netdev - Re: [net-next 03/14] lib: cpu_rmap: Add irq_cpu_rmap_remove to complement irq_cpu_rmap

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Message-ID: <87aa5292-d59b-9789-1326-91805da34831@nvidia.com>
Date:   Wed, 22 Mar 2023 13:24:33 +0200
From:   Eli Cohen <elic@...dia.com>
To:     Jakub Kicinski <kuba@...nel.org>, Saeed Mahameed <saeed@...nel.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Paolo Abeni <pabeni@...hat.com>,
        Eric Dumazet <edumazet@...gle.com>,
        Saeed Mahameed <saeedm@...dia.com>, netdev@...r.kernel.org,
        Tariq Toukan <tariqt@...dia.com>
Subject: Re: [net-next 03/14] lib: cpu_rmap: Add irq_cpu_rmap_remove to
 complement irq_cpu_rmap_add


On 22/03/2023 5:46, Jakub Kicinski wrote:
> On Mon, 20 Mar 2023 10:51:33 -0700 Saeed Mahameed wrote:
>> From: Eli Cohen <elic@...dia.com>
>>
>> Add a function to complement irq_cpu_rmap_add(). It removes the irq from
>> the reverse mapping by setting the notifier to NULL.
> Poor commit message. You should mention that glue is released and
> cleared via the kref.

Why is it necessary to mention glue which is internal to the 
implementation and is not part of the API?


>
> BTW who can hold the kref? What are the chances that user will call:

The glue kref is used to ensure the glue is not remove when the callback 
is called in the workqueue context.

Re chances, not really high since a driver usually deals with rmap at 
load and unload time.

>
> 	irq_cpu_rmap_remove()
> 	irq_cpu_rmap_add()
>
> and the latter will fail because glue was held?
The kref is taken for the duration of the callback
>
>> diff --git a/include/linux/cpu_rmap.h b/include/linux/cpu_rmap.h
>> index 0ec745e6cd36..58284f1f3a58 100644
>> --- a/include/linux/cpu_rmap.h
>> +++ b/include/linux/cpu_rmap.h
>> @@ -60,6 +60,8 @@ static inline struct cpu_rmap *alloc_irq_cpu_rmap(unsigned int size)
>>   }
>>   extern void free_irq_cpu_rmap(struct cpu_rmap *rmap);
>>   
>> +extern int irq_cpu_rmap_remove(struct cpu_rmap *rmap, int irq);
>>   extern int irq_cpu_rmap_add(struct cpu_rmap *rmap, int irq);
>>   
>> +
> use checkpatch, please :(
Sorry about this :-)