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