Back out rev 1.240; it is unnecessary.  In particular, p1 == curthread, so _PHOLD(p1) will not have to block to swap in p1.
Back out rev 1.240; it is unnecessary.  In particular,
p1 == curthread, so _PHOLD(p1) will not have to block
to swap in p1.

Noticed by:	jhb

jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase,jrobhoward/SCADAbase