Some platforms define scaling_max|min_freq but not scaling_cur_freq

[sethmlarson]

This is an issue regarding psutil.cpu_freq() and in this instance the platform is RedHat Linux 7.2. Psutil is installed with Python 3.5.2. When attempting to call psutil.cpu_freq() I receive the following error:

>>> psutil.cpu_freq()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/usr/lib/python3.5/site-packages/psutil/__init__.py", line 1895, in cpu_freq
    ret = _psplatform.cpu_freq()
  File "/usr/lib/python3.5/site-packages/psutil/_pslinux.py", line 666, in cpu_freq
    curr = int(cat(os.path.join(path, "scaling_cur_freq"))) / 1000
  File "/usr/lib/python3.5/site-packages/psutil/_pslinux.py", line 298, in cat
    with open_binary(fname) if binary else open_text(fname) as f:
  File "/usr/lib/python3.5/site-packages/psutil/_pslinux.py", line 190, in open_binary
    return open(fname, "rb", **kwargs)
FileNotFoundError: [Errno 2] No such file or directory: '/sys/devices/system/cpu/cpu0/cpufreq/scaling_cur_freq'

This is what I get when I run ls -Al /sys/devices/system/cpu/cpu0/cpufreq

total 0
-r--r--r-- 1 root root 4096 May 15 08:48 affected_cpus
-r-------- 1 root root 4096 May 15 08:48 cpuinfo_cur_freq
-r--r--r-- 1 root root 4096 May 15 08:48 cpuinfo_max_freq
-r--r--r-- 1 root root 4096 May 15 08:48 cpuinfo_min_freq
-r--r--r-- 1 root root 4096 May 15 08:48 cpuinfo_transition_latency
-r--r--r-- 1 root root 4096 May 15 08:48 related_cpus
-r--r--r-- 1 root root 4096 May 15 08:48 scaling_available_governors
-r--r--r-- 1 root root 4096 May 15 08:48 scaling_driver
-rw-r--r-- 1 root root 4096 May 15 08:48 scaling_governor
-rw-r--r-- 1 root root 4096 May 15 08:48 scaling_max_freq
-rw-r--r-- 1 root root 4096 May 15 08:48 scaling_min_freq
-rw-r--r-- 1 root root 4096 May 15 16:50 scaling_setspeed

[giampaolo]

It sucks that Linux sucks so much about this. Not sure what to do, whether to set it to 0 or skip to the next frequency.

[giampaolo]

OK, I should have fixed this.

[jiabinruan]

by the way, this file "cpuinfo_cur_freq" can be ready only by root, other user will still got failed