Signal handlers should not hang during blocked main thread

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2020-06-26.17:34:49.637>
labels = ['extension-modules', '3.8', 'type-bug', '3.7']
title = 'Signal handlers should not hang during blocked main thread'
updated_at = <Date 2020-07-13.08:21:45.840>
user = 'https://bugs.python.org/JosefHavrnek'

bugs.python.org fields:

activity = <Date 2020-07-13.08:21:45.840>
actor = 'SilentGhost'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Extension Modules']
creation = <Date 2020-06-26.17:34:49.637>
creator = 'Josef Havr\xc3\xa1nek'
dependencies = []
files = ['49265']
hgrepos = []
issue_num = 41128
keywords = []
message_count = 1.0
messages = ['372435']
nosy_count = 3.0
nosy_names = ['pitrou', 'vstinner', 'serhiy.storchaka']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue41128'
versions = ['Python 3.7', 'Python 3.8']