tools/env: Serialize calls to fw_*env

Use a lock file at /var/lock/fw_printenv.lock.
Avoids seriously confusing the MTD driver.

Signed-off-by: Joe Hershberger <joe.hershberger@ni.com>

diff --git a/tools/env/fw_env_main.c b/tools/env/fw_env_main.c
index c654057..c855f4c 100644 (file)
--- a/tools/env/fw_env_main.c
+++ b/tools/env/fw_env_main.c
@@ -39,10 +39,13 @@
  *               variable "name"
  */
 
+#include <fcntl.h>
+#include <getopt.h>
 #include <stdio.h>
 #include <string.h>
 #include <stdlib.h>
-#include <getopt.h>
+#include <sys/file.h>
+#include <unistd.h>
 #include "fw_env.h"
 
 #define        CMD_PRINTENV    "fw_printenv"
@@ -81,13 +84,27 @@ void usage(void)
        );
 }
 
-int
-main(int argc, char *argv[])
+int main(int argc, char *argv[])
 {
        char *p;
        char *cmdname = *argv;
        char *script_file = NULL;
        int c;
+       const char *lockname = "/var/lock/" CMD_PRINTENV ".lock";
+       int lockfd = -1;
+       int retval = EXIT_SUCCESS;
+
+       lockfd = open(lockname, O_WRONLY | O_CREAT | O_TRUNC);
+       if (-1 == lockfd) {
+               fprintf(stderr, "Error opening lock file %s\n", lockname);
+               return EXIT_FAILURE;
+       }
+
+       if (-1 == flock(lockfd, LOCK_EX)) {
+               fprintf(stderr, "Error locking file %s\n", lockname);
+               close(lockfd);
+               return EXIT_FAILURE;
+       }
 
        if ((p = strrchr (cmdname, '/')) != NULL) {
                cmdname = p + 1;
@@ -104,38 +121,36 @@ main(int argc, char *argv[])
                        break;
                case 'h':
                        usage();
-                       return EXIT_SUCCESS;
+                       goto exit;
                default: /* '?' */
                        fprintf(stderr, "Try `%s --help' for more information."
                                "\n", cmdname);
-                       return EXIT_FAILURE;
+                       retval = EXIT_FAILURE;
+                       goto exit;
                }
        }
 
-
        if (strcmp(cmdname, CMD_PRINTENV) == 0) {
-
-               if (fw_printenv (argc, argv) != 0)
-                       return EXIT_FAILURE;
-
-               return EXIT_SUCCESS;
-
+               if (fw_printenv(argc, argv) != 0)
+                       retval = EXIT_FAILURE;
        } else if (strcmp(cmdname, CMD_SETENV) == 0) {
                if (!script_file) {
                        if (fw_setenv(argc, argv) != 0)
-                               return EXIT_FAILURE;
+                               retval = EXIT_FAILURE;
                } else {
                        if (fw_parse_script(script_file) != 0)
-                               return EXIT_FAILURE;
+                               retval = EXIT_FAILURE;
                }
-
-               return EXIT_SUCCESS;
-
+       } else {
+               fprintf(stderr,
+                       "Identity crisis - may be called as `" CMD_PRINTENV
+                       "' or as `" CMD_SETENV "' but not as `%s'\n",
+                       cmdname);
+               retval = EXIT_FAILURE;
        }
 
-       fprintf (stderr,
-               "Identity crisis - may be called as `" CMD_PRINTENV
-               "' or as `" CMD_SETENV "' but not as `%s'\n",
-               cmdname);
-       return EXIT_FAILURE;
+exit:
+       flock(lockfd, LOCK_UN);
+       close(lockfd);
+       return retval;
 }