Re: [PATCH RFC net-next v2 7/7] net: skbuff: always try to recycle PP pages directly when in softirq

[Alexander Lobakin]

From: Yunsheng Lin <linyunsheng@xxxxxxxxxx>
Date: Fri, 21 Jul 2023 19:53:33 +0800

> On 2023/7/21 3:46, Jakub Kicinski wrote:
>> On Thu, 20 Jul 2023 21:33:40 +0200 Alexander Lobakin wrote:
>>>> We can as well check
>>>> 	(in_softirq() && !irqs_disabled() && !in_hardirq())
>>>> ?  
>>>
>>> Yes, something like that. Messy, but I see no other options...
>>>
>>> So, I guess you want to add an assertion to make sure that we're *not*
>>> in this:
>>>
>>> in_hardirq() || irqs_disabled()
>>>
>>> Does this mean that after it's added, my patch is sane? :p
>>
>> Well... it's acceptable. Make sure you add a good, informative
>> but concise comment :)
>>
> 
> Does it mean ptr_ring_produce_any() is needed in
> page_pool_recycle_in_ring() too?
> 
> As it is assumed that page pool API can be called in the context with
> irqs_disabled() || in_hardirq(), and force recylcling happens in the
> prt_ring.
> 
> Isn't it conflit with the below patch? as the below patch assume page
> pool API can not be called in the context with irqs_disabled() || in_hardirq():
> [PATCH net-next] page_pool: add a lockdep check for recycling in hardirq
> 
> Or am I missing something obvious here?

No, Page Pool is *not* intended to be called when IRQs are disabled,
hence the fix Jakub's posted in the separate thread.

Thanks,
Olek