Re: Threads & independant main loops/contexts

[Tristan Van Berkom <vantr touchtunes com>]

> So my problem - cut down to one essential - is the following: I have
> one thread which has to be independant of all others (as completely as
> possible, speaking of the MainLoop and probably of the MainContext also
> ...), but it has to insert watches of io channels into the main loop of
> a third thread.

I did something like that a month ago.

I have a parent thread which is `server' thread
and listens on an IPC channel for IO requests.

the parent thread adds the request to a request queue
like so:

g_mutex_lock(hm->queue_mutex);
g_queue_push_tail(hm->job_queue, (gpointer)node);
g_cond_signal(hm->jobs_queued);
g_mutex_unlock(hm->queue_mutex);


there is no `mainloop' in the child thread.
the child thread loops like so:


while (am_running) {

        g_mutex_lock(hm->queue_mutex);
        if ((node = g_queue_pop_head(hm->job_queue)) == NULL) {
            _ib_debug((__FUNCTION__ ": waiting on condition jobs_queued"));
            g_cond_wait(hm->jobs_queued, hm->queue_mutex);
            /* this should not be null */
            node = g_queue_pop_head(hm->job_queue);
        }
        g_mutex_unlock(hm->queue_mutex);


        /* write to underlying hardware */
        if (node) {
            switch (node->action) {
            case IBACTION_WRITE:
                write_node(node);
                break;

        .....


This code was to write to a device that takes
seconds at a time to write where the 
kernel module makes extensive use of
`schedule()' in order to ease execution.



Hope this helps.
                -Tristan


Axel Bock wrote:
> Hi all,
>
> I just dont get it. :-(
>
> Please listen: I have three threads with three main loops (I intend to
> use). These main loops I want to be independant, so they can do stuff
> without blocking / interfering with each other. It seems not to be
> sufficient just to create a new main loop in each of the threads, which
> would be the most easy solution I can think of. Now I read a lot about
> these GMainContext's, but these I dont really understand a bit :-((
>
> So my problem - cut down to one essential - is the following: I have
> one thread which has to be independant of all others (as completely as
> possible, speaking of the MainLoop and probably of the MainContext also
> ...), but it has to insert watches of io channels into the main loop of
> a third thread.
>
> How can I realize this? I think there has to be a way, but I'm quite
> blinded at the moment ...
>
> Thanks for all help and greetings,
>
>                 Axel.
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