dbus-mainloop.c
/* -*- mode: C; c-file-style: "gnu"; indent-tabs-mode: nil; -*- */
/* dbus-mainloop.c Main loop utility
*
* Copyright © 2003, 2004 Red Hat, Inc.
* Copyright © 2011 Nokia Corporation
*
* Licensed under the Academic Free License version 2.1
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*
*/
#include <config.h>
#include "dbus-mainloop.h"
#ifndef DOXYGEN_SHOULD_SKIP_THIS
#include <dbus/dbus-hash.h>
#include <dbus/dbus-list.h>
#include <dbus/dbus-socket-set.h>
#include <dbus/dbus-watch.h>
#define MAINLOOP_SPEW 0
#if MAINLOOP_SPEW
#ifdef DBUS_ENABLE_VERBOSE_MODE
static const char*
watch_flags_to_string (int flags)
{
const char *watch_type;
if ((flags & DBUS_WATCH_READABLE) &&
(flags & DBUS_WATCH_WRITABLE))
watch_type = "readwrite";
else if (flags & DBUS_WATCH_READABLE)
watch_type = "read";
else if (flags & DBUS_WATCH_WRITABLE)
watch_type = "write";
else
watch_type = "not read or write";
return watch_type;
}
#endif /* DBUS_ENABLE_VERBOSE_MODE */
#endif /* MAINLOOP_SPEW */
struct DBusLoop
{
int refcount;
DBusHashTable *watches;
DBusSocketSet *socket_set;
DBusList *timeouts;
int callback_list_serial;
int watch_count;
int timeout_count;
int depth;
DBusList *need_dispatch;
unsigned oom_watch_pending : 1;
};
typedef struct
{
DBusTimeout *timeout;
unsigned long last_tv_sec;
unsigned long last_tv_usec;
} TimeoutCallback;
#define TIMEOUT_CALLBACK(callback) ((TimeoutCallback*)callback)
static TimeoutCallback*
timeout_callback_new (DBusTimeout *timeout)
{
TimeoutCallback *cb;
cb = dbus_new (TimeoutCallback, 1);
if (cb == NULL)
return NULL;
cb->timeout = timeout;
_dbus_get_monotonic_time (&cb->last_tv_sec,
&cb->last_tv_usec);
return cb;
}
static void
timeout_callback_free (TimeoutCallback *cb)
{
dbus_free (cb);
}
static void
free_watch_table_entry (void *data)
{
DBusList **watches = data;
DBusWatch *watch;
/* DBusHashTable sometimes calls free_function(NULL) even if you never
* have NULL as a value */
if (watches == NULL)
return;
for (watch = _dbus_list_pop_first (watches);
watch != NULL;
watch = _dbus_list_pop_first (watches))
{
_dbus_watch_unref (watch);
}
_dbus_assert (*watches == NULL);
dbus_free (watches);
}
DBusLoop*
_dbus_loop_new (void)
{
DBusLoop *loop;
loop = dbus_new0 (DBusLoop, 1);
if (loop == NULL)
return NULL;
loop->watches = _dbus_hash_table_new (DBUS_HASH_INT, NULL,
free_watch_table_entry);
loop->socket_set = _dbus_socket_set_new (0);
if (loop->watches == NULL || loop->socket_set == NULL)
{
if (loop->watches != NULL)
_dbus_hash_table_unref (loop->watches);
if (loop->socket_set != NULL)
_dbus_socket_set_free (loop->socket_set);
dbus_free (loop);
return NULL;
}
loop->refcount = 1;
return loop;
}
DBusLoop *
_dbus_loop_ref (DBusLoop *loop)
{
_dbus_assert (loop != NULL);
_dbus_assert (loop->refcount > 0);
loop->refcount += 1;
return loop;
}
void
_dbus_loop_unref (DBusLoop *loop)
{
_dbus_assert (loop != NULL);
_dbus_assert (loop->refcount > 0);
loop->refcount -= 1;
if (loop->refcount == 0)
{
while (loop->need_dispatch)
{
DBusConnection *connection = _dbus_list_pop_first (&loop->need_dispatch);
dbus_connection_unref (connection);
}
_dbus_hash_table_unref (loop->watches);
_dbus_socket_set_free (loop->socket_set);
dbus_free (loop);
}
}
