SIGTERM leaves zombie process, SIGKILL must be used

[mturquette]

SIGTERM is not enough to kill child processes when running cpuloadgen on multiple CPUs. Log below illustrates:

/sys/devices/system/cpu/cpu0/cpufreq # cpuloadgen &
/sys/devices/system/cpu/cpu0/cpufreq # CPULOADGEN (REV 0.94 built Wed Feb 26 18:51:18 PST 2014)

Press CTRL+C to stop load generation at any tating 100% load on CPU0...
Generating 100% load on CPU1...

/sys/devices/system/cpu/cpu0/cpufreq # ps
PID   USER     TIME   COMMAND
  ...
  118 root       0:04 cpuloadgen
  120 root       0:00 ps
/sys/devices/system/cpu/cpu0/cpufreq # killall cpuloadgen
Halting load generation.
/sys/devices/system/cpu/cpu0/cpufreq # ps
PID   USER     TIME   COMMAND
  ...
  118 root       0:18 cpuloadgen
  123 root       0:00 ps
/sys/devices/system/cpu/cpu0/cpufreq # killall -9 cpuloadgen
/sys/devices/system/cpu/cpu0/cpufreq #
[1]+  Killed       cpuloadgen
/sys/devices/system/cpu/cpu0/cpufreq #
/sys/devices/system/cpu/cpu0/cpufreq # ps
PID   USER     TIME   COMMAND
  127 root       0:00 ps