fix(task): prevent deadlock when MISE_JOBS=1 with sub-task references by jdx · Pull Request #8976 · jdx/mise

jdx · 2026-04-09T14:51:46Z

Summary

Fixes deadlock when MISE_JOBS=1 and a task's run array contains both sub-task references ({ task = "foo" }) and scripts
The parent task acquires the single semaphore permit, then waits for the sub-task which also needs that permit — classic deadlock
Fix: temporarily release the parent's permit before inject_and_wait, re-acquire afterward

Test plan

Added e2e test test_run_subtask_jobs1 that reproduces the exact scenario from the discussion
Verified the test hangs without the fix and passes with it
Verified normal (non-MISE_JOBS=1) execution still works

🤖 Generated with Claude Code

Note

Medium Risk
Changes task scheduling/semaphore permit handling during nested sub-task execution; mistakes could impact task concurrency limits or cause hangs under certain job configurations.

Overview
Prevents a deadlock when running tasks with MISE_JOBS=1 whose run array mixes sub-task entries (e.g. { task = "foo" }) and script lines by releasing the parent task’s semaphore permit before inject_and_wait and re-acquiring it afterward.

This threads the scheduler Semaphore and the current OwnedSemaphorePermit through Run::run_task_sched into TaskExecutor::exec_task_run_entries so nested sub-task execution can yield the permit while waiting. Adds an e2e regression test test_run_subtask_jobs1 to reproduce the hang and verify correct output ordering.

^{Reviewed by Cursor Bugbot for commit cb780c0. Bugbot is set up for automated code reviews on this repo. Configure here.}

When a task contains both sub-task references ({ task = "foo" }) and scripts in its run array, it acquires a semaphore permit. With MISE_JOBS=1, the sub-task also needs the single available permit, causing a deadlock. Fix by temporarily releasing the parent's permit before inject_and_wait and re-acquiring it afterward for subsequent script entries. Fixes #8967 Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

greptile-apps · 2026-04-09T14:54:02Z

Greptile Summary

This PR fixes a classic deadlock that occurs when MISE_JOBS=1 and a task's run array mixes sub-task references ({ task = \"foo\" }) with scripts. The parent task holds the sole semaphore permit, then blocks inside inject_and_wait for the sub-task — which can never acquire a permit of its own.

The fix releases the parent's OwnedSemaphorePermit immediately before each inject_and_wait call and re-acquires it afterward, threading Arc<Semaphore> and &mut Option<OwnedSemaphorePermit> through run_task_sched → exec_task_run_entries. Both RunEntry::SingleTask and RunEntry::TaskGroup arms are handled symmetrically, and a focused e2e regression test is included.

Confidence Score: 5/5

Safe to merge — the fix is minimal, targeted, logically sound, and covered by a regression e2e test.

Both run-entry arms (SingleTask and TaskGroup) are handled symmetrically. The had_permit flag correctly preserves intent (non-permit orchestrator tasks are unaffected). Releasing the permit while blocked on inject_and_wait also marginally improves throughput in multi-job scenarios. No existing behavior is changed outside the deadlock path, and the regression test verifies the exact scenario from the bug report.

No files require special attention.

Vulnerabilities

No security concerns identified. The change only affects internal semaphore permit management in the task execution concurrency layer and introduces no new attack surface.

Important Files Changed

Filename	Overview
src/task/task_executor.rs	Core fix: releases semaphore permit before inject_and_wait and re-acquires after; both SingleTask and TaskGroup arms handled symmetrically with correct had_permit guard.
src/cli/run.rs	Threads Arc and &mut Option from spawn_sched_job through run_task_sched to exec_task_run_entries; no functional logic changed in the call site.
e2e/cli/test_run_subtask_jobs1	Regression test that reproduces the exact deadlock scenario (MISE_JOBS=1, mixed sub-task + script run array) and asserts ordered output "foo\nbar".

Sequence Diagram

sequenceDiagram
    participant Sched as Scheduler
    participant Parent as parent task
    participant Sem as Semaphore (JOBS=1)
    participant Sub as sub-task (foo)

    Sched->>Sem: acquire_owned() → permit
    Sem-->>Sched: permit ✓
    Sched->>Parent: run_task_sched(permit)
    Note over Parent: exec_task_run_entries
    Note over Parent: RunEntry::SingleTask detected
    Parent->>Sem: drop permit (had_permit=true)
    Parent->>Sched: inject_and_wait → sched_tx.send(sub-task)
    Sched->>Sem: acquire_owned() for sub-task
    Sem-->>Sched: permit ✓  (now available)
    Sched->>Sub: run sub-task
    Sub-->>Sched: done
    Sched->>Sem: drop sub-task permit
    Parent->>Sem: re-acquire permit
    Sem-->>Parent: permit ✓
    Note over Parent: RunEntry::Script → exec_script("echo bar")
    Parent-->>Sched: done

_{Reviews (4): Last reviewed commit: "fix(task): allow clippy::too_many_argume..." | Re-trigger Greptile}

gemini-code-assist

Code Review

This pull request addresses a deadlock issue that occurs when MISE_JOBS=1 by ensuring that semaphore permits are released before waiting on sub-tasks and re-acquired afterward. It also adds a regression test to verify this behavior. I have no feedback to provide.

