From 605841baade709e28734db2080e0afea6b940c0f Mon Sep 17 00:00:00 2001
From: Andrei Vagin <avagin@google.com>
Date: Sat, 11 Jun 2022 00:19:05 -0700
Subject: [PATCH] lockdep: print more info for the unbalance unlock case

* print a lock type
* print a list of taken locks

PiperOrigin-RevId: 454310284
---
 pkg/sync/locking/lockdep.go      |  9 ++++++++-
 pkg/sync/locking/lockdep_test.go | 14 ++++++++++++++
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/pkg/sync/locking/lockdep.go b/pkg/sync/locking/lockdep.go
index 0e1703b08..f5739f874 100644
--- a/pkg/sync/locking/lockdep.go
+++ b/pkg/sync/locking/lockdep.go
@@ -117,6 +117,7 @@ func AddGLock(class *MutexClass, subclass uint32) {
 
 // DelGLock deletes a lock from the current goroutine.
 func DelGLock(class *MutexClass, subclass uint32) {
+	origClass := class
 	if subclass != 0 {
 		class = class.subclasses.Load(subclass)
 	}
@@ -126,7 +127,13 @@ func DelGLock(class *MutexClass, subclass uint32) {
 		panic("the current goroutine doesn't have locks")
 	}
 	if _, ok := (*currentLocks)[class]; !ok {
-		panic("unlock of an unknown lock")
+		var b strings.Builder
+		fmt.Fprintf(&b, "unbalance unlock: %s:%d:\n", *classMap.Load(origClass), subclass)
+		fmt.Fprintf(&b, "Current locks:\n")
+		for c := range *currentLocks {
+			fmt.Fprintf(&b, "\t%s\n", *classMap.Load(c))
+		}
+		panic(b.String())
 	}
 
 	delete(*currentLocks, class)
diff --git a/pkg/sync/locking/lockdep_test.go b/pkg/sync/locking/lockdep_test.go
index 9a9d12b01..c00d39b91 100644
--- a/pkg/sync/locking/lockdep_test.go
+++ b/pkg/sync/locking/lockdep_test.go
@@ -104,3 +104,17 @@ func TestReverseNested(t *testing.T) {
 
 	t.Error("The reverse lock order hasn't been detected")
 }
+
+func TestUnknownLock(t *testing.T) {
+	m1 := testMutex{}
+	m2 := test2RWMutex{}
+	m1.Lock()
+	m2.Lock()
+	defer func() {
+		if r := recover(); r != nil {
+			t.Logf("Got expected panic: %s", r)
+		}
+	}()
+	m2.NestedUnlock()
+	t.Error("An unknown lock has not been detected.")
+}