Merge branch 'MTX-3262-single-instance-guard' into 'master'

Mtx 3262 single instance guard

See merge request !3

3 files changed, 50 insertions, 42 deletions

diff --git a/src/atcmd.c b/src/atcmd.c
index 97fd34b..eab4210 100644
--- a/src/atcmd.c
+++ b/src/atcmd.c
@@ -1471,7 +1471,7 @@ static int sms_atcmd_init(int fd)
 	return 0;
 }
 
-static char *lock_path;
+static struct Lock *lock_file;
 
 int sms_device_close(int fd)
 {
@@ -1479,11 +1479,7 @@ int sms_device_close(int fd)
 
 	ret = tty_close(fd);
 
-	if (lock_path) {
-		unlink(lock_path);
-		free(lock_path);
-		lock_path = NULL;
-	}
+	lock_file = device_unlock(lock_file);
 
 	return ret;
 }
@@ -1498,8 +1494,8 @@ int sms_device_open(void)
 		return -1;
 	}
 
-	lock_path = device_lock(Global.core.device);
-	if (!lock_path) {
+	lock_file = device_lock(Global.core.device);
+	if (!lock_file) {
 		sms_device_close(fd);
 		return -1;
 	}
diff --git a/src/utils.c b/src/utils.c
index b93634c..e7d6b69 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -33,6 +33,7 @@
 #include <fcntl.h>
 #include <string.h>
 #include <linux/limits.h>
+#include <sys/file.h>
 
 #include "utils.h"
 #include "log.h"
@@ -248,44 +249,49 @@ char *shell_path_expand(const char *path)
 
 #define MAX_TRY 10
 
-char *device_lock(const char *path)
+struct Lock *device_lock(const char *path)
 {
-	int tmp;
-	char *name = basename(path);
-	int fd;
-	char str[32];
-	char *lock;
-	unsigned char num_try=0;
-
-	tmp = asprintf(&lock, "/var/lock/LCK..%s", name);
-	if (tmp < 0) {
+	struct Lock *result = (struct Lock*)calloc(1, sizeof(struct Lock));
+	if (result == NULL) {
 		log_error("out of memory");
 		return NULL;
 	}
 
-	do{
-	  fd = open(lock, O_CREAT | O_WRONLY | O_TRUNC | O_EXCL, 0644);
-	  if (fd > 0) {
-	    break;
-	  }else{
-	    log_error("%i number of trying to create %s: %m",num_try+1,lock);
-	  };
-	  if(num_try++>=MAX_TRY){
-		  //something locks device too long
-		  log_error("failed to create %s: %m", lock);
-		  free(lock);
-		  return NULL;
-	  }
-	  usleep(100000ul);//100ms
-	}while(1);
-
-	snprintf(str, sizeof(str), "%10d\n", getpid());
-
-	full_write(fd, str, strlen(str));
-
-	close(fd);
-
-	return lock;
+	if (asprintf(&result->path, "/var/lock/LCK..%s", basename(path)) < 0) {
+		log_error("out of memory");
+		return NULL;
+	}
+
+	result->fd = open(result->path, O_CREAT | O_RDWR, 0644);
+	if (result->fd >= 0) {
+		unsigned char num_try = 0;
+		while (1) {
+			int lockErr = flock(result->fd, LOCK_EX | LOCK_NB);
+			if (lockErr == 0) {
+				return result;
+			} else if (errno != EWOULDBLOCK) {
+				break;
+			}
+			if (num_try++>=MAX_TRY) {
+				//something locks device too long
+				break;
+			}
+			usleep(100000ul);//100ms
+		}
+		log_error("failed to create %s: %m", result->path);
+		device_unlock(result);
+	}
+	return NULL;
+}
+
+struct Lock *device_unlock(struct Lock *lock)
+{
+	if (lock) {
+		close(lock->fd);
+		free(lock->path);
+		free(lock);
+	}
+	return NULL;
 }
 
 int indexOfChar(const char *array, int len, char character)
diff --git a/src/utils.h b/src/utils.h
index 04a71b6..eb9d5bc 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -30,12 +30,18 @@ enum {
 	USER_YESNO_YES = 1,
 };
 
+struct Lock {
+    char *path;
+    int fd;
+};
+
 int user_yesno(int def, const char *fmt, ...);
 int systemf(const char *fmt, ...);
 FILE *popenf(const char *mode, const char *fmt, ...);
 char *shell_path_expand(const char *path);
 
-char *device_lock(const char *path);
+struct Lock *device_lock(const char *path);
+struct Lock *device_unlock(struct Lock *lock);
 
 int indexOfChar(const char *array, int len, char character);