rcu: Changes from reviews: avoid casts, fix/add warnings, improve comments

Changes suggested by review comments from Josh Triplett and
Mathieu Desnoyers.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Josh Triplett <josh@joshtriplett.org>
Acked-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: akpm@linux-foundation.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
LKML-Reference: <20090827220012.GA30525@linux.vnet.ibm.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 6 insertions, 4 deletions

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index 04343bee646..47789369ea5 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -92,7 +92,7 @@ static void rcu_preempt_qs(int cpu)
                 rnp = rdp->mynode;
                 spin_lock(&rnp->lock);
                 t->rcu_read_unlock_special |= RCU_READ_UNLOCK_BLOCKED;
-                t->rcu_blocked_node = (void *)rnp;
+                t->rcu_blocked_node = rnp;
 
                 /*
                  * If this CPU has already checked in, then this task
@@ -176,9 +176,9 @@ static void rcu_read_unlock_special(struct task_struct *t)
                  * most one time.  So at most two passes through loop.
                  */
                 for (;;) {
-                        rnp = (struct rcu_node *)t->rcu_blocked_node;
+                        rnp = t->rcu_blocked_node;
                         spin_lock(&rnp->lock);
-                        if (rnp == (struct rcu_node *)t->rcu_blocked_node)
+                        if (rnp == t->rcu_blocked_node)
                                 break;
                         spin_unlock(&rnp->lock);
                 }
@@ -288,8 +288,10 @@ static void rcu_preempt_offline_tasks(struct rcu_state *rsp,
         struct rcu_node *rnp_root = rcu_get_root(rsp);
         struct task_struct *tp;
 
-        if (rnp == rnp_root)
+        if (rnp == rnp_root) {
+                WARN_ONCE(1, "Last CPU thought to be offlined?");
                 return;  /* Shouldn't happen: at least one CPU online. */
+        }
 
         /*
          * Move tasks up to root rcu_node.  Rely on the fact that the