static DBusList **
ensure_watch_table_entry (DBusLoop *loop,
int fd)
{
DBusList **watches;
watches = _dbus_hash_table_lookup_int (loop->watches, fd);
if (watches == NULL)
{
watches = dbus_new0 (DBusList *, 1);
if (watches == NULL)
return watches;
if (!_dbus_hash_table_insert_int (loop->watches, fd, watches))
{
dbus_free (watches);
watches = NULL;
}
}
return watches;
}
static void
cull_watches_for_invalid_fd (DBusLoop *loop,
int fd)
{
DBusList *link;
DBusList **watches;
_dbus_warn ("invalid request, socket fd %d not open\n", fd);
watches = _dbus_hash_table_lookup_int (loop->watches, fd);
if (watches != NULL)
{
for (link = _dbus_list_get_first_link (watches);
link != NULL;
link = _dbus_list_get_next_link (watches, link))
_dbus_watch_invalidate (link->data);
}
_dbus_hash_table_remove_int (loop->watches, fd);
}
static dbus_bool_t
gc_watch_table_entry (DBusLoop *loop,
DBusList **watches,
int fd)
{
/* If watches is already NULL we have nothing to do */
if (watches == NULL)
return FALSE;
/* We can't GC hash table entries if they're non-empty lists */
if (*watches != NULL)
return FALSE;
_dbus_hash_table_remove_int (loop->watches, fd);
return TRUE;
}
static void
refresh_watches_for_fd (DBusLoop *loop,
DBusList **watches,
int fd)
{
DBusList *link;
unsigned int flags = 0;
dbus_bool_t interested = FALSE;
_dbus_assert (fd != -1);
if (watches == NULL)
watches = _dbus_hash_table_lookup_int (loop->watches, fd);
/* we allocated this in the first _dbus_loop_add_watch for the fd, and keep
* it until there are none left */
_dbus_assert (watches != NULL);
for (link = _dbus_list_get_first_link (watches);
link != NULL;
link = _dbus_list_get_next_link (watches, link))
{
if (dbus_watch_get_enabled (link->data) &&
!_dbus_watch_get_oom_last_time (link->data))
{
flags |= dbus_watch_get_flags (link->data);
interested = TRUE;
}
}
if (interested)
_dbus_socket_set_enable (loop->socket_set, fd, flags);
else
_dbus_socket_set_disable (loop->socket_set, fd);
}
dbus_bool_t
_dbus_loop_add_watch (DBusLoop *loop,
DBusWatch *watch)
{
int fd;
DBusList **watches;
fd = dbus_watch_get_socket (watch);
_dbus_assert (fd != -1);
watches = ensure_watch_table_entry (loop, fd);
if (watches == NULL)
return FALSE;
if (!_dbus_list_append (watches, _dbus_watch_ref (watch)))
{
_dbus_watch_unref (watch);
gc_watch_table_entry (loop, watches, fd);
return FALSE;
}
if (_dbus_list_length_is_one (watches))
{
if (!_dbus_socket_set_add (loop->socket_set, fd,
dbus_watch_get_flags (watch),
dbus_watch_get_enabled (watch)))
{
_dbus_hash_table_remove_int (loop->watches, fd);
return FALSE;
}
}
else
{
/* we're modifying, not adding, which can't fail with OOM */
refresh_watches_for_fd (loop, watches, fd);
}
loop->callback_list_serial += 1;
loop->watch_count += 1;
return TRUE;
}
void
_dbus_loop_toggle_watch (DBusLoop *loop,
DBusWatch *watch)
{
refresh_watches_for_fd (loop, NULL, dbus_watch_get_socket (watch));
}
void
_dbus_loop_remove_watch (DBusLoop *loop,
DBusWatch *watch)
{
DBusList **watches;
DBusList *link;
int fd;
/* This relies on people removing watches before they invalidate them,
* which has been safe since fd.o #33336 was fixed. Assert about it
* so we don't regress. */
fd = dbus_watch_get_socket (watch);
_dbus_assert (fd != -1);
