From: Eric Dumazet <eric.dumazet@gmail.com>
To: Vladimir Davydov <VDavydov@parallels.com>
Cc: "netdev@vger.kernel.org" <netdev@vger.kernel.org>
Subject: Re: Possible deadlock in ipv6?
Date: Wed, 06 Jun 2012 19:02:28 +0200 [thread overview]
Message-ID: <1339002148.26966.14.camel@edumazet-glaptop> (raw)
In-Reply-To: <D0983DA9-2545-4007-8A69-31DDCB9B7CCF@parallels.com>
On Wed, 2012-06-06 at 20:01 +0400, Vladimir Davydov wrote:
> On Jun 6, 2012, at 7:58 PM, Eric Dumazet wrote:
>
> > On Wed, 2012-06-06 at 17:53 +0200, Eric Dumazet wrote:
> >> On Wed, 2012-06-06 at 18:49 +0400, Vladimir Davydov wrote:
> >>> I'm not familiar with the linux net subsystem, so I would appreciate if
> >>> someone could clarify if the following call chain is possible:
> >>>
> >>> addrconf_ifdown() calls neigh_ifdown(nd_tbl) which locks nd_tbl.lock for
> >>> writing and calls
> >>>
> >>> pneigh_ifdown
> >>> pndisc_destructor
> >>> ipv6_dev_mc_dec
> >>> __ipv6_dev_mc_dec
> >>> igmp6_group_dropped
> >>> igmp6_leave_group
> >>> igmp6_send
> >>> icmp6_dst_alloc
> >>> ip6_neigh_lookup
> >>> neigh_create
> >>>
> >>> and neigh_create() locks nd_tbl.lock for writing again resulting in a
> >>> deadlock.
> >>
> >> It seems a deadlock is possible indeed, good catch !
> >>
> >>
> >
> > And it seems this neigh_down() can be removed, its called later
> > (after dev->ip6_ptr is cleared)
> >
>
> BTW, commit d1ed113f1669390da9898da3beddcc058d938587 did exactly the same, but it was reverted along with a bundle of other commits by 73a8bd74e2618990dbb218c3d82f53e60acd9af0.
Yes, but the revert was a 'revert a serie', while this particular patch
seems fine, especially if fixing a deadlock ;)
next prev parent reply other threads:[~2012-06-06 17:02 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-06 14:49 Possible deadlock in ipv6? Vladimir Davydov
2012-06-06 15:53 ` Eric Dumazet
2012-06-06 15:58 ` Eric Dumazet
2012-06-06 16:01 ` Vladimir Davydov
2012-06-06 17:02 ` Eric Dumazet [this message]
2012-06-12 6:54 ` David Miller
2012-06-12 9:09 ` Eric Dumazet
2012-06-21 4:05 ` David Miller
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