netdev - Re: [PATCH net 2/2] netpoll: Use rcu_access_pointer() in netpoll_poll

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Message-ID: <ZzwKipL-4Lo9L4zV@gondor.apana.org.au>
Date: Tue, 19 Nov 2024 11:48:26 +0800
From: Herbert Xu <herbert@...dor.apana.org.au>
To: Breno Leitao <leitao@...ian.org>
Cc: "David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	Simon Horman <horms@...nel.org>,
	Stephen Hemminger <stephen@...workplumber.org>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	paulmck@...nel.org
Subject: Re: [PATCH net 2/2] netpoll: Use rcu_access_pointer() in
 netpoll_poll_lock

On Mon, Nov 18, 2024 at 03:15:18AM -0800, Breno Leitao wrote:
>
> diff --git a/include/linux/netpoll.h b/include/linux/netpoll.h
> index cd4e28db0cbd77572a579aff2067b5864d1a904a..959a4daacea1f2f76536e309d198bc14407942a4 100644
> --- a/include/linux/netpoll.h
> +++ b/include/linux/netpoll.h
> @@ -72,7 +72,7 @@ static inline void *netpoll_poll_lock(struct napi_struct *napi)
>  {
>  	struct net_device *dev = napi->dev;
>  
> -	if (dev && dev->npinfo) {
> +	if (dev && rcu_access_pointer(dev->npinfo)) {

This function is only ever called in a BH context and as such
the correct primitive would be rcu_dereference.  Indeed calling
this outside of BH/RCU context would be silly.

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt