[PATCH 2/3 v3] rcu: Remove swake_up_one_online() bandaid

Frederic Weisbecker
2024-12-31T17:07:32Z

It's now ok to perform a wake-up from an offline CPU because the
resulting armed scheduler bandwidth hrtimers are now correctly targeted
by hrtimer infrastructure.

Remove the obsolete hackerry.

Reviewed-by: Usama Arif <usamaarif642@gmail.com>
Signed-off-by: Frederic Weisbecker <frederic@kernel.org>
---
kernel/rcu/tree.c | 34 +---------------------------------
kernel/rcu/tree_exp.h | 2 +-
kernel/rcu/tree_nocb.h | 2 +-
3 files changed, 3 insertions(+), 35 deletions(-)

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index ff98233d4aa5..7c433c6b35ea 100644
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -1061,38 +1061,6 @@ static bool rcu_future_gp_cleanup(struct rcu_node *rnp)
return needmore;
}

-static void swake_up_one_online_ipi(void *arg)
-{
- struct swait_queue_head *wqh = arg;
-
- swake_up_one(wqh);
-}
-
-static void swake_up_one_online(struct swait_queue_head *wqh)
-{
- int cpu = get_cpu();
-
- /*
- * If called from rcutree_report_cpu_starting(), wake up
- * is dangerous that late in the CPU-down hotplug process. The
- * scheduler might queue an ignored hrtimer. Defer the wake up
- * to an online CPU instead.
- */
- if (unlikely(cpu_is_offline(cpu))) {
- int target;
-
- target = cpumask_any_and(housekeeping_cpumask(HK_TYPE_RCU),
- cpu_online_mask);
-
- smp_call_function_single(target, swake_up_one_online_ipi,
- wqh, 0);
- put_cpu();
- } else {
- put_cpu();
- swake_up_one(wqh);
- }
-}
-
/*
* Awaken the grace-period kthread. Don't do a self-awaken (unless in an
* interrupt or softirq handler, in which case we just might immediately
@@ -1117,7 +1085,7 @@ static void rcu_gp_kthread_wake(void)
return;
WRITE_ONCE(rcu_state.gp_wake_time, jiffies);
WRITE_ONCE(rcu_state.gp_wake_seq, READ_ONCE(rcu_state.gp_seq));
- swake_up_one_online(&rcu_state.gp_wq);
+ swake_up_one(&rcu_state.gp_wq);
}

/*
diff --git a/kernel/rcu/tree_exp.h b/kernel/rcu/tree_exp.h
index fb664d3a01c9..17b1a5e3590c 100644
--- a/kernel/rcu/tree_exp.h
+++ b/kernel/rcu/tree_exp.h
@@ -200,7 +200,7 @@ static void __rcu_report_exp_rnp(struct rcu_node *rnp,
if (rnp->parent == NULL) {
raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
if (wake)
- swake_up_one_online(&rcu_state.expedited_wq);
+ swake_up_one(&rcu_state.expedited_wq);

break;
}
diff --git a/kernel/rcu/tree_nocb.h b/kernel/rcu/tree_nocb.h
index 2605dd234a13..a43141a1b3a5 100644
--- a/kernel/rcu/tree_nocb.h
+++ b/kernel/rcu/tree_nocb.h
@@ -216,7 +216,7 @@ static bool __wake_nocb_gp(struct rcu_data *rdp_gp,
raw_spin_unlock_irqrestore(&rdp_gp->nocb_gp_lock, flags);
if (needwake) {
trace_rcu_nocb_wake(rcu_state.name, rdp->cpu, TPS("DoWake"));
- swake_up_one_online(&rdp_gp->nocb_gp_wq);
+ swake_up_one(&rdp_gp->nocb_gp_wq);
}

return needwake;
--
2.46.0