oom: deprecate oom_adj tunable

/proc/pid/oom_adj is now deprecated so that that it may eventually be
removed.  The target date for removal is August 2012.

A warning will be printed to the kernel log if a task attempts to use this
interface.  Future warning will be suppressed until the kernel is rebooted
to prevent spamming the kernel log.

Signed-off-by: David Rientjes <rientjes@google.com>
Cc: Nick Piggin <npiggin@suse.de>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Balbir Singh <balbir@in.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/include/linux/oom.h b/include/linux/oom.h
index 73b8d7b..f209b68 100644
--- a/include/linux/oom.h
+++ b/include/linux/oom.h
@@ -2,6 +2,9 @@
 #define __INCLUDE_LINUX_OOM_H
 
 /*
+ * /proc/<pid>/oom_adj is deprecated, see
+ * Documentation/feature-removal-schedule.txt.
+ *
  * /proc/<pid>/oom_adj set to -17 protects from the oom-killer
  */
 #define OOM_DISABLE (-17)