From c2d88b9017e8a92eb34a3b6ceeccf66c9091c2e9 Mon Sep 17 00:00:00 2001
From: Michal Sojka <sojkam1@fel.cvut.cz>
Date: Thu, 11 Jun 2009 18:20:18 +0200
Subject: [PATCH] Added option to go to background

This was necessary to safely start slave and master from the same script
without inserting sleep(). With the new -b option, parent process
returns, when the child is ready to receive (in case of slave) messages.
---
 src/vca_canping.c | 47 ++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 44 insertions(+), 3 deletions(-)

diff --git a/src/vca_canping.c b/src/vca_canping.c
index 2123976..8de0af5 100644
--- a/src/vca_canping.c
+++ b/src/vca_canping.c
@@ -31,6 +31,8 @@
 #include <ul_list.h>
 #include <errno.h>
 #include <semaphore.h>
+#include <stdbool.h>
+#include <error.h>
 
 /* TODO: Handle the case where there are more canping slaves running
  * on one CAN bus. */
@@ -98,6 +100,7 @@ int option_wait_ms = 1000;
 int option_timeout = 4;
 int option_open_once = 0;
 int option_synch_start = 0;
+bool option_background = false;
 
 /* Lists */
 typedef struct threads {
@@ -404,6 +407,9 @@ void *slave_thread(void *arg)
 	pongmsg.length = option_length;
 	for (i=0; i < option_length; i++) pongmsg.data[i] = i;
 
+	/* Signal that I'm ready */
+	sem_post(&ready_sem);
+
 	while (!IS_FINISH_FLAG()) {
 		/* Receive a ping message */
 		pingmsg.flags=0;
@@ -472,6 +478,9 @@ void start_slaves(int slaves, int first_id)
 		pthread_create(&td->tid, NULL, slave_thread, (void *)td);
 		dbg(2, "Slave thread: %p\n", (void *)td->tid);
 	}
+
+	/* Wait for all threads beeing ready */
+	for (i = 0; i < slaves; i++) sem_wait(&ready_sem);
 }
 
 #ifdef WITH_RTPRIO
@@ -501,6 +510,7 @@ void print_help(void)
 	printf("Usage: canping -m <master threads> [other options]\n"
 	       "       canping -s <slave threads> [other options]\n\n"
 	       "Other options:\n"
+	       "  -b            go to background (fork) after initialization, prints child PID\n"
 	       "  -c count	how many messages each master sends\n"
 	       "  -d dev	device (e.g. /dev/can1)\n"
 	       "  -h		print this help\n"
@@ -526,9 +536,12 @@ int parse_options(int argc, char *argv[])
 	int c;
 	
 	opterr = 0;
-	while ((c = getopt (argc, argv, "c:d:hi:l:m:os:t:vw:yrR:")) != -1)
+	while ((c = getopt (argc, argv, "bc:d:hi:l:m:os:t:vw:yrR:")) != -1)
 		switch (c)
 		{
+		case 'b':
+			option_background = true;
+			break;
 		case 'c':
 			option_count = atoi(optarg);
 			break;
@@ -712,9 +725,37 @@ int main(int argc, char *argv[])
 		}
 	}
 
-	if (option_masters) start_masters(option_masters, option_first_id);
-	if (option_slaves) start_slaves(option_slaves, option_first_id);
+	sem_t *child_ready;
+	int fork_ret = 0;
+	if ((child_ready = sem_open("canping", O_CREAT)) == NULL)
+		error(1, errno, "sem_open");
+	if (option_background) {
+		/* Go to background when everything is ready */
+		fork_ret = fork();
+		if (fork_ret < 0)
+			error(1, errno, "Cannot go to background");
+		if (fork_ret == 0) {
+			int devnull = open("/dev/null", O_WRONLY);
+			dup2(devnull, 1);
+		}
+	}
 
+	fprintf(stderr, "Common\n");
+	if (fork_ret == 0) {
+		/* Child */
+		fprintf(stderr, "Child starting childs\n");
+		if (option_masters) start_masters(option_masters, option_first_id);
+		if (option_slaves) start_slaves(option_slaves, option_first_id);
+		sem_post(child_ready);
+		fprintf(stderr, "Child ready\n");
+	} else {
+		/* Parent */
+		fflush(stderr);
+		sem_wait(child_ready);
+		printf("%d\n", fork_ret);
+		exit(0);
+	}
+	
 	wait_for_threads();
 
 	if (option_open_once) {
-- 
2.39.2