Re: [PATCH RFC v3 03/13] rcu-tasks: Add a Tasks RCU implementation for reader-marked trampolines

+static void rcu_tasks_tramp_hold(struct task_struct *t)
+{
+	unsigned long flags;
+
+	if (t->rcu_tasks_holdout)
+		return;
+	raw_spin_lock_irqsave(&rcu_tasks_tramp_lock, flags);
+	list_add_tail(&t->rcu_tasks_holdout_list, &rcu_tasks_tramp_holdouts);
+	WRITE_ONCE(t->rcu_tasks_holdout, true);
+	raw_spin_unlock_irqrestore(&rcu_tasks_tramp_lock, flags);
+}
+
+static void rcu_tasks_tramp_release(struct task_struct *t)
+{
+	unsigned long flags;
+
+	if (likely(!t->rcu_tasks_holdout))
+		return;
+	raw_spin_lock_irqsave(&rcu_tasks_tramp_lock, flags);
+	list_del_init(&t->rcu_tasks_holdout_list);
+	WRITE_ONCE(t->rcu_tasks_holdout, false);
+	raw_spin_unlock_irqrestore(&rcu_tasks_tramp_lock, flags);
+}
+
+/**
+ * rcu_tasks_irq_resched_enter - Tasks RCU hook for the irq-exit reschedule check
+ * @ip: instruction pointer of the interrupted (task-level) context
+ *
+ * Called with interrupts disabled when an interrupt returning to kernel
+ * mode is about to preempt_schedule_irq(), the one context switch that can
+ * catch a task inside unmarked trampoline text.  Record where the task is
+ * parked for as long as it is (rcu_tasks_wait_irq_preempted() looks at
+ * that), and if it is inside such text make it a holdout before
+ * __schedule() reports the quiescent event; if it is not, this is as good
+ * as a voluntary switch for ending an earlier hold.
+ */
+void rcu_tasks_irq_resched_enter(unsigned long ip)
+{
+	struct task_struct *t = current;
+	struct rcu_tasks_percpu *rtpcp = this_cpu_ptr(rcu_tasks.rtpcpu);
+
+	lockdep_assert_irqs_disabled();
+	WRITE_ONCE(t->rcu_tasks_irq_ip, ip);
+	t->rcu_tasks_exit_cpu = smp_processor_id();
+	raw_spin_lock_rcu_node(rtpcp);
+	list_add(&t->rcu_tasks_exit_list, &rtpcp->rtp_exit_list);
+	raw_spin_unlock_rcu_node(rtpcp);