filters/readahead/bgthread.c

   1 /* nbdkit
   2  * Copyright Red Hat
   3  *
   4  * Redistribution and use in source and binary forms, with or without
   5  * modification, are permitted provided that the following conditions are
   6  * met:
   7  *
   8  * * Redistributions of source code must retain the above copyright
   9  * notice, this list of conditions and the following disclaimer.
  10  *
  11  * * Redistributions in binary form must reproduce the above copyright
  12  * notice, this list of conditions and the following disclaimer in the
  13  * documentation and/or other materials provided with the distribution.
  14  *
  15  * * Neither the name of Red Hat nor the names of its contributors may be
  16  * used to endorse or promote products derived from this software without
  17  * specific prior written permission.
  18  *
  19  * THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
  20  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
  21  * THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
  22  * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
  23  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  24  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  25  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  26  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  27  * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
  28  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
  29  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  30  * SUCH DAMAGE.
  31  */
  32
  33 #include <config.h>
  34
  35 #include <stdio.h>
  36 #include <stdlib.h>
  37 #include <stdint.h>
  38 #include <pthread.h>
  39
  40 #include <nbdkit-filter.h>
  41
  42 #include "readahead.h"
  43
  44 #include "cleanup.h"
  45
  46 void *
  47 readahead_thread (void *vp)
  48 {
  49   struct bgthread_ctrl *ctrl = vp;
  50
  51   for (;;) {
  52     struct command cmd;
  53
  54     /* Wait until we are sent at least one command. */
  55     {
  56       ACQUIRE_LOCK_FOR_CURRENT_SCOPE (&ctrl->lock);
  57       while (ctrl->cmds.len == 0)
  58         pthread_cond_wait (&ctrl->cond, &ctrl->lock);
  59       cmd = ctrl->cmds.ptr[0];
  60       command_queue_remove (&ctrl->cmds, 0);
  61     }
  62
  63     switch (cmd.type) {
  64     case CMD_QUIT:
  65       /* Finish processing and exit the thread. */
  66       return NULL;
  67
  68     case CMD_CACHE:
  69       /* Issue .cache (readahead) to underlying plugin.  We ignore any
  70        * errors because there's no way to communicate that back to the
  71        * client, and readahead is only advisory.
  72        */
  73       cmd.next->cache (cmd.next, cmd.count, cmd.offset, 0, NULL);
  74     }
  75   }
  76 }