Fix pipe read race in exec_service server#12
Merged
afq984 merged 1 commit intogoogle:mainfrom Apr 8, 2026
Merged
Conversation
SetReadDeadline(time.Now()) can fire before the read loop consumes
buffered pipe data. Go's poller checks the deadline before attempting
syscall.Read, so ErrDeadlineExceeded is returned and buffered output
is silently dropped.
Fix: kill the process group after cmd.Wait() so background children
close their inherited pipe fds, letting the read loop reach EOF
without any deadline. A 100ms deadline fallback handles the rare case
of children that escaped the process group (e.g. via setsid).
Reproducer (fails 10/10 without the fix):
bazel test //exec_service/cmd/exec_client:exec_client_test \
--test_arg=-test.run=TestStderrOutput \
--test_arg=-test.count=500 \
--test_arg=-test.cpu=1 \
--runs_per_test=10 --local_test_jobs=10
This file contains hidden or 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
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
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Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be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.
SetReadDeadline(time.Now()) can fire before the read loop consumes buffered pipe data. Go's poller checks the deadline before attempting syscall.Read, so ErrDeadlineExceeded is returned and buffered output is silently dropped.
Fix: kill the process group after cmd.Wait() so background children close their inherited pipe fds, letting the read loop reach EOF without any deadline. A 100ms deadline fallback handles the rare case of children that escaped the process group (e.g. via setsid).
Reproducer (fails 10/10 without the fix):