linux-kernel - Re: [PATCH v2] genirq/irqdesc: fix WARNING in irq_sysfs

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Date:   Mon, 28 Nov 2022 18:20:24 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Yang Yingliang <yangyingliang@...wei.com>
Cc:     tglx@...utronix.de, kraig@...gle.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] genirq/irqdesc: fix WARNING in irq_sysfs_del()

On Mon, Nov 28, 2022 at 11:16:12PM +0800, Yang Yingliang wrote:
> I got the lots of WARNING report when doing fault injection test:
> 
> kernfs: can not remove 'chip_name', no directory
> WARNING: CPU: 0 PID: 253 at fs/kernfs/dir.c:1616 kernfs_remove_by_name_ns+0xce/0xe0
> RIP: 0010:kernfs_remove_by_name_ns+0xce/0xe0
> Call Trace:
>  <TASK>
>  remove_files.isra.1+0x3f/0xb0
>  sysfs_remove_group+0x68/0xe0
>  sysfs_remove_groups+0x41/0x70
>  __kobject_del+0x45/0xc0
>  kobject_del+0x29/0x40
>  free_desc+0x42/0x70
>  irq_free_descs+0x5e/0x90
> 
> kernfs: can not remove 'hwirq', no directory
> WARNING: CPU: 0 PID: 253 at fs/kernfs/dir.c:1616 kernfs_remove_by_name_ns+0xce/0xe0
> RIP: 0010:kernfs_remove_by_name_ns+0xce/0xe0
> Call Trace:
>  <TASK>
>  remove_files.isra.1+0x3f/0xb0
>  sysfs_remove_group+0x68/0xe0
>  sysfs_remove_groups+0x41/0x70
>  __kobject_del+0x45/0xc0
>  kobject_del+0x29/0x40
>  free_desc+0x42/0x70
>  irq_free_descs+0x5e/0x90
> 
> If irq_sysfs_add() fails in alloc_descs(), the directory of interrupt
> informations is not added to sysfs, it causes the WARNINGs when removing
> the information files. Add 'sysfs_added' field in struct irq_desc to
> indicate if it is added, and check it before calling kobject_del() to
> avoid these WARNINGs.
> 
> Fixes: ecb3f394c5db ("genirq: Expose interrupt information through sysfs")
> Signed-off-by: Yang Yingliang <yangyingliang@...wei.com>
> ---
> v1 -> v2:
>   Don't use state_in_sysfs, introduce 'sysfs_added' to indicate if it is added.
> ---
>  include/linux/irqdesc.h | 1 +
>  kernel/irq/irqdesc.c    | 7 +++++--
>  2 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/include/linux/irqdesc.h b/include/linux/irqdesc.h
> index 844a8e30e6de..fec0f3946a34 100644
> --- a/include/linux/irqdesc.h
> +++ b/include/linux/irqdesc.h
> @@ -97,6 +97,7 @@ struct irq_desc {
>  #ifdef CONFIG_SPARSE_IRQ
>  	struct rcu_head		rcu;
>  	struct kobject		kobj;
> +	bool			sysfs_added;
>  #endif
>  	struct mutex		request_mutex;
>  	int			parent_irq;
> diff --git a/kernel/irq/irqdesc.c b/kernel/irq/irqdesc.c
> index a91f9001103c..9bf74d11bad5 100644
> --- a/kernel/irq/irqdesc.c
> +++ b/kernel/irq/irqdesc.c
> @@ -292,6 +292,8 @@ static void irq_sysfs_add(int irq, struct irq_desc *desc)
>  		 */
>  		if (kobject_add(&desc->kobj, irq_kobj_base, "%d", irq))
>  			pr_warn("Failed to add kobject for irq %d\n", irq);
> +		else
> +			desc->sysfs_added = true;

Wait, no.  Why are you just not properly failing and unwinding here?
Why do you need a special flag just to say "sysfs worked" or not unlike
all other users of kobjects.

Fix this up properly please.

thanks,

greg k-h