smp_rendezvous: master cpu should wait until all slaves are fully done

This is a followup to r222032 and a reimplementation of it.
While that revision fixed the race for the smp_rv_waiters[2] exit
sentinel, it still left a possibility for a target CPU to access
stale or wrong smp_rv_func_arg in smp_rv_teardown_func.
To fix this race the slave CPUs signal when they are really fully
done with the rendezvous and the master CPU waits until all slaves
are done.

Diagnosed by:	kib
Reviewed by:	jhb, mlaier, neel
Approved by:	re (kib)
MFC after:	2 weeks

0 files changed, 0 insertions, 0 deletions