/****************
* Do a lock on H. A TIMEOUT of 0 returns immediately,
* -1 waits forever (hopefully not), other
* values are timeouts in milliseconds.
* Returns: 0 on success
*/
int
make_dotlock( DOTLOCK h, long timeout )
{
#if defined (HAVE_DOSISH_SYSTEM)
return 0;
#else
int pid;
const char *maybe_dead="";
int backoff=0;
if( h->disable ) {
return 0;
}
if( h->locked ) {
#ifndef __riscos__
log_debug("oops, `%s' is already locked\n", h->lockname );
#endif /* !__riscos__ */
return 0;
}
for(;;) {
#ifndef __riscos__
if( !link(h->tname, h->lockname) ) {
/* fixme: better use stat to check the link count */
h->locked = 1;
return 0; /* okay */
}
if( errno != EEXIST ) {
log_error( "lock not made: link() failed: %s\n", strerror(errno) );
return -1;
}
#else /* __riscos__ */
if( !renamefile(h->tname, h->lockname) ) {
h->locked = 1;
return 0; /* okay */
}
if( errno != EEXIST ) {
log_error( "lock not made: rename() failed: %s\n", strerror(errno) );
return -1;
}
#endif /* __riscos__ */
if( (pid = read_lockfile(h->lockname)) == -1 ) {
if( errno != ENOENT ) {
log_info("cannot read lockfile\n");
return -1;
}
log_info( "lockfile disappeared\n");
continue;
}
else if( pid == getpid() ) {
log_info( "Oops: lock already held by us\n");
h->locked = 1;
return 0; /* okay */
}
else if( kill(pid, 0) && errno == ESRCH ) {
#ifndef __riscos__
maybe_dead = " - probably dead";
#if 0 /* we should not do this without checking the permissions */
/* and the hostname */
log_info( "removing stale lockfile (created by %d)", pid );
#endif
#else /* __riscos__ */
/* we are *pretty* sure that the other task is dead and therefore
we remove the other lock file */
maybe_dead = " - probably dead - removing lock";
unlink(h->lockname);
#endif /* __riscos__ */
}
if( timeout == -1 ) {
struct timeval tv;
log_info( "waiting for lock (held by %d%s) %s...\n",
pid, maybe_dead, maybe_deadlock(h)? "(deadlock?) ":"");
/* can't use sleep, cause signals may be blocked */
tv.tv_sec = 1 + backoff;
tv.tv_usec = 0;
select(0, NULL, NULL, NULL, &tv);
if( backoff < 10 )
backoff++ ;
}
else
return -1;
}
/*not reached */
#endif
}
/* Unix specific code of make_dotlock. Returns 0 on success and -1 on
error. */
static int
dotlock_take_unix (dotlock_t h, long timeout)
{
int wtime = 0;
int sumtime = 0;
int pid;
int lastpid = -1;
int ownerchanged;
const char *maybe_dead="";
int same_node;
again:
if (h->use_o_excl)
{
/* No hardlink support - use open(O_EXCL). */
int fd;
do
{
jnlib_set_errno (0);
fd = open (h->lockname, O_WRONLY|O_CREAT|O_EXCL,
S_IRUSR|S_IRGRP|S_IROTH|S_IWUSR );
}
while (fd == -1 && errno == EINTR);
if (fd == -1 && errno == EEXIST)
; /* Lock held by another process. */
else if (fd == -1)
{
my_error_2 ("lock not made: open(O_EXCL) of `%s' failed: %s\n",
h->lockname, strerror (errno));
return -1;
}
else
{
char pidstr[16];
snprintf (pidstr, sizeof pidstr, "%10d\n", (int)getpid());
if (write (fd, pidstr, 11 ) == 11
&& write (fd, h->tname + h->nodename_off,h->nodename_len)
== h->nodename_len
&& write (fd, "\n", 1) == 1
&& !close (fd))
{
h->locked = 1;
return 0;
}
/* Write error. */
my_error_2 ("lock not made: writing to `%s' failed: %s\n",
h->lockname, strerror (errno));
close (fd);
unlink (h->lockname);
return -1;
}
}
else /* Standard method: Use hardlinks. */
{
struct stat sb;
link (h->tname, h->lockname);
if (stat (h->tname, &sb))
{
my_error_1 ("lock not made: Oops: stat of tmp file failed: %s\n",
strerror (errno));
/* In theory this might be a severe error: It is possible
that link succeeded but stat failed due to changed
permissions. We can't do anything about it, though. */
return -1;
}
if (sb.st_nlink == 2)
{
h->locked = 1;
return 0; /* Okay. */
}
}
/* Check for stale lock files. */
if ( (pid = read_lockfile (h, &same_node)) == -1 )
{
if ( errno != ENOENT )
{
my_info_0 ("cannot read lockfile\n");
return -1;
}
my_info_0 ("lockfile disappeared\n");
goto again;
}
else if ( pid == getpid() && same_node )
{
my_info_0 ("Oops: lock already held by us\n");
h->locked = 1;
return 0; /* okay */
}
else if ( same_node && kill (pid, 0) && errno == ESRCH )
{
/* Note: It is unlikley that we get a race here unless a pid is
reused too fast or a new process with the same pid as the one
of the stale file tries to lock right at the same time as we. */
my_info_1 (_("removing stale lockfile (created by %d)\n"), pid);
unlink (h->lockname);
goto again;
}
if (lastpid == -1)
lastpid = pid;
ownerchanged = (pid != lastpid);
if (timeout)
{
struct timeval tv;
/* Wait until lock has been released. We use increasing retry
intervals of 50ms, 100ms, 200ms, 400ms, 800ms, 2s, 4s and 8s
but reset it if the lock owner meanwhile changed. */
if (!wtime || ownerchanged)
wtime = 50;
else if (wtime < 800)
wtime *= 2;
else if (wtime == 800)
wtime = 2000;
else if (wtime < 8000)
wtime *= 2;
if (timeout > 0)
{
if (wtime > timeout)
wtime = timeout;
timeout -= wtime;
}
sumtime += wtime;
if (sumtime >= 1500)
{
sumtime = 0;
my_info_3 (_("waiting for lock (held by %d%s) %s...\n"),
pid, maybe_dead, maybe_deadlock(h)? _("(deadlock?) "):"");
}
tv.tv_sec = wtime / 1000;
tv.tv_usec = (wtime % 1000) * 1000;
select (0, NULL, NULL, NULL, &tv);
goto again;
}
jnlib_set_errno (EACCES);
return -1;
}
