psutil fails to return the nice value for some processes on Solaris 10

[gsauthof]

How to reproduce - chose xntp on Solaris 10:

>>> p = psutil.Process(960)
>>> p.name()
'xntpd'
>>> p.nice()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/path/to/venv/lib/python3.5/site-packages/psutil/__init__.py", line 755, in nice
return self._proc.nice_get()
  File "/path/to/venv/lib/python3.5/site-packages/psutil/_pssunos.py", line 346, in wrapper
return fun(self, *args, **kwargs)
  File "/path/to/venv/lib/python3.5/site-packages/psutil/_pssunos.py", line 451, in nice_get
return cext_posix.getpriority(self.pid)
OSError: [Errno 22] Invalid argument

The system's ps is able to return the nice value:

$ ps -e -o pid,uid,gid,ruid,nice | grep 960
   960     0     0     0 RT

A simple C test program that just calls getpriority() on that PID also fails with EINVAL.

Perhaps getpriority() always fails for realtime processes, on Solaris 10. Is kind of plausible - since priorities doesn't really make sense for realtime. The man page doesn't include details on that topic, though.

This breaks psutil.process_iter() unless one uses a non-default attribute set that doesn't include 'nice'. Example how to make it fail with a minimal attribute set:

>>> for p in psutil.process_iter(): print(p.as_dict(attrs=['nice']))
{'nice': 0}
{'nice': -20}
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/path/to/venv/lib/python3.5/site-packages/psutil/__init__.py", line 574, in as_dict
ret = meth()
  File "/path/to/venv/lib/python3.5/site-packages/psutil/__init__.py", line 755, in nice
return self._proc.nice_get()
  File "/path/to/venv/lib/python3.5/site-packages/psutil/_pssunos.py", line 346, in wrapper
return fun(self, *args, **kwargs)
  File "/path/to/venv/lib/python3.5/site-packages/psutil/_pssunos.py", line 451, in nice_get
return cext_posix.getpriority(self.pid)
OSError: [Errno 22] Invalid argument

The psutil Solaris-specific code contains a note regarding getpriority() vs. psinfo that mentions issue #1082.

There are several ways how to fix this:

• call getpriority() first and fall back to psinfo
• switch to psinfo as it's good enough for ps
• default to 0 if getpriority() fails

See also:

• how ps prints the nice value: https://github.com/illumos/illumos-gate/blob/f7877f5d39900cfd8b20dd673e5ccc1ef7cc7447/usr/src/cmd/ps/ps.c#L1812-L1816

[giampaolo]

I would say let's just get priority from psinfo then. The change is simple. In _pssunos.py:

    @wrap_exceptions
    def nice_get(self):
        return self._proc_basic_info()[proc_info_map['nice']]

Can you check if this fixes the issue?