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Every time I suspend or resume my laptop (Dell Latitude E6520, bought this year), I get 2 messages of the form displayed on the console just before shutting down/starting up:

[  407.107610] ehci_hcd 0000:00:1d.0: dma_pool_free buffer-128, f6f18000/36f18000 (bad dma)

On occasion, I get a message of the form:

[ 3753.979066] do_IRQ: 0.177 No irq handler for vector (irq -1)

On occasion, my machine freezes with a flashing Caps Lock button when suspending, after which I need to do a hard shutdown. This never happened before the messages started appearing (a while back), and I think it never happens without a do_IRQ message appearing (although I'm not sure about that). [There's nothing in the owner's manual on a flashing Caps Lock button; apparently it may be a kernel panic if the scroll lock also flashes, but the laptop doesn't have a scroll lock light, and there's no message on the console saying kernel panic.]

Are these bad DMA/do IRQ messages serious, and what can I do to investigate/troubleshoot them and the freezing?

Edit: I've also now received the following error messages a few times:

[246943.023908] JBD: I/O error detected when updating journal superblock for sdb1.
[246943.023958] Buffer I/O error on device sdb1, logical block 0
[246943.023996] EXT3-fs (sdb1): I/O error while writing superblock

Edit: Output of dmesg at ; contents of /var/log/kern.log at

Edit: the output of some smartctl (-a, -x, --log=error, --log=xerror) instructions is available at .

Edit (31/8/2012): Output of dmesg|grep -i ehci available at .

Edit: (3/9/2012):Output of lshw is at

share|improve this question
I really don't know, but I will suggest that you paste the output of the following command: dmesg | grep -i ehci to see if there is a hard disk or a usb drive involved. Otherwise sdb1 has nothing to do with sda1. If you check (fsck) your root partition (maybe sda1) withing you system it seems that you can lost everything. If it is an error of any usb drive maybe the error could be at your external mouse or external keyboard. – Salvador Aug 30 '12 at 17:42
I am now wondering if the kern.log is correctly pasted. Before you paste this file you should reboot your laptop. – Salvador Aug 31 '12 at 17:51
The issues I have are at suspend and resume. I pasted the kern.log after resuming. Do you want to me reboot and post that kern.log as well? – Steve Kroon Sep 2 '12 at 13:08
up vote 4 down vote accepted

1. "Bad DMA"

Let's deal with the "bad dma" errors first, since they're the only consistent ones which are reflected in your logs.

  • These, as well as any problems suspending/resuming, are caused by your internal USB 3G modem, which from the MAC address is an Ericsson F3507g.
    • Yes, you read that right. Not every USB device has to be external or plugged into one of the visible USB ports. Modern laptops will run a whole bunch of internal peripherals such as Wireless/3G cards, bluetooth, webcams, etc. from an internal USB "hub".

Notice this tell-tale sequence, which repeats every time the "bad dma" errors occur:

[171783.085166] usb 2-1.6: USB disconnect, device number 10
[171783.086623] ehci_hcd 0000:00:1d.0: dma_pool_free buffer-128, eafaa000/2afaa000 (bad dma)
[171783.087046] cdc_ncm 2-1.6:1.6: usb0: unregister 'cdc_ncm' usb-0000:00:1d.0-1.6, CDC NCM
[171783.092382] done.
[171783.129959] ehci_hcd 0000:00:1d.0: dma_pool_free buffer-128, eb1aa000/2b1aa000 (bad dma)
  • The cdc_ncm module is implicated; this is a low-level USB interface to high-speed cellular modems
  • This bug indicates that the F3507g WWAN cards have had similar problems with Ubuntu/Linux before, and a kernel update fixed it.
    • The error should only affect suspend/resume/freezing, and should NOT affect normal operation of the 3G card.
    • But I'd recommend you try one of the mainline kernels (or the Quantal 3.5 kernel), to see if it makes any difference.
    • The other extreme alternative, of course, is to either disable your 3G card in the BIOS, or if you actively use it, consider replacing it with another brand/model.

2. "do_IRQ" and "sdb1"

It's harder to debug these isolated warnings without context (which can be the key, as shown above). So we'll just have to guesstimate until you can provide a kern.log containing one or both of these errors.

