On Thu, 21 Oct 2021 19:02:22 +0100,
Mark Rutland [off-list ref] wrote:

quoted

As bcm6345_l1_irq_handle() is a chained irqchip handler, it will be
invoked within the context of the root irqchip handler, which must have
entered IRQ context already.

When bcm6345_l1_irq_handle() calls arch/mips's do_IRQ() , this will nest
another call to irq_enter(), and the resulting nested increment to
`rcu_data.dynticks_nmi_nesting` will cause rcu_is_cpu_rrupt_from_idle()
to fail to identify wakeups from idle, resulting in failure to preempt,
and RCU stalls.

Chained irqchip handlers must invoke IRQ handlers by way of thee core
irqchip code, i.e. generic_handle_irq() or generic_handle_domain_irq()
and should not call do_IRQ(), which is intended only for root irqchip
handlers.

Fix bcm6345_l1_irq_handle() by calling generic_handle_irq() directly.

Fixes: c7c42ec2baa1de7a ("irqchips/bmips: Add bcm6345-l1 interrupt controller")
Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Thomas Gleixner <redacted>
---
 drivers/irqchip/irq-bcm6345-l1.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/irqchip/irq-bcm6345-l1.c b/drivers/irqchip/irq-bcm6345-l1.c
index e3483789f4df..1bd0621c4ce2 100644
--- a/drivers/irqchip/irq-bcm6345-l1.c
+++ b/drivers/irqchip/irq-bcm6345-l1.c

@@ -140,7 +140,7 @@ static void bcm6345_l1_irq_handle(struct irq_desc *desc)
 		for_each_set_bit(hwirq, &pending, IRQS_PER_WORD) {
 			irq = irq_linear_revmap(intc->domain, base + hwirq);
 			if (irq)
-				do_IRQ(irq);
+				generic_handle_irq(irq);
 			else
 				spurious_interrupt();
 		}

A marginally better fix would be to have:

diff --git a/drivers/irqchip/irq-bcm6345-l1.c b/drivers/irqchip/irq-bcm6345-l1.c
index 1bd0621c4ce2..fd079215c17f 100644
--- a/drivers/irqchip/irq-bcm6345-l1.c
+++ b/drivers/irqchip/irq-bcm6345-l1.c

@@ -132,16 +132,12 @@ static void bcm6345_l1_irq_handle(struct irq_desc *desc)
 		int base = idx * IRQS_PER_WORD;
 		unsigned long pending;
 		irq_hw_number_t hwirq;
-		unsigned int irq;
 
 		pending = __raw_readl(cpu->map_base + reg_status(intc, idx));
 		pending &= __raw_readl(cpu->map_base + reg_enable(intc, idx));
 
 		for_each_set_bit(hwirq, &pending, IRQS_PER_WORD) {
-			irq = irq_linear_revmap(intc->domain, base + hwirq);
-			if (irq)
-				generic_handle_irq(irq);
-			else
+			if (generic_handle_domain_irq(intc->domain, base + hwirq))
 				spurious_interrupt();
 		}
 	}

but we can also tackle that separately if you'd rather keep the change
minimal.