subprocess - Fix a bug where trio isn't notified about pidfd closes #2209
Conversation
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
If you have 1. Task A blocks in `Process.wait` 2. The child process exits 3. Task B calls `Process.returncode` (3) will close the pidfd, but nothing will ever wake up Task A, since trio wasn't notified. I noticed this when I wrote a `deliver_cancel` function that was slow enough that the child actually exited before the call to `Process.returncode`. In the default `_posix_deliver_cancel`, everything is so fast that the usual ordering is that (3) comes before (2), and there isn't an early call to `_pidfd_close`. This fixes the bug by ensuring we notify trio about closing the pidfd when we do it!
Codecov Report
@@ Coverage Diff @@
## master #2209 +/- ##
==========================================
+ Coverage 99.51% 99.55% +0.04%
==========================================
Files 114 114
Lines 14780 14803 +23
Branches 2346 2349 +3
==========================================
+ Hits 14708 14737 +29
+ Misses 47 44 -3
+ Partials 25 22 -3
|
oremanj
reviewed
Jan 12, 2022
|
Please add a newsfragment for this change. |
oremanj
reviewed
Jan 12, 2022
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
If you have
Process.waitProcess.returncode(3) will close the pidfd, but nothing will ever wake up Task A, since
trio wasn't notified.
I noticed this when I wrote a
deliver_cancelfunction that was slowenough that the child actually exited before the call to
Process.returncode. In the default_posix_deliver_cancel, everything is sofast that the usual ordering is that (3) comes before (2), and there
isn't an early call to
_pidfd_close.This fixes the bug by ensuring we notify trio about closing the pidfd
when we do it!