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

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Message-ID: <667a3b25-32a0-745f-a1a5-e76e2ffc7c8b@cumulusnetworks.com>
Date:   Sat, 22 Apr 2017 08:14:16 -0600
From:   David Ahern <dsa@...ulusnetworks.com>
To:     Dmitry Vyukov <dvyukov@...gle.com>, Martin KaFai Lau <kafai@...com>
Cc:     netdev <netdev@...r.kernel.org>,
        andreyknvl <andreyknvl@...gle.com>, mmanning@...cade.com
Subject: Re: [PATCH net] net: ipv6: regenerate host route if moved to gc list

On 4/22/17 3:14 AM, Dmitry Vyukov wrote:
>> One small question.  Why cmpxchg is needed instead
>> of a ip6_rt_put() and then assign?
>> Is it fixing another bug?
> cmpxchg here looks fishy.
> If there are no concurrent modifications, then it is not needed.
> If there are and cmpxchg fails, then we will put the installed rt and
> leak the new one.
> 

Yes, I need to convert that to changing the rt under a lock.

Leftover from the beginning of the investigation when I suspected
locking and recalled Li's patch. I'll send a v2.