2 files changed, 10 insertions, 0 deletions

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 7f872721c54e..50e4f7ebf8cf 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -101,6 +101,7 @@ struct rcu_state sname##_state = { \
         .abbr = sabbr, \
         .exp_mutex = __MUTEX_INITIALIZER(sname##_state.exp_mutex), \
         .exp_wake_mutex = __MUTEX_INITIALIZER(sname##_state.exp_wake_mutex), \
+        .ofl_lock = __SPIN_LOCK_UNLOCKED(sname##_state.ofl_lock), \
 }
 
 RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched);
@@ -1900,11 +1901,13 @@ static bool rcu_gp_init(struct rcu_state *rsp)
          */
         rcu_for_each_leaf_node(rsp, rnp) {
                 rcu_gp_slow(rsp, gp_preinit_delay);
+                spin_lock(&rsp->ofl_lock);
                 raw_spin_lock_irq_rcu_node(rnp);
                 if (rnp->qsmaskinit == rnp->qsmaskinitnext &&
                     !rnp->wait_blkd_tasks) {
                         /* Nothing to do on this leaf rcu_node structure. */
                         raw_spin_unlock_irq_rcu_node(rnp);
+                        spin_unlock(&rsp->ofl_lock);
                         continue;
                 }
 
@@ -1940,6 +1943,7 @@ static bool rcu_gp_init(struct rcu_state *rsp)
                 }
 
                 raw_spin_unlock_irq_rcu_node(rnp);
+                spin_unlock(&rsp->ofl_lock);
         }
 
         /*
@@ -3749,6 +3753,7 @@ static void rcu_cleanup_dying_idle_cpu(int cpu, struct rcu_state *rsp)
 
         /* Remove outgoing CPU from mask in the leaf rcu_node structure. */
         mask = rdp->grpmask;
+        spin_lock(&rsp->ofl_lock);
         raw_spin_lock_irqsave_rcu_node(rnp, flags); /* Enforce GP memory-order guarantee. */
         if (rnp->qsmask & mask) { /* RCU waiting on outgoing CPU? */
                 /* Report quiescent state -before- changing ->qsmaskinitnext! */
@@ -3757,6 +3762,7 @@ static void rcu_cleanup_dying_idle_cpu(int cpu, struct rcu_state *rsp)
         }
         rnp->qsmaskinitnext &= ~mask;
         raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
+        spin_unlock(&rsp->ofl_lock);
 }
 
 /*
diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index 3def94fc9c74..6683da6e4ecc 100644
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -363,6 +363,10 @@ struct rcu_state {
         const char *name;                       /* Name of structure. */
         char abbr;                              /* Abbreviated name. */
         struct list_head flavors;               /* List of RCU flavors. */
+
+        spinlock_t ofl_lock ____cacheline_internodealigned_in_smp;
+                                                /* Synchronize offline with */
+                                                /*  GP pre-initialization. */
 };
 
 /* Values for rcu_state structure's gp_flags field. */