From 921f1acebb2d0e4f5582e03cdd829cc6876a478c Mon Sep 17 00:00:00 2001
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Date: Mon, 15 Feb 2021 18:44:12 +0100
Subject: [PATCH 131/327] smp: Wake ksoftirqd on PREEMPT_RT instead
 do_softirq().

The softirq implementation on PREEMPT_RT does not provide do_softirq().
The other user of do_softirq() is replaced with a local_bh_disable()
+ enable() around the possible raise-softirq invocation. This can not be
done here because migration_cpu_stop() is invoked with disabled
preemption.

Wake the softirq thread on PREEMPT_RT if there are any pending softirqs.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
---
 kernel/smp.c | 14 ++++++++++++--
 1 file changed, 12 insertions(+), 2 deletions(-)

diff --git a/kernel/smp.c b/kernel/smp.c
index c6b3ad79c72b..f5493a8ff1db 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -450,8 +450,18 @@ void flush_smp_call_function_from_idle(void)
 
 	local_irq_save(flags);
 	flush_smp_call_function_queue(true);
-	if (local_softirq_pending())
-		do_softirq();
+
+	if (local_softirq_pending()) {
+
+		if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
+			do_softirq();
+		} else {
+			struct task_struct *ksoftirqd = this_cpu_ksoftirqd();
+
+			if (ksoftirqd && ksoftirqd->state != TASK_RUNNING)
+				wake_up_process(ksoftirqd);
+		}
+	}
 
 	local_irq_restore(flags);
 }
-- 
2.49.0

