[PATCH] netprio_cgroup: explicitly init the early_init field

[PATCH] netprio_cgroup: explicitly init the early_init field

[Jianyu Zhan]

For a cgroup subsystem who should init early, then it should carefully
take care of the implementation of css_alloc, because it will be called
before mm_init() setup the world.

Luckily we don't, and we better explicitly assign the early_init field
to 0, for document reason.

Signed-off-by: Jianyu Zhan <nasa4836@gmail.com>
---
 net/core/netprio_cgroup.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
index 13ddd68..fc21035 100644
--- a/net/core/netprio_cgroup.c
+++ b/net/core/netprio_cgroup.c
@@ -250,6 +250,7 @@ struct cgroup_subsys net_prio_cgrp_subsys = {
 	.css_free	= cgrp_css_free,
 	.attach		= net_prio_attach,
 	.base_cftypes	= ss_files,
+	.early_init	= 0,
 };
 
 static int netprio_device_event(struct notifier_block *unused,
-- 
2.0.0-rc0

Re: [PATCH] netprio_cgroup: explicitly init the early_init field

[Neil Horman]

On Tue, Apr 22, 2014 at 01:32:02PM +0800, Jianyu Zhan wrote:
> For a cgroup subsystem who should init early, then it should carefully
> take care of the implementation of css_alloc, because it will be called
> before mm_init() setup the world.
> 
> Luckily we don't, and we better explicitly assign the early_init field
> to 0, for document reason.
> 
> Signed-off-by: Jianyu Zhan <nasa4836@gmail.com>
> ---
>  net/core/netprio_cgroup.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/net/core/netprio_cgroup.c b/net/core/netprio_cgroup.c
> index 13ddd68..fc21035 100644
> --- a/net/core/netprio_cgroup.c
> +++ b/net/core/netprio_cgroup.c
> @@ -250,6 +250,7 @@ struct cgroup_subsys net_prio_cgrp_subsys = {
>  	.css_free	= cgrp_css_free,
>  	.attach		= net_prio_attach,
>  	.base_cftypes	= ss_files,
> +	.early_init	= 0,
>  };
>  
>  static int netprio_device_event(struct notifier_block *unused,
> -- 
> 2.0.0-rc0
> 
> 
NACK, for the same reason that it doesn't make sense for net_classid.
Early_init should already be zero.  What problem are you trying to solve here?

Neil

Re: [PATCH] netprio_cgroup: explicitly init the early_init field

[Jianyu Zhan]

On Tue, Apr 22, 2014 at 7:19 PM, Neil Horman <nhorman@tuxdriver.com> wrote:
> NACK, for the same reason that it doesn't make sense for net_classid.
> Early_init should already be zero.  What problem are you trying to solve here?

Hi, Neil,

I'm sorry I should have made this more clear.

Sure, for this global variable struct, if not initailized, its all
fields will be initialized
to 0 or null(depending on its type).  The point here is no to deprive
the rights of compiler/linker of doing this initialization, it is mainly for
documentation reason. Actually this field's value would affect how ->css_alloc
should implemented.

Concretely, if early_init is nonzero, then ->css_alloc *must not* call kzalloc,
because in cgroup implementation, ->css_alloc will be called earlier before
mm_init().

I don't think that the value of one field(early_init) has a so subtle
restrition on the another field(css_alloc) is a good thing, but since
it is there, docment it should be needed.

Thanks,
Jianyu Zhan

Re: [PATCH] netprio_cgroup: explicitly init the early_init field

[David Miller]

From: Jianyu Zhan <nasa4836@gmail.com>
Date: Tue, 22 Apr 2014 19:25:41 +0800

> I don't think that the value of one field(early_init) has a so subtle
> restrition on the another field(css_alloc) is a good thing, but since
> it is there, docment it should be needed.

This is not a reasonable change.

We depend upon implicit initialization to zero all over the kernel,
and adding explicit assignments hurts rather then helps.