From bce2937acead6988b0f0b84b2b339f1fd8d54122 Mon Sep 17 00:00:00 2001
From: Pierre-Marc Fournier <pierre-marc.fournier@polymtl.ca>
Date: Tue, 13 Oct 2009 17:55:01 -0400
Subject: [PATCH] ustd: add daemon mode

---
 ustd/ustd.c | 97 ++++++++++++++++++++++++++++++++++++++++++++++++-----
 usttrace    |  5 ++-
 2 files changed, 93 insertions(+), 9 deletions(-)

diff --git a/ustd/ustd.c b/ustd/ustd.c
index 2393ea3d..00197766 100644
--- a/ustd/ustd.c
+++ b/ustd/ustd.c
@@ -52,6 +52,7 @@
 
 char *sock_path=NULL;
 char *trace_path=NULL;
+int daemon_mode = 0;
 
 /* Number of active buffers and the mutex to protect it. */
 int active_buffers = 0;
@@ -473,7 +474,9 @@ void usage(void)
 	fprintf(stderr, "Usage:\nustd OPTIONS\n\nOptions:\n"
 			"\t-h\t\tDisplay this usage.\n"
 			"\t-o DIR\t\tSpecify the directory where to output the traces.\n"
-			"\t-s PATH\t\tSpecify the path to use for the daemon socket.\n");
+			"\t-s PATH\t\tSpecify the path to use for the daemon socket.\n"
+			"\t-d\t\tStart as a daemon.\n"
+			"\t--pidfile FILE\tWrite the PID in this file (when using -d).\n");
 }
 
 int parse_args(int argc, char **argv)
@@ -483,12 +486,13 @@ int parse_args(int argc, char **argv)
 	while (1) {
 		int option_index = 0;
 		static struct option long_options[] = {
+			{"pidfile", 1, 0, 'p'},
 			{"help", 0, 0, 'h'},
 			{"version", 0, 0, 'V'},
 			{0, 0, 0, 0}
 		};
 
-		c = getopt_long(argc, argv, "hs:o:", long_options, &option_index);
+		c = getopt_long(argc, argv, "hs:o:d", long_options, &option_index);
 		if (c == -1)
 			break;
 
@@ -509,6 +513,9 @@ int parse_args(int argc, char **argv)
 				return -1;
 			}
 			break;
+		case 'd':
+			daemon_mode = 1;
+			break;
 		case 'h':
 			usage();
 			exit(0);
@@ -531,7 +538,7 @@ void sigterm_handler(int sig)
 	terminate_req = 1;
 }
 
-int main(int argc, char **argv)
+int start_ustd(int fd)
 {
 	struct ustcomm_ustd ustd;
 	int result;
@@ -552,11 +559,6 @@ int main(int argc, char **argv)
 		return 1;
 	}
 
-	result = parse_args(argc, argv);
-	if(result == -1) {
-		exit(1);
-	}
-
 	result = ustcomm_init_ustd(&ustd, sock_path);
 	if(result == -1) {
 		ERR("failed to initialize socket");
@@ -580,6 +582,24 @@ int main(int argc, char **argv)
 		return 1;
 	}
 
+	/* Notify parent that we are successfully started. */
+	if(fd != -1) {
+		/* write any one character */
+		result = write(fd, "!", 1);
+		if(result == -1) {
+			PERROR("write");
+			return -1;
+		}
+		if(result != 1) {
+			ERR("Problem sending confirmation of daemon start to parent");
+			return -1;
+		}
+		result = close(fd);
+		if(result == -1) {
+			PERROR("close");
+		}
+	}
+
 	/* app loop */
 	for(;;) {
 		char *recvbuf;
@@ -629,3 +649,64 @@ int main(int argc, char **argv)
 
 	return 0;
 }
+
+int start_ustd_daemon()
+{
+	int result;
+	int fd[2];
+
+	result = pipe(fd);
+
+	result = fork();
+	if(result == -1) {
+		PERROR("fork");
+		return -1;
+	}
+	else if(result == 0) {
+		return start_ustd(fd[1]);
+	}
+	else {
+		char buf;
+
+		result = read(fd[0], &buf, 1);
+		if(result == -1) {
+			PERROR("read");
+			return -1;
+		}
+		if(result != 1) {
+			ERR("did not receive valid confirmation that the daemon is started");
+			return -1;
+		}
+
+		result = close(fd[0]);
+		if(result == -1) {
+			PERROR("close");
+		}
+
+		DBG("The daemon is now successfully started");
+	}
+
+	/* Wait for confirmation that the server is ready. */
+
+
+	return 0;
+}
+
+int main(int argc, char **argv)
+{
+	int result;
+
+	result = parse_args(argc, argv);
+	if(result == -1) {
+		exit(1);
+	}
+
+	if(daemon_mode) {
+		result = start_ustd_daemon();
+	}
+	else {
+		result = start_ustd(-1);
+	}
+
+	return result;
+}
diff --git a/usttrace b/usttrace
index e8ab13c7..cb946408 100755
--- a/usttrace
+++ b/usttrace
@@ -79,7 +79,10 @@ fi
 # Wait for the daemon to settle
 # If we don't, the process may try to connect to its socket before
 # it's ready.
-# FIXME: is there a way to make sure this works every time?
+# FIXME: is there a way to make sure this works every time? Yes,
+# we could have a mode where ustd daemonizes itself. Therefore
+# by the time the control returns to the console, it's ready.
+
 sleep 0.5
 
 # Establish the environment for the command
-- 
2.34.1