netdev - Re: problem with noop and pfifo

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]

Date:	Thu, 19 Jan 2012 14:15:33 +0100
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Hemant-vilas RAMDASI <hemant.ramdasi@...ricsson.com>
Cc:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"netdev-owner@...r.kernel.org" <netdev-owner@...r.kernel.org>
Subject: Re: problem with noop and pfifo_fast Qdisc switching

Le jeudi 19 janvier 2012 à 13:47 +0100, Hemant-vilas RAMDASI a écrit :
> Hi,
> 
> I have a situation where one of important message (phonet pipe message) gets dropped because of 'noop' Qdisc.
> This situation mostly happens when coming out of sleep and there is a message to send.
> What I have observed is this.
> In normal case the qdisc used id pfifo_fast. When CPU goes to sleep, it changes the qdisc to noop.
> When CPU wakes up (because of a message from lower layers), phonet tries to send a control packet to driver and finds qdisc is still 'noop'. 
> Because the concerned message is a control message, this packet drop is creating deadlock situation.
> 
> How the switch between pfifo_fast and noop is handled? Is this something solved in 3.0?
> We are running a older version of kernel (2.6.35 based).

If message is important, you should check return code from xmit
(NET_XMIT_CN is returned by noop_enqueue), and maybe resend it later.

Not sure by what you mean by 'cpu goes to sleep' or 'cpu wakes up' ?

Is it the machine going to suspend mode ?


--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html