1 files changed, 29 insertions, 3 deletions

diff --git a/kernel/rcu/tasks.h b/kernel/rcu/tasks.h
index 1fa631168594..f54d5782eca0 100644
--- a/kernel/rcu/tasks.h
+++ b/kernel/rcu/tasks.h
@@ -895,10 +895,36 @@ static void rcu_tasks_pregp_step(struct list_head *hop)
 	synchronize_rcu();
 }
 
+/* Check for quiescent states since the pregp's synchronize_rcu() */
+static bool rcu_tasks_is_holdout(struct task_struct *t)
+{
+	int cpu;
+
+	/* Has the task been seen voluntarily sleeping? */
+	if (!READ_ONCE(t->on_rq))
+		return false;
+
+	/*
+	 * Idle tasks (or idle injection) within the idle loop are RCU-tasks
+	 * quiescent states. But CPU boot code performed by the idle task
+	 * isn't a quiescent state.
+	 */
+	if (is_idle_task(t))
+		return false;
+
+	cpu = task_cpu(t);
+
+	/* Idle tasks on offline CPUs are RCU-tasks quiescent states. */
+	if (t == idle_task(cpu) && !rcu_cpu_online(cpu))
+		return false;
+
+	return true;
+}
+
 /* Per-task initial processing. */
 static void rcu_tasks_pertask(struct task_struct *t, struct list_head *hop)
 {
-	if (t != current && READ_ONCE(t->on_rq) && !is_idle_task(t)) {
+	if (t != current && rcu_tasks_is_holdout(t)) {
 		get_task_struct(t);
 		t->rcu_tasks_nvcsw = READ_ONCE(t->nvcsw);
 		WRITE_ONCE(t->rcu_tasks_holdout, true);
@@ -947,7 +973,7 @@ static void check_holdout_task(struct task_struct *t,
 
 	if (!READ_ONCE(t->rcu_tasks_holdout) ||
 	    t->rcu_tasks_nvcsw != READ_ONCE(t->nvcsw) ||
-	    !READ_ONCE(t->on_rq) ||
+	    !rcu_tasks_is_holdout(t) ||
 	    (IS_ENABLED(CONFIG_NO_HZ_FULL) &&
 	     !is_idle_task(t) && t->rcu_tasks_idle_cpu >= 0)) {
 		WRITE_ONCE(t->rcu_tasks_holdout, false);
@@ -1525,7 +1551,7 @@ static int trc_inspect_reader(struct task_struct *t, void *bhp_in)
 	} else {
 		// The task is not running, so C-language access is safe.
 		nesting = t->trc_reader_nesting;
-		WARN_ON_ONCE(ofl && task_curr(t) && !is_idle_task(t));
+		WARN_ON_ONCE(ofl && task_curr(t) && (t != idle_task(task_cpu(t))));
 		if (IS_ENABLED(CONFIG_TASKS_TRACE_RCU_READ_MB) && ofl)
 			n_heavy_reader_ofl_updates++;
 	}