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synced 2026-05-07 21:28:01 +02:00
Maintain the set of polled sockets over time
This enables us to benefit from epoll(4): polling is now O(number of watch changes + number of active fds), whereas with poll(2) it's O(total number of fds). Bug: https://bugs.freedesktop.org/show_bug.cgi?id=33337 Bug-NB: NB#197191
This commit is contained in:
Simon McVittie
parent
40b5dc824a
commit
0110a3b13a
1 changed files with 132 additions and 99 deletions
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@ -60,12 +60,16 @@ struct DBusLoop
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int refcount;
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/** fd => dbus_malloc'd DBusList ** of references to DBusWatch */
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DBusHashTable *watches;
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DBusSocketSet *socket_set;
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DBusList *timeouts;
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int callback_list_serial;
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int watch_count;
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int timeout_count;
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int depth; /**< number of recursive runs */
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DBusList *need_dispatch;
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/** TRUE if we will skip a watch next time because it was OOM; becomes
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* FALSE between polling, and dealing with the results of the poll */
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unsigned oom_watch_pending : 1;
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};
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typedef struct
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@ -151,6 +155,8 @@ _dbus_loop_new (void)
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loop->watches = _dbus_hash_table_new (DBUS_HASH_INT, NULL,
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free_watch_table_entry);
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loop->socket_set = _dbus_socket_set_new (0);
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if (loop->watches == NULL)
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{
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dbus_free (loop);
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@ -190,6 +196,7 @@ _dbus_loop_unref (DBusLoop *loop)
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}
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_dbus_hash_table_unref (loop->watches);
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_dbus_socket_set_free (loop->socket_set);
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dbus_free (loop);
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}
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}
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@ -241,20 +248,57 @@ cull_watches_for_invalid_fd (DBusLoop *loop,
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_dbus_hash_table_remove_int (loop->watches, fd);
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}
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static void
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static dbus_bool_t
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gc_watch_table_entry (DBusLoop *loop,
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DBusList **watches,
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int fd)
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{
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/* If watches is already NULL we have nothing to do */
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if (watches == NULL)
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return;
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return FALSE;
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/* We can't GC hash table entries if they're non-empty lists */
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if (*watches != NULL)
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return;
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return FALSE;
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_dbus_hash_table_remove_int (loop->watches, fd);
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return TRUE;
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}
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static void
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refresh_watches_for_fd (DBusLoop *loop,
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DBusList **watches,
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int fd)
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{
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DBusList *link;
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unsigned int flags = 0;
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dbus_bool_t interested;
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_dbus_assert (fd != -1);
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if (watches == NULL)
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watches = _dbus_hash_table_lookup_int (loop->watches, fd);
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/* we allocated this in the first _dbus_loop_add_watch for the fd, and keep
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* it until there are none left */
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_dbus_assert (watches != NULL);
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for (link = _dbus_list_get_first_link (watches);
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link != NULL;
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link = _dbus_list_get_next_link (watches, link))
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{
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if (dbus_watch_get_enabled (link->data) &&
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!_dbus_watch_get_oom_last_time (link->data))
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{
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flags |= dbus_watch_get_flags (link->data);
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interested = TRUE;
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}
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}
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if (interested)
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_dbus_socket_set_enable (loop->socket_set, fd, flags);
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else
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_dbus_socket_set_disable (loop->socket_set, fd);
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}
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dbus_bool_t
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@ -272,19 +316,32 @@ _dbus_loop_add_watch (DBusLoop *loop,
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if (watches == NULL)
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return FALSE;
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if (_dbus_list_append (watches, _dbus_watch_ref (watch)))
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{
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loop->callback_list_serial += 1;
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loop->watch_count += 1;
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}
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else
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if (!_dbus_list_append (watches, _dbus_watch_ref (watch)))
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{
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_dbus_watch_unref (watch);
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gc_watch_table_entry (loop, watches, fd);
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return FALSE;
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}
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return FALSE;
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}
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if (_dbus_list_length_is_one (watches))
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{
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if (!_dbus_socket_set_add (loop->socket_set, fd,
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dbus_watch_get_flags (watch),
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dbus_watch_get_enabled (watch)))
