linux-kernel - Re: [PATCH v2 net-next] net: poll/select low latency socket support

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Message-ID: <1371546510.3252.224.camel@edumazet-glaptop>
Date:	Tue, 18 Jun 2013 02:08:30 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Eliezer Tamir <eliezer.tamir@...ux.intel.com>
Cc:	David Miller <davem@...emloft.net>, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org,
	Jesse Brandeburg <jesse.brandeburg@...el.com>,
	Don Skidmore <donald.c.skidmore@...el.com>,
	e1000-devel@...ts.sourceforge.net,
	Willem de Bruijn <willemb@...gle.com>,
	Ben Hutchings <bhutchings@...arflare.com>,
	Andi Kleen <andi@...stfloor.org>, HPA <hpa@...or.com>,
	Eilon Greenstien <eilong@...adcom.com>,
	Or Gerlitz <or.gerlitz@...il.com>,
	Amir Vadai <amirv@...lanox.com>,
	Alex Rosenbaum <alexr@...lanox.com>,
	Avner Ben Hanoch <avnerb@...lanox.com>,
	Or Kehati <ork@...lanox.com>, sockperf-dev@...glegroups.com,
	Eliezer Tamir <eliezer@...ir.org.il>
Subject: Re: [PATCH v2 net-next] net: poll/select low latency socket support

On Tue, 2013-06-18 at 11:58 +0300, Eliezer Tamir wrote:
> select/poll busy-poll support.
> 


>   */
> -static inline u64 ll_end_time(struct sock *sk)
> +static inline u64 ll_sk_end_time(struct sock *sk)
>  {
> -	u64 end_time = ACCESS_ONCE(sk->sk_ll_usec);
> -
> -	/* we don't mind a ~2.5% imprecision
> -	 * sk->sk_ll_usec is a u_int so this can't overflow
> -	 */
> -	end_time = (end_time << 10) + sched_clock();
> +	return (ACCESS_ONCE(sk->sk_ll_usec) << 10) + sched_clock();
> +}
>  

This is the fourth time you try to introduce an overflow in this code.

(same for ll_end_time())




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