+/*
+ * Reset the ->expmaskinit values in the rcu_node tree to reflect any
+ * recent CPU-online activity. Note that these masks are not cleared
+ * when CPUs go offline, so they reflect the union of all CPUs that have
+ * ever been online. This means that this function normally takes its
+ * no-work-to-do fastpath.
+ */
+static void sync_exp_reset_tree_hotplug(struct rcu_state *rsp)
+{
+ bool done;
+ unsigned long flags;
+ unsigned long mask;
+ unsigned long oldmask;
+ int ncpus = READ_ONCE(rsp->ncpus);
+ struct rcu_node *rnp;
+ struct rcu_node *rnp_up;
+
+ /* If no new CPUs onlined since last time, nothing to do. */
+ if (likely(ncpus == rsp->ncpus_snap))
+ return;
+ rsp->ncpus_snap = ncpus;
+
+ /*
+ * Each pass through the following loop propagates newly onlined
+ * CPUs for the current rcu_node structure up the rcu_node tree.
+ */
+ rcu_for_each_leaf_node(rsp, rnp) {
+ raw_spin_lock_irqsave(&rnp->lock, flags);
+ smp_mb__after_unlock_lock();
+ if (rnp->expmaskinit == rnp->expmaskinitnext) {
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
+ continue; /* No new CPUs, nothing to do. */
+ }
+
+ /* Update this node's mask, track old value for propagation. */
+ oldmask = rnp->expmaskinit;
+ rnp->expmaskinit = rnp->expmaskinitnext;
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
+
+ /* If was already nonzero, nothing to propagate. */
+ if (oldmask)
+ continue;
+
+ /* Propagate the new CPU up the tree. */
+ mask = rnp->grpmask;
+ rnp_up = rnp->parent;
+ done = false;
+ while (rnp_up) {
+ raw_spin_lock_irqsave(&rnp_up->lock, flags);
+ smp_mb__after_unlock_lock();
+ if (rnp_up->expmaskinit)
+ done = true;
+ rnp_up->expmaskinit |= mask;
+ raw_spin_unlock_irqrestore(&rnp_up->lock, flags);
+ if (done)
+ break;
+ mask = rnp_up->grpmask;
+ rnp_up = rnp_up->parent;
+ }
+ }
+}
+
+/*
+ * Reset the ->expmask values in the rcu_node tree in preparation for
+ * a new expedited grace period.
+ */
+static void __maybe_unused sync_exp_reset_tree(struct rcu_state *rsp)
+{
+ unsigned long flags;
+ struct rcu_node *rnp;
+
+ sync_exp_reset_tree_hotplug(rsp);
+ rcu_for_each_node_breadth_first(rsp, rnp) {
+ raw_spin_lock_irqsave(&rnp->lock, flags);
+ smp_mb__after_unlock_lock();
+ WARN_ON_ONCE(rnp->expmask);
+ rnp->expmask = rnp->expmaskinit;
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
+ }
+}
+
+/*
+ * Return non-zero if there is no RCU expedited grace period in progress
+ * for the specified rcu_node structure, in other words, if all CPUs and
+ * tasks covered by the specified rcu_node structure have done their bit
+ * for the current expedited grace period. Works only for preemptible
+ * RCU -- other RCU implementation use other means.
+ *
+ * Caller must hold the root rcu_node's exp_funnel_mutex.
+ */
+static int sync_rcu_preempt_exp_done(struct rcu_node *rnp)
+{
+ return rnp->exp_tasks == NULL &&
+ READ_ONCE(rnp->expmask) == 0;
+}
+
+/*
+ * Report the exit from RCU read-side critical section for the last task
+ * that queued itself during or before the current expedited preemptible-RCU
+ * grace period. This event is reported either to the rcu_node structure on
+ * which the task was queued or to one of that rcu_node structure's ancestors,
+ * recursively up the tree. (Calm down, calm down, we do the recursion
+ * iteratively!)
+ *
+ * Caller must hold the root rcu_node's exp_funnel_mutex and the
+ * specified rcu_node structure's ->lock.
+ */
+static void __rcu_report_exp_rnp(struct rcu_state *rsp, struct rcu_node *rnp,
+ bool wake, unsigned long flags)
+ __releases(rnp->lock)
+{
+ unsigned long mask;
+
+ for (;;) {
+ if (!sync_rcu_preempt_exp_done(rnp)) {
+ if (!rnp->expmask)
+ rcu_initiate_boost(rnp, flags);
+ else
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
+ break;
+ }
+ if (rnp->parent == NULL) {
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
+ if (wake) {
+ smp_mb(); /* EGP done before wake_up(). */
+ wake_up(&rsp->expedited_wq);
+ }
+ break;
+ }
+ mask = rnp->grpmask;
+ raw_spin_unlock(&rnp->lock); /* irqs remain disabled */
+ rnp = rnp->parent;
+ raw_spin_lock(&rnp->lock); /* irqs already disabled */
+ smp_mb__after_unlock_lock();
+ WARN_ON_ONCE(!(rnp->expmask & mask));
+ rnp->expmask &= ~mask;
+ }
+}
+
+/*
+ * Report expedited quiescent state for specified node. This is a
+ * lock-acquisition wrapper function for __rcu_report_exp_rnp().
+ *
+ * Caller must hold the root rcu_node's exp_funnel_mutex.
+ */
+static void __maybe_unused rcu_report_exp_rnp(struct rcu_state *rsp,
+ struct rcu_node *rnp, bool wake)
+{
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&rnp->lock, flags);
+ smp_mb__after_unlock_lock();
+ __rcu_report_exp_rnp(rsp, rnp, wake, flags);
+}
+
+/*
+ * Report expedited quiescent state for multiple CPUs, all covered by the
+ * specified leaf rcu_node structure. Caller must hold the root
+ * rcu_node's exp_funnel_mutex.
+ */
+static void rcu_report_exp_cpu_mult(struct rcu_state *rsp, struct rcu_node *rnp,
+ unsigned long mask, bool wake)
+{
+ unsigned long flags;
+
+ raw_spin_lock_irqsave(&rnp->lock, flags);
+ smp_mb__after_unlock_lock();
+ if (!(rnp->expmask & mask)) {
+ raw_spin_unlock_irqrestore(&rnp->lock, flags);
+ return;
+ }
+ rnp->expmask &= ~mask;
+ __rcu_report_exp_rnp(rsp, rnp, wake, flags); /* Releases rnp->lock. */
+}
+
+/*
+ * Report expedited quiescent state for specified rcu_data (CPU).
+ * Caller must hold the root rcu_node's exp_funnel_mutex.
+ */
+static void rcu_report_exp_rdp(struct rcu_state *rsp, struct rcu_data *rdp,
+ bool wake)
+{
+ rcu_report_exp_cpu_mult(rsp, rdp->mynode, rdp->grpmask, wake);
+}
+