rcu: Remove TINY_PREEMPT_RCU

TINY_PREEMPT_RCU adds significant code and complexity, but does not
offer commensurate benefits.  People currently using TINY_PREEMPT_RCU
can get much better memory footprint with TINY_RCU, or, if they really
need preemptible RCU, they can use TREE_PREEMPT_RCU with a relatively
minor degradation in memory footprint.  Please note that this move
has been widely publicized on LKML (https://lkml.org/lkml/2012/11/12/545)
and on LWN (http://lwn.net/Articles/541037/).

This commit therefore removes TINY_PREEMPT_RCU.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: Updated to eliminate #else in rcutiny.h as suggested by Josh ]
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

1 files changed, 1 insertions, 9 deletions

diff --git a/init/Kconfig b/init/Kconfig
index 2d9b83104dcf..e7fb255413d2 100644
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -459,18 +459,10 @@ config TINY_RCU
           is not required.  This option greatly reduces the
           memory footprint of RCU.
 
-config TINY_PREEMPT_RCU
-        bool "Preemptible UP-only small-memory-footprint RCU"
-        depends on PREEMPT && !SMP
-        help
-          This option selects the RCU implementation that is designed
-          for real-time UP systems.  This option greatly reduces the
-          memory footprint of RCU.
-
 endchoice
 
 config PREEMPT_RCU
-        def_bool ( TREE_PREEMPT_RCU || TINY_PREEMPT_RCU )
+        def_bool TREE_PREEMPT_RCU
         help
           This option enables preemptible-RCU code that is common between
           the TREE_PREEMPT_RCU and TINY_PREEMPT_RCU implementations.