Optimistically acquire eventq and recvq slots and release them if we went too far
Optimistically acquire eventq and recvq slots and release them if we went too far

This draws the line towards using atomics instead of spin_lock_bh'ed modifications
of the indexes.

ananos/xen2mx,ananos/open-mx,ananos/xen2mx,ananos/open-mx,ananos/xen2mx,ananos/xen2mx,ananos/open-mx