watches = _dbus_hash_table_lookup_int (loop->watches, fd);
if (watches != NULL)
{
link = _dbus_list_get_first_link (watches);
while (link != NULL)
{
DBusList *next = _dbus_list_get_next_link (watches, link);
DBusWatch *this = link->data;
if (this == watch)
{
_dbus_list_remove_link (watches, link);
loop->callback_list_serial += 1;
loop->watch_count -= 1;
_dbus_watch_unref (this);
/* if that was the last watch for that fd, drop the hash table
* entry, and stop reserving space for it in the socket set */
if (gc_watch_table_entry (loop, watches, fd))
{
_dbus_socket_set_remove (loop->socket_set, fd);
}
return;
}
link = next;
}
}
_dbus_warn ("could not find watch %p to remove\n", watch);
}
dbus_bool_t
_dbus_loop_add_timeout (DBusLoop *loop,
DBusTimeout *timeout)
{
TimeoutCallback *tcb;
tcb = timeout_callback_new (timeout);
if (tcb == NULL)
return FALSE;
if (_dbus_list_append (&loop->timeouts, tcb))
{
loop->callback_list_serial += 1;
loop->timeout_count += 1;
}
else
{
timeout_callback_free (tcb);
return FALSE;
}
return TRUE;
}
void
_dbus_loop_remove_timeout (DBusLoop *loop,
DBusTimeout *timeout)
{
DBusList *link;
link = _dbus_list_get_first_link (&loop->timeouts);
while (link != NULL)
{
DBusList *next = _dbus_list_get_next_link (&loop->timeouts, link);
TimeoutCallback *this = link->data;
if (this->timeout == timeout)
{
_dbus_list_remove_link (&loop->timeouts, link);
loop->callback_list_serial += 1;
loop->timeout_count -= 1;
timeout_callback_free (this);
return;
}
link = next;
}
_dbus_warn ("could not find timeout %p to remove\n", timeout);
}
/* Convolutions from GLib, there really must be a better way
* to do this.
*/
static dbus_bool_t
check_timeout (unsigned long tv_sec,
unsigned long tv_usec,
TimeoutCallback *tcb,
int *timeout)
{
long sec_remaining;
long msec_remaining;
unsigned long expiration_tv_sec;
unsigned long expiration_tv_usec;
long interval_seconds;
long interval_milliseconds;
int interval;
/* I'm pretty sure this function could suck (a lot) less */
interval = dbus_timeout_get_interval (tcb->timeout);
interval_seconds = interval / 1000L;
interval_milliseconds = interval % 1000L;
expiration_tv_sec = tcb->last_tv_sec + interval_seconds;
expiration_tv_usec = tcb->last_tv_usec + interval_milliseconds * 1000;
if (expiration_tv_usec >= 1000000)
{
expiration_tv_usec -= 1000000;
expiration_tv_sec += 1;
}
sec_remaining = expiration_tv_sec - tv_sec;
/* need to force this to be signed, as it is intended to sometimes
* produce a negative result
*/
msec_remaining = ((long) expiration_tv_usec - (long) tv_usec) / 1000L;
#if MAINLOOP_SPEW
_dbus_verbose ("Interval is %ld seconds %ld msecs\n",
interval_seconds,
interval_milliseconds);
_dbus_verbose ("Now is %lu seconds %lu usecs\n",
tv_sec, tv_usec);
_dbus_verbose ("Last is %lu seconds %lu usecs\n",
tcb->last_tv_sec, tcb->last_tv_usec);
_dbus_verbose ("Exp is %lu seconds %lu usecs\n",
expiration_tv_sec, expiration_tv_usec);
_dbus_verbose ("Pre-correction, sec_remaining %ld msec_remaining %ld\n",
sec_remaining, msec_remaining);
#endif
/* We do the following in a rather convoluted fashion to deal with
* the fact that we don't have an integral type big enough to hold
* the difference of two timevals in milliseconds.
