Fix ld-decode deadlock on exit. #394
Merged
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
On machines with small numbers of CPUs, ld-decode would sometimes
deadlock on exit, with two threads in different processes blocked
reading from pipes.
This turned out to be a race in the DemodCache destructor. It was doing:
for i in self.threads:
if i.is_alive():
self.q_in.put(None)
with the workers exiting when they received a None message. However,
suppose you've got two workers, and the following happens:
- DemodCache checks if A is alive - it is
- DemodCache sends None
- B receives None and exits
- DemodCache checks if B is alive - it isn't
A is now stuck waiting for a message that'll never arrive. I've fixed
this by removing the is_alive checks -- so it may now send more None
messages than necessary, but that's harmless.
happycube
reviewed
Jan 1, 2020
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Outdated suggestions cannot be applied.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.
On machines with small numbers of CPUs (e.g. the GitHub CI machines!), ld-decode would sometimes deadlock on exit, with two threads in different processes blocked reading from pipes.
This turned out to be a race in the DemodCache destructor. It was doing:
with the workers exiting when they received a None message. However, suppose you've got two workers, and the following happens:
A is now stuck waiting for a message that'll never arrive. I've fixed this by removing the is_alive checks -- so it may now send more None messages than necessary, but that's harmless.