#1197 / linux / cpu_freq(): parse /proc/cpuinfo in case /sys/devices/system/cpu fs is not available

4 files changed, 58 insertions, 2 deletions

diff --git a/HISTORY.rst b/HISTORY.rst
index 4b2e7ed2..44837094 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -7,6 +7,8 @@ XXXX-XX-XX
 
 **Enhancements**
 
+- 1197_: [Linux] cpu_freq() is now implemented by parsing /proc/cpuinfo in case
+  /sys/devices/system/cpu/* filesystem is not available.
 - 1310_: [Linux] psutil.sensors_temperatures() now parses /sys/class/thermal
   in case /sys/class/hwmon fs is not available (e.g. Raspberry Pi).  (patch
   by Alex Manuskin)
diff --git a/psutil/__init__.py b/psutil/__init__.py
index f43ef7b6..c2a83fb1 100644
--- a/psutil/__init__.py
+++ b/psutil/__init__.py
@@ -1861,13 +1861,25 @@ if hasattr(_psplatform, "cpu_freq"):
                 return ret[0]
             else:
                 currs, mins, maxs = 0.0, 0.0, 0.0
+                set_none = False
                 for cpu in ret:
                     currs += cpu.current
+                    # On Linux if /proc/cpuinfo is used min/max are set
+                    # to None.
+                    if LINUX and cpu.min is None:
+                        set_none = True
+                        continue
                     mins += cpu.min
                     maxs += cpu.max
+
                 current = currs / num_cpus
-                min_ = mins / num_cpus
-                max_ = maxs / num_cpus
+
+                if set_none:
+                    min_ = max_ = None
+                else:
+                    min_ = mins / num_cpus
+                    max_ = maxs / num_cpus
+
                 return _common.scpufreq(current, min_, max_)
 
     __all__.append("cpu_freq")
diff --git a/psutil/_pslinux.py b/psutil/_pslinux.py
index a69b1d66..1520261c 100644
--- a/psutil/_pslinux.py
+++ b/psutil/_pslinux.py
@@ -704,6 +704,19 @@ if os.path.exists("/sys/devices/system/cpu/cpufreq") or \
             ret.append(_common.scpufreq(curr, min_, max_))
         return ret
 
+elif os.path.exists("/proc/cpuinfo"):
+    def cpu_freq():
+        """Alternate implementation using /proc/cpuinfo.
+        min and max frequencies are not available and are set to None.
+        """
+        ret = []
+        with open_binary('%s/cpuinfo' % get_procfs_path()) as f:
+            for line in f:
+                if line.lower().startswith(b'cpu mhz'):
+                    key, value = line.split(b'\t:', 1)
+                    ret.append(_common.scpufreq(float(value), None, None))
+        return ret
+
 
 # =====================================================================
 # --- network
diff --git a/psutil/tests/test_linux.py b/psutil/tests/test_linux.py
index 4e4bd565..115a6af8 100755
--- a/psutil/tests/test_linux.py
+++ b/psutil/tests/test_linux.py
@@ -704,6 +704,35 @@ class TestSystemCPU(unittest.TestCase):
             self.assertEqual(len(flags), 2)
 
     @unittest.skipIf(not HAS_CPU_FREQ, "not supported")
+    def test_cpu_freq_use_cpuinfo(self):
+        # Emulate a case where /sys/devices/system/cpu/cpufreq* does not
+        # exist and /proc/cpuinfo is used instead.
+        def path_exists_mock(path):
+            if path.startswith('/sys/devices/system/cpu/'):
+                return False
+            else:
+                if path == "/proc/cpuinfo":
+                    flags.append(None)
+                return os_path_exists(path)
+
+        flags = []
+        os_path_exists = os.path.exists
+        try:
+            with mock.patch("os.path.exists", side_effect=path_exists_mock):
+                reload_module(psutil._pslinux)
+                ret = psutil.cpu_freq()
+                assert ret
+                assert flags
+                self.assertIsNone(ret.min)
+                self.assertIsNone(ret.max)
+                for freq in psutil.cpu_freq(percpu=True):
+                    self.assertIsNone(freq.min)
+                    self.assertIsNone(freq.max)
+        finally:
+            reload_module(psutil._pslinux)
+            reload_module(psutil)
+
+    @unittest.skipIf(not HAS_CPU_FREQ, "not supported")
     def test_cpu_freq_emulate_data(self):
         def open_mock(name, *args, **kwargs):
             if name.endswith('/scaling_cur_freq'):