diff options
Diffstat (limited to 'login/utmp_file.c')
| -rw-r--r-- | login/utmp_file.c | 19 |
1 files changed, 17 insertions, 2 deletions
diff --git a/login/utmp_file.c b/login/utmp_file.c index 2bb6c926f9..c728d9a1f2 100644 --- a/login/utmp_file.c +++ b/login/utmp_file.c @@ -92,6 +92,8 @@ setutent_file (int reset) } else if (reset) { + lseek (file_fd, 0, SEEK_SET); + /* Remember we are at beginning of file. */ file_offset = 0; @@ -117,6 +119,7 @@ static int getutent_r_file (struct utmp *buffer, struct utmp **result) { int nbytes; + struct flock fl; /* Information struct for locking. */ /* Open utmp file if not already done. */ if (file_fd == INT_MIN) @@ -129,10 +132,22 @@ getutent_r_file (struct utmp *buffer, struct utmp **result) return -1; } + /* XXX The following is not perfect. Instead of locking the file itself + Marek Michalkiewicz <marekm@i17linuxb.ists.pwr.wroc.pl> suggests to + use an extra locking file. */ + + /* Try to get the lock. */ + memset (&fl, '\0', sizeof (struct flock)); + fl.l_type = F_WRLCK; + fl.l_whence = SEEK_SET; + result = fcntl (file_fd, F_SETLKW, &fl); + /* Read the next entry. */ - flock (file_fd, LOCK_SH); nbytes = read (file_fd, &last_entry, sizeof (struct utmp)); - flock (file_fd, LOCK_UN); + + /* And unlock the file. */ + fl.l_type = F_UNLCK; + result = fcntl (file_fd, F_SETLKW, &fl); if (nbytes != sizeof (struct utmp)) { |