Bug 62678

Description of Problem:

At 02:00:31 this morning my X server hung.  Strangely the mouse was still working even though none of my current X processes could output any changes to the screen.  I could not select windows or do anything on the desktop.  Attempts to start new X processes, while logged in via SSH from annother machine were unsuccessful.  Also the keyboard was non-functional, and I was not able to even switch to a different VT.

After logging in via SSH from annother workstation, I noticed that the system load was hovering around 5 (on a VA Linux 420, i810 m/b, Celeron 550MHz, 256MB RAM).  TOP showed that "X" was soaking up all the available CPU, but luckilly only had an RSS of 17MB.  An strace of the X process showed:


02:21:04.499334 [4010f581] gettimeofday({1017908464, 500095}, NULL)             = 0 <0.000044>
02:21:04.500281 [4010f581] gettimeofday({1017908464, 500531}, NULL)             = 0 <0.000886>
02:21:04.501463 [4010f581] gettimeofday({1017908464, 501555}, NULL)             = 0 <0.000012>
02:21:04.501630 [4010f581] gettimeofday({1017908464, 501682}, NULL)             = 0 <0.000013>
02:21:04.501755 [4010f581] gettimeofday({1017908464, 501807}, NULL)             = 0 <0.000011>
02:21:04.501880 [4010f581] gettimeofday({1017908464, 501933}, NULL)             = 0 <0.000012>
02:21:04.502007 [4010f581] gettimeofday({1017908464, 502059}, NULL)             = 0 <0.000012>
02:21:04.502133 [4010f581] gettimeofday({1017908464, 502185}, NULL)             = 0 <0.000012>
02:21:04.502260 [4010f581] gettimeofday({1017908464, 502313}, NULL)             = 0 <0.000011>
02:21:04.502387 [4010f581] gettimeofday({1017908464, 502439}, NULL)             = 0 <0.000012>

Note:  I don't show it here, but the X server process was responding to SIGIO, generated when I moved the mouse.  I don't know why the keyboard didn't work similarily.

Searching around for annother report/solution for this problem turned up this relevant link at xfree86.org:

http://www.xfree86.org/pipermail/xpert/2001-January/004736.html

This thread shows that annother person had their X server hang, likely because the system time changed underneath the X server causing the X protocol messages to have inconsistant timestamps.   In their case it was XFree86 4.0.2 looping in the WaitForSomething function, called from Dispatch().

In my case I am running DJB's clockspeed to synch the clock, it seems possible to me that clockspeed corrected some minor drift in the system time and caused some sort of internal race within the X server process.  Just my guess.

We do run clockadj to manually reset the system time, but that runs out of cron.daily which doesn't kick off until 04:02 AM, and according to gkrellm the X server stopped at 02:00:31 AM.

ps output:

root      6313  2.9  6.7 113820 17232 ?      R<   Mar26 384:25 /etc/X11/X :0 -auth /var/gdm/:0.Xauth

Note:  I run the X server at nice -10, I also run artsd at nice -20, and I was playing MP3's over NFS when this happened.  It's all Rob Zombie's fault 8^).

root      5396  0.0  0.1  1352  320 pts/9    S    02:32   0:00 supervise /var/service/clockspeed
root      5398  0.0  0.1  1348  300 pts/9    S    02:32   0:00 /etc/clockspeed/bin/clockspeed

Note:  I restarted clockspeed myself while diagnosing this problem.

Version-Release number of selected component (if applicable):

XFree86-4.1.0-15
kernel-2.4.9-21 (I have 2.4.9-31 installed but I haven't rebooted yet)

How Reproducible:

Not sure, probably putz with the system time while X is running.  I may try an experiment but I also want to go home and catch some ZZzzzz's. 8^)

Steps to Reproduce:
1. 
2. 
3. 

Actual Results:

X server hangs, mouse works but it does not accept input, programs do not output and any new programs that try to talk to the X server just sit there looking dumb.

Expected Results:

It should keep on trucking.

Additional Information:
	
URLs and file snippets listed above