include/lttng/lttng-kconsumerd.h

   1 /*
   2  * Copyright (C) 2011 - Julien Desfossez <julien.desfossez@polymtl.ca>
   3  *
   4  * This program is free software; you can redistribute it and/or
   5  * modify it under the terms of the GNU General Public License
   6  * as published by the Free Software Foundation; only version 2
   7  * of the License.
   8  *
   9  * This program is distributed in the hope that it will be useful,
  10  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
  12  * GNU General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU General Public License
  15  * along with this program; if not, write to the Free Software
  16  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
  17  */
  18
  19 #ifndef _LTTNG_KCONSUMERD_H
  20 #define _LTTNG_KCONSUMERD_H
  21
  22 #include <limits.h>
  23 #include <lttng/lttng.h>
  24
  25 /*
  26  * When the receiving thread dies, we need to have a way to make the polling
  27  * thread exit eventually. If all FDs hang up (normal case when the
  28  * ltt-sessiond stops), we can exit cleanly, but if there is a problem and for
  29  * whatever reason some FDs remain open, the consumer should still exit
  30  * eventually.
  31  *
  32  * If the timeout is reached, it means that during this period no events
  33  * occurred on the FDs so we need to force an exit. This case should not happen
  34  * but it is a safety to ensure we won't block the consumer indefinitely.
  35  *
  36  * The value of 2 seconds is an arbitrary choice.
  37  */
  38 #define LTTNG_KCONSUMERD_POLL_GRACE_PERIOD 2000
  39
  40 /* Commands for kconsumerd */
  41 enum lttng_kconsumerd_command {
  42         ADD_STREAM,
  43         UPDATE_STREAM, /* pause, delete, active depending on fd state */
  44         STOP, /* inform the kconsumerd to quit when all fd has hang up */
  45 };
  46
  47 /* State of each fd in consumerd */
  48 enum lttng_kconsumerd_fd_state {
  49         ACTIVE_FD,
  50         PAUSE_FD,
  51         DELETE_FD,
  52 };
  53
  54 struct lttng_kconsumerd_fd_list {
  55         struct cds_list_head head;
  56 };
  57
  58 /*
  59  * Internal representation of the FDs, sessiond_fd is used to identify uniquely
  60  * a fd
  61  */
  62 struct lttng_kconsumerd_fd {
  63         struct cds_list_head list;
  64         int sessiond_fd; /* used to identify uniquely a fd with sessiond */
  65         int consumerd_fd; /* fd to consume */
  66         int out_fd; /* output file to write the data */
  67         off_t out_fd_offset; /* write position in the output file descriptor */
  68         char path_name[PATH_MAX]; /* tracefile name */
  69         enum lttng_kconsumerd_fd_state state;
  70         unsigned long max_sb_size; /* the subbuffer size for this channel */
  71         void *mmap_base;
  72         size_t mmap_len;
  73         enum lttng_event_output output; /* splice or mmap */
  74 };
  75
  76 /*
  77  * Kernel consumer local data to the program.
  78  */
  79 struct lttng_kconsumerd_local_data {
  80         /* function to call when data is available on a buffer */
  81         int (*on_buffer_ready)(struct lttng_kconsumerd_fd *kconsumerd_fd);
  82         /* socket to communicate errors with sessiond */
  83         int kconsumerd_error_socket;
  84         /* socket to exchange commands with sessiond */
  85         char *kconsumerd_command_sock_path;
  86         /* communication with splice */
  87         int kconsumerd_thread_pipe[2];
  88         /* pipe to wake the poll thread when necessary */
  89         int kconsumerd_poll_pipe[2];
  90         /* to let the signal handler wake up the fd receiver thread */
  91         int kconsumerd_should_quit[2];
  92 };
  93
  94 /*
  95  * Initialise the necessary environnement:
  96  * - create a new context
  97  * - create the poll_pipe
  98  * - create the should_quit pipe (for signal handler)
  99  * - create the thread pipe (for splice)
 100  *
 101  * Takes a function pointer as argument, this function is called when data is
 102  * available on a buffer. This function is responsible to do the
 103  * kernctl_get_next_subbuf, read the data with mmap or splice depending on the
 104  * buffer configuration and then kernctl_put_next_subbuf at the end.
 105  *
 106  * Returns a pointer to the new context or NULL on error.
 107  */
 108 extern struct lttng_kconsumerd_local_data *lttng_kconsumerd_create(
 109                 int (*buffer_ready)(struct lttng_kconsumerd_fd *kconsumerd_fd));
 110
 111 /*
 112  * Close all fds associated with the instance and free the context.
 113  */
 114 extern void lttng_kconsumerd_destroy(struct lttng_kconsumerd_local_data *ctx);
 115
 116 /*
 117  * Mmap the ring buffer, read it and write the data to the tracefile.
 118  *
 119  * Returns the number of bytes written.
 120  */
 121 extern int lttng_kconsumerd_on_read_subbuffer_mmap(
 122                 struct lttng_kconsumerd_local_data *ctx,
 123                 struct lttng_kconsumerd_fd *kconsumerd_fd, unsigned long len);
 124
 125 /*
 126  * Splice the data from the ring buffer to the tracefile.
 127  *
 128  * Returns the number of bytes spliced.
 129  */
 130 extern int lttng_kconsumerd_on_read_subbuffer_splice(
 131                 struct lttng_kconsumerd_local_data *ctx,
 132                 struct lttng_kconsumerd_fd *kconsumerd_fd, unsigned long len);
 133
 134 /*
 135  * Send return code to session daemon.
 136  *
 137  * Returns the return code of sendmsg : the number of bytes transmitted or -1
 138  * on error.
 139  */
 140 extern int lttng_kconsumerd_send_error(
 141                 struct lttng_kconsumerd_local_data *ctx, int cmd);
 142
 143 /*
 144  * Poll on the should_quit pipe and the command socket return -1 on error and
 145  * should exit, 0 if data is available on the command socket.
 146  */
 147 extern int lttng_kconsumerd_poll_socket(struct pollfd *kconsumerd_sockpoll);
 148
 149 /*
 150  * This thread polls the fds in the ltt_fd_list to consume the data and write
 151  * it to tracefile if necessary.
 152  */
 153 extern void *lttng_kconsumerd_thread_poll_fds(void *data);
 154
 155 /*
 156  * This thread listens on the consumerd socket and receives the file
 157  * descriptors from ltt-sessiond.
 158  */
 159 extern void *lttng_kconsumerd_thread_receive_fds(void *data);
 160
 161 /*
 162  * Called from signal handler to ensure a clean exit.
 163  */
 164 extern void lttng_kconsumerd_should_exit(
 165                 struct lttng_kconsumerd_local_data *ctx);
 166
 167 /*
 168  * Cleanup the daemon's socket on exit.
 169  */
 170 extern void lttng_kconsumerd_cleanup(void);
 171
 172 /*
 173  * Set the error socket for communication with a session daemon.
 174  */
 175 extern void lttng_kconsumerd_set_error_sock(
 176                 struct lttng_kconsumerd_local_data *ctx, int sock);
 177
 178 /*
 179  * Set the command socket path for communication with a session daemon.
 180  */
 181 extern void lttng_kconsumerd_set_command_sock_path(
 182                 struct lttng_kconsumerd_local_data *ctx, char *sock);
 183
 184 #endif /* _LTTNG_KCONSUMERD_H */