}
/*
+ * Awaken the grace-period kthread for the specified flavor of RCU.
+ * Don't do a self-awaken, and don't bother awakening when there is
+ * nothing for the grace-period kthread to do (as in several CPUs
+ * raced to awaken, and we lost), and finally don't try to awaken
+ * a kthread that has not yet been created.
+ */
+static void rcu_gp_kthread_wake(struct rcu_state *rsp)
+{
+ if (current == rsp->gp_kthread ||
+ !ACCESS_ONCE(rsp->gp_flags) ||
+ !rsp->gp_kthread)
+ return;
+ wake_up(&rsp->gp_wq);
+}
+
+/*
* If there is room, assign a ->completed number to any callbacks on
* this CPU that have not already been assigned. Also accelerate any
* callbacks that were previously assigned a ->completed number that has
struct rcu_state *rsp = container_of(work, struct rcu_state, wakeup_work);
/* Wake up rcu_gp_kthread() to start the grace period. */
- wake_up(&rsp->gp_wq);
+ rcu_gp_kthread_wake(rsp);
}
/*
{
WARN_ON_ONCE(!rcu_gp_in_progress(rsp));
raw_spin_unlock_irqrestore(&rcu_get_root(rsp)->lock, flags);
- wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */
+ rcu_gp_kthread_wake(rsp);
}
/*
}
rsp->gp_flags |= RCU_GP_FLAG_FQS;
raw_spin_unlock_irqrestore(&rnp_old->lock, flags);
- wake_up(&rsp->gp_wq); /* Memory barrier implied by wake_up() path. */
+ rcu_gp_kthread_wake(rsp);
}
/*