From 0961f7e1e300ef633b0c1ad95d0999fb5c169f4e Mon Sep 17 00:00:00 2001 From: Jeff Layton Date: Wed, 23 Jul 2014 14:21:05 -0400 Subject: 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. --- manual/examples/ofdlocks.c | 77 ++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 77 insertions(+) create mode 100644 manual/examples/ofdlocks.c (limited to 'manual/examples') 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 . +*/ + +#define _GNU_SOURCE +#include +#include +#include +#include +#include +#include + +#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; +} -- cgit v1.2.3