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{
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_dbus_hash_table_remove_int (loop->watches, fd);
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return FALSE;
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}
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}
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else
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{
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/* we're modifying, not adding, which can't fail with OOM */
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refresh_watches_for_fd (loop, watches, fd);
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}
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loop->callback_list_serial += 1;
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loop->watch_count += 1;
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return TRUE;
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}
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@ -292,7 +349,7 @@ void
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_dbus_loop_toggle_watch (DBusLoop *loop,
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DBusWatch *watch)
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{
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/* stub */
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refresh_watches_for_fd (loop, NULL, dbus_watch_get_socket (watch));
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}
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void
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@ -327,8 +384,11 @@ _dbus_loop_remove_watch (DBusLoop *loop,
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_dbus_watch_unref (this);
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/* if that was the last watch for that fd, drop the hash table
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* entry too */
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gc_watch_table_entry (loop, watches, fd);
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* entry, and stop reserving space for it in the socket set */
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if (gc_watch_table_entry (loop, watches, fd))
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{
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_dbus_socket_set_remove (loop->socket_set, fd);
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}
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return;
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}
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@ -546,20 +606,16 @@ _dbus_loop_iterate (DBusLoop *loop,
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{
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#define N_STACK_DESCRIPTORS 64
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dbus_bool_t retval;
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DBusSocketSet *socket_set = NULL;
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DBusSocketEvent ready_fds[N_STACK_DESCRIPTORS];
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int i;
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DBusList *link;
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int n_ready;
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int initial_serial;
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long timeout;
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dbus_bool_t oom_watch_pending;
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int orig_depth;
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DBusHashIter hash_iter;
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retval = FALSE;
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oom_watch_pending = FALSE;
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orig_depth = loop->depth;
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#if MAINLOOP_SPEW
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@ -571,77 +627,6 @@ _dbus_loop_iterate (DBusLoop *loop,
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loop->timeouts == NULL)
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goto next_iteration;
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socket_set = _dbus_socket_set_new (loop->watch_count);
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while (socket_set == NULL)
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{
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_dbus_wait_for_memory ();
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socket_set = _dbus_socket_set_new (loop->watch_count);
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}
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/* fill our array of fds and watches */
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_dbus_hash_iter_init (loop->watches, &hash_iter);
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while (_dbus_hash_iter_next (&hash_iter))
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{
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DBusList **watches;
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unsigned int flags;
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int fd;
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dbus_bool_t enabled;
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fd = _dbus_hash_iter_get_int_key (&hash_iter);
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watches = _dbus_hash_iter_get_value (&hash_iter);
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flags = 0;
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enabled = FALSE;
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for (link = _dbus_list_get_first_link (watches);
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link != NULL;
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link = _dbus_list_get_next_link (watches, link))
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{
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DBusWatch *watch = link->data;
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if (_dbus_watch_get_oom_last_time (watch))
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{
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/* we skip this one this time, but reenable it next time,
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* and have a timeout on this iteration
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*/
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_dbus_watch_set_oom_last_time (watch, FALSE);
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oom_watch_pending = TRUE;
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retval = TRUE; /* return TRUE here to keep the loop going,
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* since we don't know the watch is inactive
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*/
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#if MAINLOOP_SPEW
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_dbus_verbose (" skipping watch on fd %d as it was out of memory last time\n",
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fd);
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#endif
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}
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else if (dbus_watch_get_enabled (watch))
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{
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flags |= dbus_watch_get_flags (watch);
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enabled = TRUE;
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}
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}
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if (enabled)
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{
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_dbus_socket_set_add (socket_set, fd, flags, TRUE);
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#if MAINLOOP_SPEW
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_dbus_verbose (" polling watch on fd %d %s\n",
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fd, watch_flags_to_string (flags));
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#endif
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}
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else
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{
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#if MAINLOOP_SPEW
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_dbus_verbose (" skipping disabled watch on fd %d %s\n",
