Revert "rcu/nocb: Fix rcuog wake-up from offline softirq"

JIRA: https://issues.redhat.com/browse/RHEL-79879

commit b95d159
Author: Frederic Weisbecker <frederic@kernel.org>
Date:   Tue Dec 31 18:07:12 2024 +0100

	This reverts commit f7345cc.

	swake_up_one_online() has been removed because hrtimers can now assign
	a proper online target to hrtimers queued from offline CPUs. Therefore
	remove the related hackery.

	Link: https://lore.kernel.org/all/20241231170712.149394-4-frederic@kernel.org/
	Reviewed-by: Usama Arif <usamaarif642@gmail.com>
	Reviewed-by: Joel Fernandes <joelagnelf@nvidia.com>
	Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
	Signed-off-by: Joel Fernandes <joelagnelf@nvidia.com>

Signed-off-by: Čestmír Kalina <ckalina@redhat.com>

Author: ckalina

kernel/rcu/tree_nocb.h

@@ -554,19 +554,13 @@ static void __call_rcu_nocb_wake(struct rcu_data *rdp, bool was_alldone,
 			rcu_nocb_unlock(rdp);
 			wake_nocb_gp_defer(rdp, RCU_NOCB_WAKE_LAZY,
 					   TPS("WakeLazy"));
-		} else if (!irqs_disabled_flags(flags) && cpu_online(rdp->cpu)) {
+		} else if (!irqs_disabled_flags(flags)) {
 			/* ... if queue was empty ... */
 			rcu_nocb_unlock(rdp);
 			wake_nocb_gp(rdp, false);
 			trace_rcu_nocb_wake(rcu_state.name, rdp->cpu,
 					    TPS("WakeEmpty"));
 		} else {
-			/*
-			 * Don't do the wake-up upfront on fragile paths.
-			 * Also offline CPUs can't call swake_up_one_online() from
-			 * (soft-)IRQs. Rely on the final deferred wake-up from
-			 * rcutree_report_cpu_dead()
-			 */
 			rcu_nocb_unlock(rdp);
 			wake_nocb_gp_defer(rdp, RCU_NOCB_WAKE,
 					   TPS("WakeEmptyIsDeferred"));