Re: [PATCH 3.18-rc3 v8 1/4] irqchip: gic: Make gic_raise_softirq() FIQ-safe

From: Thomas Gleixner
Date: Mon Nov 24 2014 - 13:20:30 EST


On Fri, 14 Nov 2014, Daniel Thompson wrote:
> diff --git a/drivers/irqchip/irq-gic.c b/drivers/irqchip/irq-gic.c
> index 38493ff28fa5..0db62a6f1ee3 100644
> --- a/drivers/irqchip/irq-gic.c
> +++ b/drivers/irqchip/irq-gic.c
> @@ -73,6 +73,13 @@ struct gic_chip_data {
> static DEFINE_RAW_SPINLOCK(irq_controller_lock);
>
> /*
> + * This lock may be locked for reading by FIQ handlers. Thus although
> + * read locking may be used liberally, write locking must only take
> + * place only when local FIQ handling is disabled.
> + */
> +static DEFINE_RWLOCK(fiq_safe_cpu_map_lock);
> +
> +/*
> * The GIC mapping of CPU interfaces does not necessarily match
> * the logical CPU numbering. Let's use a mapping as returned
> * by the GIC itself.
> @@ -624,7 +631,7 @@ static void gic_raise_softirq(const struct cpumask *mask, unsigned int irq)
> int cpu;
> unsigned long flags, map = 0;
>
> - raw_spin_lock_irqsave(&irq_controller_lock, flags);
> + read_lock_irqsave(&fiq_safe_cpu_map_lock, flags);

Just for the record:

You might have noticed that you replace a raw lock with a non raw
one. That's not an issue on mainline, but that pretty much renders
that code broken for RT.

Surely nothing I worry too much about given the current state of RT.

Thanks,

tglx
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