Date:	Wed, 21 Jan 2009 22:20:05 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	"Waskiewicz Jr, Peter P" <peter.p.waskiewicz.jr@...el.com>
Cc:	"Allan, Bruce W" <bruce.w.allan@...el.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	"Brandeburg, Jesse" <jesse.brandeburg@...el.com>,
	"e1000-devel@...ts.sourceforge.net" 
	<e1000-devel@...ts.sourceforge.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"Rafael J. Wysocki" <rjw@...k.pl>
Subject: Re: igb regression (interface hang) with latest -git


* Ingo Molnar <mingo@...e.hu> wrote:

> > One other piece of info (in addition to what Bruce requested) that 
> > would be useful is after you've done ifconfig eht0 up, cat 
> > /proc/interrupts | grep eth0 and send that output (I want to see your 
> > MSI-X configuration).
> 
> here it is:
> 
>  79:         35          0       9836       7451       1197       1360        766          0       2196        995        770          0       2051        863       4714       1879   PCI-MSI-edge      eth0-tx-0
>  80:       2335          0       2718       3651       5024       9850        533          0       1405       1095          0          0       4421       1229          0       2002   PCI-MSI-edge      eth0-tx-1
>  81:         33          0          0       5478       1125       6585       4865       6306          0          0          0        714       3757          0       2662       1020   PCI-MSI-edge      eth0-tx-2
>  82:         21       1428       3136       3783       4249       6833          0          0       4175          0          0       1465       1940       1780       6286          0   PCI-MSI-edge      eth0-tx-3
>  83:         40          0          0       4788          0       1486          0       7185       3998       8637       1409       6785          0          0          0      10060   PCI-MSI-edge      eth0-rx-0
>  84:         70       1441       2606       1342          0       1678       4301       1839          0       6507       6910      16470          0       1484       1004          0   PCI-MSI-edge      eth0-rx-1
>  85:         40       1368          0       3560       5022       2040          5       1719          0       2037        956         40          0      17264       6456       2833   PCI-MSI-edge      eth0-rx-2
>  86:         44        414          5       1164         30       4513       4595       1542          0      10033       1151          0       4961       4203          0      10703   PCI-MSI-edge      eth0-rx-3
>  87:          1          0          0          0          0          0          0          0          0          0          0          0          0          0          0          0   PCI-MSI-edge      eth0

btw., i turned off CONFIG_PCI_MSI and that worked around the interface 
hang - the box has 40 minutes uptime now and still no hang. (it would hang 
within 5 minutes previously)

can test the revert of any of these commits:

e42e4ba: igb: fix anoying type mismatch warning on rx/tx queue sizing
8d25332: igb: Fix build warning when DCA is disabled.
26bc19e: igb: re-order queues to support cleaner use of ivar on 82576
0e014cb: igb: defeature tx head writeback
678c610: drivers/net/igb: remove dead code (function 'igb_read_pci_cfg')
908a7a1: net: Remove unused netdev arg from some NAPI interfaces.
ea943d4: igb: fixup AER with proper error handling
5e8427e: igb: Correctly determine pci-e function number in virtual environment
b4557be: igb: update handling of RCTL for smaller buffer sizes
cb7b48f: igb/e1000e: Naming interrupt vectors
40a914f: igb: Add support for pci-e Advanced Error Reporting
527d47c: igb: link up/down messages must follow a specific format
5b9ab2e: Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6
69d728b: igb: loopback bits not correctly cleared from RCTL register
9b07f3d: igb: remove unneeded bit refrence when enabling jumbo frames
f5f4cf0: igb: do not use phy ops in ethtool test cleanup for non-copper parts
0082982: netdev: add more functions to netdevice ops
68fd991: igb: Fix tx/rx_ring_count parameters for igb on suspend/resume/ring resize
b2d5653: igb: simplify swap in clean_rx_irq if using packet split
2e5c692: igb: convert to net_device_ops
198d6ba: Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6
4cf1653: netdevice: safe convert to netdev_priv() #part-2
babcda7: drivers/net: Kill now superfluous ->last_rx stores.
7c510e4: net: convert more to %pM

i had a quick look at all of them but none seem to have a direct 
connection to MSI-X interrupt generation.

There's a couple of ones that could have side effects:

Maybe this one:

  26bc19e: igb: re-order queues to support cleaner use of ivar on 82576

due to its sheer commit size and due to its impact on the hw programming.

or:

  0e014cb: igb: defeature tx head writeback

Might have some side-effect on tx-completion IRQs and might tickle 
firmware bugs?

Or:

  5e8427e: igb: Correctly determine pci-e function number in virtual environment

while it should have no impact on a native kernel, it does change the PCI 
config space access sequences.

Or maybe:

  69d728b: igb: loopback bits not correctly cleared from RCTL register

as this impacts the PCI programming too.

But ... i dont really know this code so i'm guessing around.

	Ingo
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