igb_poll - device driver failed to check map error

[Christoph Paasch <christoph.paasch@uclouvain.be>]

Hello,

I'm seeing a warning while booting my machine when DMA_API_DEBUG is set:

[   36.402824] ------------[ cut here ]------------
[   36.458070] WARNING: at /home/cpaasch/builder/net-next/lib/dma-debug.c:934 
check_unmap+0x648/0x702()
[   36.567377] Hardware name: ProLiant DL165 G7
[   36.618452] igb 0000:04:00.0: DMA-API: device driver failed to check map 
error[device address=0x0000000233d9b232] [size=154 bytes] [mapped as single]
[   36.776640] Modules linked in:
[   36.815446] Pid: 0, comm: swapper/7 Not tainted 3.9.0-rc1-mptcp+ #101
[   36.892515] Call Trace:
[   36.921745]  <IRQ>  [<ffffffff8102ad7f>] warn_slowpath_common+0x80/0x9a
[   37.001023]  [<ffffffff8102ae2d>] warn_slowpath_fmt+0x41/0x43
[   37.069771]  [<ffffffff811db17f>] check_unmap+0x648/0x702
[   37.134363]  [<ffffffff811db3e9>] debug_dma_unmap_page+0x50/0x52
[   37.206234]  [<ffffffff8136676a>] igb_poll+0x144/0xf7c
[   37.267706]  [<ffffffff8104dd19>] ? sched_clock_cpu+0x46/0xd1
[   37.336456]  [<ffffffff814458ce>] net_rx_action+0xa7/0x1d0
[   37.402085]  [<ffffffff81030b65>] __do_softirq+0xb4/0x16f
[   37.466673]  [<ffffffff81030c90>] irq_exit+0x40/0x87
[   37.526067]  [<ffffffff81002db1>] do_IRQ+0x98/0xaf
[   37.583378]  [<ffffffff815210aa>] common_interrupt+0x6a/0x6a
[   37.651086]  <EOI>  [<ffffffff8105d4be>] ? 
__tick_nohz_idle_enter+0x116/0x31f
[   37.736595]  [<ffffffff81008a04>] ? default_idle+0x24/0x39
[   37.802224]  [<ffffffff81008c62>] cpu_idle+0x68/0xa4
[   37.861616]  [<ffffffff81519f78>] start_secondary+0x1a9/0x1ad
[   37.930364] ---[ end trace 01b5bb0fd75a464c ]---


It happens shortly after mounting the NFS-root filesystem.

I tried to understand what is going on, but I am now at my wit's end.

By adding some print-statements, here is what I found out (not sure if this is 
anyhow helpful):

The difference between tx_buffer->time_stamp and the current 'jiffies' is up 
to 2000 jiffies (HZ==1000) at the first time the above warning happens (this 
seems too much for me). From then on, I see my print 3-4 times appear but 
without such a big difference between the timestamps (difference around 1 and 
2 jiffies).

Some other stuff, I printed:
tx_buffer->skb: ffff880235054c80
tx_buffer->bytecount: 154 
tx_buffer->gso_segs: 1
tx_buffer->protocol: 8 
tx_buffer->tx_flags 0x20


One last thing:
Am I right that after each call to dma_map_single/page a call to 
dma_mapping_error is needed? If that's the case, I have some patches that add 
this statement at missing places in the e1000, e1000e and ixgb driver. But 
these patches do not fix my above problem.


Thanks for your help,
Christoph

-- 
IP Networking Lab --- http://inl.info.ucl.ac.be
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UCLouvain
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