[PATCH] net: Statically initialize init_net.dev_base_head

[PATCH] net: Statically initialize init_net.dev_base_head

[Mark Rustad]

This change eliminates an initialization-order hazard most
recently seen when netprio_cgroup is built into the kernel.

With thanks to Eric Dumazet for catching a bug.

Signed-off-by: Mark Rustad <mark.d.rustad@intel.com>
---

 net/core/dev.c           |    3 ++-
 net/core/net_namespace.c |    4 +++-
 2 files changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 0f28a9e..1cb0d8a 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6283,7 +6283,8 @@ static struct hlist_head *netdev_create_hash(void)
 /* Initialize per network namespace state */
 static int __net_init netdev_init(struct net *net)
 {
-	INIT_LIST_HEAD(&net->dev_base_head);
+	if (net != &init_net)
+		INIT_LIST_HEAD(&net->dev_base_head);
 
 	net->dev_name_head = netdev_create_hash();
 	if (net->dev_name_head == NULL)
diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
index dddbacb..42f1e1c 100644
--- a/net/core/net_namespace.c
+++ b/net/core/net_namespace.c
@@ -27,7 +27,9 @@ static DEFINE_MUTEX(net_mutex);
 LIST_HEAD(net_namespace_list);
 EXPORT_SYMBOL_GPL(net_namespace_list);
 
-struct net init_net;
+struct net init_net = {
+	.dev_base_head = LIST_HEAD_INIT(init_net.dev_base_head),
+};
 EXPORT_SYMBOL(init_net);
 
 #define INITIAL_NET_GEN_PTRS	13 /* +1 for len +2 for rcu_head */

Re: [PATCH] net: Statically initialize init_net.dev_base_head

[Eric Dumazet]

On Wed, 2012-07-18 at 12:06 -0700, Mark Rustad wrote:
> This change eliminates an initialization-order hazard most
> recently seen when netprio_cgroup is built into the kernel.
> 
> With thanks to Eric Dumazet for catching a bug.
> 
> Signed-off-by: Mark Rustad <mark.d.rustad@intel.com>
> ---
> 
>  net/core/dev.c           |    3 ++-
>  net/core/net_namespace.c |    4 +++-
>  2 files changed, 5 insertions(+), 2 deletions(-)

Acked-by: Eric Dumazet <edumazet@google.com>

Re: [PATCH] net: Statically initialize init_net.dev_base_head

[David Miller]

From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Wed, 18 Jul 2012 21:13:29 +0200

> On Wed, 2012-07-18 at 12:06 -0700, Mark Rustad wrote:
>> This change eliminates an initialization-order hazard most
>> recently seen when netprio_cgroup is built into the kernel.
>> 
>> With thanks to Eric Dumazet for catching a bug.
>> 
>> Signed-off-by: Mark Rustad <mark.d.rustad@intel.com>
>> ---
>> 
>>  net/core/dev.c           |    3 ++-
>>  net/core/net_namespace.c |    4 +++-
>>  2 files changed, 5 insertions(+), 2 deletions(-)
> 
> Acked-by: Eric Dumazet <edumazet@google.com>

Applied, thanks everyone.

Re: [PATCH] net: Statically initialize init_net.dev_base_head

[Neil Horman]

