diff options
Diffstat (limited to 'sysdeps')
| -rw-r--r-- | sysdeps/generic/utmp_file.c | 107 |
1 files changed, 53 insertions, 54 deletions
diff --git a/sysdeps/generic/utmp_file.c b/sysdeps/generic/utmp_file.c index 08675185ce..1f7abb088b 100644 --- a/sysdeps/generic/utmp_file.c +++ b/sysdeps/generic/utmp_file.c @@ -21,6 +21,7 @@ #include <assert.h> #include <errno.h> #include <fcntl.h> +#include <signal.h> #include <stdio.h> #include <string.h> #include <unistd.h> @@ -37,6 +38,48 @@ static off_t file_offset; static struct utmp last_entry; +/* Locking timeout. */ +#ifndef TIMEOUT +# define TIMEOUT 1 +#endif + +/* Do-nothing handler for locking timeout. */ +static void timeout_handler (int signum) {}; + +#define LOCK_FILE(fd, type) \ +{ \ + struct flock fl; \ + struct sigaction action, old_action; \ + unsigned int old_timeout; \ + \ + /* Cancel any existing alarm. */ \ + old_timeout = alarm (0); \ + \ + /* Establish signal handler. */ \ + action.sa_handler = timeout_handler; \ + sigemptyset (&action.sa_mask); \ + action.sa_flags = 0; \ + sigaction (SIGALRM, &action, &old_action); \ + \ + alarm (TIMEOUT); \ + \ + /* Try to get the lock. */ \ + memset (&fl, '\0', sizeof (struct flock)); \ + fl.l_type = (type); \ + fl.l_whence = SEEK_SET; \ + fcntl ((fd), F_SETLKW, &fl) + +#define UNLOCK_FILE(fd) \ + /* Unlock the file. */ \ + fl.l_type = F_UNLCK; \ + fcntl ((fd), F_SETLKW, &fl); \ + \ + /* Reset the signal handler and alarm. */ \ + sigaction (SIGALRM, &old_action, NULL); \ + alarm (old_timeout); \ +} while (0) + + /* Functions defined here. */ static int setutent_file (void); static int getutent_r_file (struct utmp *buffer, struct utmp **result); @@ -100,7 +143,6 @@ static int getutent_r_file (struct utmp *buffer, struct utmp **result) { ssize_t nbytes; - struct flock fl; /* Information struct for locking. */ assert (file_fd >= 0); @@ -111,26 +153,12 @@ 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. */ - /* XXX I think using an extra locking file does not solve the - problems. Instead we should set an alarm, which causes fcntl to - fail, as in ../nis/lckcache.c. - Mark Kettenis <kettenis@phys.uva.nl>. */ - - /* Try to get the lock. */ - memset (&fl, '\0', sizeof (struct flock)); - fl.l_type = F_RDLCK; - fl.l_whence = SEEK_SET; - fcntl (file_fd, F_SETLK, &fl); + LOCK_FILE (file_fd, F_RDLCK); /* Read the next entry. */ nbytes = read (file_fd, &last_entry, sizeof (struct utmp)); - /* And unlock the file. */ - fl.l_type = F_UNLCK; - fcntl (file_fd, F_SETLKW, &fl); + UNLOCK_FILE (file_fd); if (nbytes != sizeof (struct utmp)) { @@ -180,13 +208,8 @@ static int internal_getut_r (const struct utmp *id, struct utmp *buffer) { int result = -1; - struct flock fl; - /* Try to get the lock. */ - memset (&fl, '\0', sizeof (struct flock)); - fl.l_type = F_RDLCK; - fl.l_whence = SEEK_SET; - fcntl (file_fd, F_SETLKW, &fl); + LOCK_FILE (file_fd, F_RDLCK); #if _HAVE_UT_TYPE - 0 if (id->ut_type == RUN_LVL || id->ut_type == BOOT_TIME @@ -237,9 +260,7 @@ internal_getut_r (const struct utmp *id, struct utmp *buffer) result = 0; unlock_return: - /* And unlock the file. */ - fl.l_type = F_UNLCK; - fcntl (file_fd, F_SETLK, &fl); + UNLOCK_FILE (file_fd); return result; } @@ -278,8 +299,6 @@ static int getutline_r_file (const struct utmp *line, struct utmp *buffer, struct utmp **result) { - struct flock fl; - assert (file_fd >= 0); if (file_offset == -1l) @@ -288,11 +307,7 @@ getutline_r_file (const struct utmp *line, struct utmp *buffer, return -1; } - /* Try to get the lock. */ - memset (&fl, '\0', sizeof (struct flock)); - fl.l_type = F_RDLCK; - fl.l_whence = SEEK_SET; - fcntl (file_fd, F_SETLKW, &fl); + LOCK_FILE (file_fd, F_RDLCK); while (1) { @@ -322,9 +337,7 @@ getutline_r_file (const struct utmp *line, struct utmp *buffer, *result = buffer; unlock_return: - /* And unlock the file. */ - fl.l_type = F_UNLCK; - fcntl (file_fd, F_SETLK, &fl); + UNLOCK_FILE (file_fd); return ((*result == NULL) ? -1 : 0); } @@ -333,7 +346,6 @@ unlock_return: static struct utmp * pututline_file (const struct utmp *data) { - struct flock fl; /* Information struct for locking. */ struct utmp buffer; struct utmp *pbuf; int found; @@ -356,11 +368,7 @@ pututline_file (const struct utmp *data) else found = internal_getut_r (data, &buffer); - /* Try to lock the file. */ - memset (&fl, '\0', sizeof (struct flock)); - fl.l_type = F_WRLCK; - fl.l_whence = SEEK_SET; - fcntl (file_fd, F_SETLK, &fl); + LOCK_FILE (file_fd, F_WRLCK); if (found < 0) { @@ -401,9 +409,7 @@ pututline_file (const struct utmp *data) } unlock_return: - /* And unlock the file. */ - fl.l_type = F_UNLCK; - fcntl (file_fd, F_SETLK, &fl); + UNLOCK_FILE (file_fd); return pbuf; } @@ -423,7 +429,6 @@ static int updwtmp_file (const char *file, const struct utmp *utmp) { int result = -1; - struct flock fl; off_t offset; int fd; @@ -432,11 +437,7 @@ updwtmp_file (const char *file, const struct utmp *utmp) if (fd < 0) return -1; - /* Try to get the lock. */ - memset (&fl, '\0', sizeof (struct flock)); - fl.l_type = F_WRLCK; - fl.l_whence = SEEK_SET; - fcntl (fd, F_SETLK, &fl); + LOCK_FILE (fd, F_WRLCK); /* Remember original size of log file. */ offset = lseek (fd, 0, SEEK_END); @@ -461,9 +462,7 @@ updwtmp_file (const char *file, const struct utmp *utmp) result = 0; unlock_return: - /* And unlock the file. */ - fl.l_type = F_UNLCK; - fcntl (fd, F_SETLKW, &fl); + UNLOCK_FILE (fd); /* Close WTMP file. */ close (fd); |