Re: [PATCH v5 04/17] net/nbl: add Channel layer definitions and implementation

[Stephen Hemminger <stephen@networkplumber.org>]

On Tue, 19 Aug 2025 03:22:24 -0700
Dimon Zhao <dimon.zhao@nebula-matrix.com> wrote:

> +
> +static uint32_t nbl_chan_thread_polling_task(void *param)
> +{
> +	struct nbl_channel_mgt *chan_mgt = (struct nbl_channel_mgt *)param;
> +	union nbl_chan_info *chan_info = NBL_CHAN_MGT_TO_CHAN_INFO(chan_mgt);
> +	struct timespec time;
> +	char unused[16];
> +	ssize_t nr = 0;
> +
> +	time.tv_sec = 0;
> +	time.tv_nsec = 100000;
> +
> +	while (true) {
> +		if (rte_bitmap_get(chan_info->mailbox.state_bmp, NBL_CHAN_INTERRUPT_READY)) {
> +			nr = read(chan_info->mailbox.fd[0], &unused, sizeof(unused));
> +			if (nr < 0)
> +				break;
> +		}
> +		nbl_chan_clean_queue(chan_mgt);
> +		nanosleep(&time, 0);
> +	}
> +
> +	return 0;
> +}

This is going to make embedded application developers upset because it uses
a significant part of a CPU polling.

Since you are reading from mailbox, why not implement select/poll/epoll and
have the thread block waiting to read mailbox instead.