mirror of
git://sourceware.org/git/glibc.git
synced 2024-12-09 04:11:27 +08:00
78 lines
1.8 KiB
C
78 lines
1.8 KiB
C
/* Open File Description Locks Usage Example
|
|
Copyright (C) 1991-2023 Free Software Foundation, Inc.
|
|
|
|
This program is free software; you can redistribute it and/or
|
|
modify it under the terms of the GNU General Public License
|
|
as published by the Free Software Foundation; either version 2
|
|
of the License, or (at your option) any later version.
|
|
|
|
This program is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
GNU General Public License for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with this program; if not, see <https://www.gnu.org/licenses/>.
|
|
*/
|
|
|
|
#define _GNU_SOURCE
|
|
#include <stdio.h>
|
|
#include <sys/types.h>
|
|
#include <sys/stat.h>
|
|
#include <unistd.h>
|
|
#include <fcntl.h>
|
|
#include <pthread.h>
|
|
|
|
#define FILENAME "/tmp/foo"
|
|
#define NUM_THREADS 3
|
|
#define ITERATIONS 5
|
|
|
|
void *
|
|
thread_start (void *arg)
|
|
{
|
|
int i, fd, len;
|
|
long tid = (long) arg;
|
|
char buf[256];
|
|
struct flock lck = {
|
|
.l_whence = SEEK_SET,
|
|
.l_start = 0,
|
|
.l_len = 1,
|
|
};
|
|
|
|
fd = open ("/tmp/foo", O_RDWR | O_CREAT, 0666);
|
|
|
|
for (i = 0; i < ITERATIONS; i++)
|
|
{
|
|
lck.l_type = F_WRLCK;
|
|
fcntl (fd, F_OFD_SETLKW, &lck);
|
|
|
|
len = sprintf (buf, "%d: tid=%ld fd=%d\n", i, tid, fd);
|
|
|
|
lseek (fd, 0, SEEK_END);
|
|
write (fd, buf, len);
|
|
fsync (fd);
|
|
|
|
lck.l_type = F_UNLCK;
|
|
fcntl (fd, F_OFD_SETLK, &lck);
|
|
|
|
/* sleep to ensure lock is yielded to another thread */
|
|
usleep (1);
|
|
}
|
|
pthread_exit (NULL);
|
|
}
|
|
|
|
int
|
|
main (int argc, char **argv)
|
|
{
|
|
long i;
|
|
pthread_t threads[NUM_THREADS];
|
|
|
|
truncate (FILENAME, 0);
|
|
|
|
for (i = 0; i < NUM_THREADS; i++)
|
|
pthread_create (&threads[i], NULL, thread_start, (void *) i);
|
|
|
|
pthread_exit (NULL);
|
|
return 0;
|
|
}
|