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queue.c

/* queue.c --
 * Copyright 2007 Red Hat Inc., Durham, North Carolina.
 * All Rights Reserved.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Authors:
 *      Steve Grubb <sgrubb@redhat.com>
 */

#include "config.h"
#include <pthread.h>
#include <stdlib.h>
#include <unistd.h>
#include <syslog.h>
#include "queue.h"

static volatile event_t **q;
static pthread_mutex_t queue_lock;
static pthread_cond_t queue_nonempty;
static unsigned int q_next, q_last, q_depth, processing_suspended;
static const char *SINGLE = "1";
static const char *HALT = "0";

void reset_suspended(void)
{
      processing_suspended = 0;
}

int init_queue(unsigned int size)
{
      unsigned int i;

      processing_suspended = 0;
      q_next = 0;
      q_last = 0;
      q_depth = size;
      q = malloc(q_depth * sizeof(event_t *));
      if (q == NULL)
            return -1;

      for (i=0; i<q_depth; i++) 
            q[i] = NULL;

      /* Setup IPC mechanisms */
      pthread_mutex_init(&queue_lock, NULL);
      pthread_cond_init(&queue_nonempty, NULL);

      return 0;
}

static void change_runlevel(const char *level)
{
      char *argv[3];
      int pid;
      static const char *init_pgm = "/sbin/init";

      pid = fork();
      if (pid < 0) {
            syslog(LOG_ALERT, "Audispd failed to fork switching runlevels");
            return;
      }
      if (pid)    /* Parent */
            return;
      /* Child */
      argv[0] = (char *)init_pgm;
      argv[1] = (char *)level;
      argv[2] = NULL;
      execve(init_pgm, argv, NULL);
      syslog(LOG_ALERT, "Audispd failed to exec %s", init_pgm);
      exit(1);
}

static void do_overflow_action(struct daemon_conf *config)
{
        switch (config->overflow_action)
        {
                case O_IGNORE:
                  break;
                case O_SYSLOG:
                  syslog(LOG_ERR, "queue is full - dropping event");
                        break;
                case O_SUSPEND:
                        syslog(LOG_ALERT,
                            "Audispd is suspending event processing due to overflowing its queue.");
                        processing_suspended = 1;
                        break;
                case O_SINGLE:
                        syslog(LOG_ALERT,
                                "Audisp is now changing the system to single user mode due to overflowing its queue");
                        change_runlevel(SINGLE);
                        break;
                case O_HALT:
                        syslog(LOG_ALERT,
                                "Audispd is now halting the system due to overflowing its queue");
                        change_runlevel(HALT);
                        break;
                default:
                        syslog(LOG_ALERT, "Unknown overflow action requested");
                        break;
        }
}

void enqueue(event_t *e, struct daemon_conf *config)
{
      unsigned int n, retry_cnt = 0;

      if (processing_suspended) {
            free(e);
            return;
      }

retry:
      // We allow 3 retries and then its over
      if (retry_cnt > 3) {
            do_overflow_action(config);
            free(e);
            return;
      }
      pthread_mutex_lock(&queue_lock);

      // OK, have lock add event
      n = q_next%q_depth;
      if (q[n] == NULL) {
            q[n] = e;
            q_next = (n+1) % q_depth;
            pthread_cond_signal(&queue_nonempty);
            pthread_mutex_unlock(&queue_lock);
      } else {
            pthread_mutex_unlock(&queue_lock);
            struct timespec ts;
            ts.tv_sec = 0;
            ts.tv_nsec = 2 * 1000 * 1000; // 2 milliseconds
            nanosleep(&ts, NULL); /* Let other thread try to log it. */
            retry_cnt++;
            goto retry;
      }
}

event_t *dequeue(void)
{
      event_t *e;
      unsigned int n;

      // Wait until its got something in it
      pthread_mutex_lock(&queue_lock);
      n = q_last%q_depth;
      if (q[n] == NULL) {
            pthread_cond_wait(&queue_nonempty, &queue_lock);
            n = q_last%q_depth;
      }

      // OK, grab the next event
      if (q[n] != NULL) {
            e = (event_t *)q[n];
            q[n] = NULL;
            q_last = (n+1) % q_depth;
      } else
            e = NULL;

      pthread_mutex_unlock(&queue_lock);

      // Process the event
      return e;
}

void nudge_queue(void)
{
      pthread_cond_signal(&queue_nonempty);
}

void increase_queue_depth(unsigned int size)
{
      pthread_mutex_lock(&queue_lock);
      if (size > q_depth) {
            int i;
            void *tmp_q;

            tmp_q = realloc(q, size * sizeof(event_t *));
            q = tmp_q;
            for (i=q_depth; i<size; i++)
                  q[i] = NULL;
            q_depth = size;
      }
      pthread_mutex_unlock(&queue_lock);
}

void destroy_queue(void)
{
      unsigned int i;

      for (i=0; i<q_depth; i++)
            free((void *)q[i]);

      free(q);
}


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