Popen should use pidfd_open to implement a non-busy wait

[SpecLad]

BPO	38888
Nosy	@gpshead, @vstinner, @benjaminp, @SpecLad

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

Show more details

GitHub fields:

assignee = None
closed_at = None
created_at = <Date 2019-11-21.21:43:43.189>
labels = ['type-feature', 'library', '3.9']
title = 'Popen should use pidfd_open to implement a non-busy wait'
updated_at = <Date 2019-11-21.22:20:50.812>
user = 'https://github.com/SpecLad'

bugs.python.org fields:

activity = <Date 2019-11-21.22:20:50.812>
actor = 'SpecLad'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['Library (Lib)']
creation = <Date 2019-11-21.21:43:43.189>
creator = 'SpecLad'
dependencies = []
files = []
hgrepos = []
issue_num = 38888
keywords = []
message_count = 3.0
messages = ['357222', '357223', '357225']
nosy_count = 4.0
nosy_names = ['gregory.p.smith', 'vstinner', 'benjamin.peterson', 'SpecLad']
pr_nums = []
priority = 'normal'
resolution = None
stage = None
status = 'open'
superseder = None
type = 'enhancement'
url = 'https://bugs.python.org/issue38888'
versions = ['Python 3.9']

Linked PRs

• gh-83069: Use efficient event-driven subprocess.Popen.wait() on Linux / macOS / BSD #144047

[SpecLad]

Popen.wait(timeout) is currently implemented on Unix-like systems using a busy wait, since the waitpid system call doesn't have a timeout argument.

On Linux, it's now possible to do better than that. You can create a PID file descriptor using pidfd_create and poll that descriptor with the specified timeout. Popen.wait should make use of that.

[vstinner]

os.pidfd_open() was added to Python 3.9. Do you mean pidfd_open()?

[SpecLad]

Right, of course. I keep confusing it with timerfd_create.

[giampaolo]

Hi. Since I recently implemented this in psutil (giampaolo/psutil#2706), I decided to give this a try and port this change to the subprocess module. I created a PR which uses pidfd_open() on Linux and also adds support for macOS and BSD by using kqueue(): #144047.

[vstinner]

The feature is now implemented, I close the issue.