oom: thaw threads if oom killed thread is frozen before deferring

oom: thaw threads if oom killed thread is frozen before deferring

If a thread has been oom killed and is frozen, thaw it before returning to
the page allocator.  Otherwise, it can stay frozen indefinitely and no
memory will be freed.

Signed-off-by: David Rientjes <[email protected]>
Reported-by: Konstantin Khlebnikov <[email protected]>
Cc: Oleg Nesterov <[email protected]>
Cc: KOSAKI Motohiro <[email protected]>
Cc: KAMEZAWA Hiroyuki <[email protected]>
Cc: "Rafael J. Wysocki" <[email protected]>
Acked-by: Michal Hocko <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>