Red Hat Bugzilla – Bug 486260
Xorg hangs with 100% CPU usage when X starts
Last modified: 2014-06-16 16:39:17 EDT
Description of problem:
I recently updated a system from Fedora 9 to Fedora 10. After the update, the Xorg server hangs with 100% CPU usage and the X desktop seems frozen. I can log into the system remotely. The system has an intel chip (more details below) and this may actually be an issue with the intel xorg driver.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. Boot system (system starts X automatically)
Xorg hangs with 100% CPU usage
Normal X desktop experience
Here is the graphics chip in this system:
00:02.0 VGA compatible controller: Intel Corporation 82865G Integrated Graphics Controller (rev 02) (prog-if 00 [VGA controller])
Subsystem: IBM Device 0285
Flags: fast devsel, IRQ 11
Memory at f0000000 (32-bit, prefetchable) [size=128M]
Memory at e0000000 (32-bit, non-prefetchable) [size=512K]
I/O ports at 1800 [size=8]
Capabilities: [d0] Power Management version 1
Kernel modules: intelfb
I am attaching my xorg.conf file. I tried disabling DRI by adding Option "DRI" "false", but the server crashes in the same way with or without the switch.
I have backtraces and the error log, which I will post below.
Created attachment 332498 [details]
Xorg server log
Some strange things seem to be going on there...
Created attachment 332499 [details]
After Xorg hangs, I installed the debuginfos for xorg-x11-server-Xorg and deps. I attached gdb and did some backtraces. It seems stuck in some infinite memory allocate/deallocate loop. But its difficult to debug, since after a few steps something issues a breakpoint signal. You can see this result in the last backtrace in that file.
If you need any further info to debug this please let me know.
I tried renaming the xorg.conf file and I think this solved the problem. However, it still seems like a bug. The config file worked with previous versions of the X server. I'm setting priority to low.
I'm changing the severity of this back to high, since it has the annoying side effect of preventing me from running at any resolution other than 1024x768.
I have tried updating to xorg-x11-server-Xorg-1.5.3-13.fc10.i386 and there is no change. There is a new intel xorg driver available, 2.6.0 (http://intellinuxgraphics.org/) but I can't compile it since the libdrm available from the repos is too old. Also, the release notes from the intel 2.6.0 driver say "i855 XV may cause hangs. This was present in the previous release, and no workaround is known." I don't know if this is related to my problem - I have the i865 as shown above. Here's what I've tried in diagnosing the problem:
Found the minimal xorg.conf that creates the problem. See the xorg.conf attached below. This xorg.conf file causes Xorg to hang with 100% cpu usage. Commenting out the HorizSync and VertRefresh lines in the monitor section will allow Xorg to work. However, the system will be limited to running at 1024x768. If those lines are present, Xorg enumerates many more possible resolutions, and then the problem manifests. I have added the ModeDebug option to print additional debugging information in the log. Two additional logs are attached - one with the lines commented that shows the system working at 1024x768, and one with the lines uncommented that shows the system when it hangs. You can see in the latter case the system fails to allocate some buffers where it succeeded before. Based on the traces above this may be significant.
The symptoms remain the same when using EXA or XAA acceleration, and when disabling XVideo (see commented lines in xorg.conf).
I will try limiting the range of HorizSync and VertRefresh to see if there are specific resolutions that cause the problem.
There may be yet another bug in all of this. Once upon a time, the intel driver used to detect that the native resolution of the connected monitor is 1360x768. However, maybe a year ago it stopped auto-detecting this and I was forced to use the modeline you see present in the xorg.conf file. Without any xorg.conf file it only detects a resolution of 1024x768.
Please tell me what other information I can give you to help solve this. Can you recommend another place this bug report might be more appropriate? I would like to be as helpful as possible.
Created attachment 333661 [details]
Minimal xorg.conf that causes the hangup.
Created attachment 333662 [details]
Xorg log file showing the system working at 1024x768
This log file shows the system working with the minimal xorg.conf attached above with the HorizSync and VertRefresh lines commented.
Created attachment 333663 [details]
This Xorg log file shows the crash with the minimal xorg.conf file
Note the failure to allocate some buffers in this log file, and the additional resolutions that were enabled.
Adding Option "Tiling" "false" with the HorizSync and VertRefresh lines uncommented still causes a hangup. The buffer allocation still fails.
When I set:
HorizSync 47.0 - 50.0
VertRefresh 58.0 - 61.0
The server doesn't hang anymore, and I can use my custom modeline to get 1360x768. My guess is that the intel driver can't allocate enough memory for larger resolutions and does not fail gracefully.
Is this still true for Fedora 11? A lot has changed since then.
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I'm commenting so this bug stops appearing in my outstanding requests list.