linux-kernel - Re: [PATCH v3 3/3] genirq: Use the maple tree for IRQ descriptors management

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Date:   Wed, 10 May 2023 12:15:30 -0500
From:   Shanker Donthineni <sdonthineni@...dia.com>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Yujie Liu <yujie.liu@...el.com>, oe-lkp@...ts.linux.dev,
        lkp@...el.com, linux-kernel@...r.kernel.org,
        Marc Zyngier <maz@...nel.org>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>,
        Michael Walle <michael@...le.cc>,
        Vikram Sethi <vsethi@...dia.com>
Subject: Re: [PATCH v3 3/3] genirq: Use the maple tree for IRQ descriptors
 management

Hi Thomas,

On 5/10/23 10:19, Shanker Donthineni wrote:
> 
> Apologies for my lack of familiarity with the maple tree data structure and
> not testing all functions. I received advice from the review comments below
> regarding the iterator. I am looking for your guidance to address the issue
> with the iterator if not possible can we increase NR_IRQS for ARM64 arch.
> 
> 
> https://lore.kernel.org/linux-arm-kernel/875ydej9ur.ffs@tglx/
> 
> static unsigned int irq_find_next_irq(unsigned int offset)
> {
>          MA_STATE(mas, &sparse_irqs, offset, nr_irqs);
>          struct irq_desc *desc = mas_next(&mas, nr_irqs);
> 
>          return desc ? irq_desc_get_irq(desc) : nr_irqs;
> }

The problem has been resolved, and I have confirmed the functionality of
CPU hot-unplug on ARM64 systems. I have posted v4 to fix the issue.

https://lore.kernel.org/lkml/20230510170033.3303076-4-sdonthineni@nvidia.com/T/#mfa8e2a5490f275cfecb2e93473c24f35db7adcaf

I have made the change of replacing mt_next() with mt_find() in irq_find_next_irq() function.
  
static unsigned int irq_find_next_irq(unsigned int offset)
{
         unsigned long index = offset;
         struct irq_desc *desc = mt_find(&sparse_irqs, &index, nr_irqs);

         return desc ? irq_desc_get_irq(desc) : nr_irqs;
}

-Shanker