Subject: Re: [PATCH net-next v2 3/5] netconsole: add support for sysdata and CPU population

From: Jakub Kicinski <[email-masked]>
Date: Thu, 16 Jan 2025 17:44:05 -0800

On Wed, 15 Jan 2025 05:35:20 -0800 Breno Leitao wrote:
> +	WARN_ON_ONCE(userdata_len + sysdata_len >
> +		     MAX_EXTRADATA_ENTRY_LEN * MAX_EXTRADATA_ITEMS);
> +
> +	/* nt->sysdata_length will be used later to decide if the message
> +	 * needs to be fragmented.
> +	 * userdata_len cannot be used for it, once next sysdata append should
> +	 * start from the same userdata_len location, and only overwrite old
> +	 * sysdata.
> +	 */
> +	nt->sysdata_length = sysdata_len;

Updating nt-> fields at runtime is something we haven't done before,
right? What's the locking? We depend on target_list_lock ?

Looks like previously all the data was on the stack, now we have a mix.
Maybe we can pack all the bits of state into a struct for easier
passing around, but still put it on the stack?