[PATCH -v2 0/6] spin_unlock_wait borkage

[Peter Zijlstra]

This version rewrites all spin_unlock_wait() implementations to provide the
acquire order against the spin_unlock() release we wait on, ensuring we can
fully observe the critical section we waited on.

It pulls in the smp_cond_acquire() rewrite because it introduces a lot more
users of it. All simple spin_unlock_wait implementations end up being an
smp_cond_load_acquire().

And while this still introduces smp_acquire__after_ctrl_dep() it keeps its
usage contained to a few sites.

Please consider.. carefully.