netdev - Re: [PATCH] bonding: various fixes for bonding, netpoll & netconsole (v2)

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Date:	Fri, 15 Oct 2010 20:41:15 -0300
From:	Flavio Leitner <fleitner@...hat.com>
To:	nhorman@...driver.com
Cc:	netdev@...r.kernel.org, bonding-devel@...ts.sourceforge.net,
	fubar@...ibm.com, davem@...emloft.net, andy@...yhouse.net,
	amwang@...hat.com
Subject: Re: [PATCH] bonding: various fixes for bonding, netpoll & netconsole
 (v2)

On Wed, Oct 13, 2010 at 08:35:29AM -0400, nhorman@...driver.com wrote:
> Version 2, taking teh following changes into account:
> 
> 1) Moved tx blocking/checking macros to netpoll.h as suggested by amwang
> 
> 2) Added tx blocking macro calls to sysfs paths, as they can deadlock in the
> same way that the link monitoring paths can.
> 
> Summary: 
> A while ago we tried to enable netpoll on the bonding driver to enable
> netconsole.  That worked well in a steady state, but deadlocked frequently in
> failover conditions due to some recursive lock-taking (as well as a few other
> problems).  I've gone through the driver, netconsole and netpoll code, fixed up
> those deadlocks, and confirmed that, with this patch series, we can use
> netconsole on bonding without deadlock in all bonding modes with all slaves,
> even accross failovers.  I've also fixed up some incidental bugs that I ran
> across while looking through this code, as described in individual patches
> 
> Signed-off-by: Neil Horman <nhorman@...driver.com>

I've tested these patch series and found this:

netconsole: network logging started
bonding: bond0: making interface eth0 the new active one.
------------[ cut here ]------------
WARNING: at kernel/softirq.c:143 _local_bh_enable_ip+0x4e/0xd7()
Hardware name: Precision WorkStation 490    
Modules linked in: netconsole configfs sunrpc bonding ip6t_REJECT
nf_conntrack_ipv6 ip6table_filter ip6_tables ipv6 p4_clockmod freq_table
speedstep_lib dm_multipath uinput snd_hda_codec_idt snd_hda_intel
snd_hda_codec snd_hwdep snd_seq snd_seq_device i5k_amb snd_pcm hwmon
i5000_edac snd_timer edac_core e1000 snd ppdev parport_pc iTCO_wdt
parport iTCO_vendor_support soundcore tg3 dcdbas pcspkr shpchp i2c_i801
serio_raw snd_page_alloc nouveau ttm drm_kms_helper drm i2c_algo_bit
video output i2c_core [last unloaded: netconsole]
Pid: 8, comm: kworker/1:0 Not tainted 2.6.36-rc7+ #26
Call Trace:
 [<ffffffff810510c5>] warn_slowpath_common+0x85/0x9d
 [<ffffffff813cfcf2>] ? rcu_read_unlock_bh+0x26/0x28
 [<ffffffff810510f7>] warn_slowpath_null+0x1a/0x1c
 [<ffffffff810574fa>] _local_bh_enable_ip+0x4e/0xd7
 [<ffffffff810575a5>] local_bh_enable+0x12/0x14 <-- enabling again
 [<ffffffff813cfcf2>] rcu_read_unlock_bh+0x26/0x28
 [<ffffffff813d08a1>] dev_queue_xmit+0x363/0x375
 [<ffffffff813d053e>] ? dev_queue_xmit+0x0/0x375
 [<ffffffffa028c1e0>] bond_dev_queue_xmit+0xbe/0xdb [bonding]
 [<ffffffffa028c46e>] bond_start_xmit+0x271/0x4df [bonding]
 [<ffffffff813e0a15>] queue_process+0xcd/0x18a <- interrupts disabled
 [<ffffffff813e0948>] ? queue_process+0x0/0x18a
 [<ffffffff810673cf>] process_one_work+0x216/0x37d
 [<ffffffff81067344>] ? process_one_work+0x18b/0x37d
 [<ffffffff8106920d>] ? manage_workers+0x10b/0x195
 [<ffffffff810693d8>] worker_thread+0x141/0x21e
 [<ffffffff81069297>] ? worker_thread+0x0/0x21e
 [<ffffffff8106c988>] kthread+0x9d/0xa5
 [<ffffffff8100aaa4>] kernel_thread_helper+0x4/0x10
 [<ffffffff8147f950>] ? restore_args+0x0/0x30
 [<ffffffff8106c8eb>] ? kthread+0x0/0xa5
 [<ffffffff8100aaa0>] ? kernel_thread_helper+0x0/0x10
---[ end trace 55688f5173e9b393 ]---
e1000: eth1 NIC Link is Up 1000 Mbps Full Duplex, Flow Control: RX/TX
bonding: bond0: link status definitely up for interface eth1.
0)

It happens because queue_process() disables the local
interrupts before call ->ndo_start_xmit() and then
dev_queue_xmit() will enable them back.

I have CONFIG_TRACE_IRQFLAGS=y on my .config.


-- 
Flavio
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