On Wed, Jul 18, 2012 at 12:06:07PM -0700, Mark Rustad wrote:
> This change eliminates an initialization-order hazard most
> recently seen when netprio_cgroup is built into the kernel.
> 
> With thanks to Eric Dumazet for catching a bug.
> 
> Signed-off-by: Mark Rustad <mark.d.rustad@intel.com>
> ---
> 
>  net/core/dev.c           |    3 ++-
>  net/core/net_namespace.c |    4 +++-
>  2 files changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/net/core/dev.c b/net/core/dev.c
> index 0f28a9e..1cb0d8a 100644
> --- a/net/core/dev.c
> +++ b/net/core/dev.c
> @@ -6283,7 +6283,8 @@ static struct hlist_head *netdev_create_hash(void)
>  /* Initialize per network namespace state */
>  static int __net_init netdev_init(struct net *net)
>  {
> -	INIT_LIST_HEAD(&net->dev_base_head);
> +	if (net != &init_net)
> +		INIT_LIST_HEAD(&net->dev_base_head);
>  
>  	net->dev_name_head = netdev_create_hash();
>  	if (net->dev_name_head == NULL)
> diff --git a/net/core/net_namespace.c b/net/core/net_namespace.c
> index dddbacb..42f1e1c 100644
> --- a/net/core/net_namespace.c
> +++ b/net/core/net_namespace.c
> @@ -27,7 +27,9 @@ static DEFINE_MUTEX(net_mutex);
>  LIST_HEAD(net_namespace_list);
>  EXPORT_SYMBOL_GPL(net_namespace_list);
>  
> -struct net init_net;
> +struct net init_net = {
> +	.dev_base_head = LIST_HEAD_INIT(init_net.dev_base_head),
> +};
>  EXPORT_SYMBOL(init_net);
>  
>  #define INITIAL_NET_GEN_PTRS	13 /* +1 for len +2 for rcu_head */
> 
> 

I think dave was going to take John Fastabends patch from earlier today, but
this works just as well.  Long term I'm going to look into delaying
initzlization for cgroups, as it creates a strange initialization state when you
have a module_init routine registered.
Neil

Re: [PATCH] net: Statically initialize init_net.dev_base_head

[David Miller]

From: Neil Horman <nhorman@tuxdriver.com>
Date: Wed, 18 Jul 2012 16:11:49 -0400

> On Wed, Jul 18, 2012 at 12:06:07PM -0700, Mark Rustad wrote:
>> This change eliminates an initialization-order hazard most
>> recently seen when netprio_cgroup is built into the kernel.
>> 
>> With thanks to Eric Dumazet for catching a bug.
>> 
>> Signed-off-by: Mark Rustad <mark.d.rustad@intel.com>
 ...
> I think dave was going to take John Fastabends patch from earlier today, but
> this works just as well.  Long term I'm going to look into delaying
> initzlization for cgroups, as it creates a strange initialization state when you
> have a module_init routine registered.

Neil, any particular preference between John's and Mark's version
of the fix?

Re: [PATCH] net: Statically initialize init_net.dev_base_head

[Neil Horman]

On Wed, Jul 18, 2012 at 01:20:10PM -0700, David Miller wrote:
> From: Neil Horman <nhorman@tuxdriver.com>
> Date: Wed, 18 Jul 2012 16:11:49 -0400
> 
> > On Wed, Jul 18, 2012 at 12:06:07PM -0700, Mark Rustad wrote:
> >> This change eliminates an initialization-order hazard most
> >> recently seen when netprio_cgroup is built into the kernel.
> >> 
> >> With thanks to Eric Dumazet for catching a bug.
> >> 
> >> Signed-off-by: Mark Rustad <mark.d.rustad@intel.com>
>  ...
> > I think dave was going to take John Fastabends patch from earlier today, but
> > this works just as well.  Long term I'm going to look into delaying
> > initzlization for cgroups, as it creates a strange initialization state when you
> > have a module_init routine registered.
> 
> Neil, any particular preference between John's and Mark's version
> of the fix?
> 
I think they're both perfectly good.  If I had to choose I'd say Marks, just
because its done by initializing data, rather than adding more code to run every
time we create a cgroup.

Neil

Re: [PATCH] net: Statically initialize init_net.dev_base_head

[John Fastabend]

On 7/18/2012 1:21 PM, Neil Horman wrote:
> On Wed, Jul 18, 2012 at 01:20:10PM -0700, David Miller wrote:
>> From: Neil Horman <nhorman@tuxdriver.com>
>> Date: Wed, 18 Jul 2012 16:11:49 -0400
>>
>>> On Wed, Jul 18, 2012 at 12:06:07PM -0700, Mark Rustad wrote:
>>>> This change eliminates an initialization-order hazard most
>>>> recently seen when netprio_cgroup is built into the kernel.
>>>>
>>>> With thanks to Eric Dumazet for catching a bug.
>>>>
>>>> Signed-off-by: Mark Rustad <mark.d.rustad@intel.com>
>>   ...
>>> I think dave was going to take John Fastabends patch from earlier today, but
>>> this works just as well.  Long term I'm going to look into delaying
>>> initzlization for cgroups, as it creates a strange initialization state when you
>>> have a module_init routine registered.
>>
>> Neil, any particular preference between John's and Mark's version
>> of the fix?
>>
> I think they're both perfectly good.  If I had to choose I'd say Marks, just
> because its done by initializing data, rather than adding more code to run every
> time we create a cgroup.
>
> Neil
>

Fine by me if we take this version instead.

