The patch below should fix a race which could cause stale TLB entries.
Specifically, when 2 CPUs ended up racing for entrance to
wrap_mmu_context().  The losing CPU would find that by the time it
acquired ctx.lock, mm->context already had a valid value, but then it
failed to (re-)check the delayed TLB flushing logic and hence could
end up using a context number when there were still stale entries in
its TLB.  The fix is to check for delayed TLB flushes only after
mm->context is valid (non-zero).  The patch also makes GCC v4.x
happier by defining a non-volatile variant of mm_context_t called
nv_mm_context_t.
Signed-off-by: NDavid Mosberger-Tang <David.Mosberger@acm.org>
Signed-off-by: NTony Luck <tony.luck@intel.com>

Initial git repository build. I'm not bothering with the full history,
even though we have it. We can create a separate "historical" git
archive of that later if we want to, and in the meantime it's about
3.2GB when imported into git - space that would just make the early
git days unnecessarily complicated, when we don't have a lot of good
infrastructure for it.

Let it rip!