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fd, watch_flags_to_string (flags));
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#endif
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}
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}
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timeout = -1;
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if (loop->timeout_count > 0)
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{
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@ -697,19 +682,59 @@ _dbus_loop_iterate (DBusLoop *loop,
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#endif
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}
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/* if a watch is OOM, don't wait longer than the OOM
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/* if a watch was OOM last time, don't wait longer than the OOM
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* wait to re-enable it
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*/
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if (oom_watch_pending)
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if (loop->oom_watch_pending)
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timeout = MIN (timeout, _dbus_get_oom_wait ());
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#if MAINLOOP_SPEW
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_dbus_verbose (" polling on %d descriptors timeout %ld\n", n_fds, timeout);
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#endif
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n_ready = _dbus_socket_set_poll (socket_set, ready_fds,
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n_ready = _dbus_socket_set_poll (loop->socket_set, ready_fds,
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_DBUS_N_ELEMENTS (ready_fds), timeout);
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/* re-enable any watches we skipped this time */
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if (loop->oom_watch_pending)
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{
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DBusHashIter hash_iter;
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loop->oom_watch_pending = FALSE;
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_dbus_hash_iter_init (loop->watches, &hash_iter);
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while (_dbus_hash_iter_next (&hash_iter))
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{
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DBusList **watches;
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int fd;
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dbus_bool_t changed;
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changed = FALSE;
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fd = _dbus_hash_iter_get_int_key (&hash_iter);
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watches = _dbus_hash_iter_get_value (&hash_iter);
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for (link = _dbus_list_get_first_link (watches);
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link != NULL;
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link = _dbus_list_get_next_link (watches, link))
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{
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DBusWatch *watch = link->data;
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if (_dbus_watch_get_oom_last_time (watch))
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{
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_dbus_watch_set_oom_last_time (watch, FALSE);
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changed = TRUE;
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}
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}
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if (changed)
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refresh_watches_for_fd (loop, watches, fd);
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}
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retval = TRUE; /* return TRUE here to keep the loop going,
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* since we don't know the watch was inactive */
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}
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initial_serial = loop->callback_list_serial;
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if (loop->timeout_count > 0)
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@ -779,6 +804,7 @@ _dbus_loop_iterate (DBusLoop *loop,
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DBusList **watches;
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DBusList *next;
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unsigned int condition;
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dbus_bool_t any_oom;
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/* FIXME I think this "restart if we change the watches"
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* approach could result in starving watches
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@ -813,6 +839,8 @@ _dbus_loop_iterate (DBusLoop *loop,
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if (watches == NULL)
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continue;
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any_oom = FALSE;
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for (link = _dbus_list_get_first_link (watches);
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link != NULL;
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link = next)
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@ -830,6 +858,8 @@ _dbus_loop_iterate (DBusLoop *loop,
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if (oom)
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{
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_dbus_watch_set_oom_last_time (watch, TRUE);
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loop->oom_watch_pending = TRUE;
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any_oom = TRUE;
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}
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#if MAINLOOP_SPEW
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@ -840,13 +870,19 @@ _dbus_loop_iterate (DBusLoop *loop,
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/* We re-check this every time, in case the callback
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* added/removed watches, which might make our position in
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* the linked list invalid. See the FIXME above. */
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if (initial_serial != loop->callback_list_serial)
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goto next_iteration;
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if (initial_serial != loop->callback_list_serial ||
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loop->depth != orig_depth)
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{
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if (any_oom)
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refresh_watches_for_fd (loop, NULL, ready_fds[i].fd);
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if (loop->depth != orig_depth)
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goto next_iteration;
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goto next_iteration;
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}
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}
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}
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if (any_oom)
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refresh_watches_for_fd (loop, watches, ready_fds[i].fd);
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}
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}
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@ -855,9 +891,6 @@ _dbus_loop_iterate (DBusLoop *loop,
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_dbus_verbose (" moving to next iteration\n");
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#endif
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if (socket_set)
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_dbus_socket_set_free (socket_set);
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if (_dbus_loop_dispatch (loop))
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retval = TRUE;
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