package/utils/busybox/patches/220-add_lock_util.patch

   1 --- /dev/null
   2 +++ b/miscutils/lock.c
   3 @@ -0,0 +1,155 @@
   4 +/*
   5 + * Copyright (C) 2006 Felix Fietkau <nbd@nbd.name>
   6 + *
   7 + * This is free software, licensed under the GNU General Public License v2.
   8 + */
   9 +
  10 +//config:config LOCK
  11 +//config:      bool "lock"
  12 +//config:      default n
  13 +//config:      help
  14 +//config:        Small utility for using locks in scripts
  15 +
  16 +//applet:IF_LOCK(APPLET(lock, BB_DIR_BIN, BB_SUID_DROP))
  17 +
  18 +//kbuild:lib-$(CONFIG_LOCK) += lock.o
  19 +
  20 +//usage:#define lock_trivial_usage NOUSAGE_STR
  21 +//usage:#define lock_full_usage ""
  22 +
  23 +#include <sys/types.h>
  24 +#include <sys/file.h>
  25 +#include <sys/stat.h>
  26 +#include <signal.h>
  27 +#include <fcntl.h>
  28 +#include <unistd.h>
  29 +#include <stdio.h>
  30 +#include "busybox.h"
  31 +
  32 +static int unlock = 0;
  33 +static int shared = 0;
  34 +static int waitonly = 0;
  35 +static int try_lock = 0;
  36 +static int fd;
  37 +static char *file;
  38 +
  39 +static void usage(char *name)
  40 +{
  41 +       fprintf(stderr, "Usage: %s [-suw] <filename>\n"
  42 +                       "       -s      Use shared locking\n"
  43 +                       "       -u      Unlock\n"
  44 +                       "       -w      Wait for the lock to become free, don't acquire lock\n"
  45 +                       "       -n      Don't wait for the lock to become free. Fail with exit code\n"
  46 +                                       "\n", name);
  47 +       exit(1);
  48 +}
  49 +
  50 +static void exit_unlock(int sig)
  51 +{
  52 +       flock(fd, LOCK_UN);
  53 +       exit(0);
  54 +}
  55 +
  56 +static int do_unlock(void)
  57 +{
  58 +       FILE *f;
  59 +       int i;
  60 +
  61 +       if ((f = fopen(file, "r")) == NULL)
  62 +               return 0;
  63 +
  64 +       fscanf(f, "%d", &i);
  65 +       if (i > 0)
  66 +               kill(i, SIGTERM);
  67 +
  68 +       fclose(f);
  69 +
  70 +       return 0;
  71 +}
  72 +
  73 +static int do_lock(void)
  74 +{
  75 +       pid_t pid;
  76 +       int flags;
  77 +       char pidstr[12];
  78 +
  79 +       if ((fd = open(file, O_RDWR | O_CREAT | O_EXCL, 0700)) < 0) {
  80 +               if ((fd = open(file, O_RDWR)) < 0) {
  81 +                       fprintf(stderr, "Can't open %s\n", file);
  82 +                       return 1;
  83 +               }
  84 +       }
  85 +
  86 +       flags = shared ? LOCK_SH : LOCK_EX;
  87 +       flags |= try_lock ? LOCK_NB : 0;
  88 +
  89 +       if (flock(fd, flags) < 0) {
  90 +               fprintf(stderr, "Can't lock %s\n", file);
  91 +               return 1;
  92 +       }
  93 +
  94 +       pid = fork();
  95 +
  96 +       if (pid < 0)
  97 +               return -1;
  98 +
  99 +       if (pid == 0) {
 100 +               signal(SIGKILL, exit_unlock);
 101 +               signal(SIGTERM, exit_unlock);
 102 +               signal(SIGINT, exit_unlock);
 103 +               if (waitonly)
 104 +                       exit_unlock(0);
 105 +               else
 106 +                       while (1)
 107 +                               sleep(1);
 108 +       } else {
 109 +               if (!waitonly) {
 110 +                       lseek(fd, 0, SEEK_SET);
 111 +                       ftruncate(fd, 0);
 112 +                       snprintf(pidstr, sizeof(pidstr), "%d\n", pid);
 113 +                       write(fd, pidstr, strlen(pidstr));
 114 +                       close(fd);
 115 +               }
 116 +
 117 +               return 0;
 118 +       }
 119 +       return 0;
 120 +}
 121 +
 122 +int lock_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
 123 +int lock_main(int argc, char **argv)
 124 +{
 125 +       char **args = &argv[1];
 126 +       int c = argc - 1;
 127 +
 128 +       while ((*args != NULL) && (*args)[0] == '-') {
 129 +               char *ch = *args;
 130 +               while (*(++ch) > 0) {
 131 +                       switch(*ch) {
 132 +                               case 'w':
 133 +                                       waitonly = 1;
 134 +                                       break;
 135 +                               case 's':
 136 +                                       shared = 1;
 137 +                                       break;
 138 +                               case 'u':
 139 +                                       unlock = 1;
 140 +                                       break;
 141 +                               case 'n':
 142 +                                       try_lock = 1;
 143 +                                       break;
 144 +                       }
 145 +               }
 146 +               c--;
 147 +               args++;
 148 +       }
 149 +
 150 +       if (c != 1)
 151 +               usage(argv[0]);
 152 +
 153 +       file = *args;
 154 +       if (unlock)
 155 +               return do_unlock();
 156 +       else
 157 +               return do_lock();
 158 +}