  • "do_IRQ" seems to stem most often from PCI-Express bus issues, including graphics cards, and VIA chipsets are often implicated.
    • This message can otherwise be safely ignored.
  • Given that your SMART logs look OK, the "sdb1" errors probably come from even more USB communication issues with the external drive.

    • If you find more USB errors around these, I'd chalk it down to an occasional USB incompatibility and not worry; but if they occur only by themselves, it may indicate a problem with the drive. A more complete log would help :)
  • Again, I'd recommend trying one of the Quantal 3.5 kernels and seeings if things change, especially for the "do_IRQ".

3. Trying the 3.5-series Quantal Kernel (or a mainline build)

  • Once Ubuntu 12.10 is released, its kernel will be made available for 12.04 as a "backport" (the same goes for 13.04 and 13.10).
  • Right now, you can get the "beta" kernels from the Ubuntu-X team PPA
  • BUT this PPA also contains a number of extra packages which you have no need to upgrade.
  • So I've made just the backported kernel available in another PPA
  • To install:

    sudo apt-add-repository ppa:auanswers/lts-backported-kernels-prerelease
    sudo apt-get update
    sudo apt-get inst all linux-generic-lts-quantal
  • Reboot, and you should boot into the new kernel (check with uname -a). Nvidia/AMD graphics and Broadcom wireless cards may be problematic. You can always select your old 3.2-series kernel by keeping Shift pressed at boot until the Grub menu shows, and then going into "Previous Linux Versions"

  • For even more bleeding-edge kernels, you can try one of the mainline builds. Please see this question and answer for more information:

Should I upgrade to the "mainline" kernels?

share|improve this answer
FYI: I upgraded from Oneiric to precise to see if that would help as a first step, but no luck. In fact, I now get other errors from watchdog and mei about devices registering a watchdog... So, I'll try the Quantal kernel next. – Steve Kroon Sep 3 '12 at 10:05
Wait, you're on Oneiric !? – izx Sep 3 '12 at 10:12
I was, but not anymore. – Steve Kroon Sep 3 '12 at 17:17
The Quantal kernel got rid of the bad dma errors, thanks! How should I proceed in the future? (When/how should I remove the PPA and add the backports?) – Steve Kroon Sep 3 '12 at 18:33

The errors you added on the Edit seem to refer to a broken disk sector.

Have you tried running fsck or badblocks?

I suggest you to perform everything from a Live CD environment as follows

  1. Boot the live Ubuntu CD (or any other distro)
  2. Scan for disks and partitions with fdisk

    sudo fdisk -l
  3. Once you identified the correct disk label (For example /dev/sda1) try running these two commands. The -c parameter to the fsck command tries to identify and isolate bad blocks

    sudo e2fsck -cv /dev/sda1
    sudo badblocks -sv /dev/sda
share|improve this answer
Thanks - will follow up on this when I can get a Live CD - hopefully tomorrow. Meanwhile, it's disappointing to note that neither the -c nor the -v option of fsck appear in its man page. (What does the -v do?) – Steve Kroon Aug 30 '12 at 6:45
sorry the program to use was e2fsck not fsck. with e2fsck you can see from the manual that -c is to isolate bad block and -v to be verbose. – Andrea Olivato Aug 30 '12 at 9:51
Well, this is all academic, since there is only one hard drive in my machine, and it's /dev/sda, not /dev/sdb. (In fact, there doesn't seem to be a /dev/sdb on my machine at all.) However, perhaps /dev/sdb is my external drive that I have plugged in on occasion. I will try running these tests on that drive. – Steve Kroon Aug 31 '12 at 10:02
I ran e2fsck on /dev/sdb1, output at - no bad blocks found. – Steve Kroon Sep 2 '12 at 13:06
1 large file 1 directory ?? This means you have just one file, are you sure you ran the command on the right volume? can you post the output of sudo fdisk -l ? – Andrea Olivato Sep 3 '12 at 14:51

For the "no irq for vector" issue, try adding "pci=nomsi" to the kernel boot options.

share|improve this answer
Thanks - this is sporadic, as I say, so I can't say if it will help or not, but I'm trying it – Steve Kroon Aug 31 '12 at 10:15

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