From 9989b8779cef3c243ee58e273c0b2709fb11e31b Mon Sep 17 00:00:00 2001
From: Shaun Ruffell <sruffell@digium.com>
Date: Thu, 2 Jan 2014 17:31:19 -0600
Subject: [PATCH] dahdi_cfg: Add semaphore to prevent parallel execution.

When dahdi is configured for fully dynamic configuration on a device and
span basis via sysfs and udev it is possible for multiple instances of
dahdi_cfg to be run in parallel on different spans. If this happens it
is possible to see errors on the console that tone zones are already
registered since the check for the existence of a tone zone and the
re-registering needs to be atomic.

dahdi_cfg will now prevent itself from running in parallel.

Signed-off-by: Shaun Ruffell <sruffell@digium.com>
Signed-off-by: Russ Meyerriecks <rmeyerriecks@digium.com>
---
 Makefile    |  2 +-
 dahdi_cfg.c | 58 ++++++++++++++++++++++++++++++++++++++++++-----------
 2 files changed, 47 insertions(+), 13 deletions(-)

diff --git a/Makefile b/Makefile
index eea390e..144b292 100644
--- a/Makefile
+++ b/Makefile
@@ -168,7 +168,7 @@ $(LTZ_SO): $(LTZ_SO_OBJS)
 	$(CC) $(CFLAGS) -shared -Wl,-soname,$(LTZ_SO).$(LTZ_SO_MAJOR_VER).$(LTZ_SO_MINOR_VER) -o $@ $^ -lm
 
 dahdi_cfg: $(LTZ_A)
-dahdi_cfg: LIBS+=-lm
+dahdi_cfg: LIBS+=-lm -lpthread
 dahdi_pcap:
 	$(CC) $(CFLAGS) dahdi_pcap.c -lpcap -o $@ $<
 	
diff --git a/dahdi_cfg.c b/dahdi_cfg.c
index 0de1091..c86eaac 100644
--- a/dahdi_cfg.c
+++ b/dahdi_cfg.c
@@ -35,6 +35,8 @@
 #include <unistd.h>
 #include <sys/ioctl.h>
 #include <fcntl.h>
+#include <sys/stat.h>
+#include <semaphore.h>
 #include <errno.h>
 #include <dirent.h>
 #include <stdbool.h>
@@ -794,7 +796,7 @@ static int setfiftysixkhdlc(char *keyword, char *args)
 	return 0;
 }
 
-static void apply_fiftysix(void)
+static int apply_fiftysix(void)
 {
 	int x;
 	int rate;
@@ -808,7 +810,7 @@ static void apply_fiftysix(void)
 			fprintf(stderr, 
 			    "Couldn't open /dev/dahdi/channel: %s\n", 
 			    strerror(errno));
-			exit(-1);
+			return -1;	
 		}
 
 		if (ioctl(chanfd, DAHDI_SPECIFY, &x)) {
@@ -829,6 +831,7 @@ static void apply_fiftysix(void)
 		}
 		close(chanfd);
 	}
+	return 0;
 }
 
 static int setechocan(char *keyword, char *args)
@@ -1530,6 +1533,9 @@ int main(int argc, char *argv[])
 	char *buf;
 	char *key, *value;
 	int x,found;
+	sem_t *lock = SEM_FAILED;
+	const char *SEM_NAME = "dahdi_cfg";
+	int exit_code = 0;
 
 	while((c = getopt(argc, argv, "fthc:vsd::C:S:")) != -1) {
 		switch(c) {
@@ -1656,6 +1662,20 @@ finish:
 		printf("About to open Master device\n");
 		fflush(stdout);
 	}
+
+	lock = sem_open(SEM_NAME, O_CREAT, O_RDWR, 1);
+	if (SEM_FAILED == lock) {
+		error("Unable to create 'dahdi_cfg' mutex.\n");
+		exit_code = 1;
+		goto release_sem;
+	}
+
+	if (-1 == sem_wait(lock)) {
+		error("Failed to wait for dahdi_cfg mutex.\n");
+		exit_code = 1;
+		goto release_sem;
+	}
+
 	for (x=0;x<numdynamic;x++) {
 		/* destroy them all */
 		ioctl(fd, DAHDI_DYNAMIC_DESTROY, &zds[x]);
@@ -1667,10 +1687,12 @@ finish:
 			if (ioctl(fd, DAHDI_SHUTDOWN, &lc[x].span)) {
 				fprintf(stderr, "DAHDI shutdown failed: %s\n", strerror(errno));
 				close(fd);
-				exit(1);
+				exit_code = 1;
+				goto release_sem;
 			}
 		}
-		exit(1);
+		exit_code = 1;
+		goto release_sem;
 	}
 	for (x=0;x<spans;x++) {
 		if (only_span && lc[x].span != only_span)
@@ -1678,14 +1700,16 @@ finish:
 		if (ioctl(fd, DAHDI_SPANCONFIG, lc + x)) {
 			fprintf(stderr, "DAHDI_SPANCONFIG failed on span %d: %s (%d)\n", lc[x].span, strerror(errno), errno);
 			close(fd);
-			exit(1);
+			exit_code = 1;
+			goto release_sem;
 		}
 	}
 	for (x=0;x<numdynamic;x++) {
 		if (ioctl(fd, DAHDI_DYNAMIC_CREATE, &zds[x])) {
 			fprintf(stderr, "DAHDI dynamic span creation failed: %s\n", strerror(errno));
 			close(fd);
-			exit(1);
+			exit_code = 1;
+			goto release_sem;
 		}
 	}
 	for (x=1;x<DAHDI_MAX_CHANNELS;x++) {
@@ -1810,7 +1834,8 @@ finish:
 					" to channel 16 of an E1 CAS span\n");
 			}
 			close(fd);
-			exit(1);
+			exit_code = 1;
+			goto release_sem;
 		}
 
 		ae[x].chan = x;
@@ -1821,7 +1846,8 @@ finish:
 		if (ioctl(fd, DAHDI_ATTACH_ECHOCAN, &ae[x])) {
 			fprintf(stderr, "DAHDI_ATTACH_ECHOCAN failed on channel %d: %s (%d)\n", x, strerror(errno), errno);
 			close(fd);
-			exit(1);
+			exit_code = 1;
+			goto release_sem;
 		}
 	}
 	if (0 == numzones) {
@@ -1848,7 +1874,8 @@ finish:
 		if (ioctl(fd, DAHDI_DEFAULTZONE, &deftonezone)) {
 			fprintf(stderr, "DAHDI_DEFAULTZONE failed: %s (%d)\n", strerror(errno), errno);
 			close(fd);
-			exit(1);
+			exit_code = 1;
+			goto release_sem;
 		}
 	}
 	for (x=0;x<spans;x++) {
@@ -1857,9 +1884,16 @@ finish:
 		if (ioctl(fd, DAHDI_STARTUP, &lc[x].span)) {
 			fprintf(stderr, "DAHDI startup failed: %s\n", strerror(errno));
 			close(fd);
-			exit(1);
+			exit_code = 1;
+			goto release_sem;
 		}
 	}
-	apply_fiftysix();
-	exit(0);
+	exit_code = apply_fiftysix();
+
+release_sem:
+	if (SEM_FAILED != lock) {
+		sem_post(lock);
+		sem_unlink(SEM_NAME);
+	}
+	exit(exit_code);
 }