Message-ID: <1371546510.3252.224.camel@edumazet-glaptop>
Subject: Re: [PATCH v2 net-next] net: poll/select low latency socket support
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Eliezer Tamir <eliezer.tamir@linux.intel.com>
Cc: David Miller <davem@davemloft.net>, linux-kernel@vger.kernel.org,
        netdev@vger.kernel.org, Jesse Brandeburg <jesse.brandeburg@intel.com>,
        Don Skidmore <donald.c.skidmore@intel.com>,
        e1000-devel@lists.sourceforge.net,
        Willem de Bruijn <willemb@google.com>,
        Ben Hutchings <bhutchings@solarflare.com>,
        Andi Kleen <andi@firstfloor.org>, HPA <hpa@zytor.com>,
        Eilon Greenstien <eilong@broadcom.com>,
        Or Gerlitz <or.gerlitz@gmail.com>, Amir Vadai <amirv@mellanox.com>,
        Alex Rosenbaum <alexr@mellanox.com>,
        Avner Ben Hanoch <avnerb@mellanox.com>, Or Kehati <ork@mellanox.com>,
        sockperf-dev@googlegroups.com, Eliezer Tamir <eliezer@tamir.org.il>
Date: Tue, 18 Jun 2013 02:08:30 -0700
In-Reply-To: <20130618085810.10941.55039.stgit@ladj378.jer.intel.com>
References: <20130618085759.10941.15811.stgit@ladj378.jer.intel.com>
	 <20130618085810.10941.55039.stgit@ladj378.jer.intel.com>
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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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