linux-kernel - [PATCH] genirq/irq_sim: Make the irq_work always run in hard irq context.

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Message-ID: <YnuZBoEVMGwKkLm+@linutronix.de>
Date:   Wed, 11 May 2022 13:07:50 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     linux-kernel@...r.kernel.org
Cc:     Thomas Gleixner <tglx@...utronix.de>
Subject: [PATCH] genirq/irq_sim: Make the irq_work always run in hard irq
 context.

The IRQ simulator uses irq_work to trigger an interrupt. Without the
IRQ_WORK_HARD_IRQ flag the irq_work will be performed in thread context
on PREEMPT_RT. This causes locking errors later in handle_simple_irq()
which expects to be invoked with disabled interrupts.

Triggering individual interrupts in hardirq context should not lead to
unexpected high latencies since this is also what the hardware
controller does. Also it is used as a simulator so…

Use IRQ_WORK_INIT_HARD() to carry out the irq_work in hardirq context on
PREEMPT_RT.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 kernel/irq/irq_sim.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/kernel/irq/irq_sim.c b/kernel/irq/irq_sim.c
index 0cd02efa3a742..dd76323ea3fd7 100644
--- a/kernel/irq/irq_sim.c
+++ b/kernel/irq/irq_sim.c
@@ -181,7 +181,7 @@ struct irq_domain *irq_domain_create_sim(struct fwnode_handle *fwnode,
 		goto err_free_bitmap;

 	work_ctx->irq_count = num_irqs;
-	init_irq_work(&work_ctx->work, irq_sim_handle_irq);
+	work_ctx->work = IRQ_WORK_INIT_HARD(irq_sim_handle_irq);

 	return work_ctx->domain;

-- 
2.36.1