runtime: only count an in-flight timer send as pending once by h2zi · Pull Request #80762 · golang/go

h2zi · 2026-08-06T16:02:52Z

unlockAndRun increments isSending and publishes when=0 while holding
t.mu, but acquires t.sendLock only after releasing t.mu. If the firing
goroutine is descheduled between the two locks, both a Stop and a Reset
can complete inside the gap. Stop observes isSending>0, voids the send
by incrementing seq, and correctly returns true: the send will never
be delivered. But a subsequent Reset (or Stop) observes isSending
still >0 and counts the same voided send again, so Reset reports an
active timer immediately after Stop reported having stopped it.
Pooled timers check exactly this invariant and break.

Record the seq value that unlockAndRun snapshots for the send, and
have stop and modify treat the in-flight send as pending only while
that snapshot still matches t.seq. Once a stop or reset voids the
send, later calls see the seq mismatch and no longer count it.

Fixes #80760

google-cla · 2026-08-06T16:03:03Z

Thanks for your pull request! It looks like this may be your first contribution to a Google open source project. Before we can look at your pull request, you'll need to sign a Contributor License Agreement (CLA).

View this failed invocation of the CLA check for more information.

For the most up to date status, view the checks section at the bottom of the pull request.

unlockAndRun increments isSending and publishes when=0 while holding t.mu, but acquires t.sendLock only after releasing t.mu. If the firing goroutine is descheduled between the two locks, both a Stop and a Reset can complete inside the gap. Stop observes isSending>0, voids the send by incrementing seq, and correctly returns true: the send will never be delivered. But a subsequent Reset (or Stop) observes isSending still >0 and counts the same voided send again, so Reset reports an active timer immediately after Stop reported having stopped it. Pooled timers check exactly this invariant and break. Record the seq value that unlockAndRun snapshots for the send, and have stop and modify treat the in-flight send as pending only while that snapshot still matches t.seq. Once a stop or reset voids the send, later calls see the seq mismatch and no longer count it. Fixes golang#80760

gopherbot · 2026-08-06T16:18:23Z

This PR (HEAD: 810bc43) has been imported to Gerrit for code review.

Please visit Gerrit at https://go-review.googlesource.com/c/go/+/811520.

Important tips:

Don't comment on this PR. All discussion takes place in Gerrit.
You need a Gmail or other Google account to log in to Gerrit.
To change your code in response to feedback:
- Push a new commit to the branch used by your GitHub PR.
- A new "patch set" will then appear in Gerrit.
- Respond to each comment by marking as Done in Gerrit if implemented as suggested. You can alternatively write a reply.
- Critical: you must click the blue Reply button near the top to publish your Gerrit responses.
- Multiple commits in the PR will be squashed by GerritBot.
The title and description of the GitHub PR are used to construct the final commit message.
- Edit these as needed via the GitHub web interface (not via Gerrit or git).
- You should word wrap the PR description at ~76 characters unless you need longer lines (e.g., for tables or URLs).
See the Sending a change via GitHub and Reviews sections of the Contribution Guide as well as the FAQ for details.

gopherbot · 2026-08-06T16:38:02Z

Message from Gopher Robot:

Patch Set 1:

Congratulations on opening your first change. Thank you for your contribution!

Next steps:
A maintainer will review your change and provide feedback. See
https://go.dev/doc/contribute#review for more info and tips to get your
patch through code review.

Most changes in the Go project go through a few rounds of revision. This can be
surprising to people new to the project. The careful, iterative review process
is our way of helping mentor contributors and ensuring that their contributions
have a lasting impact.

During May-July and Nov-Jan the Go project is in a code freeze, during which
little code gets reviewed or merged. If a reviewer responds with a comment like
R=go1.11 or adds a tag like "wait-release", it means that this CL will be
reviewed as part of the next development cycle. See https://go.dev/s/release
for more details.