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 #include <poll.h>
  25 #include <urcu/list.h>
  26
  27 /*
  28  * When the receiving thread dies, we need to have a way to make the polling
  29  * thread exit eventually. If all FDs hang up (normal case when the
  30  * ltt-sessiond stops), we can exit cleanly, but if there is a problem and for
  31  * whatever reason some FDs remain open, the consumer should still exit
  32  * eventually.
  33  *
  34  * If the timeout is reached, it means that during this period no events
  35  * occurred on the FDs so we need to force an exit. This case should not happen
  36  * but it is a safety to ensure we won't block the consumer indefinitely.
  37  *
  38  * The value of 2 seconds is an arbitrary choice.
  39  */
  40 #define LTTNG_KCONSUMERD_POLL_GRACE_PERIOD 2000
  41
  42 /* Commands for kconsumerd */
  43 enum lttng_kconsumerd_command {
  44         ADD_STREAM,
  45         UPDATE_STREAM, /* pause, delete, active depending on fd state */
  46         STOP, /* inform the kconsumerd to quit when all fd has hang up */
  47 };
  48
  49 /* State of each fd in consumerd */
  50 enum lttng_kconsumerd_fd_state {
  51         ACTIVE_FD,
  52         PAUSE_FD,
  53         DELETE_FD,
  54 };
  55
  56 struct lttng_kconsumerd_fd_list {
  57         struct cds_list_head head;
  58 };
  59
  60 /*
  61  * Internal representation of the FDs, sessiond_fd is used to identify uniquely
  62  * a fd
  63  */
  64 struct lttng_kconsumerd_fd {
  65         struct cds_list_head list;
  66         int sessiond_fd; /* used to identify uniquely a fd with sessiond */
  67         int consumerd_fd; /* fd to consume */
  68         int out_fd; /* output file to write the data */
  69         off_t out_fd_offset; /* write position in the output file descriptor */
  70         char path_name[PATH_MAX]; /* tracefile name */
  71         enum lttng_kconsumerd_fd_state state;
  72         unsigned long max_sb_size; /* the subbuffer size for this channel */
  73         void *mmap_base;
  74         size_t mmap_len;
  75         enum lttng_event_output output; /* splice or mmap */
  76 };
  77
  78 /*
  79  * Kernel consumer local data to the program.
  80  */
  81 struct lttng_kconsumerd_local_data {
  82         /* function to call when data is available on a buffer */
  83         int (*on_buffer_ready)(struct lttng_kconsumerd_fd *kconsumerd_fd);
  84         /*
  85          * function to call when we receive a new fd, it receives a
  86          * newly allocated kconsumerd_fd, depending on the return code
  87          * of this function, the new FD will be handled by the
  88          * application or the library.
  89          *
  90          * Returns:
  91          *    > 0 (success, FD is kept by application)
  92          *   == 0 (success, FD is left to library)
  93          *    < 0 (error)
  94          */
  95         int (*on_recv_fd)(struct lttng_kconsumerd_fd *kconsumerd_fd);
  96         /*
  97          * function to call when a FD is getting updated by the session
  98          * daemon, this function receives the FD as seen by the session
  99          * daemon (sessiond_fd) and the new state, depending on the
 100          * return code of this function the update of state for the FD
 101          * is handled by the application or the library.
 102          *
 103          * Returns:
 104          *    > 0 (success, FD is kept by application)
 105          *   == 0 (success, FD is left to library)
 106          *    < 0 (error)
 107          */
 108         int (*on_update_fd)(int sessiond_fd, uint32_t state);
 109         /* socket to communicate errors with sessiond */
 110         int kconsumerd_error_socket;
 111         /* socket to exchange commands with sessiond */
 112         char *kconsumerd_command_sock_path;
 113         /* communication with splice */
 114         int kconsumerd_thread_pipe[2];
 115         /* pipe to wake the poll thread when necessary */
 116         int kconsumerd_poll_pipe[2];
 117         /* to let the signal handler wake up the fd receiver thread */
 118         int kconsumerd_should_quit[2];
 119 };
 120
 121 /*
 122  * Initialise the necessary environnement:
 123  * - create a new context
 124  * - create the poll_pipe
 125  * - create the should_quit pipe (for signal handler)
 126  * - create the thread pipe (for splice)
 127  *
 128  * Takes the function pointers to the on_buffer_ready, on_recv_fd, and
 129  * on_update_fd callbacks.
