python-linux-procfs: Fix UnicodeDecodeError

Commit 7570fc0d6082 meant to solve the UnicodeDecodeError

Instead it actually increased the problem by reading lines as bytes
and decoding them.

The original problem is hard to trigger and doesn't trigger consistently
with reproducers. In addition there seems to be a difference in how this
is handled between python-3.6 to python-3.9

For now, we should return the code to reading as utf-8 (the default)
since that handles more cases than the current code.

We can catch the UnicodeDecodeError and ignore it for now. It is not
ideal because we are not handling some pids that trigger the error.

This patch also includes a fix for a FileNotFoundError which can occur if
a pid exits and disappears before we try to read it in the /proc file

Signed-off-by: John Kacur <>
diff --git a/procfs/ b/procfs/
index a78bac5..de55dfc 100755
--- a/procfs/
+++ b/procfs/
@@ -44,7 +44,11 @@
     if pid_info["cmdline"]:
         return reduce(lambda a, b: a + " %s" % b, pid_info["cmdline"]).strip()
-    return pid_info["stat"]["comm"]
+    try:
+        """ If a pid disappears before we query it, return None """
+        return pid_info["stat"]["comm"]
+    except:
+        return None
 class pidstat:
@@ -374,9 +378,15 @@
         return hasattr(self, attr)
     def load_cmdline(self):
-        with open("/proc/%d/cmdline" %, mode='rb') as f:
-            cmdline = f.readline().decode(encoding='unicode_escape')
-            self.cmdline = cmdline.strip().split('\0')[:-1]
+        try:
+            with open("/proc/%d/cmdline" % as f:
+                self.cmdline = f.readline().strip().split('\0')[:-1]
+        except FileNotFoundError:
+            """ This can happen when a pid disappears """
+            self.cmdline = None
+        except UnicodeDecodeError:
+            """ TODO - this shouldn't happen, needs to be investigated """
+            self.cmdline = None
     def load_threads(self):
         self.threads = pidstats("/proc/%d/task/" %