multiprocessing should use time.monotonic() for timeout

[vstinner]

BPO	34054
Nosy	@vstinner, @miss-islington
PRs	bpo-34054: multiprocessing uses time.monotonic() #8118 [3.7] bpo-34054: multiprocessing uses time.monotonic() (GH-8118) #8139 [3.6] bpo-34054: multiprocessing uses time.monotonic() (GH-8118) #8140

^{Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.}

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GitHub fields:

assignee = None
closed_at = <Date 2018-07-06.15:45:51.082>
created_at = <Date 2018-07-05.16:33:47.826>
labels = ['3.8', '3.7', 'library']
title = 'multiprocessing should use time.monotonic() for timeout'
updated_at = <Date 2018-07-06.15:45:51.081>
user = 'https://github.com/vstinner'

bugs.python.org fields:

activity = <Date 2018-07-06.15:45:51.081>
actor = 'vstinner'
assignee = 'none'
closed = True
closed_date = <Date 2018-07-06.15:45:51.082>
closer = 'vstinner'
components = ['Library (Lib)']
creation = <Date 2018-07-05.16:33:47.826>
creator = 'vstinner'
dependencies = []
files = []
hgrepos = []
issue_num = 34054
keywords = ['patch']
message_count = 5.0
messages = ['321115', '321116', '321168', '321169', '321170']
nosy_count = 2.0
nosy_names = ['vstinner', 'miss-islington']
pr_nums = ['8118', '8139', '8140']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = None
url = 'https://bugs.python.org/issue34054'
versions = ['Python 3.6', 'Python 3.7', 'Python 3.8']

[vstinner]

In different functions, the multiprocessing module uses the system clock: time.time(). The system clock can be updated manually by the system administrator or automatically by NTP (for example).

Attached PR modifies multiprocessing to use time.monotonic() instead to not be affected by system clock changes.

time.monotonic() is always available since Python 3.5. See also the PEP-418.

[vstinner]

Monotonic clock: https://docs.python.org/dev/library/time.html#time.monotonic

[vstinner]

New changeset c2368cb by Victor Stinner in branch 'master':
bpo-34054: multiprocessing uses time.monotonic() (GH-8118)
c2368cb

[miss-islington]

New changeset 4bd5fce by Miss Islington (bot) in branch '3.7':
bpo-34054: multiprocessing uses time.monotonic() (GH-8118)
4bd5fce

[miss-islington]

New changeset 972458a by Miss Islington (bot) in branch '3.6':
bpo-34054: multiprocessing uses time.monotonic() (GH-8118)
972458a