From: Jonathan Morton <chromatix99@gmail.com>
To: Wen Yang <wenyang@linux.alibaba.com>
Cc: "Toke Høiland-Jørgensen" <toke@toke.dk>,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
cake@lists.bufferbloat.net,
"Kevin Darbyshire-Bryant" <ldir@darbyshire-bryant.me.uk>,
"Cong Wang" <xiyou.wangcong@gmail.com>,
"David S . Miller" <davem@davemloft.net>
Subject: Re: [Cake] [PATCH] sch_cake: avoid possible divide by zero in cake_enqueue()
Date: Thu, 2 Jan 2020 23:58:02 +0200 [thread overview]
Message-ID: <0750BA89-01A1-4126-9BEF-2C6AC607A5BD@gmail.com> (raw)
In-Reply-To: <20200102092143.8971-1-wenyang@linux.alibaba.com>
> On 2 Jan, 2020, at 11:21 am, Wen Yang <wenyang@linux.alibaba.com> wrote:
>
> The variables 'window_interval' is u64 and do_div()
> truncates it to 32 bits, which means it can test
> non-zero and be truncated to zero for division.
> The unit of window_interval is nanoseconds,
> so its lower 32-bit is relatively easy to exceed.
> Fix this issue by using div64_u64() instead.
That might actually explain a few things. I approve.
Honestly the *correct* fix is for the compiler to implement division in a way that doesn't require substituting it with function calls. As this shows, it's error-prone to do this manually.
- Jonathan Morton
next prev parent reply other threads:[~2020-01-02 21:58 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-02 9:21 Wen Yang
2020-01-02 21:58 ` Jonathan Morton [this message]
2020-01-02 23:34 ` Toke Høiland-Jørgensen
2020-01-03 0:35 ` [Cake] " David Miller
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