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Popen should use pidfd_open to implement a non-busy wait #83069
Description
| 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.
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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']
Activity
SpecLad commented on Nov 21, 2019
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 commented on Nov 21, 2019
os.pidfd_open() was added to Python 3.9. Do you mean pidfd_open()?
SpecLad commented on Nov 21, 2019
Right, of course. I keep confusing it with timerfd_create.
giampaolo commented on Jan 19, 2026
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.
gh-83069: Use efficient event-driven `subprocess.Popen.wait()` on Lin…
vstinner commented on Jan 28, 2026
The feature is now implemented, I close the issue.
pythongh-83069: Use efficient event-driven `subprocess.Popen.wait()` …
gh-154836: Fix Popen.wait() with very large timeouts on the pidfd/kqu…
[3.15] gh-154836: Fix Popen.wait() with very large timeouts on the pi…
pythongh-154836: Fix Popen.wait() with very large timeouts on the pid…