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Date: Tue, 17 Apr 2007 08:26:32 -0500 From: Michal Ostrowski <mostrows@...thlink.net> To: Jarek Poplawski <jarkao2@...pl> CC: "Yuriy N. Shkandybin" <jura@...ams.com>, Andrew Morton <akpm@...ux-foundation.org>, Paul Mackerras <paulus@...ba.org>, netdev@...r.kernel.org, Michal Ostrowski <mostrows@...akeasy.net> Subject: Re: + ppp_generic-fix-lockdep-warning.patch added to -mm tree The "xmit" function of a PPP channel is a synchronous operation. If the transmission fails, we must notify the caller and let them re-submit the skb later. The return status of dev_queue_xmit is needed to determine the return code passed back to the caller and thus the call is made synchronously and not in a tasklet. Looking at the stack traces earlier in this thread, it seems to me that even if the PPPoE call was made in a tasklet, this same warning could be generated. -- Michal Ostrowski mostrows@...thlink.net Jarek Poplawski wrote: > On Wed, Apr 11, 2007 at 12:52:28PM +0400, Yuriy N. Shkandybin wrote: > ... >>> On Wed, 11 Apr 2007 09:57:33 +0400 "Yuriy N. Shkandybin" <jura@...ams.com> >>> wrote: >>> >>>> I've tested 2.6.21-rc6-mm1 >>>> Linux vpn1 2.6.21-rc6-mm1 #4 SMP Wed Apr 11 03:34:26 MSD 2007 x86_64 >>>> Intel(R) Pentium(R) D CPU 2.80GHz GenuineIntel GNU/Linux >>>> >>>> warn appeares upon first pppoe connection to rp-pppoe server in kernel >>>> mode >>>> >>> Thanks. So you're saying that >>> ftp://ftp.kernel.org/pub/linux/kernel/people/akpm/patches/2.6/2.6.21-rc6/2.6.21-rc6-mm1/broken-out/ppp_generic-fix-lockdep-warning.patch >>> did not fix anything? >> As i understand this patch already in -mm tree, so I've booted into last mm >> kernel and received this locked warning. >> Or i've mistaked and should apply this patch manually? > > Hi! > > Yuriy - thanks for testing my patch ...(pause) Not! > > It seems this patch is not visible in this version - probably > is overpatched by something else. But your new log shows there > is another connection between these locks (ppp_xmit_process > and ppp_push instead of ppp_channel_push in "-> #0"), so the > patch is not sufficient (and could be dumped). > > I don't know your vlans configuration, but it seems the real > lockup isn't very probable here - it's rather lockdep question. > I think vlan's too broad lockdep class is the main "guilty" > here, but probably pppoe also could be enhanced: it's making > the things unnecessarily complicated by calling dev_queue_xmit > under ppp_generic's xmit locks. I wonder if there is any reason > against using a tasklet here. > > I'll try to find more time to untie this yet - or maybe some > maintainer will find this interesting, too... > > Regards, > Jarek P. > > PS: sorry for late responding (vacations). > > - 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
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