netdev - Re: [PATCH v2 net] net: ipv6: regenerate host route if moved to gc list

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Message-ID: <607a26c5-4cb4-b84b-37a0-b79ea6b9df26@cumulusnetworks.com>
Date:   Sun, 23 Apr 2017 08:08:05 -0600
From:   David Ahern <dsa@...ulusnetworks.com>
To:     Martin KaFai Lau <kafai@...com>
Cc:     netdev@...r.kernel.org, dvyukov@...gle.com, andreyknvl@...gle.com,
        mmanning@...cade.com
Subject: Re: [PATCH v2 net] net: ipv6: regenerate host route if moved to gc
 list

On 4/22/17 8:28 PM, Martin KaFai Lau wrote:
>> The code path to fixup_permanent_addr is under RTNL, so the if check on
>> ifp->rt and rt6i_ref is ok -- neither can be changed since RTNL is held.
>>
>> Since ifp->rt can be accessed outside of RTNL, the spinlock is needed to
>> change its value.
> Got it. It is to protect the readers which are not under RTNL.
> Many thanks for pointing out what I was missing.  It all makes sense now.
> 
>> Arguably only 'ifp->rt = rt;' needs the spinlock.
> It still seems like the existing 'ifp->rt = rt;' needs protection
> anyway regardless of the rt regeneration change.  It would be nice to
> explain it in the commit log or even better separating it out
> into another patch.

I'll add a comment to the commit log when I send a v3 tomorrow morning.