`/usr/lib/pm-utils/睡眠.d/94cpufreq‘试图做什么？

Question

在我的Ubuntu16.04上，我正在尝试理解一个系统默认文件/usr/lib/pm-utils/sleep.d/94cpufreq (关于它的内容，请参阅本文的结尾)。

考虑到"${PM_FUNCTIONS}"是由.提供的，它是脚本吗？

当我在bash中echo "${PM_FUNCTIONS}"时，它什么也不输出。PM_FUNCTIONS是在另一个调用脚本的脚本中定义的吗？

savestate、state_exists和restorestate函数是否在"${PM_FUNCTIONS}"中定义？

TEMPORARY_CPUFREQ_GOVERNOR"是在"${PM_FUNCTIONS}"中定义的变量吗？

脚本试图在suspend|hibernate和thaw|resume上做什么？

谢谢。

#!/bin/sh                                                                                                                                                                          
# Ensure cpu governor is set to something sane.                                                                                                                                    
# TODO: Which of the cpu governors is still insane?  File bugs against                                                                                                             
#       those that are.                                                                                                                                                            

. "${PM_FUNCTIONS}"

[ -d /sys/devices/system/cpu/ ] || exit $NA

hibernate_cpufreq()
{
  ( cd /sys/devices/system/cpu/
  for x in cpu[0-9]*; do
    # if cpufreq is a symlink, it is handled by another cpu. Skip.                                                                                                                 
    [ -L "$x/cpufreq" ] && continue
    gov="$x/cpufreq/scaling_governor"
    # if we do not have a scaling_governor file, skip.                                                                                                                             
    [ -f "$gov" ] || continue
    # if our temporary governor is not available, skip.                                                                                                                            
    grep -q "$TEMPORARY_CPUFREQ_GOVERNOR" \
            "$x/cpufreq/scaling_available_governors" || continue
    savestate "${x}_governor" < "$gov"
    echo "$TEMPORARY_CPUFREQ_GOVERNOR" > "$gov"
  done )
}

thaw_cpufreq()
{
  ( cd /sys/devices/system/cpu/
  for x in cpu[0-9]*/cpufreq/scaling_governor ; do
    [ -f "$x" ] || continue
    state_exists "${x%%/*}_governor" || continue
    restorestate "${x%%/*}_governor" > "$x"
  done )
}

case "$1" in
  suspend|hibernate)
    hibernate_cpufreq
    ;;
  resume|thaw)
    thaw_cpufreq
    ;;
  *) exit $NA
    ;;
esac

Answer 1

state_exists等函数是在/usr/lib/pm-utils/函数中定义的，PM_FUNCTIONS是指脚本/usr/lib/pm-utils/pm-函数。是的，TEMPORARY_CPUFREQ_GOVERNOR是在PM_FUNCTIONS中定义的。