We'll need to lock the listener a little bit more during accept() and tests show that a spinlock is a massive performance killer, so let's first switch to an rwlock for this lock. This patch might have to be backported for the next patch to work, and if so, the change is almost mechanical (look for LISTENER_LOCK), but do not forget about the few HA_SPIN_INIT() in the file. There's no reference to this lock outside of listener.c nor listener-t.h.