Hi,

following appears to me as a bug and might be a subject for solving/discussing.

The internal state of the mainloop is wrong, after one do restarts it. Following example illustrates it:

// start and stop for the first time
pa_threaded_mainloop_start(m); 
pa_threaded_mainloop_stop(m);  // stop causes m->state = STATE_QUIT

// start and stop for the second time fails, because of an assertion
pa_threaded_mainloop_start(m);

this fails, since this assertion assert(m->state == STATE_PASSIVE) : mainloop.c:827 fires. 

The problem here is that the internal state hasn't been changed back to STATE_PASSIVE, as soon as it was restarted and remains STATE_QUIT, hence assertion fails. A solution might be to change the state accordingly in pa_mainloop_run, i.e.:

int pa_mainloop_run(pa_mainloop *m, int *retval) {
    int r;

    m->state = STATE_PASSIVE; // ADD THIS HERE
    while ((r = pa_mainloop_iterate(m, 1, retval)) >= 0);
...