Wednesday, 7 December 2016

Re: cups-browsed uses GMainLoop and global variables, how to introduce locks against race conditions?

On 12/02/2016 04:13 PM, Till Kamppeter wrote:
> The way how cups-browsed works is the following:
>
> First, a GMainLoop is created:
>
> gmainloop = g_main_loop_new (NULL, FALSE);
>
> Browsing for legacy CUPS broadcasts is attached to the mail loop via
>
> GIOChannel *browse_channel = g_io_channel_unix_new (browsesocket);
> g_io_channel_set_close_on_unref (browse_channel, FALSE);
> g_io_add_watch (browse_channel, G_IO_IN, process_browse_data, NULL);
>
> Many other things are added via
>
> g_idle_add ()
>
> and
>
> g_timeout_add_seconds ()
>
> Reaction to D-Bus notifications is added via the
>
> g_signal_connect()
>
> function.
>
> Avahi browsing is set up with these calls
>
> /* Allocate main loop object */
> if (!glib_poll)
> if (!(glib_poll = avahi_glib_poll_new(NULL, G_PRIORITY_DEFAULT)))
> {
> debug_printf("ERROR: Failed to create glib poll object.\n");
> goto avahi_init_fail;
> }
>
> /* Allocate a new client */
> if (!client)
> client = avahi_client_new(avahi_glib_poll_get(glib_poll),
> AVAHI_CLIENT_NO_FAIL,
> client_callback, NULL, &error);
>
> /* Check wether creating the client object succeeded */
> if (!client) {
> debug_printf("ERROR: Failed to create client: %s\n",
> avahi_strerror(error));
> goto avahi_init_fail;
> }
>
> Strange is that this Avahi browsing setup is done before creation of the
> main loop. Also some g_timeout_add_seconds () calls are done before
> creating the main loop.
>
> After that, the main loop gets started via
>
> g_main_loop_run (gmainloop);
>
> My questions are now:
>
> - Is this way everything attached to the main loop?
>
> - Do I have to do function calls in the beginning and in the end of each
> callback function to acquire and release a lock? Which ones?
>
> - If something of this is not attached to the main loop, how do I attach
> it?
>
> I do not explicitly start any new threads.
>
> Till
>

No one has any idea to help me here?

Till


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