Comment 40 for bug 585765

I have Lucid installed on three PCs. Here are the devices and status:

1. ThinkPad T41p
ATI FireGL (128 MB); Compiz enabled
Version: Lucid 32 bit upgraded from Karmic via Update Manager
Status: stable

2. ThinkPad T42
ATI Mobility Radeon 7500 (32 MB); Compiz enabled
Version: Lucid 32 bit; fresh install
Status: random freezing; always freezing at blank screensaver; freezing usually on Firefox or Chromium; freezes tend to be clustered (suspect possible issue with certain web sites which may be reloaded after hard reboot); this laptop was stable with Karmic and openSUSE 11.2 - no hardware issues are suspected

3. Custom Desktop (Intel Pentium D 805)
ATI Mobility Radeon 9600 (256 MB); Compiz enabled
Version: Lucid 64 bit; fresh install
Status: stable

I have scoured various blogs and forums and tried every suggestion I could find to stabilize the T42, including:
a. Custom xorg.conf
b. radeon.modeset=0 in GRUB (also tried nomodeset)
c. Set screensaver to other than blank screen (the laptop would still freeze at some point after the screensaver kicked in)

Initially, I thought that some changes had made a difference. However, the randomness of this issue can make a one hour freeze-free session seem like an improvement. Soon enough, though, I would find the system locking every two minutes, five minutes, ten minutes, etc.

However, I think I have finally found a solution without downgrading to Karmic: I had seen where some users with Intel graphics cards had experienced success downgrading the kernel to linux-image-rt (2.6.31.10.12). While I certainly don't have a need for a real time kernel, this was the only kernel in the default Ubuntu Lucid repositories that was based on 2.6.31 and not 2.6.32. I didn't want to go with a nightly build or PPA. I wanted to stick with the stock repo, if possible. Sure enough, I've been operating nearly two full days without a lockup. The screensaver kicks in appropriately and comes out of screensaver mode (which the laptop previously had not done). In aggregate, I've had hours of use without any issue whatsoever. Previously, I would have expected anywhere from 4-12 freezes.

This laptop still has all the various changes that I've made, so I can't yet tell whether it is the kernel alone or if it is the downgraded (plus real time) kernel in conjunction with one of the other changes I have made. I will shortly rebuild this laptop with a custom remaster (using Remastersys) with the linux-image-rt kernel as the sole change. I expect this will work without any special change to xorg.conf or GRUB, but will report back if this fails and the freezes return