linux-kernel - Re: [PATCH 1/2] net: ethernet: sxgbe: remove private tx queue lock

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Message-ID: <f007ba4c-71ea-0abf-8715-be7b0bec6080@gmx.de>
Date:   Mon, 19 Dec 2016 23:49:25 +0100
From:   Lino Sanfilippo <LinoSanfilippo@....de>
To:     Pavel Machek <pavel@....cz>
Cc:     Francois Romieu <romieu@...zoreil.com>, bh74.an@...sung.com,
        ks.giri@...sung.com, vipul.pandya@...sung.com,
        peppe.cavallaro@...com, alexandre.torgue@...com,
        davem@...emloft.net, linux-kernel@...r.kernel.org,
        netdev@...r.kernel.org
Subject: Re: [PATCH 1/2] net: ethernet: sxgbe: remove private tx queue lock

Hi,

On 18.12.2016 19:30, Pavel Machek wrote:
> Hi!
> 
>> > - e1efa87241272104d6a12c8b9fcdc4f62634d447
>> 
>> Yep, a sync of the dma descriptors before the hardware gets ownership of the tx tail
>> idx is missing in the stmmac, too.
> 
> I can reproduce failure with 4.4 fairly easily. I tried with dma_
> variant of barriers, and it failed, too
> 
> [ 1018.410012] stmmac: early irq
> [ 1023.939702] fpga_cmd_read:wait_event timed out!
> [ 1033.128692] ------------[ cut here ]------------
> [ 1033.133329] WARNING: CPU: 0 PID: 0 at net/sched/sch_generic.c:303
> dev_watchdog+0x264/0x284()
> [ 1033.141748] NETDEV WATCHDOG: eth0 (socfpga-dwmac): transmit queue 0
> timed out
> [ 1033.148861] Modules linked in:

This watchdog warning clearly says that for some reason the tx queue was stopped
but never woken up in a certain timespan (5 sec in our case, which is a lot).

Does this occur after the queue has been stopped and woken up again a few times or
is it already the first time the queue is stopped (and never woken up)? 

Regards,
Lino