madvise should be accessible outside of mmap instance

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-05-26.22:30:35.038>
labels = ['3.8', 'library', '3.9', '3.10']
title = 'madvise should be accessible outside of mmap instance'
updated_at = <Date 2020-05-26.22:31:15.539>
user = 'https://github.com/ngie-eign'

bugs.python.org fields:

activity = <Date 2020-05-26.22:31:15.539>
actor = 'ngie'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2020-05-26.22:30:35.038>
creator = 'ngie'
dependencies = []
files = []
hgrepos = []
issue_num = 40786
keywords = []
message_count = 1.0
messages = ['370036']
nosy_count = 1.0
nosy_names = ['ngie']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = None
url = 'https://bugs.python.org/issue40786'
versions = ['Python 3.8', 'Python 3.9', 'Python 3.10']