linux-kernel - Re: [ 33/52] net: Fix issue with netdev_tx_reset_queue not resetting queue from XOFF state

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Message-ID: <20120510194658.GA9858@burratino>
Date:	Thu, 10 May 2012 14:46:58 -0500
From:	Jonathan Nieder <jrnieder@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	alexander.h.duyck@...el.com, gregkh@...uxfoundation.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	alan@...rguk.ukuu.org.uk, stephen.s.ko@...el.com,
	jeffrey.t.kirsher@...el.com
Subject: Re: [ 33/52] net: Fix issue with netdev_tx_reset_queue not resetting
 queue from XOFF state

David Miller wrote:
> From: Alexander Duyck <alexander.h.duyck@...el.com>

>> All of the changes in igb are unnecessary.  I think they can be dropped
>> from the patch as they have already been reverted from the latest
>> net-next.  The only change that is really needed is the piece in
>> netdevice.h below.
>
> Does it hurt?  If not, just let it be.

Based on the commit description for dad8a3b3eaa0 ("igb, ixgbe:
netdev_tx_reset_queue incorrectly called from tx init path"), yes, it
hurts.  I don't know if it hurts enough to justify holding up this
patch until dad8a3b3eaa0 hits mainline.

|                            this sort of works in most cases except
| when the number of real tx queues changes. When the number of real
| tx queues changes netdev_tx_reset_queue() only gets called on the
| new number of queues so when we reduce the number of queues we risk
| triggering the watchdog timer and repeated device resets.
|
| So this is not only a cosmetic issue but causes real bugs. For
| example enabling/disabling DCB or FCoE in ixgbe will trigger this.
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