1 /* vi: set sw=4 ts=4: */
2 /* Handle locking of password file.
3 Copyright (C) 1996,98,2000,02 Free Software Foundation, Inc.
4 This file is part of the GNU C Library.
5 Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
7 The GNU C Library is free software; you can redistribute it and/or
8 modify it under the terms of the GNU Lesser General Public
9 License as published by the Free Software Foundation; either
10 version 2.1 of the License, or (at your option) any later version.
12 The GNU C Library is distributed in the hope that it will be useful,
13 but WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 Lesser General Public License for more details.
17 You should have received a copy of the GNU Lesser General Public
18 License along with the GNU C Library; if not, write to the Free
19 Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
31 /* How long to wait for getting the lock before returning with an error. */
32 #define TIMEOUT 15 /* sec */
34 /* File descriptor for lock file. */
35 static int lock_fd = -1;
37 /* Prevent problems in multithreaded program by using mutex. */
38 #include <bits/uClibc_mutex.h>
39 __UCLIBC_MUTEX_STATIC(mylock, PTHREAD_MUTEX_INITIALIZER);
41 /* Prototypes for local functions. */
42 static void noop_handler (int __sig);
48 sigset_t saved_set; /* Saved set of caught signals. */
49 struct sigaction saved_act; /* Saved signal action. */
50 sigset_t new_set; /* New set of caught signals. */
51 struct sigaction new_act; /* New signal action. */
52 struct flock fl; /* Information struct for locking. */
57 /* Still locked by own process. */
60 /* Prevent problems caused by multiple threads. */
61 __UCLIBC_MUTEX_LOCK(mylock);
63 lock_fd = open (_PATH_PASSWD, O_WRONLY | O_CLOEXEC);
67 #ifndef __ASSUME_O_CLOEXEC
68 /* Make sure file gets correctly closed when process finished. */
69 fcntl (lock_fd, F_SETFD, FD_CLOEXEC);
72 /* Now we have to get exclusive write access. Since multiple
73 process could try this we won't stop when it first fails.
74 Instead we set a timeout for the system call. Once the timer
75 expires it is likely that there are some problems which cannot be
76 resolved by waiting. (sa_flags have no SA_RESTART. Thus SIGALRM
77 will EINTR fcntl(F_SETLKW)
79 It is important that we don't change the signal state. We must
80 restore the old signal behaviour. */
81 memset (&new_act, '\0', sizeof (new_act));
82 new_act.sa_handler = noop_handler;
83 __sigfillset (&new_act.sa_mask);
85 /* Install new action handler for alarm and save old.
86 * This never fails in Linux. */
87 sigaction (SIGALRM, &new_act, &saved_act);
89 /* Now make sure the alarm signal is not blocked. */
90 __sigemptyset (&new_set);
91 __sigaddset (&new_set, SIGALRM);
92 sigprocmask (SIG_UNBLOCK, &new_set, &saved_set);
94 /* Start timer. If we cannot get the lock in the specified time we
98 /* Try to get the lock. */
99 memset (&fl, '\0', sizeof (fl));
103 fl.l_whence = SEEK_SET;
104 result = fcntl (lock_fd, F_SETLKW, &fl);
109 sigprocmask (SIG_SETMASK, &saved_set, NULL);
110 sigaction (SIGALRM, &saved_act, NULL);
120 __UCLIBC_MUTEX_UNLOCK(mylock);
131 /* There is no lock set. */
135 /* Prevent problems caused by multiple threads. */
136 __UCLIBC_MUTEX_LOCK(mylock);
138 result = close (lock_fd);
140 /* Mark descriptor as unused. */
144 __UCLIBC_MUTEX_UNLOCK(mylock);
152 noop_handler (int sig attribute_unused) {
154 /* We simply return which makes the `fcntl' call return with an error. */