSUMERD_OUTFD_ERROR);
	266	goto end;
	267	}
	268	if (ctx->on_recv_stream != NULL) {
	269	ret = ctx->on_recv_stream(new_stream);
	270	if (ret == 0) {
	271	consumer_add_stream(new_stream);
	272	} else if (ret < 0) {
	273	goto end;
	274	}
	275	} else {
	276	consumer_add_stream(new_stream);
	277	}
	278	break;
	279	}
	280	case LTTNG_CONSUMER_UPDATE_STREAM:
	281	{
	282	if (ctx->on_update_stream != NULL) {
	283	ret = ctx->on_update_stream(msg.u.stream.stream_key, msg.u.stream.state);
	284	if (ret == 0) {
	285	consumer_change_stream_state(msg.u.stream.stream_key, msg.u.stream.state);
	286	} else if (ret < 0) {
	287	goto end;
	288	}
	289	} else {
	290	consumer_change_stream_state(msg.u.stream.stream_key,
	291	msg.u.stream.state);
	292	}
	293	break;
	294	}
	295	default:
	296	break;
	297	}
	298	end:
	299	/* signal the poll thread */
	300	ret = write(ctx->consumer_poll_pipe[1], "4", 1);
	301	if (ret < 0) {
	302	perror("write consumer poll");
	303	}
	304	end_nosignal:
	305	return 0;
	306	}
d41f73b7 MD	307
	308	/*
	309	* Consume data on a file descriptor and write it on a trace file.
	310	*/
	311	int lttng_kconsumer_read_subbuffer(struct lttng_consumer_stream *stream,
	312	struct lttng_consumer_local_data *ctx)
	313	{
	314	unsigned long len;
	315	int err;
	316	long ret = 0;
	317	int infd = stream->wait_fd;
	318
	319	DBG("In read_subbuffer (infd : %d)", infd);
	320	/* Get the next subbuffer */
	321	err = kernctl_get_next_subbuf(infd);
	322	if (err != 0) {
	323	ret = errno;
	324	/*
	325	* This is a debug message even for single-threaded consumer,
	326	* because poll() have more relaxed criterions than get subbuf,
	327	* so get_subbuf may fail for short race windows where poll()
	328	* would issue wakeups.
	329	*/
	330	DBG("Reserving sub buffer failed (everything is normal, "
	331	"it is due to concurrency)");
	332	goto end;
	333	}
	334
	335	switch (stream->output) {
	336	case LTTNG_EVENT_SPLICE:
	337	/* read the whole subbuffer */
	338	err = kernctl_get_padded_subbuf_size(infd, &len);
	339	if (err != 0) {
	340	ret = errno;
	341	perror("Getting sub-buffer len failed.");
	342	goto end;
	343	}
	344
	345	/* splice the subbuffer to the tracefile */
	346	ret = lttng_consumer_on_read_subbuffer_splice(ctx, stream, len);
	347	if (ret < 0) {
	348	/*
	349	* display the error but continue processing to try
	350	* to release the subbuffer
	351	*/
	352	ERR("Error splicing to tracefile");
	353	}
	354	break;
	355	case LTTNG_EVENT_MMAP:
	356	/* read the used subbuffer size */
	357	err = kernctl_get_padded_subbuf_size(infd, &len);
	358	if (err != 0) {
	359	ret = errno;
	360	perror("Getting sub-buffer len failed.");
	361	goto end;
	362	}
	363	/* write the subbuffer to the tracefile */
	364	ret = lttng_consumer_on_read_subbuffer_mmap(ctx, stream, len);
	365	if (ret < 0) {
	366	/*
	367	* display the error but continue processing to try
	368	* to release the subbuffer
	369	*/
	370	ERR("Error writing to tracefile");
371	}
372	break;
373	default:
374	ERR("Unknown output method");
375	ret = -1;
376	}
377
378	err = kernctl_put_next_subbuf(infd);
379	if (err != 0) {
380	ret = errno;
381	if (errno == EFAULT) {
382	perror("Error in unreserving sub buffer\n");
383	} else if (errno == EIO) {
384	/* Should never happen with newer LTTng versions */
385	perror("Reader has been pushed by the writer, last sub-buffer corrupted.");
386	}
387	goto end;
388	}
389
390	end:
391	return ret;
392	}
393
394	int lttng_kconsumer_on_recv_stream(struct lttng_consumer_stream *stream)
395	{
396	int ret;
397
398	/* Opening the tracefile in write mode */
399	if (stream->path_name != NULL) {
e11d277b	400	ret = run_as_open(stream->path_name,
60b6c79c MD	401	O_WRONLY\|O_CREAT\|O_TRUNC,
	402	S_IRWXU\|S_IRWXG\|S_IRWXO,
	403	stream->uid, stream->gid);
d41f73b7 MD	404	if (ret < 0) {
	405	ERR("Opening %s", stream->path_name);
	406	perror("open");
	407	goto error;
	408	}
	409	stream->out_fd = ret;
	410	}
	411
	412	if (stream->output == LTTNG_EVENT_MMAP) {
	413	/* get the len of the mmap region */
	414	unsigned long mmap_len;
	415
	416	ret = kernctl_get_mmap_len(stream->wait_fd, &mmap_len);
	417	if (ret != 0) {
	418	ret = errno;
	419	perror("kernctl_get_mmap_len");
	420	goto error_close_fd;
	421	}
	422	stream->mmap_len = (size_t) mmap_len;
	423
	424	stream->mmap_base = mmap(NULL, stream->mmap_len,
	425	PROT_READ, MAP_PRIVATE, stream->wait_fd, 0);
	426	if (stream->mmap_base == MAP_FAILED) {
	427	perror("Error mmaping");
	428	ret = -1;
	429	goto error_close_fd;
	430	}
	431	}
	432
	433	/* we return 0 to let the library handle the FD internally */
	434	return 0;
	435
	436	error_close_fd:
	437	{
	438	int err;
	439
	440	err = close(stream->out_fd);
	441	assert(!err);
	442	}
	443	error:
	444	return ret;
	445	}
	446