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

This reverts commit f7345ccc62a4b880cf76458db5f320725f28e400.

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/[e-mail]/
Reviewed-by: Usama Arif <[e-mail]>
Reviewed-by: Joel Fernandes <[e-mail]>
Signed-off-by: Frederic Weisbecker <[e-mail]>
Signed-off-by: Joel Fernandes <[e-mail]>

kernel/rcu/tree_nocb.h

···
 			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"));