From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Hemminger Subject: Re: [Kgdb-bugreport] [PATCH 2.6.20-rc7] 8139too KGDBoE fix Date: Fri, 23 Feb 2007 11:22:46 -0800 Message-ID: <20070223112246.0712e7de@freekitty> References: <200701312144.56497.sshtylyov@ru.mvista.com> <45DDBD96.10000@ru.mvista.com> <45DDC7C0.8050100@ru.mvista.com> <200702231238.40474.amitkale@linsyssoft.com> <45DF2E20.305@mvista.com> <20070223110451.44066f09@freekitty> <45DF3BDC.2070806@ru.mvista.com> <20070223111354.2e25db9d@freekitty> <45DF3DAB.3010902@ru.mvista.com> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Cc: Mark Huth , "Amit S. Kale" , netdev@vger.kernel.org, Mithlesh Thukral , Vitaly Wool To: Sergei Shtylyov Return-path: Received: from smtp.osdl.org ([65.172.181.24]:55134 "EHLO smtp.osdl.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933191AbXBWTX3 (ORCPT ); Fri, 23 Feb 2007 14:23:29 -0500 In-Reply-To: <45DF3DAB.3010902@ru.mvista.com> Sender: netdev-owner@vger.kernel.org List-Id: netdev.vger.kernel.org On Fri, 23 Feb 2007 22:16:59 +0300 Sergei Shtylyov wrote: > Hello. > > Stephen Hemminger wrote: > > >>>>>This thread came up on kgdb-bugreport mailing list. Could you please suggest > >>>>>us what's the correct way of fixing this problem? > > >>>>>1. When running a kgdb on RTL8139 ethernet interface: 8139too driver prints > >>>>>too many "Out-of-sync dirty pointer" messages on console and gdb can't > >>>>>connect to kgdb stub. These messages can be suppressed, though it still > >>>>>results in connection failures frequently. > > >>>>We think this comes from calling the driver while the queue is stopped. > >>>>Drivers should not do horrible things when hard start is called with the > >>>>queue stopped, but unfortunately, at this time, at least some drivers > >>>>do explode or complain under that condition. > > >>>The kernel is built on a set of assumptions about calling context. Your > >>>out of tree code is violating one of them. Why not check for stopped queue > >>>and do some action to try and clear it, that is what netconsole does. > > >> The queue can't be stopped when the netpoll traffic trapping is enabled > >>(cause this effectively bypasses queue control), So, the stopped queue > >>indoication doesn't work also -- *that* is the problem. It's not at all > >>specific to KGBoE -- only to traffic trapping. > > > You can't ask a device to send a packet when it has no resources. > > When traffic trapping is enabled, and driver stops the queue, the > __LINK_STATE_XOFF flag does *not* get set, so netif_queue_stopped() resturns > *zero*. What may be done in this situation? Read netpoll_send_skb() int status = NETDEV_TX_BUSY; ... if (netif_tx_trylock(dev)) { /* try until next clock tick */ for (tries = jiffies_to_usecs(1)/USEC_PER_POLL; tries > 0; --tries) { if (!netif_queue_stopped(dev)) status = dev->hard_start_xmit(skb, dev); if (status == NETDEV_TX_OK) break; /* tickle device maybe there is some cleanup */ netpoll_poll(np); udelay(USEC_PER_POLL); } netif_tx_unlock(dev); netpoll_poll() allows device to try and cleanup transmit resources. -- Stephen Hemminger