2021-09-18 15:02:04

by Yajun Deng

Subject: [PATCH net-next] net: rtnetlink: convert rcu_assign_pointer to RCU_INIT_POINTER

It no need barrier when assigning a NULL value to an RCU protected
pointer. So use RCU_INIT_POINTER() instead for more fast.

Signed-off-by: Yajun Deng <[email protected]>
---
net/core/rtnetlink.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 972c8cb303a5..327ca6bc6e6d 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -301,7 +301,7 @@ int rtnl_unregister(int protocol, int msgtype)
}

link = rtnl_dereference(tab[msgindex]);
- rcu_assign_pointer(tab[msgindex], NULL);
+ RCU_INIT_POINTER(tab[msgindex], NULL);
rtnl_unlock();

kfree_rcu(link, rcu);
@@ -337,7 +337,7 @@ void rtnl_unregister_all(int protocol)
if (!link)
continue;

- rcu_assign_pointer(tab[msgindex], NULL);
+ RCU_INIT_POINTER(tab[msgindex], NULL);
kfree_rcu(link, rcu);
}
rtnl_unlock();
--
2.32.0

2021-09-19 17:01:29

by patchwork-bot+netdevbpf

Subject: Re: [PATCH net-next] net: rtnetlink: convert rcu_assign_pointer to RCU_INIT_POINTER

Hello:

This patch was applied to netdev/net-next.git (refs/heads/master):

On Sat, 18 Sep 2021 14:36:07 +0800 you wrote:
> It no need barrier when assigning a NULL value to an RCU protected
> pointer. So use RCU_INIT_POINTER() instead for more fast.
>
> Signed-off-by: Yajun Deng <[email protected]>
> ---
> net/core/rtnetlink.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)

Here is the summary with links:
- [net-next] net: rtnetlink: convert rcu_assign_pointer to RCU_INIT_POINTER
https://git.kernel.org/netdev/net-next/c/4fc29989835a

You are awesome, thank you!
--
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2021-09-23 17:11:45

by Eric Dumazet

Subject: Re: [PATCH net-next] net: rtnetlink: convert rcu_assign_pointer to RCU_INIT_POINTER

On 9/17/21 11:36 PM, Yajun Deng wrote:
> It no need barrier when assigning a NULL value to an RCU protected
> pointer. So use RCU_INIT_POINTER() instead for more fast.
>
> Signed-off-by: Yajun Deng <[email protected]>
> ---
> net/core/rtnetlink.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
> index 972c8cb303a5..327ca6bc6e6d 100644
> --- a/net/core/rtnetlink.c
> +++ b/net/core/rtnetlink.c
> @@ -301,7 +301,7 @@ int rtnl_unregister(int protocol, int msgtype)
> }
>
> link = rtnl_dereference(tab[msgindex]);
> - rcu_assign_pointer(tab[msgindex], NULL);
> + RCU_INIT_POINTER(tab[msgindex], NULL);
> rtnl_unlock();
>
> kfree_rcu(link, rcu);
> @@ -337,7 +337,7 @@ void rtnl_unregister_all(int protocol)
> if (!link)
> continue;
>
> - rcu_assign_pointer(tab[msgindex], NULL);
> + RCU_INIT_POINTER(tab[msgindex], NULL);
> kfree_rcu(link, rcu);
> }
> rtnl_unlock();
>

FYI, there is no memory barrier involved in

rcu_assign_pointer(tab[msgindex], NULL);

This has been the case for the last 5 years.

Your patch was not needed really.