diff options
author | Jeff Layton <jlayton@poochiereds.net> | 2014-07-23 14:21:05 -0400 |
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committer | Carlos O'Donell <carlos@redhat.com> | 2014-07-29 23:27:21 -0400 |
commit | 0961f7e1e300ef633b0c1ad95d0999fb5c169f4e (patch) | |
tree | 08b1ae51840c0b69a0c4bf9f98b8a71b919d2fa0 /manual/examples | |
parent | cc5fb300fce0c7ce1923d6f5c776fa83be47d55e (diff) |
fcntl-linux.h: add new definitions and manual updates for open file description locks
Open file description locks have been merged into the Linux kernel for
v3.15. Add the appropriate command-value definitions and an update to
the manual that describes their usage.
Diffstat (limited to 'manual/examples')
-rw-r--r-- | manual/examples/ofdlocks.c | 77 |
1 files changed, 77 insertions, 0 deletions
diff --git a/manual/examples/ofdlocks.c b/manual/examples/ofdlocks.c new file mode 100644 index 0000000000..85e193cdab --- /dev/null +++ b/manual/examples/ofdlocks.c @@ -0,0 +1,77 @@ +/* Open File Description Locks Usage Example + Copyright (C) 1991-2014 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 <http://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; +} |