On Wed, Sep 16, 2015 at 8:41 PM, Herbert Xu <herb...@gondor.apana.org.au> wrote:
> On Thu, Sep 17, 2015 at 11:08:45AM +0800, Herbert Xu wrote:
>>
>> Good catch! I think your explanation makes perfect sense. Linus
>> ran into this previously too after suspend-and-resume.
>
> Unfortunately you can't just postpone the setting of portid because
> once you pass it onto rhashtable the portid must never change while
> it's in custody.
>
> So what I've done is essentially revert my previous fix and instead
> add a new boolean "bound" to indicate whether the socket has been
> bound.
>
> ---8<---
> netlink: Fix autobind race condition that leads to zero port ID
>
> The commit c0bb07df7d981e4091432754e30c9c720e2c0c78 ("netlink:
> Reset portid after netlink_insert failure") introduced a race
> condition where if two threads tried to autobind the same socket
> one of them may end up with a zero port ID.
>
> This patch reverts that commit and instead fixes it by introducing
> a separte "bound" variable to indicate whether a socket has been
> bound.
>
> Fixes: c0bb07df7d98 ("netlink: Reset portid after netlink_insert failure")
> Reported-by: Tejun Heo <t...@kernel.org>
> Reported-by: Linus Torvalds <torva...@linux-foundation.org>
We saw similar soft lockup with the one Tejun reported, in our data
center.
> Signed-off-by: Herbert Xu <herb...@gondor.apana.org.au>
Just one comment below.
[...]
> @@ -1285,7 +1287,7 @@ static int netlink_release(struct socket *sock)
>
> skb_queue_purge(&sk->sk_write_queue);
>
> - if (nlk->portid) {
> + if (nlk->bound) {
> struct netlink_notify n = {
> .net = sock_net(sk),
> .protocol = sk->sk_protocol,
This part doesn't look correct, seems it is checking if this is a kernel
netlink socket rather than if it is bound. But I am not sure...
Other than this, looks good to me:
Reviewed-by: Cong Wang <cw...@twopensource.com>
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