netdev - Re: [PATCH net-next 1/1] tcp: sysctl: Fix a race to avoid unexpected 0 window from space

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Date:   Fri, 24 Mar 2017 13:29:28 -0700 (PDT)
From:   David Miller <davem@...emloft.net>
To:     gfree.wind@...mail.com
Cc:     netdev@...r.kernel.org, fgao@...ai8.com
Subject: Re: [PATCH net-next 1/1] tcp: sysctl: Fix a race to avoid
 unexpected 0 window from space

From: gfree.wind@...mail.com
Date: Fri, 24 Mar 2017 07:05:12 +0800

> From: Gao Feng <fgao@...ai8.com>
> 
> Because sysctl_tcp_adv_win_scale could be changed any time, so there
> is one race in tcp_win_from_space.
> For example,
> 1.sysctl_tcp_adv_win_scale<=0 (sysctl_tcp_adv_win_scale is negative now)
> 2.space>>(-sysctl_tcp_adv_win_scale) (sysctl_tcp_adv_win_scale is postive now)
> 
> As a result, tcp_win_from_space returns 0. It is unexpected.
> 
> Certainly if the compiler put the sysctl_tcp_adv_win_scale into one
> register firstly, then use the register directly, it would be ok.
> But we could not depend on the compiler behavior.
> 
> Signed-off-by: Gao Feng <fgao@...ai8.com>

Applied.