linux-kernel - Re: [PATCH v4] net: ocelot: fix wrong time

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Date:   Wed, 6 Jul 2022 13:30:42 +0000
From:   Vladimir Oltean <vladimir.oltean@....com>
To:     Pavel Skripkin <paskripkin@...il.com>
CC:     Claudiu Manoil <claudiu.manoil@....com>,
        "alexandre.belloni@...tlin.com" <alexandre.belloni@...tlin.com>,
        "davem@...emloft.net" <davem@...emloft.net>,
        "edumazet@...gle.com" <edumazet@...gle.com>,
        "kuba@...nel.org" <kuba@...nel.org>,
        "pabeni@...hat.com" <pabeni@...hat.com>,
        "clement.leger@...tlin.com" <clement.leger@...tlin.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Lunn <andrew@...n.ch>
Subject: Re: [PATCH v4] net: ocelot: fix wrong time_after usage

On Wed, Jul 06, 2022 at 04:28:45PM +0300, Pavel Skripkin wrote:
> Accidentally noticed, that this driver is the only user of
> while (time_after(jiffies...)).
> 
> It looks like typo, because likely this while loop will finish after 1st
> iteration, because time_after() returns true when 1st argument _is after_
> 2nd one.
> 
> There is one possible problem with this poll loop: the scheduler could put
> the thread to sleep, and it does not get woken up for
> OCELOT_FDMA_CH_SAFE_TIMEOUT_US. During that time, the hardware has done
> its thing, but you exit the while loop and return -ETIMEDOUT.
> 
> Fix it by using sane poll API that avoids all problems described above
> 
> Fixes: 753a026cfec1 ("net: ocelot: add FDMA support")
> Suggested-by: Andrew Lunn <andrew@...n.ch>
> Signed-off-by: Pavel Skripkin <paskripkin@...il.com>
> ---

Reviewed-by: Vladimir Oltean <vladimir.oltean@....com>

This patch should target the "net" tree.