[Bug 439138] Re: [karmic] Xorg 100% CPU utilization -- only after first login

[Brian Candler]

FYI I just saw this bug in Xubuntu 10.04, running as a VM under
Virtualbox 4.2 and OSX.

top showed 100% for Xorg process. Attaching strace to it gave the
attached screenshot. After a few seconds of this scrolling up the whole
graphic system froze, but I can still ssh to the VM happily, and CPU
utilisation has dropped back down to zero.

>From the ssh session:

brian at gateway:~$ ps auxwww | grep X
root       739 77.7  5.7 116344 29136 ?        Ts   15:17  18:07 /usr/bin/X :1 -br -verbose -auth /var/run/gdm/auth-for-gdm-6yRsVu/database -nolisten tcp
brian     1129  0.0  0.1   4108   632 ?        Ss   15:18   0:00 /bin/sh /etc/xdg/xfce4/xinitrc -- /etc/X11/xinit/xserverrc
brian     1325  0.0  2.8 232464 14516 ?        Sl   15:18   0:00 /usr/lib/xfce4/panel-plugins/xfce4-menu-plugin socket_id 37748789 name xfce4-menu id 1 display_name Xfce Menu size 24 screen_position 1
brian     1682  0.0  0.1   7644   980 pts/4    S+   15:41   0:00 grep --color=auto X
brian at gateway:~$ ps auxwww | grep strace
root      1669  0.0  0.1   4348   760 pts/1    S+   15:37   0:00 strace -p 739
brian     1684  0.0  0.1   7640   920 pts/4    S+   15:41   0:00 grep --color=auto strace
brian at gateway:~$ uptime
 15:41:41 up 23 min,  6 users,  load average: 0.01, 0.42, 0.52


** Attachment added: "Screen Shot 2013-02-15 at 15.39.52.png"
   https://bugs.launchpad.net/ubuntu/+source/usplash/+bug/439138/+attachment/3530238/+files/Screen%20Shot%202013-02-15%20at%2015.39.52.png

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https://bugs.launchpad.net/bugs/439138

Title:
  [karmic] Xorg 100% CPU utilization -- only after first login

Status in cryptsetup:
  Invalid
Status in “cryptsetup” package in Ubuntu:
  Fix Released
Status in “upstart” package in Ubuntu:
  Invalid
Status in “usplash” package in Ubuntu:
  Invalid
Status in “cryptsetup” source package in Karmic:
  Fix Released
Status in “upstart” source package in Karmic:
  Invalid
Status in “usplash” source package in Karmic:
  Invalid

Bug description:
  On my system, Xorg takes up 100% of (one of the) CPUs after startup.
  The problem goes away once the X server is restarted.  This happens
  both with the xserver from the archive and the latest 1.7 snapshot.
  This might be a race related to the fact that ubuntu is installed on
  an SSD.  It seems to be the same problem that is discussed in this
  ubuntuforums thread:

  http://swiss.ubuntuforums.org/showthread.php?t=1272691

  Here is what I could find out about the problem:

  strace reports repeated (failing) calls to

  ioctl(5, TCFLSH, 0x2)                   = -1 EIO (Input/output error)

  where fd 5 is /dev/tty7.  This translates to a tcflush call in
  drain_console().  Backtrace:

  Breakpoint 6, drain_console (fd=5, closure=0x0) at ../../../../../hw/xfree86/os-support/linux/lnx_init.c:89
  89      ../../../../../hw/xfree86/os-support/linux/lnx_init.c: No such file or directory.
          in ../../../../../hw/xfree86/os-support/linux/lnx_init.c
  (gdb) bt
  #0  drain_console (fd=5, closure=0x0) at ../../../../../hw/xfree86/os-support/linux/lnx_init.c:89
  #1  0x000000000046ecd1 in xf86Wakeup (blockData=<value optimized out>, err=<value optimized out>, pReadmask=<value optimized out>)
      at ../../../../hw/xfree86/common/xf86Events.c:285
  #2  0x0000000000443c7b in WakeupHandler (result=7, pReadmask=0x7d8440) at ../../dix/dixutils.c:413
  #3  0x00000000004609d5 in WaitForSomething (pClientsReady=<value optimized out>) at ../../os/WaitFor.c:232
  #4  0x0000000000440ef2 in Dispatch () at ../../dix/dispatch.c:381
  #5  0x00000000004265fc in main (argc=9, argv=0x7d7228, envp=<value optimized out>) at ../../dix/main.c:285
  o

  So we have a fd in some kind of error state that causes select() to
  always return right away.  I don't know enugh about how select() works
  to identify the problem, though.

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