github-actions · 2026-04-09T15:13:04Z

Hyperfine Performance

`mise x -- echo`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`mise-2026.4.7 x -- echo`	24.1 ± 0.8	22.4	27.5	1.00
`mise x -- echo`	25.1 ± 0.8	22.9	27.4	1.04 ± 0.05

`mise env`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`mise-2026.4.7 env`	23.7 ± 0.7	22.2	28.9	1.00
`mise env`	24.0 ± 0.7	22.0	29.8	1.01 ± 0.04

`mise hook-env`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`mise-2026.4.7 hook-env`	24.6 ± 0.7	22.5	26.7	1.00
`mise hook-env`	24.7 ± 0.7	23.1	28.3	1.00 ± 0.04

`mise ls`

Command	Mean [ms]	Min [ms]	Max [ms]	Relative
`mise-2026.4.7 ls`	21.8 ± 0.9	20.0	25.3	1.00
`mise ls`	22.1 ± 0.8	20.2	26.3	1.01 ± 0.05

`xtasks/test/perf`

Command	mise-2026.4.7	mise	Variance
install (cached)	154ms	155ms	+0%
ls (cached)	81ms	83ms	-2%
bin-paths (cached)	85ms	85ms	+0%
task-ls (cached)	818ms	814ms	+0%

# Conflicts: # src/cli/run.rs # src/task/task_executor.rs

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

@cameronbrill

### 🚀 Features - **(config)** add lockfile_platforms setting to restrict lockfile platforms by @cameronbrill in [#8966](#8966) - **(sandbox)** support wildcard patterns in allow_env by @jdx in [#8974](#8974) - bump usage-lib v2 → v3 to render examples in task --help by @baby-joel in [#8890](#8890) ### 🐛 Bug Fixes - **(activate)** handle empty __MISE_FLAGS array with set -u on bash 3.2 by @jdx in [#8988](#8988) - **(env)** add trace logging for module hook PATH diagnostics by @jdx in [#8981](#8981) - **(go)** Query module proxy directly for version resolution by @c22 in [#8968](#8968) - **(install)** render tera templates in tool postinstall hooks by @jdx in [#8978](#8978) - **(install)** add missing env vars to tool postinstall hooks by @jdx in [#8977](#8977) - **(task)** prevent hang when skipped task has dependents by @jdx in [#8937](#8937) - **(task)** invalidate dependent task sources when dependency runs by @jdx in [#8975](#8975) - **(task)** prevent deadlock when MISE_JOBS=1 with sub-task references by @jdx in [#8976](#8976) - **(task)** fetch remote task files before parsing usage specs by @jdx in [#8979](#8979) - **(task)** prevent panic when running parallel sub-tasks with replacing output by @jdx in [#8986](#8986) - **(upgrade)** update lockfile and config when upgrading to specific version by @jdx in [#8983](#8983) ### 📚 Documentation - **(node)** remove "recommended for teams" from pin example by @jdx in [b334363](b334363) ### 📦️ Dependency Updates - update ghcr.io/jdx/mise:alpine docker digest to 17a29f2 by @renovate[bot] in [#8995](#8995) - update docker/dockerfile:1 docker digest to 2780b5c by @renovate[bot] in [#8994](#8994) ### New Contributors - @baby-joel made their first contribution in [#8890](#8890) - @cameronbrill made their first contribution in [#8966](#8966) - @c22 made their first contribution in [#8968](#8968)

gemini-code-assist Bot reviewed Apr 9, 2026

View reviewed changes

jdx enabled auto-merge (squash) April 9, 2026 15:01

jdx and others added 3 commits April 9, 2026 15:26

Merge remote-tracking branch 'origin/main' into fix/task-hang-jobs-1

4677144

Merge remote-tracking branch 'origin/main' into fix/task-hang-jobs-1

8c555d4

# Conflicts: # src/cli/run.rs # src/task/task_executor.rs

fix(task): allow clippy::too_many_arguments for run_task_sched

cb780c0

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

jdx merged commit edd79aa into main Apr 9, 2026
36 checks passed

jdx deleted the fix/task-hang-jobs-1 branch April 9, 2026 16:07

mise-en-dev mentioned this pull request Apr 9, 2026

chore: release 2026.4.8 #8972

Merged

BrewTestBot mentioned this pull request Apr 10, 2026

mise 2026.4.8 Homebrew/homebrew-core#276976

Merged

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fix(task): prevent deadlock when MISE_JOBS=1 with sub-task references#8976

fix(task): prevent deadlock when MISE_JOBS=1 with sub-task references#8976
jdx merged 4 commits intomainfrom
fix/task-hang-jobs-1

jdx commented Apr 9, 2026 •

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Greptile Summary

Confidence Score: 5/5

Vulnerabilities

Important Files Changed

Sequence Diagram

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jdx commented Apr 9, 2026 •

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`mise x -- echo`

`mise env`

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`mise ls`

`xtasks/test/perf`