linux-kernel - Re: [PATCH] irqdomain: remove debugfs_file from struct irq

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Message-ID: <9da32aa719280d2056a84b784d43976e@walle.cc>
Date:   Wed, 17 Feb 2021 23:21:22 +0100
From:   Michael Walle <michael@...le.cc>
To:     Marc Zyngier <maz@...nel.org>
Cc:     gregkh@...uxfoundation.org, linux-kernel@...r.kernel.org,
        tglx@...utronix.de
Subject: Re: [PATCH] irqdomain: remove debugfs_file from struct irq_domain

Am 2021-02-17 22:50, schrieb Marc Zyngier:
> On Wed, 17 Feb 2021 20:10:50 +0000,
> Michael Walle <michael@...le.cc> wrote:
>> 
>> Am 2021-02-17 21:02, schrieb Marc Zyngier:
>> > On 2021-02-17 19:57, Michael Walle wrote:
>> >> Hi Greg,
>> >>
>> >>> There's no need to keep around a dentry pointer to a simple file that
>> >>> debugfs itself can look up when we need to remove it from the system.
>> >>> So simplify the code by deleting the variable and cleaning up the
>> >>> logic
>> >>> around the debugfs file.
>> >>
>> >> This will generate the following oops on my board (arm64,
>> >> freescale/fsl-ls1028a-kontron-sl28-var3-ads2.dts). In debugfs_lookup()
>> >> debugfs_mount is NULL.
>> >
>> > That's odd. I gave it a go yesterday, and nothing blew up.
>> > Which makes me wonder whether I had the debug stuff enabled
>> > the first place...
>> >
>> > I've dropped the patch from -next for now until I figure it out
>> > (probably tomorrow).
>> 
>> Mh, maybe its my .config, I've attached it. I also noticed that
>> the board boots just fine in our kernel-ci [1].
> 
> I reproduced here. I had disabled GENERIC_IRQ_DEBUGFS for obscure
> reasons, and it caught fire as I re-enabled it.
> 
> Adding this fixes it for me:
> 
> diff --git a/kernel/irq/irqdomain.c b/kernel/irq/irqdomain.c
> index 367ff1c35f75..d8a14cf1a7b6 100644
> --- a/kernel/irq/irqdomain.c
> +++ b/kernel/irq/irqdomain.c
> @@ -1904,7 +1904,8 @@ static void debugfs_add_domain_dir(struct 
> irq_domain *d)
> 
>  static void debugfs_remove_domain_dir(struct irq_domain *d)
>  {
> -	debugfs_remove(debugfs_lookup(d->name, domain_dir));
> +	if (domain_dir)
> +		debugfs_remove(debugfs_lookup(d->name, domain_dir));
>  }
> 
>  void __init irq_domain_debugfs_init(struct dentry *root)
> 
> 
> Could you please check whether it works for you?

Works for me, too. Thanks.

-michael