rcu: Create rcutree plugins to handle hotplug CPU for multi-level trees

When offlining CPUs from a multi-level tree, there is the
possibility of offlining the last CPU from a given node when
there are preempted RCU read-side critical sections that
started life on one of the CPUs on that node.

In this case, the corresponding tasks will be enqueued via the
task_struct's rcu_node_entry list_head onto one of the
rcu_node's blocked_tasks[] lists.  These tasks need to be moved
somewhere else so that they will prevent the current grace
period from ending. That somewhere is the root rcu_node.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: akpm@linux-foundation.org
Cc: mathieu.desnoyers@polymtl.ca
Cc: josht@linux.vnet.ibm.com
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
LKML-Reference: <20090827215816.GA30472@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 1 insertions, 1 deletions

diff --git a/include/linux/init_task.h b/include/linux/init_task.h
index 79d4baee31b6..9e7f2e8fc66e 100644
--- a/include/linux/init_task.h
+++ b/include/linux/init_task.h
@@ -98,7 +98,7 @@ extern struct group_info init_groups;
 #define INIT_TASK_RCU_PREEMPT(tsk)                                      \
         .rcu_read_lock_nesting = 0,                                     \
         .rcu_read_unlock_special = 0,                                   \
-        .rcu_blocked_cpu = -1,                                          \
+        .rcu_blocked_node = NULL,                                       \
         .rcu_node_entry = LIST_HEAD_INIT(tsk.rcu_node_entry),
 #else
 #define INIT_TASK_RCU_PREEMPT(tsk)