System Freeze with Kernel 3.19.0 after graphics startup (radeon)

[Heineken]

The first restart after Kernel upgrade to 3.19.0-31 this morning, the computer freezes when showing the graphical login-screen. Num-lock key is non-responsive, hard reset is required. System is equipped with Cypress XT [Radeon HD 5870] and runs the open source radeon driver.

Sometimes only a black screen is shown and the system freezes, sometime the Scroll-lock and Caps-lock keys are blinking (kernel-panik).

Starting the system with kernel version 3.16.0-36, it's rock-solid.

ProblemType: Bug
DistroRelease: Ubuntu 15.04
Package: linux-signed-image-3.19.0-30-generic (not installed)
ProcVersionSignature: Ubuntu 3.16.0-36.48-generic 3.16.7-ckt9
Uname: Linux 3.16.0-36-generic x86_64
ApportVersion: 2.17.2-0ubuntu1.5
Architecture: amd64
CurrentDesktop: Unity
Date: Thu Oct 8 09:28:08 2015
InstallationDate: Installed on 2015-01-28 (252 days ago)
InstallationMedia: Ubuntu 14.10 "Utopic Unicorn" - Release amd64 (20141022.1)
SourcePackage: linux-signed
UpgradeStatus: No upgrade log present (probably fresh install)

[Heineken (lars-heineken)]

This bug is a duplicate of bug #1503655. The issue has been identified in several kernel versions, and a fix has been uploaded. In the meantime, I've a test kernel that can be used to confirm if this is *really* the same bug.

People running Trusty (3.13 kernel) can try: http://people.canonical.com/~henrix/lp1503655/t/amd64/
People running Vivid (3.19 kernel) can try: http://people.canonical.com/~henrix/lp1503655/v/amd64/