netdev - Re: [PATCH] iavf: fix locking of critical sections

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Message-ID: <3a4078fe-0be5-745c-91a3-ed83d4dc372f@kpanic.de>
Date:   Wed, 17 Mar 2021 08:49:37 +0100
From:   Stefan Assmann <sassmann@...nic.de>
To:     Jesse Brandeburg <jesse.brandeburg@...el.com>,
        Jakub Kicinski <kuba@...nel.org>
Cc:     intel-wired-lan@...ts.osuosl.org, netdev@...r.kernel.org,
        anthony.l.nguyen@...el.com, lihong.yang@...el.com,
        slawomirx.laba@...el.com, nicholas.d.nunley@...el.com
Subject: Re: [PATCH] iavf: fix locking of critical sections

On 16.03.21 23:02, Jesse Brandeburg wrote:
> Jakub Kicinski wrote:
>>>> I personally think that the overuse of flags in Intel drivers brings
>>>> nothing but trouble. At which point does it make sense to just add a
>>>> lock / semaphore here rather than open code all this with no clear
>>>> semantics? No code seems to just test the __IAVF_IN_CRITICAL_TASK flag,
>>>> all the uses look like poor man's locking at a quick grep. What am I
>>>> missing?
>>>
>>> I agree with you that the locking could be done with other locking
>>> mechanisms just as good. I didn't invent the current method so I'll let
>>> Intel comment on that part, but I'd like to point out that what I'm
>>> making use of is fixing what is currently in the driver.
>>
>> Right, I should have made it clear that I don't blame you for the
>> current state of things. Would you mind sending a patch on top of 
>> this one to do a conversion to a semaphore? 

Sure, I'm happy to help working on the conversion once the current issue
is resolved.

>> Intel folks any opinions?
> 
> I know Slawomir has been working closely with Stefan on figuring out
> the right ways to fix this code.  Hopefully he can speak for himself,
> but I know he's on Europe time.
> 
> As for conversion to mutexes I'm a big fan, and as long as we don't
> have too many collisions with the RTNL lock I think it's a reasonable
> improvement to do, and if Stefan doesn't want to work on it, we can
> look into whether Slawomir or his team can.

I'd appreciate to be involved.
Thanks!

  Stefan