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authorJeff Layton <jlayton@poochiereds.net>2014-07-23 14:21:05 -0400
committerCarlos O'Donell <carlos@redhat.com>2014-07-29 23:27:21 -0400
commit0961f7e1e300ef633b0c1ad95d0999fb5c169f4e (patch)
tree08b1ae51840c0b69a0c4bf9f98b8a71b919d2fa0 /manual/examples
parentcc5fb300fce0c7ce1923d6f5c776fa83be47d55e (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.c77
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;
+}