Resending in plain text mode.... Bradley On Fri, Dec 27, 2013 at 2:21 PM, Bradley Baetz <bbaetz@xxxxxxxxx> wrote: > Hi, > > I have a Dell laptop (Vostro 3560). When I boot Fedora 20 with the > acpi_backlight=vendor option, the kernel locks up hard during the boot > proces, when systemd runs udevadm trigger. This is a hard lockup - > magic-sysrq doesn't work, and neither does caps lock/vt-change/etc. > > I've bisected this to: > > commit 81c0a2bb515fd4daae8cab64352877480792b515 > Author: Johannes Weiner <hannes@xxxxxxxxxxx> > Date: Wed Sep 11 14:20:47 2013 -0700 > > mm: page_alloc: fair zone allocator policy > > which seemed really unrelated, but I've confirmed that: > > - the commit before this patch doesn't cause the problem, and the commit > afterwrads does > - reverting that patch from 3.12.0 fixes the problem > - reverting that patch (and the partial revert > fff4068cba484e6b0abe334ed6b15d5a215a3b25) from master also fixes the problem > - reverting that patch from the fedora 3.12.5-302.fc20 kernel fixes the > problem > - applying that patch to 3.11.0 causes the problem > > so I'm pretty sure that that is the patch that causes (or at least triggers) > this issue > > I'm using the acpi_backlight option to get the backlight working - without > this the backlight doesn't work at all. Removing 'acpi_backlight=vendor' (or > blacklisting the dell-laptop module, which is effectively the same thing) > fixes the issue. > > The lockup happens when systemd runs "udevadm trigger", not when the module > is loaded - I can reproduce the issue by booting into emergency mode, > remounting the filesystem as rw, starting up systemd-udevd and running > udevadm trigger manually. It dies a few seconds after loading the > dell-laptop module. > > This happens even if I don't boot into X (using > systemd.unit=multi-user.target) > > Triggering udev individually for each item doesn't trigger the issue ie: > > for i in `udevadm --debug trigger --type=devices --action=add --dry-run > --verbose`; do echo $i; udevadm --debug trigger --type=devices --action=add > --verbose --parent-match=$i; sleep 1; done > > works, so I haven't been able to work out what specific combination of > actions are causing this. > > With the acpi_backlight option, I can manually read/write to the sysfs > dell-laptop backlight file, and it works (and changes the backlight as > expected) > > This is 100% reproducible. I've also tested by powering off the laptop and > pulling the battery just in case one of the previous boots with the bisect > left the hardware in a strange state - no change. > > I did successfully boot a 3.12 kernel on F19 (before I upgraded to F20), so > there's presumably something that F20 is doing differently. It was only one > boot though. > > I reported this to fedora > (https://bugzilla.redhat.com/show_bug.cgi?id=1045807) but it looks like this > is an upstream issue so I was asked to report it here. > > This is an 8-core single i7 cpu (one numa node) - its a laptop, so nothing > fancy. DMI data is attached to the fedora bug. > > Bradley -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>