netdev - Re: [Patch net] af_unix: remove redundant lockdep class

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Date:   Tue, 03 Apr 2018 11:07:01 +0200
From:   Paolo Abeni <pabeni@...hat.com>
To:     Cong Wang <xiyou.wangcong@...il.com>, netdev@...r.kernel.org
Subject: Re: [Patch net] af_unix: remove redundant lockdep class

On Mon, 2018-04-02 at 11:01 -0700, Cong Wang wrote:
> After commit 581319c58600 ("net/socket: use per af lockdep classes for sk queues")
> sock queue locks now have per-af lockdep classes, including unix socket.
> It is no longer necessary to workaround it.
> 
> I noticed this while looking at a syzbot deadlock report, this patch
> itself doesn't fix it (this is why I don't add Reported-by).
> 
> Fixes: 581319c58600 ("net/socket: use per af lockdep classes for sk queues")
> Cc: Paolo Abeni <pabeni@...hat.com>
> Signed-off-by: Cong Wang <xiyou.wangcong@...il.com>
> ---
>  net/unix/af_unix.c | 10 ----------
>  1 file changed, 10 deletions(-)
> 
> diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
> index 2d465bdeccbc..45971e173924 100644
> --- a/net/unix/af_unix.c
> +++ b/net/unix/af_unix.c
> @@ -745,14 +745,6 @@ static struct proto unix_proto = {
>  	.obj_size		= sizeof(struct unix_sock),
>  };
>  
> -/*
> - * AF_UNIX sockets do not interact with hardware, hence they
> - * dont trigger interrupts - so it's safe for them to have
> - * bh-unsafe locking for their sk_receive_queue.lock. Split off
> - * this special lock-class by reinitializing the spinlock key:
> - */
> -static struct lock_class_key af_unix_sk_receive_queue_lock_key;
> -
>  static struct sock *unix_create1(struct net *net, struct socket *sock, int kern)
>  {
>  	struct sock *sk = NULL;
> @@ -767,8 +759,6 @@ static struct sock *unix_create1(struct net *net, struct socket *sock, int kern)
>  		goto out;
>  
>  	sock_init_data(sock, sk);
> -	lockdep_set_class(&sk->sk_receive_queue.lock,
> -				&af_unix_sk_receive_queue_lock_key);
>  
>  	sk->sk_allocation	= GFP_KERNEL_ACCOUNT;
>  	sk->sk_write_space	= unix_write_space;

LGTM

Acked-by: Paolo Abeni <pabeni@...hat.com>