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Program for probing access to device files. By Ted Ts'o with modifications by me.

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This commit is contained in:
Thomas Schmitt 2007-04-18 10:32:23 +00:00
parent b634e90b2c
commit 73a564c767
1 changed files with 137 additions and 0 deletions
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137
libburn/trunk/test/open-cd-excl.c Normal file
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/*
* open-cd-excl.c --- This program tries to open a block device
* by various exclusive and non-exclusive gestures in order to explore
* their impact on running CD/DVD recordings.
*
* Copyright 2007, by Theodore Ts'o.
*
* Detail modifications 2007, by Thomas Schmitt.
*
* %Begin-Header%
* This file may be redistributed under the terms of the GNU Public
* License.
* %End-Header%
*/
#define _GNU_SOURCE /* for O_LARGEFILE *//*ts A70417: or _LARGEFILE64_SOURCE */
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#include <fcntl.h>
#include <getopt.h>
const char *progname;
static void usage(void)
{
fprintf(stderr, "Usage: %s [-feirw] device\n", progname);
exit(1);
}
/* ts A70417: added parameter do_rdwr */
static void init_flock(struct flock *fl, int do_rdwr)
{
memset(fl, 0, sizeof(struct flock));
if (do_rdwr)
fl->l_type = F_WRLCK;
else
fl->l_type = F_RDLCK;
fl->l_whence = SEEK_SET;
fl->l_start = 0;
fl->l_len = 0;
}
int main(int argc, char **argv)
{
struct flock fl;
char *device_name;
int fd, c, f_opt = 0, do_rdwr = 0, end_immediately = 0;
int flags = O_NONBLOCK|O_LARGEFILE;
progname = argv[0];
/* ts A70417: added -w and -r */
while ((c = getopt (argc, argv, "feirw")) != EOF) {
switch (c) {
case 'e':
flags |= O_EXCL;
break;
case 'f':
f_opt++;
break;
case 'i':
end_immediately = 1;
break;
case 'r':
do_rdwr = 0;
break;
case 'w':
do_rdwr = 1;
break;
case '?':
usage();
exit(1);
}
}
if (optind == argc)
usage();
device_name = argv[optind++];
/* ts A70417 : made read-write adjustable independently of f_opt */
if (do_rdwr) {
flags |= O_RDWR;
printf("Using O_RDWR\n");
} else {
flags |= O_RDONLY;
printf("Using O_RDONLY\n");
}
if (flags & O_EXCL)
printf("Trying to open %s with O_EXCL ...\n", device_name);
fd = open(device_name, flags, 0);
if (fd < 0) {
perror("open");
printf("failed\n");
exit(1);
}
if (flags & O_EXCL)
printf("succeeded\n");
if (f_opt) {
init_flock(&fl, do_rdwr);
if (fcntl(fd, F_GETLK, &fl) < 0) {
perror("fcntl: F_GETLK: ");
exit(1);
}
printf("fcntl lock apparently %sLOCKED\n",
(fl.l_type == F_UNLCK) ? "NOT " : "");
/* ts A70418: do not try to lock if it is already locked */
if (fl.l_type != F_UNLCK) {
printf("failed\n");
exit(1);
}
init_flock(&fl, do_rdwr);
printf("Trying to grab fcntl lock...\n");
if (fcntl(fd, F_SETLKW, &fl) < 0) {
perror("fcntl: F_SETLKW: ");
exit(1);
}
printf("succeeded\n");
}
/* ts A70417: added end_immediately */
printf("Holding %s open.\n", device_name);
if (end_immediately)
exit(0);
printf("Press ^C to exit.\n");
while (1) {
sleep(300);
}
/* NOTREACHED */
return 0;
}