netdev - Re: [net-next-2.6 PATCH v6 2/7 RFC] TCPCT part 1b: generate Responder Cookie

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Message-ID: <4AFD6EB8.20406@gmail.com>
Date:	Fri, 13 Nov 2009 09:35:36 -0500
From:	William Allen Simpson <william.allen.simpson@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [net-next-2.6 PATCH v6 2/7 RFC] TCPCT part 1b: generate Responder
 Cookie

Eric Dumazet wrote:
> Small point :
> 
> +	if (unlikely(time_after_eq(jiffy, tcp_secret_generating->expires))) {
> +		spin_lock_bh(&tcp_secret_locker);
> +		if (!time_after_eq(jiffy, tcp_secret_generating->expires)) {
> +			/* refreshed by another */
> +			spin_unlock_bh(&tcp_secret_locker);
> +			memcpy(bakery,
> +			       &tcp_secret_generating->secrets[0],
> +			       sizeof(tcp_secret_generating->secrets));
> 
> Technically speaking, you should perform the memcpy() before spin_unlock_bh()
> 
> +	if (unlikely(time_after_eq(jiffy, tcp_secret_generating->expires))) {
> +		spin_lock_bh(&tcp_secret_locker);
> +		if (!time_after_eq(jiffy, tcp_secret_generating->expires)) {
> +			/* refreshed by another */
> +			memcpy(bakery,
> +			       &tcp_secret_generating->secrets[0],
> +			       sizeof(tcp_secret_generating->secrets));
> +			spin_unlock_bh(&tcp_secret_locker);
> 
Technically speaking is exactly what I need!  I'd thought from your
earlier description of memory barriers that it should be after the unlock.
Done.
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