*/
if (sec_remaining < 0 || (sec_remaining == 0 && msec_remaining < 0))
{
*timeout = 0;
}
else
{
if (msec_remaining < 0)
{
msec_remaining += 1000;
sec_remaining -= 1;
}
if (sec_remaining > (_DBUS_INT_MAX / 1000) ||
msec_remaining > _DBUS_INT_MAX)
*timeout = _DBUS_INT_MAX;
else
*timeout = sec_remaining * 1000 + msec_remaining;
}
if (*timeout > interval)
{
/* This indicates that the system clock probably moved backward */
_dbus_verbose ("System clock set backward! Resetting timeout.\n");
tcb->last_tv_sec = tv_sec;
tcb->last_tv_usec = tv_usec;
*timeout = interval;
}
#if MAINLOOP_SPEW
_dbus_verbose (" timeout expires in %d milliseconds\n", *timeout);
#endif
return *timeout == 0;
}
dbus_bool_t
_dbus_loop_dispatch (DBusLoop *loop)
{
#if MAINLOOP_SPEW
_dbus_verbose (" %d connections to dispatch\n", _dbus_list_get_length (&loop->need_dispatch));
#endif
if (loop->need_dispatch == NULL)
return FALSE;
next:
while (loop->need_dispatch != NULL)
{
DBusConnection *connection = _dbus_list_pop_first (&loop->need_dispatch);
while (TRUE)
{
DBusDispatchStatus status;
status = dbus_connection_dispatch (connection);
if (status == DBUS_DISPATCH_COMPLETE)
{
dbus_connection_unref (connection);
goto next;
}
else
{
if (status == DBUS_DISPATCH_NEED_MEMORY)
_dbus_wait_for_memory ();
}
}
}
return TRUE;
}
dbus_bool_t
_dbus_loop_queue_dispatch (DBusLoop *loop,
DBusConnection *connection)
{
if (_dbus_list_append (&loop->need_dispatch, connection))
{
dbus_connection_ref (connection);
return TRUE;
}
else
return FALSE;
}
/* Returns TRUE if we invoked any timeouts or have ready file
* descriptors, which is just used in test code as a debug hack
*/
dbus_bool_t
_dbus_loop_iterate (DBusLoop *loop,
dbus_bool_t block)
{
#define N_STACK_DESCRIPTORS 64
dbus_bool_t retval;
DBusSocketEvent ready_fds[N_STACK_DESCRIPTORS];
int i;
DBusList *link;
int n_ready;
int initial_serial;
long timeout;
int orig_depth;
retval = FALSE;
orig_depth = loop->depth;
#if MAINLOOP_SPEW
_dbus_verbose ("Iteration block=%d depth=%d timeout_count=%d watch_count=%d\n",
block, loop->depth, loop->timeout_count, loop->watch_count);
#endif
if (_dbus_hash_table_get_n_entries (loop->watches) == 0 &&
loop->timeouts == NULL)
goto next_iteration;
timeout = -1;
if (loop->timeout_count > 0)
{
unsigned long tv_sec;
unsigned long tv_usec;
_dbus_get_monotonic_time (&tv_sec, &tv_usec);
link = _dbus_list_get_first_link (&loop->timeouts);
while (link != NULL)
{
DBusList *next = _dbus_list_get_next_link (&loop->timeouts, link);
TimeoutCallback *tcb = link->data;
if (dbus_timeout_get_enabled (tcb->timeout))
{
int msecs_remaining;
check_timeout (tv_sec, tv_usec, tcb, &msecs_remaining);
if (timeout < 0)
timeout = msecs_remaining;
else
timeout = MIN (msecs_remaining, timeout);
#if MAINLOOP_SPEW
_dbus_verbose (" timeout added, %d remaining, aggregate timeout %ld\n",
msecs_remaining, timeout);
#endif
_dbus_assert (timeout >= 0);
if (timeout == 0)
break; /* it's not going to get shorter... */
}
#if MAINLOOP_SPEW
else
{
_dbus_verbose (" skipping disabled timeout\n");
}
#endif
link = next;
}
}
/* Never block if we have stuff to dispatch */
if (!block || loop->need_dispatch != NULL)
{
timeout = 0;
#if MAINLOOP_SPEW
_dbus_verbose (" timeout is 0 as we aren't blocking\n");
#endif
}
/* if a watch was OOM last time, don't wait longer than the OOM
* wait to re-enable it
*/
if (loop->oom_watch_pending)
timeout = MIN (timeout, _dbus_get_oom_wait ());
#if MAINLOOP_SPEW
_dbus_verbose (" polling on %d descriptors timeout %ld\n", n_fds, timeout);
#endif
n_ready = _dbus_socket_set_poll (loop->socket_set, ready_fds,
_DBUS_N_ELEMENTS (ready_fds), timeout);
/* re-enable any watches we skipped this time */
if (loop->oom_watch_pending)
{
DBusHashIter hash_iter;
loop->oom_watch_pending = FALSE;
_dbus_hash_iter_init (loop->watches, &hash_iter);
while (_dbus_hash_iter_next (&hash_iter))
{
DBusList **watches;
int fd;
dbus_bool_t changed;
changed = FALSE;
fd = _dbus_hash_iter_get_int_key (&hash_iter);
watches = _dbus_hash_iter_get_value (&hash_iter);
for (link = _dbus_list_get_first_link (watches);
link != NULL;
link = _dbus_list_get_next_link (watches, link))
{
DBusWatch *watch = link->data;
if (_dbus_watch_get_oom_last_time (watch))
{
_dbus_watch_set_oom_last_time (watch, FALSE);
changed = TRUE;
}
}
if (changed)
refresh_watches_for_fd (loop, watches, fd);
}
retval = TRUE; /* return TRUE here to keep the loop going,
* since we don't know the watch was inactive */
}
initial_serial = loop->callback_list_serial;
if (loop->timeout_count > 0)
{
unsigned long tv_sec;
unsigned long tv_usec;
_dbus_get_monotonic_time (&tv_sec, &tv_usec);
/* It'd be nice to avoid this O(n) thingy here */
link = _dbus_list_get_first_link (&loop->timeouts);
while (link != NULL)
{
DBusList *next = _dbus_list_get_next_link (&loop->timeouts, link);
TimeoutCallback *tcb = link->data;
if (initial_serial != loop->callback_list_serial)
goto next_iteration;
if (loop->depth != orig_depth)
goto next_iteration;
if (dbus_timeout_get_enabled (tcb->timeout))
{
int msecs_remaining;
if (check_timeout (tv_sec, tv_usec,
tcb, &msecs_remaining))
{
/* Save last callback time and fire this timeout */
tcb->last_tv_sec = tv_sec;
tcb->last_tv_usec = tv_usec;
#if MAINLOOP_SPEW
_dbus_verbose (" invoking timeout\n");
#endif
/* can theoretically return FALSE on OOM, but we just
* let it fire again later - in practice that's what
* every wrapper callback in dbus-daemon used to do */
dbus_timeout_handle (tcb->timeout);
retval = TRUE;
}
else
{
#if MAINLOOP_SPEW
_dbus_verbose (" timeout has not expired\n");
#endif
}
}
#if MAINLOOP_SPEW
else
{
_dbus_verbose (" skipping invocation of disabled timeout\n");
}
#endif
link = next;
}
}
if (n_ready > 0)
{
for (i = 0; i < n_ready; i++)
{
DBusList **watches;
DBusList *next;
unsigned int condition;
dbus_bool_t any_oom;
/* FIXME I think this "restart if we change the watches"
* approach could result in starving watches
* toward the end of the list.
