netdev - Re: [PATCH] [v7] net: emac: emac gigabit ethernet controller driver

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <57AB589D.3010509@codeaurora.org>
Date:	Wed, 10 Aug 2016 11:38:53 -0500
From:	Timur Tabi <timur@...eaurora.org>
To:	Florian Fainelli <f.fainelli@...il.com>,
	Lino Sanfilippo <LinoSanfilippo@....de>,
	netdev@...r.kernel.org, devicetree@...r.kernel.org,
	linux-arm-msm@...r.kernel.org, sdharia@...eaurora.org,
	shankerd@...eaurora.org, vikrams@...eaurora.org,
	cov@...eaurora.org, gavidov@...eaurora.org, robh+dt@...nel.org,
	andrew@...n.ch, bjorn.andersson@...aro.org, mlangsdo@...hat.com,
	jcm@...hat.com, agross@...eaurora.org, davem@...emloft.net
Subject: Re: [PATCH] [v7] net: emac: emac gigabit ethernet controller driver

Florian Fainelli wrote:
>> >Is there an easy way for me to stop the RX path before I set rxbuf_size?
>> >  Some netif_xxx function I can call?
> napi_disable() should take care of that.

It appears that if I call netif_stop_queue() *afer* calling 
napi_disable(), I get a hang and/or TX timeout.  Since emac_mac_down() 
does this:

	netif_stop_queue(netdev);
	napi_disable(&adpt->rx_q.napi);

I cannot call just napi_disable() in emac_change_mtu(), because when I 
then call emac_mac_down(), the first thing it does is call 
netif_stop_queue(), and that's when I timeout/hang.

Unfortunately, I cannot even do this:

	netif_stop_queue(netdev);
	napi_disable(&adpt->rx_q.napi);
	netif_stop_queue(netdev);
	napi_disable(&adpt->rx_q.napi);

Even though I've already called netif_stop_queue(), calling it again 
causes the timeout/hang.

Is this expected?  I never understood why I needed to call 
netif_stop_queue() before napi_disable().  I do see some drivers do not 
call netif_stop_queue().  I even saw a driver that calls them in reverse 
order, so I don't understand why that sequence breaks for me but not him.

-- 
Qualcomm Datacenter Technologies, Inc. as an affiliate of Qualcomm
Technologies, Inc.  Qualcomm Technologies, Inc. is a member of the
Code Aurora Forum, a Linux Foundation Collaborative Project.