Re: [PATCH V5 6/9] firmware: imx: scu-irq: fix RCU complains after M4 partition reset

[Shawn Guo <shawnguo@kernel.org>]

On Mon, Jul 31, 2023 at 05:04:46PM +0800, Peng Fan (OSS) wrote:
> From: Robin Gong <yibin.gong@nxp.com>
> 
> Use blocking_notifier_chain instead of atomic_notifier_chain, otherwise
> below RCU complains would come out since unregister/register_virtio_device

s/complains/complaint, and in subject too.

> () will issue mbox message (mbox_send_message() is blocking) again after

The () should be on the same line as register_virtio_device.

> received M4 partition reset. Actually, no need atomic for notifier which

there is no need of atomic for ...?

Shawn

> is so tough for user since this notifier is called in worker instead of
> interrupt handler directly.
> 
> [  389.706645] i2c-rpmsg virtio0.rpmsg-i2c-channel.-1.2: i2c rpmsg driver is removed
> [  389.767362] Wait for remote ready timeout, use first_notify.
> [  389.774084] ------------[ cut here ]------------
> [  389.778729] WARNING: CPU: 0 PID: 397 at kernel/rcu/tree_plugin.h:293 rcu_note_context_switch+0x34/0x338
> [  389.788131] Modules linked in:
> [  389.791195] CPU: 0 PID: 397 Comm: kworker/0:13 Not tainted 5.4.0-rc5-02977-g08f78722f07b #26
> [  389.799633] Hardware name: Freescale i.MX8DXL Phantom MEK (DT)
> [  389.805481] Workqueue: events imx_scu_irq_work_handler
> 
> Signed-off-by: Robin Gong <yibin.gong@nxp.com>
> Reviewed-by: Dong Aisheng <aisheng.dong@nxp.com>
> Signed-off-by: Peng Fan <peng.fan@nxp.com>
> ---
>  drivers/firmware/imx/imx-scu-irq.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/firmware/imx/imx-scu-irq.c b/drivers/firmware/imx/imx-scu-irq.c
> index d9dcc20945c6..4408f150b3d5 100644
> --- a/drivers/firmware/imx/imx-scu-irq.c
> +++ b/drivers/firmware/imx/imx-scu-irq.c
> @@ -42,25 +42,25 @@ struct imx_sc_msg_irq_enable {
>  
>  static struct imx_sc_ipc *imx_sc_irq_ipc_handle;
>  static struct work_struct imx_sc_irq_work;
> -static ATOMIC_NOTIFIER_HEAD(imx_scu_irq_notifier_chain);
> +static BLOCKING_NOTIFIER_HEAD(imx_scu_irq_notifier_chain);
>  
>  int imx_scu_irq_register_notifier(struct notifier_block *nb)
>  {
> -	return atomic_notifier_chain_register(
> +	return blocking_notifier_chain_register(
>  		&imx_scu_irq_notifier_chain, nb);
>  }
>  EXPORT_SYMBOL(imx_scu_irq_register_notifier);
>  
>  int imx_scu_irq_unregister_notifier(struct notifier_block *nb)
>  {
> -	return atomic_notifier_chain_unregister(
> +	return blocking_notifier_chain_unregister(
>  		&imx_scu_irq_notifier_chain, nb);
>  }
>  EXPORT_SYMBOL(imx_scu_irq_unregister_notifier);
>  
>  static int imx_scu_irq_notifier_call_chain(unsigned long status, u8 *group)
>  {
> -	return atomic_notifier_call_chain(&imx_scu_irq_notifier_chain,
> +	return blocking_notifier_call_chain(&imx_scu_irq_notifier_chain,
>  		status, (void *)group);
>  }
>  
> -- 
> 2.37.1
>