From b78e38065efd5f4079564b9e8e3529950ba0dd52 Mon Sep 17 00:00:00 2001
From: Damien Neil <dneil@google.com>
Date: Wed, 21 May 2025 13:02:59 -0700
Subject: [PATCH] runtime: define lock ranking between weak pointers and
 synctest

Fixes #73817

Change-Id: I0101bdc797237b4c7eb58b414c71b009b0b44447
Reviewed-on: https://go-review.googlesource.com/c/go/+/675176
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
Auto-Submit: Damien Neil <dneil@google.com>
---
 src/internal/synctest/synctest_test.go | 13 +++++++++++++
 src/runtime/lockrank.go                |  2 +-
 src/runtime/mklockrank.go              | 10 +++++++++-
 3 files changed, 23 insertions(+), 2 deletions(-)

diff --git a/src/internal/synctest/synctest_test.go b/src/internal/synctest/synctest_test.go
index e46040e048..7f71df1710 100644
--- a/src/internal/synctest/synctest_test.go
+++ b/src/internal/synctest/synctest_test.go
@@ -9,11 +9,13 @@ import (
 	"internal/synctest"
 	"iter"
 	"reflect"
+	"runtime"
 	"slices"
 	"strconv"
 	"sync"
 	"testing"
 	"time"
+	"weak"
 )
 
 func TestNow(t *testing.T) {
@@ -625,6 +627,17 @@ func TestHappensBefore(t *testing.T) {
 	}
 }
 
+// https://go.dev/issue/73817
+func TestWeak(t *testing.T) {
+	synctest.Run(func() {
+		for range 100 {
+			runtime.GC()
+			b := make([]byte, 1024)
+			weak.Make(&b)
+		}
+	})
+}
+
 func wantPanic(t *testing.T, want string) {
 	if e := recover(); e != nil {
 		if got := fmt.Sprint(e); got != want {
diff --git a/src/runtime/lockrank.go b/src/runtime/lockrank.go
index 456f2b75e6..7f32e6397b 100644
--- a/src/runtime/lockrank.go
+++ b/src/runtime/lockrank.go
@@ -204,7 +204,7 @@ var lockPartialOrder [][]lockRank = [][]lockRank{
 	lockRankRoot:                {},
 	lockRankItab:                {},
 	lockRankReflectOffs:         {lockRankItab},
-	lockRankSynctest:            {lockRankSysmon, lockRankScavenge, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankRoot, lockRankItab, lockRankReflectOffs},
+	lockRankSynctest:            {lockRankSysmon, lockRankScavenge, lockRankSweepWaiters, lockRankStrongFromWeakQueue, lockRankSweep, lockRankTestR, lockRankTimerSend, lockRankPollDesc, lockRankWakeableSleep, lockRankHchan, lockRankNotifyList, lockRankTimers, lockRankTimer, lockRankRoot, lockRankItab, lockRankReflectOffs},
 	lockRankUserArenaState:      {},
 	lockRankTraceBuf:            {lockRankSysmon, lockRankScavenge},
 	lockRankTraceStrings:        {lockRankSysmon, lockRankScavenge, lockRankTraceBuf},
diff --git a/src/runtime/mklockrank.go b/src/runtime/mklockrank.go
index 6cccece9b5..2e3375331a 100644
--- a/src/runtime/mklockrank.go
+++ b/src/runtime/mklockrank.go
@@ -99,7 +99,15 @@ NONE
 < reflectOffs;
 
 # Synctest
-hchan, root, timers, timer, notifyList, reflectOffs < synctest;
+hchan,
+  notifyList,
+  reflectOffs,
+  root,
+  strongFromWeakQueue,
+  sweepWaiters,
+  timer,
+  timers
+< synctest;
 
 # User arena state
 NONE < userArenaState;
-- 
2.50.0