From: Martin KaFai Lau <kafai@fb.com>
To: Eric Dumazet <eric.dumazet@gmail.com>
Cc: netdev <netdev@vger.kernel.org>,
"David S. Miller" <davem@davemloft.net>,
Kernel Team <kernel-team@fb.com>
Subject: Re: [PATCH net 3/3] ipv6: Fix dst_entry refcnt bugs in ip6_tunnel
Date: Wed, 2 Sep 2015 13:58:02 -0700 [thread overview]
Message-ID: <20150902205802.GA78846@kafai-mba.local> (raw)
In-Reply-To: <1441138460.8932.182.camel@edumazet-glaptop2.roam.corp.google.com>
On Tue, Sep 01, 2015 at 01:14:20PM -0700, Eric Dumazet wrote:
> > 2. Use a spinlock to protect the dst_cache operations
>
> Well, a seqlock would be better : No need for an atomic operation in
> fast path.
>
seqlock can ensure consistency between idst->dst and idst->cookie.
However, IPv6 dst destruction is not protected by rcu. dst_free() is
directly called, like in ip6_fib.c and a few other places.
Hence, atomic_inc_not_zero() cannot be used here because the dst may
have already been kmem_cache_free() when refcnt is 0. A spinlock is
needed to stop the ip6_tnl_dst_set() side from removing the refcnt.
next prev parent reply other threads:[~2015-09-02 20:58 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-01 18:55 [PATCH net 0/3] ipv6: Fix dst_entry refcnt bugs in ip6_tunnel Martin KaFai Lau
2015-09-01 18:55 ` [PATCH net 1/3] ipv6: Refactor common ip6gre_tunnel_init codes Martin KaFai Lau
2015-09-01 18:55 ` [PATCH net 2/3] ipv6: Rename the dst_cache helper functions in ip6_tunnel Martin KaFai Lau
2015-09-01 18:55 ` [PATCH net 3/3] ipv6: Fix dst_entry refcnt bugs " Martin KaFai Lau
2015-09-01 20:14 ` Eric Dumazet
2015-09-01 20:55 ` Martin KaFai Lau
2015-09-01 21:26 ` Eric Dumazet
2015-09-01 22:25 ` Martin KaFai Lau
2015-09-01 22:38 ` Eric Dumazet
2015-09-02 0:31 ` Martin KaFai Lau
2015-09-02 0:42 ` Martin KaFai Lau
2015-09-02 1:02 ` Martin KaFai Lau
2015-09-02 1:55 ` Martin KaFai Lau
2015-09-02 20:58 ` Martin KaFai Lau [this message]
2015-09-02 21:30 ` Eric Dumazet
2015-09-02 21:52 ` Martin KaFai Lau
2015-09-02 22:48 ` Eric Dumazet
2015-09-02 23:04 ` David Miller
2015-09-02 23:10 ` Martin KaFai Lau
2015-09-02 23:14 ` David Miller
2015-09-02 23:46 ` Eric Dumazet
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