On 64bits, where the problem occurs, can someone try these boot options, one at a time: - nointremap - nox2apic - x2apic_phys
On my T420, the first two prevented the freeze when changing the brightness. See https://bugs.launchpad.net/ubuntu/+source/linux/+bug/922037/comments/7 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/776999 Title: [Lenovo W520] laptop freezes on ACPI-related actions To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/776999/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
