liblttkconsumerd/lttkconsumerd.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 _LIBLTTKCONSUMERD_H
  20 #define _LIBLTTKCONSUMERD_H
  21
  22 #include <lttng-sessiond-comm.h>
  23 #include "lttng-kconsumerd.h"
  24
  25 /*
  26  * When the receiving thread dies, we need to have a way to make
  27  * the polling thread exit eventually.
  28  * If all FDs hang up (normal case when the ltt-sessiond stops),
  29  * we can exit cleanly, but if there is a problem and for whatever
  30  * reason some FDs remain open, the consumer should still exit eventually.
  31  *
  32  * If the timeout is reached, it means that during this period
  33  * no events occurred on the FDs so we need to force an exit.
  34  * This case should not happen but it is a safety to ensure we won't block
  35  * the consumer indefinitely.
  36  *
  37  * The value of 2 seconds is an arbitrary choice.
  38  */
  39 #define KCONSUMERD_POLL_GRACE_PERIOD 2000
  40
  41 struct kconsumerd_fd_list {
  42         struct cds_list_head head;
  43 };
  44
  45 /*
  46  * Internal representation of the FDs,
  47  * sessiond_fd is used to identify uniquely a fd
  48  */
  49 struct kconsumerd_fd {
  50         struct cds_list_head list;
  51         int sessiond_fd; /* used to identify uniquely a fd with sessiond */
  52         int consumerd_fd; /* fd to consume */
  53         int out_fd; /* output file to write the data */
  54         off_t out_fd_offset; /* write position in the output file descriptor */
  55         char path_name[PATH_MAX]; /* tracefile name */
  56         enum kconsumerd_fd_state state;
  57         unsigned long max_sb_size; /* the subbuffer size for this channel */
  58         void *mmap_base;
  59         size_t mmap_len;
  60         enum lttng_event_output output; /* splice or mmap */
  61 };
  62
  63 struct kconsumerd_local_data {
  64         /* function to call when data is available on a buffer */
  65         int (*on_buffer_ready)(struct kconsumerd_fd *kconsumerd_fd);
  66         /* socket to communicate errors with sessiond */
  67         int kconsumerd_error_socket;
  68         /* socket to exchange commands with sessiond */
  69         char *kconsumerd_command_sock_path;
  70         /* communication with splice */
  71         int kconsumerd_thread_pipe[2];
  72         /* pipe to wake the poll thread when necessary */
  73         int kconsumerd_poll_pipe[2];
  74         /* to let the signal handler wake up the fd receiver thread */
  75         int kconsumerd_should_quit[2];
  76 };
  77
  78 /*
  79  * kconsumerd_create
  80  * initialise the necessary environnement :
  81  * - create a new context
  82  * - create the poll_pipe
  83  * - create the should_quit pipe (for signal handler)
  84  * - create the thread pipe (for splice)
  85  * Takes a function pointer as argument, this function is called when data is
  86  * available on a buffer. This function is responsible to do the
  87  * kernctl_get_next_subbuf, read the data with mmap or splice depending on the
  88  * buffer configuration and then kernctl_put_next_subbuf at the end.
  89  * Returns a pointer to the new context or NULL on error.
  90  */
  91 struct kconsumerd_local_data *kconsumerd_create(
  92                 int (*buffer_ready)(struct kconsumerd_fd *kconsumerd_fd));
  93
  94 /*
  95  * kconsumerd_destroy
  96  * Close all fds associated with the instance and free the context
  97  */
  98 void kconsumerd_destroy(struct kconsumerd_local_data *ctx);
  99
 100 /*
 101  * kconsumerd_on_read_subbuffer_mmap
 102  * mmap the ring buffer, read it and write the data to the tracefile.
 103  * Returns the number of bytes written
 104  */
 105 int kconsumerd_on_read_subbuffer_mmap(struct kconsumerd_local_data *ctx,
 106                 struct kconsumerd_fd *kconsumerd_fd, unsigned long len);
 107
 108 /*
 109  * kconsumerd_on_read_subbuffer
 110  *
 111  * Splice the data from the ring buffer to the tracefile.
 112  * Returns the number of bytes spliced
 113  */
 114 int kconsumerd_on_read_subbuffer_splice(struct kconsumerd_local_data *ctx,
 115                 struct kconsumerd_fd *kconsumerd_fd, unsigned long len);
 116
 117 /*
 118  * kconsumerd_send_error
 119  * send return code to ltt-sessiond
 120  * returns the return code of sendmsg : the number of bytes transmitted
 121  * or -1 on error.
 122  */
 123 int kconsumerd_send_error(struct kconsumerd_local_data *ctx,
 124                 enum lttcomm_return_code cmd);
 125
 126 /*
 127  * kconsumerd_poll_socket
 128  * Poll on the should_quit pipe and the command socket
 129  * return -1 on error and should exit, 0 if data is
 130  * available on the command socket
 131  */
 132 int kconsumerd_poll_socket(struct pollfd *kconsumerd_sockpoll);
 133
 134 /*
 135  *  kconsumerd_thread_poll_fds
 136  *  This thread polls the fds in the ltt_fd_list to consume the data
 137  *  and write it to tracefile if necessary.
 138  */
 139 void *kconsumerd_thread_poll_fds(void *data);
 140
 141 /*
 142  *  kconsumerd_thread_receive_fds
 143  *  This thread listens on the consumerd socket and
 144  *  receives the file descriptors from ltt-sessiond
 145  */
 146 void *kconsumerd_thread_receive_fds(void *data);
 147
 148 /*
 149  * kconsumerd_should_exit
 150  * Called from signal handler to ensure a clean exit
 151  */
 152 void kconsumerd_should_exit(struct kconsumerd_local_data *ctx);
 153
 154 /*
 155  *  kconsumerd_cleanup
 156  *  Cleanup the daemon's socket on exit
 157  */
 158 void kconsumerd_cleanup(void);
 159
 160 /*
 161  * kconsumerd_set_error_socket
 162  * Set the error socket for communication with a session daemon
 163  */
 164 void kconsumerd_set_error_socket(struct kconsumerd_local_data *ctx, int sock);
 165
 166 /*
 167  * kconsumerd_set_command_socket_path
 168  * Set the command socket path for communication with a session daemon
 169  */
 170 void kconsumerd_set_command_socket_path(struct kconsumerd_local_data *ctx, char *sock);
 171
 172 #endif /* _LIBLTTKCONSUMERD_H */