[1.] One line summary of the problem
Processes claim CPU indefinitely on Intel(R) Core(TM)2 Quad CPU Q6600

[2.] Full description of the problem/report
Processes hang indefinitely (but might recover after 10min. or so) while executing
forked tasks like sed, touch, mv, uic (Qt), grep etc. The processes claim a CPU,
which may be for 2min. or 30min. and continue later on. This happens very often and
changing the preemption model does not make a difference (be it Preemptible Kernel
or Voluntary Kernel preemption). I cannot reproduce this bug with a Core(TM)2 Duo
with similar hardware and the same distribution (Gentoo x86_64).

Here's the command `touch' hanging:

 PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
16692 foobar  20   0  7816  408  312 R  100  0.0   6:03.72 touch

stracing above process showed that `touch' hang for 12 minutes and then simply
continued:

# strace -p 16692
Process 16692 attached - interrupt to quit
brk(0)                                  = 0x60d000
brk(0x62e000)                           = 0x62e000
close(0)                                = 0
open("./file66.txt", O_WRONLY|O_CREAT|O_NOCTTY|O_NONBLOCK, 0666) = 0 utimensat(0,
NULL, NULL, 0)             = 0
close(0)                                = 0
close(1)                                = 0
close(2)                                = 0
exit_group(0)                           = ?
Process 16692 detached

Here's the output of /proc/16692/stat during above hang-time:

# while true; do cat /proc/16692/stat ; sleep 5; done
16692 (touch) R 22679 22677 7314 34821 22677 4194304 180 0 0 0 17803 2 0 0 20 0 1 0
15147700 8003584 102 18446744073709551615 4194304 4242292 140736481217664
18446744073709551615 140401332315429 0 0 0 0 0 0 0 17 3 0 0 0 0 0
16692 (touch) R 22679 22677 7314 34821 22677 4194304 180 0 0 0 18303 2 0 0 20 0 1 0
15147700 8003584 102 18446744073709551615 4194304 4242292 140736481217664
18446744073709551615 140401332315429 0 0 0 0 0 0 0 17 3 0 0 0 0 0
16692 (touch) R 22679 ...
[ message continues ]