How to force power-off of a Samsung Series 9 laptop?

According to this blog post the Samsung tech support confirmed that there is no way to force a reboot if the device is completely locked up. He ended up tearing it apart and unplugging the battery cable.

Kernel panic isn’t typically a huge problem, except in this case: when the system went into Kernel panic, the hard-reset itself no longer worked! I called Samsung tech support to see if a hard-reset called for anything more than holding down the power button until the system turned off, but it did not. The system was simply too deeply locked up to even be reset.

Given the machine’s seven-hour battery life, I didn’t feel like waiting out the problem, so I ultimately ended up taking apart the hardware to yank the battery cable.

EDIT

There actually is a way of enforcing a power-off. On the bottom of the laptop there is a tiny pinhole. If you put a paper clip in it while it is unplugged, it will turn off. However, it will refuse to boot until it is plugged in again!

In addition to what has been said already. As you're using Linux you might be able to use magic sysrrq to enforce a reboot on kernel level. I've had similar issues with broken disk arrays which prevented proper shutdown and reboot. So you might at least not have to wait until your battery drains completely.

Assuming 'magic sysrq' is enabled in your kernel (kernel config CONFIG_MAGIC_SYSRQ) you can use Alt+SysRq+b to reboot the machine.

NOTE: This is forcing an immediate reboot without unmounting any HDD cleanly. So a file system check on next reboot might be required/recommended.

If you're running a graphical user interface like KDE or Gnome, then either switch to a console (using CTRL+Alt+F1) or try CTRL+Alt+SysRq+b from the GUI.

You might also have to check whether your kernel has magic sysrq enabled by typing cat /proc/sys/kernel/sysrq.

You can also initiate a sysrq-reboot on remote systems:

echo 1 > /proc/sys/kernel/sysrq
echo b > /proc/sysrq-trigger

This would lead to an immediate reboot if CONFIG_MAGIC_SYSRQ was compiled into the kernel.

More details on magic sqsrq can be found here.

NOTE: on the Samsung Series 9, the key labeled "Fn Lock" serves as SysRq, though it is not printed as such.

I found a similar question on Yahoo Answers albeit with a different model.

One answer suggested holding down the power button for much longer. Failing that, it might be a sign that your motherboard might be on the way out.

If holding down the power button for longer still doesn't work and you have no access to battery, I think (like you said) your only option is to let the battery run down and switch itself off.

We let the battery run down completely. It simply would not power off. Attached the power cord and powered back on. It started up slowly, but completely and has been working fine ever since.