With Kernel 3.12.5-302 and v3.12.6-300 system doesn't boot up and gets stuck with fthe following error (repeated numerous time):
kernel: BUG: soft lockup - CPU#2 stuck for 22s! [Xorg:588] with
Everything works fine with Kernel 3.11.10-301.fc20.x86_64
Problem generted by rc.local file invoking the following command:
echo OFF > /sys/kernel/debug/vgaswitcheroo/switch
This was implemented to stop the laptop from overheating.
Removing the rc.local file containing the command removes the soft lockup problem and the system boots normally. Unfortunately that recrated the overheating problem.
Installed Kernel 3.12.8-300.fc20.x86_64 from Koji and my issue has gone..