*/
if (initial_serial != loop->callback_list_serial)
goto next_iteration;
if (loop->depth != orig_depth)
goto next_iteration;
_dbus_assert (ready_fds[i].flags != 0);
if (_DBUS_UNLIKELY (ready_fds[i].flags & _DBUS_WATCH_NVAL))
{
cull_watches_for_invalid_fd (loop, ready_fds[i].fd);
goto next_iteration;
}
condition = ready_fds[i].flags;
_dbus_assert ((condition & _DBUS_WATCH_NVAL) == 0);
/* condition may still be 0 if we got some
* weird POLLFOO thing like POLLWRBAND
*/
if (condition == 0)
continue;
watches = _dbus_hash_table_lookup_int (loop->watches,
ready_fds[i].fd);
if (watches == NULL)
continue;
any_oom = FALSE;
for (link = _dbus_list_get_first_link (watches);
link != NULL;
link = next)
{
DBusWatch *watch = link->data;
next = _dbus_list_get_next_link (watches, link);
if (dbus_watch_get_enabled (watch))
{
dbus_bool_t oom;
oom = !dbus_watch_handle (watch, condition);
if (oom)
{
_dbus_watch_set_oom_last_time (watch, TRUE);
loop->oom_watch_pending = TRUE;
any_oom = TRUE;
}
#if MAINLOOP_SPEW
_dbus_verbose (" Invoked watch, oom = %d\n", oom);
#endif
retval = TRUE;
/* We re-check this every time, in case the callback
* added/removed watches, which might make our position in
* the linked list invalid. See the FIXME above. */
if (initial_serial != loop->callback_list_serial ||
loop->depth != orig_depth)
{
if (any_oom)
refresh_watches_for_fd (loop, NULL, ready_fds[i].fd);
goto next_iteration;
}
}
}
if (any_oom)
refresh_watches_for_fd (loop, watches, ready_fds[i].fd);
}
}
next_iteration:
#if MAINLOOP_SPEW
_dbus_verbose (" moving to next iteration\n");
#endif
if (_dbus_loop_dispatch (loop))
retval = TRUE;
#if MAINLOOP_SPEW
_dbus_verbose ("Returning %d\n", retval);
#endif
return retval;
}
void
_dbus_loop_run (DBusLoop *loop)
{
int our_exit_depth;
_dbus_assert (loop->depth >= 0);
_dbus_loop_ref (loop);
our_exit_depth = loop->depth;
loop->depth += 1;
_dbus_verbose ("Running main loop, depth %d -> %d\n",
loop->depth - 1, loop->depth);
while (loop->depth != our_exit_depth)
_dbus_loop_iterate (loop, TRUE);
_dbus_loop_unref (loop);
}
void
_dbus_loop_quit (DBusLoop *loop)
{
_dbus_assert (loop->depth > 0);
loop->depth -= 1;
_dbus_verbose ("Quit main loop, depth %d -> %d\n",
loop->depth + 1, loop->depth);
}
int
_dbus_get_oom_wait (void)
{
#ifdef DBUS_BUILD_TESTS
/* make tests go fast */
return 0;
#else
return 500;
#endif
}
void
_dbus_wait_for_memory (void)
{
_dbus_verbose ("Waiting for more memory\n");
_dbus_sleep_milliseconds (_dbus_get_oom_wait ());
}
#endif /* !DOXYGEN_SHOULD_SKIP_THIS */