Sorry. I confused it with `pthread_sigqueue(3)`.
but this is inprocess, we need to send from server;
It enables us to attach a payload to `SOGUSR1`. Of course, if we can allocate a separate signal for ourselves, it seems better to use just that.
sigqueue doesn't seem to allow to specify a thread for signal.
If you still think that this can be used for our purpose somehow, may I ask you to elaborate a bit more how exactly?