Re: [PATCH] ipipe: Fix ipipe level irq end

[Jan Kiszka <jan.kiszka@siemens.com>]

On 10.02.22 16:33, Gunter Grau via Xenomai wrote:
> The following commit in the vanilla kernel introduced
> a check for the cached interrupt mask flag in mask_irq():
> 
> bf22ff45bed6 ("genirq: Avoid unnecessary low level irq function calls")
> 
> This means if the flag is not serviced correctly
> the real bit in the hardware interrupt controller may not be
> cleared or set.
> The __ipipe_end_level_irq() function does not follow this rule.
> It unmasks the bit in the hardware without setting the cached flags
> accordingly. So after the first level interrupt is finished the
> mask cache has a wrong state. If now the next interrupt fires,
> the mask_irq() function will not really mask the interrupt in
> the hardware which causes a interrupt storm after reenabeling
> the hard irqs.
> The fix now calls unmask_irq() which is handling the cached flags
> correctly.
> 
> Signed-off-by: Gunter Grau <gunter.grau@philips.com>
> ---
>  kernel/irq/chip.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/irq/chip.c b/kernel/irq/chip.c
> index 7c03e2931189..79a09b92a1b1 100644
> --- a/kernel/irq/chip.c
> +++ b/kernel/irq/chip.c
> @@ -987,7 +987,7 @@ void __ipipe_ack_level_irq(struct irq_desc *desc)
> 
>  void __ipipe_end_level_irq(struct irq_desc *desc)
>  {
> -       desc->irq_data.chip->irq_unmask(&desc->irq_data);
> +       unmask_irq(desc);
>  }
> 
>  void __ipipe_ack_fasteoi_irq(struct irq_desc *desc)
> --
> 2.25.1
> 

OK, so this is 4.14+, i.e. possibly our 4.19 and 5.4 ipipe trees, and
that generically. Need to check why we didn't see this in our tests so
far...

Jan

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