Re: [PATCH net-next] net: stop napi kthreads when THREADED napi is disabled

[Jakub Kicinski <kuba@kernel.org>]

On Tue, 13 May 2025 00:26:31 +0000 Samiullah Khawaja wrote:
> @@ -7463,6 +7482,15 @@ static int napi_thread_wait(struct napi_struct *napi)
>  			return 0;
>  		}
>  
> +		/* Since the SCHED_THREADED is not set so we do not own this
> +		 * napi and it is safe to stop here if we are asked to. Checking
> +		 * the SCHED_THREADED before stopping here makes sure that this
> +		 * napi was not schedule again while napi threaded was being
> +		 * disabled.
> +		 */

Not sure if this works:

          CPU 0 (IRQ)             CPU 1 (NAPI thr)          CPU 2 (config)

  ____napi_schedule()
    if (test_bit(NAPI_STATE_THREADED))

                                                         clear_bit(NAPI_STATE_THREADED)
                                                         kthread_stop(thread)

                              if (test_bit(NAPI_STATE_SCHED_THREADED))
                                   ..
                              if (kthread_should_stop())
                                   exit

       set_bit(NAPI_STATE_SCHED_THREADED)
       wake_up_process(thread);



> +		if (kthread_should_stop())
> +			break;
> +
>  		schedule();
>  		set_current_state(TASK_INTERRUPTIBLE);