 130  *
 131  * Returns a pointer to the new context or NULL on error.
 132  */
 133 extern struct lttng_kconsumerd_local_data *lttng_kconsumerd_create(
 134                 int (*buffer_ready)(struct lttng_kconsumerd_fd *kconsumerd_fd),
 135                 int (*recv_fd)(struct lttng_kconsumerd_fd *kconsumerd_fd),
 136                 int (*update_fd)(int sessiond_fd, uint32_t state));
 137
 138 /*
 139  * Close all fds associated with the instance and free the context.
 140  */
 141 extern void lttng_kconsumerd_destroy(struct lttng_kconsumerd_local_data *ctx);
 142
 143 /*
 144  * Mmap the ring buffer, read it and write the data to the tracefile.
 145  *
 146  * Returns the number of bytes written.
 147  */
 148 extern int lttng_kconsumerd_on_read_subbuffer_mmap(
 149                 struct lttng_kconsumerd_local_data *ctx,
 150                 struct lttng_kconsumerd_fd *kconsumerd_fd, unsigned long len);
 151
 152 /*
 153  * Splice the data from the ring buffer to the tracefile.
 154  *
 155  * Returns the number of bytes spliced.
 156  */
 157 extern int lttng_kconsumerd_on_read_subbuffer_splice(
 158                 struct lttng_kconsumerd_local_data *ctx,
 159                 struct lttng_kconsumerd_fd *kconsumerd_fd, unsigned long len);
 160
 161 /*
 162  * Take a snapshot for a specific fd
 163  *
 164  * Returns 0 on success, < 0 on error
 165  */
 166 int lttng_kconsumerd_take_snapshot(struct lttng_kconsumerd_local_data *ctx,
 167         struct lttng_kconsumerd_fd *kconsumerd_fd);
 168
 169 /*
 170  * Get the produced position
 171  *
 172  * Returns 0 on success, < 0 on error
 173  */
 174 int lttng_kconsumerd_get_produced_snapshot(
 175         struct lttng_kconsumerd_local_data *ctx,
 176         struct lttng_kconsumerd_fd *kconsumerd_fd,
 177         unsigned long *pos);
 178
 179 /*
 180  * Send return code to session daemon.
 181  *
 182  * Returns the return code of sendmsg : the number of bytes transmitted or -1
 183  * on error.
 184  */
 185 extern int lttng_kconsumerd_send_error(
 186                 struct lttng_kconsumerd_local_data *ctx, int cmd);
 187
 188 /*
 189  * Poll on the should_quit pipe and the command socket return -1 on error and
 190  * should exit, 0 if data is available on the command socket.
 191  */
 192 extern int lttng_kconsumerd_poll_socket(struct pollfd *kconsumerd_sockpoll);
 193
 194 /*
 195  * This thread polls the fds in the ltt_fd_list to consume the data and write
 196  * it to tracefile if necessary.
 197  */
 198 extern void *lttng_kconsumerd_thread_poll_fds(void *data);
 199
 200 /*
 201  * This thread listens on the consumerd socket and receives the file
 202  * descriptors from ltt-sessiond.
 203  */
 204 extern void *lttng_kconsumerd_thread_receive_fds(void *data);
 205
 206 /*
 207  * Called from signal handler to ensure a clean exit.
 208  */
 209 extern void lttng_kconsumerd_should_exit(
 210                 struct lttng_kconsumerd_local_data *ctx);
 211
 212 /*
 213  * Cleanup the daemon's socket on exit.
 214  */
 215 extern void lttng_kconsumerd_cleanup(void);
 216
 217 /*
 218  * Set the error socket for communication with a session daemon.
 219  */
 220 extern void lttng_kconsumerd_set_error_sock(
 221                 struct lttng_kconsumerd_local_data *ctx, int sock);
 222
 223 /*
 224  * Set the command socket path for communication with a session daemon.
 225  */
 226 extern void lttng_kconsumerd_set_command_sock_path(
 227                 struct lttng_kconsumerd_local_data *ctx, char *sock);
 228
 229 #endif /* _LTTNG_KCONSUMERD_H */