Patch "irq: mips: avoid nested irq_enter()" has been added to the 4.14-stable tree

[Sasha Levin <sashal@xxxxxxxxxx>]

This is a note to let you know that I've just added the patch titled

    irq: mips: avoid nested irq_enter()

to the 4.14-stable tree which can be found at:
    http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
     irq-mips-avoid-nested-irq_enter.patch
and it can be found in the queue-4.14 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.



commit 372ce4c533cb946522fc3da130bf79eec5c56a59
Author: Mark Rutland <mark.rutland@xxxxxxx>
Date:   Wed Oct 20 17:25:22 2021 +0100

    irq: mips: avoid nested irq_enter()
    
    [ Upstream commit c65b52d02f6c1a06ddb20cba175ad49eccd6410d ]
    
    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@xxxxxxx>
    Reviewed-by: Marc Zyngier <maz@xxxxxxxxxx>
    Acked-by: Thomas Bogendoerfer <tsbogend@xxxxxxxxxxxxxxxx>
    Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
    Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>

diff --git a/drivers/irqchip/irq-bcm6345-l1.c b/drivers/irqchip/irq-bcm6345-l1.c
index 43f8abe40878a..31ea6332ecb83 100644
--- a/drivers/irqchip/irq-bcm6345-l1.c
+++ b/drivers/irqchip/irq-bcm6345-l1.c
@@ -143,7 +143,7 @@ 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();
 		}