Initial commit

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

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+--- /dev/null
++++ b/miscutils/lock.c
+@@ -0,0 +1,155 @@
++/*
++ * Copyright (C) 2006 Felix Fietkau <nbd@nbd.name>
++ *
++ * This is free software, licensed under the GNU General Public License v2.
++ */
++
++//config:config LOCK
++//config:	bool "lock"
++//config:	default n
++//config:	help
++//config:	  Small utility for using locks in scripts
++
++//applet:IF_LOCK(APPLET(lock, BB_DIR_BIN, BB_SUID_DROP))
++
++//kbuild:lib-$(CONFIG_LOCK) += lock.o
++
++//usage:#define lock_trivial_usage NOUSAGE_STR
++//usage:#define lock_full_usage ""
++
++#include <sys/types.h>
++#include <sys/file.h>
++#include <sys/stat.h>
++#include <signal.h>
++#include <fcntl.h>
++#include <unistd.h>
++#include <stdio.h>
++#include "busybox.h"
++
++static int unlock = 0;
++static int shared = 0;
++static int waitonly = 0;
++static int try_lock = 0;
++static int fd;
++static char *file;
++
++static void usage(char *name)
++{
++	fprintf(stderr, "Usage: %s [-suw] <filename>\n"
++	                "	-s	Use shared locking\n"
++	                "	-u	Unlock\n"
++	                "	-w	Wait for the lock to become free, don't acquire lock\n"
++			"	-n	Don't wait for the lock to become free. Fail with exit code\n"
++					"\n", name);
++	exit(1);
++}
++
++static void exit_unlock(int sig)
++{
++	flock(fd, LOCK_UN);
++	exit(0);
++}
++
++static int do_unlock(void)
++{
++	FILE *f;
++	int i;
++
++	if ((f = fopen(file, "r")) == NULL)
++		return 0;
++
++	fscanf(f, "%d", &i);
++	if (i > 0)
++		kill(i, SIGTERM);
++
++	fclose(f);
++
++	return 0;
++}
++
++static int do_lock(void)
++{
++	pid_t pid;
++	int flags;
++	char pidstr[12];
++
++	if ((fd = open(file, O_RDWR | O_CREAT | O_EXCL, 0700)) < 0) {
++		if ((fd = open(file, O_RDWR)) < 0) {
++			fprintf(stderr, "Can't open %s\n", file);
++			return 1;
++		}
++	}
++
++	flags = shared ? LOCK_SH : LOCK_EX;
++	flags |= try_lock ? LOCK_NB : 0;
++
++	if (flock(fd, flags) < 0) {
++		fprintf(stderr, "Can't lock %s\n", file);
++		return 1;
++	}
++
++	pid = fork();
++
++	if (pid < 0)
++		return -1;
++
++	if (pid == 0) {
++		signal(SIGKILL, exit_unlock);
++		signal(SIGTERM, exit_unlock);
++		signal(SIGINT, exit_unlock);
++		if (waitonly)
++			exit_unlock(0);
++		else
++			while (1)
++				sleep(1);
++	} else {
++		if (!waitonly) {
++			lseek(fd, 0, SEEK_SET);
++			ftruncate(fd, 0);
++			snprintf(pidstr, sizeof(pidstr), "%d\n", pid);
++			write(fd, pidstr, strlen(pidstr));
++			close(fd);
++		}
++
++		return 0;
++	}
++	return 0;
++}
++
++int lock_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
++int lock_main(int argc, char **argv)
++{
++	char **args = &argv[1];
++	int c = argc - 1;
++
++	while ((*args != NULL) && (*args)[0] == '-') {
++		char *ch = *args;
++		while (*(++ch) > 0) {
++			switch(*ch) {
++				case 'w':
++					waitonly = 1;
++					break;
++				case 's':
++					shared = 1;
++					break;
++				case 'u':
++					unlock = 1;
++					break;
++				case 'n':
++					try_lock = 1;
++					break;
++			}
++		}
++		c--;
++		args++;
++	}
++
++	if (c != 1)
++		usage(argv[0]);
++
++	file = *args;
++	if (unlock)
++		return do_unlock();
++	else
++		return do_lock();
++}