From 9b99cf94012cac8772a7a7a39554a9daecc53e19 Mon Sep 17 00:00:00 2001
From: Tom Cort <tom.cort@state.vt.us>
Date: Mon, 26 Nov 2007 23:54:41 -0500
Subject: [PATCH] Add a thread monitor.

This module contains functions to manipulate a thread counter in an atomic
way. It also includes a wait function to ensure that all threads exit
before the program exits.
---
 monitor.c | 90 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 monitor.h | 46 ++++++++++++++++++++++++++++++++
 2 files changed, 136 insertions(+)
 create mode 100644 monitor.c
 create mode 100644 monitor.h

diff --git a/monitor.c b/monitor.c
new file mode 100644
index 0000000..7719761
--- /dev/null
+++ b/monitor.c
@@ -0,0 +1,90 @@
+/*
+ * inoclam - Inotify+ClamAV virus scanner
+ * Copyright (C) 2007 Vermont Department of Taxes
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Contributor(s):
+ *   Tom Cort <tom.cort@state.vt.us>
+ */
+
+#define _XOPEN_SOURCE 500
+
+#include <pthread.h>
+#include <sched.h>
+#include <signal.h>
+#include <unistd.h>
+
+#include "monitor.h"
+
+/**
+ * Counter for the number of running threads.
+ */
+int cnt;
+
+/**
+ * A lock used to serialize access to cnt.
+ */
+pthread_mutex_t mon_lock;
+
+/**
+ *  initialize monitor variables
+ */
+void monitor_init()
+{
+	pthread_mutex_init(&mon_lock, 0);
+	cnt = 0;
+}
+
+/**
+ *  increments the thread count
+ */
+void monitor_inc()
+{
+	pthread_mutex_lock(&mon_lock);
+	cnt++;
+	pthread_mutex_unlock(&mon_lock);
+}
+
+/**
+ *  decrements the thread count
+ */
+void monitor_dec()
+{
+	pthread_mutex_lock(&mon_lock);
+	cnt--;
+	pthread_mutex_unlock(&mon_lock);
+}
+
+/**
+ *  waits until no threads are running
+ *  blocks new threads from being created
+ */
+void monitor_wait()
+{
+	raise(SIGUSR1);
+
+	while (1) {
+		pthread_mutex_lock(&mon_lock);
+
+		if (!cnt) {
+			/* Do NOT release lock; we don't want any more threads starting */
+			return;
+		} else {
+			pthread_mutex_unlock(&mon_lock);
+			sched_yield();
+			sleep(3);
+		}
+	}
+}
diff --git a/monitor.h b/monitor.h
new file mode 100644
index 0000000..00c2996
--- /dev/null
+++ b/monitor.h
@@ -0,0 +1,46 @@
+/*
+ * inoclam - Inotify+ClamAV virus scanner
+ * Copyright (C) 2007 Vermont Department of Taxes
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program 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 General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ * Contributor(s):
+ *   Tom Cort <tom.cort@state.vt.us>
+ */
+
+#ifndef __MONITOR_H
+#define __MONITOR_H
+
+/**
+ *  initialize monitor variables
+ */
+void monitor_init();
+
+/**
+ *  increments the thread count
+ */
+void monitor_inc();
+
+/**
+ *  decrements the thread count
+ */
+void monitor_dec();
+
+/**
+ *  waits until no threads are running
+ *  blocks new threads from being created
+ */
+void monitor_wait();
+
+#endif
-- 
2.11.4.GIT