/* returns whether there were any poll events handled */
static dbus_bool_t
babysitter_iteration (DBusBabysitter *sitter,
dbus_bool_t block)
{
DBusPollFD fds[2];
int i;
dbus_bool_t descriptors_ready;
descriptors_ready = FALSE;
i = 0;
if (sitter->error_pipe_from_child >= 0)
{
fds[i].fd = sitter->error_pipe_from_child;
fds[i].events = _DBUS_POLLIN;
fds[i].revents = 0;
++i;
}
if (sitter->socket_to_babysitter >= 0)
{
fds[i].fd = sitter->socket_to_babysitter;
fds[i].events = _DBUS_POLLIN;
fds[i].revents = 0;
++i;
}
if (i > 0)
{
int ret;
ret = _dbus_poll (fds, i, 0);
if (ret == 0 && block)
ret = _dbus_poll (fds, i, -1);
if (ret > 0)
{
descriptors_ready = TRUE;
while (i > 0)
{
--i;
if (fds[i].fd == sitter->error_pipe_from_child)
handle_error_pipe (sitter, fds[i].revents);
else if (fds[i].fd == sitter->socket_to_babysitter)
handle_babysitter_socket (sitter, fds[i].revents);
}
}
}
return descriptors_ready;
}
static void
babysit (pid_t grandchild_pid,
int parent_pipe)
{
int sigchld_pipe[2];
/* We don't exec, so we keep parent state, such as the pid that
* _dbus_verbose() uses. Reset the pid here.
*/
_dbus_verbose_reset ();
/* I thought SIGCHLD would just wake up the poll, but
* that didn't seem to work, so added this pipe.
* Probably the pipe is more likely to work on busted
* operating systems anyhow.
*/
if (pipe (sigchld_pipe) < 0)
{
_dbus_warn ("Not enough file descriptors to create pipe in babysitter process\n");
exit (1);
}
babysit_sigchld_pipe = sigchld_pipe[WRITE_END];
#ifndef __SYMBIAN32__
_dbus_set_signal_handler (SIGCHLD, babysit_signal_handler);
#endif
write_pid (parent_pipe, grandchild_pid);
check_babysit_events (grandchild_pid, parent_pipe, 0);
while (TRUE)
{
DBusPollFD pfds[2];
pfds[0].fd = parent_pipe;
pfds[0].events = _DBUS_POLLIN;
pfds[0].revents = 0;
pfds[1].fd = sigchld_pipe[READ_END];
pfds[1].events = _DBUS_POLLIN;
pfds[1].revents = 0;
_dbus_poll (pfds, _DBUS_N_ELEMENTS (pfds), -1);
if (pfds[0].revents != 0)
{
check_babysit_events (grandchild_pid, parent_pipe, pfds[0].revents);
}
else if (pfds[1].revents & _DBUS_POLLIN)
{
char b;
read (sigchld_pipe[READ_END], &b, 1);
/* do waitpid check */
check_babysit_events (grandchild_pid, parent_pipe, 0);
}
}
exit (1);
}
/** This is basically Linux's epoll_wait(2) implemented in terms of poll(2);
* it returns results into a caller-supplied buffer so we can be reentrant. */
static int
socket_set_poll_poll (DBusSocketSet *set,
DBusSocketEvent *revents,
int max_events,
int timeout_ms)
{
DBusSocketSetPoll *self = socket_set_poll_cast (set);
int i;
int n_events;
int n_ready;
_dbus_assert (max_events > 0);
for (i = 0; i < self->n_fds; i++)
self->fds[i].revents = 0;
n_ready = _dbus_poll (self->fds, self->n_fds, timeout_ms);
if (n_ready <= 0)
return n_ready;
n_events = 0;
for (i = 0; i < self->n_fds; i++)
{
if (self->fds[i].revents != 0)
{
revents[n_events].fd = self->fds[i].fd;
revents[n_events].flags = watch_flags_from_poll_revents (self->fds[i].revents);
n_events += 1;
/* We ignore events beyond max_events because we have nowhere to
* put them. _dbus_poll is level-triggered, so we'll just be told
* about them next time round the main loop anyway. */
if (n_events == max_events)
return n_events;
}
}
return n_events;
}
/**
* @todo We need to have a way to wake up the select sleep if
* a new iteration request comes in with a flag (read/write) that
* we're not currently serving. Otherwise a call that just reads
* could block a write call forever (if there are no incoming
* messages).
