linux-kernel - Re: [PATCH v11 2/2] binder: report txn errors via generic netlink

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Message-ID: <CANBPYPjvFuhi7Pwn_CLArn-iOp=bLjPHKN0sJv+5uoUrDTZHag@mail.gmail.com>
Date: Thu, 9 Jan 2025 11:48:24 -0800
From: Li Li <dualli@...omium.org>
To: Carlos Llamas <cmllamas@...gle.com>
Cc: dualli@...gle.com, corbet@....net, davem@...emloft.net, 
	edumazet@...gle.com, kuba@...nel.org, pabeni@...hat.com, 
	donald.hunter@...il.com, gregkh@...uxfoundation.org, arve@...roid.com, 
	tkjos@...roid.com, maco@...roid.com, joel@...lfernandes.org, 
	brauner@...nel.org, surenb@...gle.com, arnd@...db.de, masahiroy@...nel.org, 
	bagasdotme@...il.com, horms@...nel.org, linux-kernel@...r.kernel.org, 
	linux-doc@...r.kernel.org, netdev@...r.kernel.org, hridya@...gle.com, 
	smoreland@...gle.com, kernel-team@...roid.com
Subject: Re: [PATCH v11 2/2] binder: report txn errors via generic netlink

Thank you for the suggestion!

Cleaning up in the NETLINK_URELEASE notifier is better since we
register the process with the netlink socket. I'll change the code
accordingly.

On Thu, Jan 9, 2025 at 11:30 AM Carlos Llamas <cmllamas@...gle.com> wrote:
>
> On Thu, Jan 09, 2025 at 06:51:59PM +0000, Carlos Llamas wrote:
> > Did you happen to look into netlink_register_notifier()? That seems like
> > an option to keep the device vs netlink socket interface from mixing up.
> > I believe we could check for NETLINK_URELEASE events and do the cleanup
> > then. I'll do a quick try.
>
> Yeah, this quick prototype worked for me. Although I haven't looked at
> the api details closely.
>
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index 536be42c531e..fa2146cf02a7 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> +static int binder_netlink_notify(struct notifier_block *nb,
> +       +       +       +        unsigned long action,
> +       +       +       +        void *data)
> +{
> +       struct netlink_notify *n = data;
> +       struct binder_device *device;
> +
> +       if (action != NETLINK_URELEASE)
> +       +       return NOTIFY_DONE;
> +
> +       hlist_for_each_entry(device, &binder_devices, hlist) {
> +       +       if (device->context.report_portid == n->portid)
> +       +       +       pr_info("%s: socket released\n", __func__);
> +       }
> +
> +       return NOTIFY_DONE;
> +}
> +
> +static struct notifier_block binder_netlink_notifier = {
> +       .notifier_call = binder_netlink_notify,
> +};
> +
>  static int __init binder_init(void)
>  {
> +       int ret;
> @@ -7244,6 +7259,8 @@ static int __init binder_init(void)
> +       +       goto err_init_binder_device_failed;
> +       }
>
> +       netlink_register_notifier(&binder_netlink_notifier);
> +
> +       return ret;
>
>  err_init_binder_device_failed:
>
>
> With that change we get notified when the socket that registered the
> report exits:
>
>   root@...ian:~# ./binder-netlink
>   report setup complete!
>   ^C[   63.682485] binder: binder_netlink_notify: socket released
>
>
> I don't know if this would be the preferred approach to "install" a
> notification callback with a netlink socket but it works. wdyt?
>
> --
> Carlos Llamas