Bisected. Bug seen after commit 045065d8a300a37218c548e9aa7becd581c6a0e8 [SCSI] fix qemu boot hang problem.
Actually, the problem is not with that commit that is perfectly fine. That commit merely lets the real bug be triggered. Real bug is with scsi host lock and likely to be triggered by mixing a slow and a fast device on the same IDE/SATA channel. Bug is also biting other distros. See https://bbs.archlinux.org/viewtopic.php?id=189324 Bug is known to kernel developers. https://lkml.org/lkml/2015/8/16/44 https://bugzilla.kernel.org/show_bug.cgi?id=87581 Bug is fixed by following patch by Christoph Hellwig, that unfortunately is not yet applied upstream https://lkml.org/lkml/2014/11/20/581 ** Bug watch added: Linux Kernel Bug Tracker #87581 http://bugzilla.kernel.org/show_bug.cgi?id=87581 ** Changed in: linux (Ubuntu) Status: Incomplete => Confirmed -- You received this bug notification because you are a member of Kernel Packages, which is subscribed to linux in Ubuntu. https://bugs.launchpad.net/bugs/1451277 Title: Extremely high IOWait and processes hungs after utopic->vivid upgrade with Iomega Zip drive (IDE) Status in linux package in Ubuntu: Confirmed Bug description: On Kubuntu, 64 bit AMD Phenom2 machine with 4 cores, and old (Geoforge 7025) Nvidia graphics. Using LVM. Machine also has a 2 disk software raid (mirroring). The machine was working fine before the upgrade, now it is almost impossible to use it... I see Wait in Top always above 60%; in dmesg after a few minutes that the machine is up even if the machine does nothing. I see hung processes (typically vgs, but occasionally also others). LVM related commands (e.g. lvdisplay) almost always hung at the terminal. I also see in ps some kernel workers almost constantly stuck in D state. Also, the machine takes ages to shutdown. Issue remains there also if I disable X (switch off the X login manager, sddm) and check at the console. Sorry I cannot provide details with apport, but the machine has been switched off and I will not be able to take it up again before a few days from now. The symptom I am observing may also be a sign of failing hardware, so please leave the bug as unconfirmed until I make some more tests or someone provide details on similar issues. In the meantime I would like to see if others are experiencing a similar serious issue. Is there anything specific that has changed between utopic and vivid, I should look into? To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1451277/+subscriptions -- Mailing list: https://launchpad.net/~kernel-packages Post to : kernel-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~kernel-packages More help : https://help.launchpad.net/ListHelp