Re: [Xen-devel] [RFC PATCH v1 06/10] xen/arm: split gic driver into generic and gicv2 driver

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Wed, 2014-03-19 at 19:47 +0530, vijay.kilari@xxxxxxxxx wrote:

> +/* Global state */
> +static struct {
> +    int hw_version;
> +    paddr_t dbase;       /* Address of distributor registers */
> +    paddr_t cbase;       /* Address of CPU interface registers */
> +    paddr_t hbase;       /* Address of virtual interface registers */
> +    paddr_t vbase;       /* Address of virtual cpu interface registers */
> +    unsigned int lines;  /* Number of interrupts (SPIs + PPIs + SGIs) */
> +    struct dt_irq maintenance; /* IRQ maintenance */
> +    unsigned int cpus;
> +    spinlock_t lock;
> +} gic;
> +
[...]
> +        spin_lock(&gic.lock);
> [...]
> +    spin_lock(&gic.lock);
> diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
> index bb718f6..e0859ae 100644
> --- a/xen/arch/arm/gic.c
> +++ b/xen/arch/arm/gic.c
[...]
> +spinlock_t gic_lock;
> [...]
> @@ -151,12 +107,12 @@ static void gic_irq_enable(struct irq_desc *desc)
>      unsigned long flags;
>  
>      spin_lock_irqsave(&desc->lock, flags);
> -    spin_lock(&gic.lock);
> +    spin_lock(&gic_lock);

You seem to have divided the gic lock into two, is that deliberate?

What is the locking hierarchy between them?

> @@ -286,9 +221,9 @@ static int gic_route_irq(unsigned int irq, bool_t level,
>  
>      desc->handler = &gic_host_irq_type;
>  
> -    spin_lock(&gic.lock);
> +    spin_lock(&gic_lock);

e.g. this function will call through to hook in the gic-v2 code which
used to require gic.lock to be taken, and accordig to the comment it
still does after this refactoring. Yet that lock isn't held here any
more (nor is it accessible to this code).

>      gic_set_irq_properties(irq, level, cpu_mask, priority);
> -    spin_unlock(&gic.lock);
> +    spin_unlock(&gic_lock);
>  
>      spin_unlock_irqrestore(&desc->lock, flags);
>      return 0;

Ian.


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