rcu: Add WARN_ON_ONCE() consistency checks covering state transitions

o Verify that qsmask bits stay clear through GP
  initialization.

o Verify that cpu_quiet_msk_finish() is never invoked unless
  there actually is an RCU grace period in progress.

o Verify that all internal-node rcu_node structures have empty
  blocked_tasks[] lists.

o Verify that child rcu_node structure's bits remain clear after
  acquiring parent's lock.

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: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
LKML-Reference: <12532926191947-git-send-email->
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 14 insertions, 6 deletions

diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h
index c9616e48379b..5f94619450af 100644
--- a/kernel/rcutree_plugin.h
+++ b/kernel/rcutree_plugin.h
@@ -206,7 +206,8 @@ static void rcu_read_unlock_special(struct task_struct *t)
                  */
                 if (!empty && rnp->qsmask == 0 &&
                     list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1])) {
-                        t->rcu_read_unlock_special &= ~RCU_READ_UNLOCK_NEED_QS;
+                        struct rcu_node *rnp_p;
+
                         if (rnp->parent == NULL) {
                                 /* Only one rcu_node in the tree. */
                                 cpu_quiet_msk_finish(&rcu_preempt_state, flags);
@@ -215,9 +216,10 @@ static void rcu_read_unlock_special(struct task_struct *t)
                         /* Report up the rest of the hierarchy. */
                         mask = rnp->grpmask;
                         spin_unlock_irqrestore(&rnp->lock, flags);
-                        rnp = rnp->parent;
-                        spin_lock_irqsave(&rnp->lock, flags);
-                        cpu_quiet_msk(mask, &rcu_preempt_state, rnp, flags);
+                        rnp_p = rnp->parent;
+                        spin_lock_irqsave(&rnp_p->lock, flags);
+                        WARN_ON_ONCE(rnp->qsmask);
+                        cpu_quiet_msk(mask, &rcu_preempt_state, rnp_p, flags);
                         return;
                 }
                 spin_unlock(&rnp->lock);
@@ -278,6 +280,7 @@ static void rcu_print_task_stall(struct rcu_node *rnp)
 static void rcu_preempt_check_blocked_tasks(struct rcu_node *rnp)
 {
         WARN_ON_ONCE(!list_empty(&rnp->blocked_tasks[rnp->gpnum & 0x1]));
+        WARN_ON_ONCE(rnp->qsmask);
 }
 
 /*
@@ -302,7 +305,8 @@ static int rcu_preempted_readers(struct rcu_node *rnp)
  * The caller must hold rnp->lock with irqs disabled.
  */
 static void rcu_preempt_offline_tasks(struct rcu_state *rsp,
-                                      struct rcu_node *rnp)
+                                      struct rcu_node *rnp,
+                                      struct rcu_data *rdp)
 {
         int i;
         struct list_head *lp;
@@ -314,6 +318,9 @@ static void rcu_preempt_offline_tasks(struct rcu_state *rsp,
                 WARN_ONCE(1, "Last CPU thought to be offlined?");
                 return;  /* Shouldn't happen: at least one CPU online. */
         }
+        WARN_ON_ONCE(rnp != rdp->mynode &&
+                     (!list_empty(&rnp->blocked_tasks[0]) ||
+                      !list_empty(&rnp->blocked_tasks[1])));
 
         /*
          * Move tasks up to root rcu_node.  Rely on the fact that the
@@ -489,7 +496,8 @@ static int rcu_preempted_readers(struct rcu_node *rnp)
  * tasks that were blocked within RCU read-side critical sections.
  */
 static void rcu_preempt_offline_tasks(struct rcu_state *rsp,
-                                      struct rcu_node *rnp)
+                                      struct rcu_node *rnp,
+                                      struct rcu_data *rdp)
 {
 }