Re: [PATCH] net: Statically initialize init_net.dev_base_head

[David Miller]

From: John Fastabend <john.r.fastabend@intel.com>
Date: Wed, 18 Jul 2012 13:31:13 -0700

> On 7/18/2012 1:21 PM, Neil Horman wrote:
>> On Wed, Jul 18, 2012 at 01:20:10PM -0700, David Miller wrote:
>>> From: Neil Horman <nhorman@tuxdriver.com>
>>> Date: Wed, 18 Jul 2012 16:11:49 -0400
>>>
>>>> On Wed, Jul 18, 2012 at 12:06:07PM -0700, Mark Rustad wrote:
>>>>> This change eliminates an initialization-order hazard most
>>>>> recently seen when netprio_cgroup is built into the kernel.
>>>>>
>>>>> With thanks to Eric Dumazet for catching a bug.
>>>>>
>>>>> Signed-off-by: Mark Rustad <mark.d.rustad@intel.com>
>>>   ...
>>>> I think dave was going to take John Fastabends patch from earlier
>>>> today, but
>>>> this works just as well.  Long term I'm going to look into delaying
>>>> initzlization for cgroups, as it creates a strange initialization
>>>> state when you
>>>> have a module_init routine registered.
>>>
>>> Neil, any particular preference between John's and Mark's version
>>> of the fix?
>>>
>> I think they're both perfectly good.  If I had to choose I'd say
>> Marks, just
>> because its done by initializing data, rather than adding more code to
>> run every
>> time we create a cgroup.
>>
>> Neil
>>
> 
> Fine by me if we take this version instead.

I think that's what I'll do, sorry for all the trouble John :)

Re: [PATCH] net: Statically initialize init_net.dev_base_head

[John Fastabend]

On 7/18/2012 1:32 PM, David Miller wrote:
> From: John Fastabend <john.r.fastabend@intel.com>
> Date: Wed, 18 Jul 2012 13:31:13 -0700
>
>> On 7/18/2012 1:21 PM, Neil Horman wrote:
>>> On Wed, Jul 18, 2012 at 01:20:10PM -0700, David Miller wrote:
>>>> From: Neil Horman <nhorman@tuxdriver.com>
>>>> Date: Wed, 18 Jul 2012 16:11:49 -0400
>>>>
>>>>> On Wed, Jul 18, 2012 at 12:06:07PM -0700, Mark Rustad wrote:
>>>>>> This change eliminates an initialization-order hazard most
>>>>>> recently seen when netprio_cgroup is built into the kernel.
>>>>>>
>>>>>> With thanks to Eric Dumazet for catching a bug.
>>>>>>
>>>>>> Signed-off-by: Mark Rustad <mark.d.rustad@intel.com>
>>>>    ...
>>>>> I think dave was going to take John Fastabends patch from earlier
>>>>> today, but
>>>>> this works just as well.  Long term I'm going to look into delaying
>>>>> initzlization for cgroups, as it creates a strange initialization
>>>>> state when you
>>>>> have a module_init routine registered.
>>>>
>>>> Neil, any particular preference between John's and Mark's version
>>>> of the fix?
>>>>
>>> I think they're both perfectly good.  If I had to choose I'd say
>>> Marks, just
>>> because its done by initializing data, rather than adding more code to
>>> run every
>>> time we create a cgroup.
>>>
>>> Neil
>>>
>>
>> Fine by me if we take this version instead.
>
> I think that's what I'll do, sorry for all the trouble John :)
>

No problem. For what its worth verified this resolved the netprio
issue on my system as expected.