ubuntu-x-swat team mailing list archive

[Bryce Harrington <bryce@xxxxxxxxxxxxxxxxxxx>]

In general, xorg 100% cpu bugs are rarely actually X bugs.  X is a
server process that serves client requests.  Client applications can
send X an endless series of requests, and this will drive the X cpu
utilization through the roof, but it is the client application which is
bugged; the X server is just doing its job.

I don't know if that is the case here, as insufficient information has
been gathered so far, but the circumstantial evidence points this way.
People are reporting the same issue on a wide variety of different video
drivers (the difference between -nvidia and -intel is HUGE; it's quite
unusual for a particular X bug to affect both.)  The original report
says that both the 1.6 server in Karmic and the 1.7 server upstream were
tested and saw the same behavior, and that rules out a lot of
possibilities of it being an X bug.  The behavior that logging out and
logging back in also sounds suspicious.  Marc's last comment regarding
the acpid socket being unavailable also sounds like a strong clue (X
doesn't manage acpi stuff anymore, but acpi includes keyboard handling
stuff, so I could imagine a broken acpi daemon could get stuck in a loop
querying X a lot.)

Anyway, for the case that it is a client application causing the
problem, the troubleshooting process is straightforward:  Just start
killing user processes until the X CPU drops, and when that happens you
have your culprit.

Or, if you find that no process killing reduces the X CPU, the next step
would be to use gdb and strace to get an idea on what section of X code
is being triggered here.

Another approach would be to bisect the problem by booting earlier
versions of Karmic to find one where the problem did *not* occur, and
then identify the one where it first started occurring, and then look at
all the packages that changed between those two points.

-- 
[karmic] Xorg 100% CPU utilization -- only after first login
https://bugs.launchpad.net/bugs/439138
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