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Suspend to RAM is broken on my Centrino 2 based notebook using Ubuntu 8.10 Linux. It is a Dell Latitude E6400 with Intel GMA X4500MHD graphics adapter. Here is my installation report. This blog entry shows how to work around the problem.

Hier findet ihr die deutsche Version dieses Berichtes.

When resuming the screen was frozen showing only the mouse pointer and the grey shades of the windows which were open. It seems the -intel driver for Xorg is not thread save. To work around this problem all CPUs, except one of course, have to be deactivated just before suspend and can be re-activated right after resume. A script can do this automatically:

/etc/pm/sleep.d/00CPU

#!/bin/sh
# Workaround for concurrency bug in xserver-xorg-video-intel 2:2.4.1-1ubuntu10.
# Save this as /etc/pm/sleep.d/00CPU

. "${PM_FUNCTIONS}"

case "$1" in
	hibernate|suspend)
		for i in /sys/devices/system/cpu/cpu*/online ; do
			echo 0 >$i
		done
		;;
	thaw|resume) 
		sleep 10	# run with one core for 10 secs
		for i in /sys/devices/system/cpu/cpu*/online ; do
			echo 1 >$i
		done
		;;
	*)
		;;
esac

The script needs execute permission (sudo chmod 755 /etc/pm/sleep.d/00CPU).

Problems

It seems that the cpu frequency scaling cannot be properly set after resume. I use the gnome applet to change the power scheme to performance or on demand as I need it. This seems to only influence one of the CPUs after resume.

Sources

This solution has been found at the following souces, thank you very much:

• www.thinkwiki.org/wiki/Install_Ubuntu_8.10_(Intrepid_Ibex)_on_a_Thinkpad_T400#Suspend.2FHibernate
• http://ubuntuforums.org/showpost.php?p=6105510&postcount=12
• The bugreport in -intel's bugtracker
• The bugreport in Ubuntu's Launchpad
• Probably a kernel fix