linux-kernel - Re: [patch] revert: [NET]: Fix races in net_rx

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Date:	Wed, 18 Jul 2007 14:48:56 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Olaf Kirch <olaf.kirch@...cle.com>
Cc:	Jarek Poplawski <jarkao2@...pl>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, davem@...emloft.net
Subject: Re: [patch] revert: [NET]: Fix races in net_rx_action vs netpoll


* Olaf Kirch <olaf.kirch@...cle.com> wrote:

> On Tuesday 17 July 2007 20:56, Ingo Molnar wrote:
> > i logged these not via netconsole but via logging on over the console 
> > and using dmesg, so it should include everything. in the 100hz case the 
> > following seems to show the anomaly:
> > 
> >   NETDEV WATCHDOG: eth0: transmit timed out
> 
> So, it seems as if for some reason, dev->poll isn't called frequently 
> enough.
> 
> Here's a debugging patch that tries to locate the problem - can you 
> give it a try, please?

it triggers here:

 netconsole: device eth0 not up yet, forcing it
 netconsole: timeout waiting for carrier
 console [netcon0] enabled
 WARNING: at kernel/softirq.c:138 local_bh_enable()
  [<c0105e4a>] show_trace_log_lvl+0x19/0x2e
  [<c0105f43>] show_trace+0x12/0x14
  [<c0105f59>] dump_stack+0x14/0x16
  [<c0130f8d>] local_bh_enable+0x95/0x15d
  [<c03cf35b>] netpoll_poll+0xaf/0x361
  [<c03cf248>] netpoll_send_skb+0xe8/0x14c
  [<c03cf8d4>] netpoll_send_udp+0x258/0x260
  [<c02f4016>] write_msg+0x53/0x8d
  [<c012c87e>] __call_console_drivers+0x4e/0x5a
  [<c012c8e7>] _call_console_drivers+0x5d/0x61
  [<c012cf06>] release_console_sem+0x120/0x1c1
  [<c012d70a>] register_console+0x22e/0x236
  [<c02f3f98>] init_netconsole+0x55/0x67
  [<c05e28e5>] kernel_init+0x154/0x2d9
  [<c0105c5f>] kernel_thread_helper+0x7/0x10

I've uploaded the full log to:

 http://redhat.com/~mingo/misc/100hz.2.log

something i noticed: netconsole output seems to trickle through though, 
but very, very slowly (a packet once every 4 seconds or so). TCP/IP is 
not functional.

also, i'm using netconsole via the command line (both the network driver 
and netconsole is built into the bzImage), maybe that makes a 
difference?

(if there's any other data you'd like to see, let me know.)

	Ingo
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