monitor.cxx

   1 /*
   2  * inoclam - Inotify+ClamAV virus scanner
   3  * Copyright (C) 2007 Vermont Department of Taxes
   4  *
   5  * This program is free software; you can redistribute it and/or modify
   6  * it under the terms of the GNU General Public License as published by
   7  * the Free Software Foundation; either version 2 of the License, or
   8  * (at your option) any later version.
   9  *
  10  * This program is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  13  * GNU General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU General Public License
  16  * along with this program; if not, write to the Free Software
  17  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  18  *
  19  * Contributor(s):
  20  *   Tom Cort <tom.cort@state.vt.us>
  21  */
  22
  23 #define _XOPEN_SOURCE 500
  24
  25 #include <pthread.h>
  26 #include <sched.h>
  27 #include <signal.h>
  28 #include <unistd.h>
  29
  30 #include "monitor.hxx"
  31
  32 /**
  33  * Counter for the number of running threads.
  34  */
  35 int cnt;
  36
  37 /**
  38  * A lock used to serialize access to cnt.
  39  */
  40 pthread_mutex_t mon_lock;
  41
  42 /**
  43  *  initialize monitor variables
  44  */
  45 void monitor_init()
  46 {
  47         pthread_mutex_init(&mon_lock, 0);
  48         cnt = 0;
  49 }
  50
  51 /**
  52  *  increments the thread count
  53  */
  54 void monitor_inc()
  55 {
  56         pthread_mutex_lock(&mon_lock);
  57         cnt++;
  58         pthread_mutex_unlock(&mon_lock);
  59 }
  60
  61 /**
  62  *  decrements the thread count
  63  */
  64 void monitor_dec()
  65 {
  66         pthread_mutex_lock(&mon_lock);
  67         cnt--;
  68         pthread_mutex_unlock(&mon_lock);
  69 }
  70
  71 /**
  72  *  waits until no threads are running
  73  *  blocks new threads from being created
  74  */
  75 void monitor_wait()
  76 {
  77         raise(SIGQUIT);
  78
  79         while (1) {
  80                 pthread_mutex_lock(&mon_lock);
  81
  82                 if (!cnt) {
  83                         /* Do NOT release lock; we don't want any more threads starting */
  84                         return;
  85                 } else {
  86                         pthread_mutex_unlock(&mon_lock);
  87                         sched_yield();
  88                         sleep(3);
  89                 }
  90         }
  91 }