rcu: merge TREE_PREEPT_RCU blocked_tasks[] lists

Combine the current TREE_PREEMPT_RCU ->blocked_tasks[] lists in the
rcu_node structure into a single ->blkd_tasks list with ->gp_tasks
and ->exp_tasks tail pointers.  This is in preparation for RCU priority
boosting, which will add a third dimension to the combinatorial explosion
in the ->blocked_tasks[] case, but simply a third pointer in the new
->blkd_tasks case.

Also update documentation to reflect blocked_tasks[] merge

Signed-off-by: Paul E. McKenney <paul.mckenney@linaro.org>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>

1 files changed, 1 insertions, 4 deletions

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 90104a19c564..0ac1cc03f935 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -1901,10 +1901,7 @@ static void __init rcu_init_one(struct rcu_state *rsp,
                                               j / rsp->levelspread[i - 1];
                         }
                         rnp->level = i;
-                        INIT_LIST_HEAD(&rnp->blocked_tasks[0]);
-                        INIT_LIST_HEAD(&rnp->blocked_tasks[1]);
-                        INIT_LIST_HEAD(&rnp->blocked_tasks[2]);
-                        INIT_LIST_HEAD(&rnp->blocked_tasks[3]);
+                        INIT_LIST_HEAD(&rnp->blkd_tasks);
                 }
         }