linux-kernel - Re: [PATCH] staging: vchiq_arm: Make use of the helper macro kthread

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Date:   Fri, 22 Oct 2021 11:03:45 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     Cai Huoqing <caihuoqing@...du.com>
Cc:     Nicolas Saenz Julienne <nsaenz@...nel.org>,
        bcm-kernel-feedback-list@...adcom.com,
        linux-rpi-kernel@...ts.infradead.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-staging@...ts.linux.dev, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: vchiq_arm: Make use of the helper macro
 kthread_run()

On Thu, Oct 21, 2021 at 04:43:27PM +0800, Cai Huoqing wrote:
> Repalce kthread_create/wake_up_process() with kthread_run()
> to simplify the code.
> 
> Signed-off-by: Cai Huoqing <caihuoqing@...du.com>
> ---
>  .../staging/vc04_services/interface/vchiq_arm/vchiq_arm.c  | 7 ++-----
>  1 file changed, 2 insertions(+), 5 deletions(-)
> 
> diff --git a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> index a5e33da74726..6130b95aaca3 100644
> --- a/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> +++ b/drivers/staging/vc04_services/interface/vchiq_arm/vchiq_arm.c
> @@ -1717,15 +1717,12 @@ void vchiq_platform_conn_state_changed(struct vchiq_state *state,
>  	write_unlock_bh(&arm_state->susp_res_lock);
>  	snprintf(threadname, sizeof(threadname), "vchiq-keep/%d",
>  		 state->id);
> -	arm_state->ka_thread = kthread_create(&vchiq_keepalive_thread_func,
> -					      (void *)state,
> -					      threadname);
> +	arm_state->ka_thread = kthread_run(&vchiq_keepalive_thread_func,
> +					   (void *)state, threadname);
>  	if (IS_ERR(arm_state->ka_thread)) {
>  		vchiq_log_error(vchiq_susp_log_level,
>  				"vchiq: FATAL: couldn't create thread %s",
>  				threadname);
> -	} else {
> -		wake_up_process(arm_state->ka_thread);
>  	}
>  }
>  

As others have pointed out for other busses where you sent this patch,
this is _VERY_ racy and probably wrong.  Be more careful when sending
changes like this that can modify functionality without testing the
code.

thanks,

greg k-h