1 files changed, 21 insertions, 19 deletions

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index 9b36d6d7fb97..b79bfcd28e95 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -51,7 +51,7 @@
 
 /* Data structures. */
 
-static struct lock_class_key rcu_root_class;
+static struct lock_class_key rcu_node_class[NUM_RCU_LVLS];
 
 #define RCU_STATE_INITIALIZER(name) { \
         .level = { &name.node[0] }, \
@@ -936,6 +936,7 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
 {
         unsigned long flags;
         unsigned long mask;
+        int need_quiet = 0;
         struct rcu_data *rdp = rsp->rda[cpu];
         struct rcu_node *rnp;
 
@@ -949,29 +950,30 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
                 spin_lock(&rnp->lock);          /* irqs already disabled. */
                 rnp->qsmaskinit &= ~mask;
                 if (rnp->qsmaskinit != 0) {
-                        spin_unlock(&rnp->lock); /* irqs remain disabled. */
+                        if (rnp != rdp->mynode)
+                                spin_unlock(&rnp->lock); /* irqs remain disabled. */
                         break;
                 }
-
-                /*
-                 * If there was a task blocking the current grace period,
-                 * and if all CPUs have checked in, we need to propagate
-                 * the quiescent state up the rcu_node hierarchy.  But that
-                 * is inconvenient at the moment due to deadlock issues if
-                 * this should end the current grace period.  So set the
-                 * offlined CPU's bit in ->qsmask in order to force the
-                 * next force_quiescent_state() invocation to clean up this
-                 * mess in a deadlock-free manner.
-                 */
-                if (rcu_preempt_offline_tasks(rsp, rnp, rdp) && !rnp->qsmask)
-                        rnp->qsmask |= mask;
-
+                if (rnp == rdp->mynode)
+                        need_quiet = rcu_preempt_offline_tasks(rsp, rnp, rdp);
+                else
+                        spin_unlock(&rnp->lock); /* irqs remain disabled. */
                 mask = rnp->grpmask;
-                spin_unlock(&rnp->lock);        /* irqs remain disabled. */
                 rnp = rnp->parent;
         } while (rnp != NULL);
 
-        spin_unlock_irqrestore(&rsp->onofflock, flags);
+        /*
+         * We still hold the leaf rcu_node structure lock here, and
+         * irqs are still disabled.  The reason for this subterfuge is
+         * because invoking task_quiet() with ->onofflock held leads
+         * to deadlock.
+         */
+        spin_unlock(&rsp->onofflock); /* irqs remain disabled. */
+        rnp = rdp->mynode;
+        if (need_quiet)
+                task_quiet(rnp, flags);
+        else
+                spin_unlock_irqrestore(&rnp->lock, flags);
 
         rcu_adopt_orphan_cbs(rsp);
 }
@@ -1731,6 +1733,7 @@ static void __init rcu_init_one(struct rcu_state *rsp)
                 rnp = rsp->level[i];
                 for (j = 0; j < rsp->levelcnt[i]; j++, rnp++) {
                         spin_lock_init(&rnp->lock);
+                        lockdep_set_class(&rnp->lock, &rcu_node_class[i]);
                         rnp->gpnum = 0;
                         rnp->qsmask = 0;
                         rnp->qsmaskinit = 0;
@@ -1753,7 +1756,6 @@ static void __init rcu_init_one(struct rcu_state *rsp)
                         INIT_LIST_HEAD(&rnp->blocked_tasks[1]);
                 }
         }
-        lockdep_set_class(&rcu_get_root(rsp)->lock, &rcu_root_class);
 }
 
 /*