fix #645: [Linux] psutil.cpu_times_percent() may produce negative res…

…ults.

HISTORY.rst

@@ -1,5 +1,14 @@
 Bug tracker at https://github.com/giampaolo/psutil/issues
 
+3.1.1 - XXXX-XX-XX
+==================
+
+**Bug fixes**
+
+- #645: [Linux] psutil.cpu_times_percent() may produce negative results.
+- #656: 'from psutil import *' does not work.
+
+
 3.1.0 - 2015-07-15
 ==================
 

psutil/__init__.py

@@ -1505,23 +1505,20 @@ def calculate(t1, t2):
             except ZeroDivisionError:
                 field_perc = 0.0
             field_perc = round(field_perc, 1)
-            if _WINDOWS:
-                # XXX
-                # Work around:
-                # https://github.com/giampaolo/psutil/issues/392
-                # CPU times are always supposed to increase over time
-                # or at least remain the same and that's because time
-                # cannot go backwards.
-                # Surprisingly sometimes this might not be the case on
-                # Windows where 'system' CPU time can be smaller
-                # compared to the previous call, resulting in corrupted
-                # percentages (< 0 or > 100).
-                # I really don't know what to do about that except
-                # forcing the value to 0 or 100.
-                if field_perc > 100.0:
-                    field_perc = 100.0
-                elif field_perc < 0.0:
-                    field_perc = 0.0
+            # CPU times are always supposed to increase over time
+            # or at least remain the same and that's because time
+            # cannot go backwards.
+            # Surprisingly sometimes this might not be the case (at
+            # least on Windows and Linux), see:
+            # https://github.com/giampaolo/psutil/issues/392
+            # https://github.com/giampaolo/psutil/issues/645
+            # I really don't know what to do about that except
+            # forcing the value to 0 or 100.
+            if field_perc > 100.0:
+                field_perc = 100.0
+            # `<=` because `-0.0 == 0.0` evaluates to True
+            elif field_perc <= 0.0:
+                field_perc = 0.0
             nums.append(field_perc)
         return _psplatform.scputimes(*nums)
 

test/test_psutil.py

@@ -807,7 +807,7 @@ def test_sys_per_cpu_times(self):
         #                 new_t, last_t, msg="%s %s" % (lastcpu, newcpu))
         #     last = new
 
-    def test_sys_per_cpu_times2(self):
+    def test_sys_per_cpu_times_2(self):
         tot1 = psutil.cpu_times(percpu=True)
         stop_at = time.time() + 0.1
         while True:
@@ -825,6 +825,7 @@ def _test_cpu_percent(self, percent, last_ret, new_ret):
         try:
             self.assertIsInstance(percent, float)
             self.assertGreaterEqual(percent, 0.0)
+            self.assertIsNot(percent, -0.0)
             self.assertLessEqual(percent, 100.0 * psutil.cpu_count())
         except AssertionError as err:
             raise AssertionError("\n%s\nlast=%s\nnew=%s" % (
@@ -866,6 +867,16 @@ def test_sys_per_cpu_times_percent(self):
                 self._test_cpu_percent(sum(cpu), last, new)
             last = new
 
+    def test_sys_per_cpu_times_percent_negative(self):
+        # see: https://github.com/giampaolo/psutil/issues/645
+        psutil.cpu_times_percent(percpu=True)
+        zero_times = [x._make([0 for x in range(len(x._fields))])
+                      for x in psutil.cpu_times(percpu=True)]
+        with mock.patch('psutil.cpu_times', return_value=zero_times):
+            for cpu in psutil.cpu_times_percent(percpu=True):
+                for percent in cpu:
+                    self._test_cpu_percent(percent, None, None)
+
     @unittest.skipIf(POSIX and not hasattr(os, 'statvfs'),
                      "os.statvfs() function not available on this platform")
     def test_disk_usage(self):
@@ -2752,7 +2763,7 @@ def test__all__(self):
                         if (fun.__doc__ is not None and
                                 'deprecated' not in fun.__doc__.lower()):
                             self.fail('%r not in psutil.__all__' % name)
-        # import 'start' will break if __all__ is inconsistent, see:
+        # import 'star' will break if __all__ is inconsistent, see:
         # https://github.com/giampaolo/psutil/issues/656
         from psutil import *  # NOQA