Re: [PATCH] can: af_can: namespace support: fix lockdep splat: properly initialize spin_lock

[Oliver Hartkopp <socketcan@hartkopp.net>]

Hi Marc,

On 06/08/2017 12:02 PM, Marc Kleine-Budde wrote:
> This patch uses spin_lock_init() instead of __SPIN_LOCK_UNLOCKED() to
> initialize the per namespace net->can.can_rcvlists_lock lock to fix this
> lockdep warning:
>
> | INFO: trying to register non-static key.
> | the code is fine but needs lockdep annotation.
> | turning off the locking correctness validator.
> | CPU: 0 PID: 186 Comm: candump Not tainted 4.12.0-rc3+ #47
> | Hardware name: Marvell Kirkwood (Flattened Device Tree)
> | [<c0016644>] (unwind_backtrace) from [<c00139a8>] (show_stack+0x18/0x1c)
> | [<c00139a8>] (show_stack) from [<c0058c8c>] (register_lock_class+0x1e4/0x55c)
> | [<c0058c8c>] (register_lock_class) from [<c005bdfc>] (__lock_acquire+0x148/0x1990)
> | [<c005bdfc>] (__lock_acquire) from [<c005deec>] (lock_acquire+0x174/0x210)
> | [<c005deec>] (lock_acquire) from [<c04a6780>] (_raw_spin_lock+0x50/0x88)
> | [<c04a6780>] (_raw_spin_lock) from [<bf02116c>] (can_rx_register+0x94/0x15c [can])
> | [<bf02116c>] (can_rx_register [can]) from [<bf02a868>] (raw_enable_filters+0x60/0xc0 [can_raw])
> | [<bf02a868>] (raw_enable_filters [can_raw]) from [<bf02ac14>] (raw_enable_allfilters+0x2c/0xa0 [can_raw])
> | [<bf02ac14>] (raw_enable_allfilters [can_raw]) from [<bf02ad38>] (raw_bind+0xb0/0x250 [can_raw])
> | [<bf02ad38>] (raw_bind [can_raw]) from [<c03b5fb8>] (SyS_bind+0x70/0xac)
> | [<c03b5fb8>] (SyS_bind) from [<c000f8c0>] (ret_fast_syscall+0x0/0x1c)
>
> Cc: Oliver Hartkopp <socketcan@hartkopp.net>
> Signed-off-by: Marc Kleine-Budde <mkl@pengutronix.de>
> ---
> Hello Oliver,
>
> feel free to review this patch.

That's definitely a better initialization.

The change was introduced in 8e8cda6d737d which moved the static 
variable into the per-net data structure.

Please CC Mario too.

Acked-by: Oliver Hartkopp <socketcan@hartkopp.net>

Tnx,
Oliver

>
> Marc
>
>  net/can/af_can.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/net/can/af_can.c b/net/can/af_can.c
> index b6406fe33c76..88edac0f3e36 100644
> --- a/net/can/af_can.c
> +++ b/net/can/af_can.c
> @@ -872,8 +872,7 @@ static int can_notifier(struct notifier_block *nb, unsigned long msg,
>
>  static int can_pernet_init(struct net *net)
>  {
> -	net->can.can_rcvlists_lock =
> -		__SPIN_LOCK_UNLOCKED(net->can.can_rcvlists_lock);
> +	spin_lock_init(&net->can.can_rcvlists_lock);
>  	net->can.can_rx_alldev_list =
>  		kzalloc(sizeof(struct dev_rcv_lists), GFP_KERNEL);
>
>