1 files changed, 14 insertions, 1 deletions

diff --git a/kernel/rcutree.c b/kernel/rcutree.c
index ddbf111e9e18..0536125b0497 100644
--- a/kernel/rcutree.c
+++ b/kernel/rcutree.c
@@ -913,7 +913,20 @@ static void __rcu_offline_cpu(int cpu, struct rcu_state *rsp)
                         spin_unlock(&rnp->lock); /* irqs remain disabled. */
                         break;
                 }
-                rcu_preempt_offline_tasks(rsp, rnp, rdp);
+
+                /*
+                 * 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;
+
                 mask = rnp->grpmask;
                 spin_unlock(&rnp->lock);        /* irqs remain disabled. */
                 rnp = rnp->parent;