*/
static void
socket_do_iteration (DBusTransport *transport,
unsigned int flags,
int timeout_milliseconds)
{
DBusTransportSocket *socket_transport = (DBusTransportSocket*) transport;
DBusPollFD poll_fd;
int poll_res;
int poll_timeout;
_dbus_verbose (" iteration flags = %s%s timeout = %d read_watch = %p write_watch = %p fd = %" DBUS_SOCKET_FORMAT "\n",
flags & DBUS_ITERATION_DO_READING ? "read" : "",
flags & DBUS_ITERATION_DO_WRITING ? "write" : "",
timeout_milliseconds,
socket_transport->read_watch,
socket_transport->write_watch,
_dbus_socket_printable (socket_transport->fd));
/* the passed in DO_READING/DO_WRITING flags indicate whether to
* read/write messages, but regardless of those we may need to block
* for reading/writing to do auth. But if we do reading for auth,
* we don't want to read any messages yet if not given DO_READING.
*/
poll_fd.fd = _dbus_socket_get_pollable (socket_transport->fd);
poll_fd.events = 0;
if (_dbus_transport_try_to_authenticate (transport))
{
/* This is kind of a hack; if we have stuff to write, then try
* to avoid the poll. This is probably about a 5% speedup on an
* echo client/server.
*
* If both reading and writing were requested, we want to avoid this
* since it could have funky effects:
* - both ends spinning waiting for the other one to read
* data so they can finish writing
* - prioritizing all writing ahead of reading
*/
if ((flags & DBUS_ITERATION_DO_WRITING) &&
!(flags & (DBUS_ITERATION_DO_READING | DBUS_ITERATION_BLOCK)) &&
!transport->disconnected &&
_dbus_connection_has_messages_to_send_unlocked (transport->connection))
{
do_writing (transport);
if (transport->disconnected ||
!_dbus_connection_has_messages_to_send_unlocked (transport->connection))
goto out;
}
/* If we get here, we decided to do the poll() after all */
_dbus_assert (socket_transport->read_watch);
if (flags & DBUS_ITERATION_DO_READING)
poll_fd.events |= _DBUS_POLLIN;
_dbus_assert (socket_transport->write_watch);
if (flags & DBUS_ITERATION_DO_WRITING)
poll_fd.events |= _DBUS_POLLOUT;
}
else
{
DBusAuthState auth_state;
auth_state = _dbus_auth_do_work (transport->auth);
if (transport->receive_credentials_pending ||
auth_state == DBUS_AUTH_STATE_WAITING_FOR_INPUT)
poll_fd.events |= _DBUS_POLLIN;
if (transport->send_credentials_pending ||
auth_state == DBUS_AUTH_STATE_HAVE_BYTES_TO_SEND)
poll_fd.events |= _DBUS_POLLOUT;
}
if (poll_fd.events)
{
int saved_errno;
if (flags & DBUS_ITERATION_BLOCK)
poll_timeout = timeout_milliseconds;
else
poll_timeout = 0;
/* For blocking selects we drop the connection lock here
* to avoid blocking out connection access during a potentially
* indefinite blocking call. The io path is still protected
* by the io_path_cond condvar, so we won't reenter this.
*/
if (flags & DBUS_ITERATION_BLOCK)
{
_dbus_verbose ("unlock pre poll\n");
_dbus_connection_unlock (transport->connection);
}
again:
poll_res = _dbus_poll (&poll_fd, 1, poll_timeout);
saved_errno = _dbus_save_socket_errno ();
if (poll_res < 0 && _dbus_get_is_errno_eintr (saved_errno))
goto again;
if (flags & DBUS_ITERATION_BLOCK)
{
_dbus_verbose ("lock post poll\n");
_dbus_connection_lock (transport->connection);
}
if (poll_res >= 0)
{
if (poll_res == 0)
poll_fd.revents = 0; /* some concern that posix does not guarantee this;
* valgrind flags it as an error. though it probably
* is guaranteed on linux at least.
*/
if (poll_fd.revents & _DBUS_POLLERR)
do_io_error (transport);
else
{
dbus_bool_t need_read = (poll_fd.revents & _DBUS_POLLIN) > 0;
dbus_bool_t need_write = (poll_fd.revents & _DBUS_POLLOUT) > 0;
dbus_bool_t authentication_completed;
_dbus_verbose ("in iteration, need_read=%d need_write=%d\n",
need_read, need_write);
do_authentication (transport, need_read, need_write,
&authentication_completed);
/* See comment in socket_handle_watch. */
if (authentication_completed)
goto out;
if (need_read && (flags & DBUS_ITERATION_DO_READING))
do_reading (transport);
if (need_write && (flags & DBUS_ITERATION_DO_WRITING))
do_writing (transport);
}
}
else
{
_dbus_verbose ("Error from _dbus_poll(): %s\n",
_dbus_strerror (saved_errno));
}
}
out:
/* We need to install the write watch only if we did not
* successfully write everything. Note we need to be careful that we
* don't call check_write_watch *before* do_writing, since it's
* inefficient to add the write watch, and we can avoid it most of
* the time since we can write immediately.
*
* However, we MUST always call check_write_watch(); DBusConnection code
* relies on the fact that running an iteration will notice that
* messages are pending.
*/
check_write_watch (transport);
_dbus_verbose (" ... leaving do_iteration()\n");
}
