I'm -1 on this patch. The introduction of a pipe makes it essentially gtk-specific: It will only work with gtk (for a while, until other frameworks catch up - which may take years), and it will only wake up a gtk thread that is in the gtk poll call.

It fails to support cases where the main thread blocks in a different blocking call (i.e. neither select nor poll). I think a better mechanism is needed to support that case, e.g. by waking up the main thread with pthread_kill.