[Bug 910287] Re: ps hangs when listing root processes

[Hans Deragon]

Currently have this problem on 12.04 when running as root and running
'ps -ef'.  'ps' alone works.  'top' works.  Below, the output of strace
where it hangs.  Seams that the problem is Xorg in my case.  I just
switch my computer to the proprietary ATI driver.  Still, regardless of
what is running, ps (or the underlining /proc) should never hang.  I
tried the following and it hangs too.  <CTRL-C> does not help.

# cat /proc/1899/cmdline

strace of ps:

[... deleted lines ...]
write(1, "bind      1881     1  0 07:35 ? "..., 72bind      1881     1  0 07:35 ?        00:00:00 /usr/sbin/named -u bind
) = 72
stat("/proc/1899", {st_mode=S_IFDIR|0555, st_size=0, ...}) = 0
open("/proc/1899/stat", O_RDONLY)       = 6
read(6, "1899 (Xorg) D 1867 1899 1899 103"..., 1023) = 380
close(6)                                = 0
open("/proc/1899/status", O_RDONLY)     = 6
read(6, "Name:\tXorg\nState:\tD (disk sleep)"..., 1023) = 763
close(6)                                = 0
open("/proc/1899/cmdline", O_RDONLY)    = 6
read(6,

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https://bugs.launchpad.net/bugs/910287

Title:
  ps hangs when listing root processes

Status in “procps” package in Ubuntu:
  Confirmed

Bug description:
  when running "ps a" on my system, the command just blocks, and will
  not respond to Ctrl+C, nor killall -9 ps.

  This also happens in gnome-system-monitor, if and only if viewing all
  processes (not just "my processes").

  Strace output attached. Curiously, I can cancel out with Ctrl+C if
  using the strace wrapped process.

  ProblemType: Bug
  DistroRelease: Ubuntu 11.10
  Package: procps 1:3.2.8-10ubuntu5
  ProcVersionSignature: Ubuntu 3.0.0-12.20-generic 3.0.4
  Uname: Linux 3.0.0-12-generic x86_64
  ApportVersion: 1.23-0ubuntu3
  Architecture: amd64
  Date: Sat Dec 31 02:22:15 2011
  InstallationMedia: Ubuntu 11.10 "Oneiric Ocelot" - Release amd64 (20111012)
  SourcePackage: procps
  UpgradeStatus: No upgrade log present (probably fresh install)
  mtime.conffile..etc.sysctl.conf: 2011-12-21T19:15:22.651303

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