From 0e7173b4473fa954a24ffa7064891451351e0021 Mon Sep 17 00:00:00 2001
From: lzhfromustc <43191155+lzhfromustc@users.noreply.github.com>
Date: Mon, 29 Jul 2019 18:23:09 -0700
Subject: [PATCH] pkg/types: Avoid potential double lock of tsafeSet.

(tsafeSet).Sub and (tsafeSet).Equals can cause double lock bug if ts and other is pointing the same variable

gofmt the code and add some comments
---
 pkg/types/set.go | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/pkg/types/set.go b/pkg/types/set.go
index c111b0c0c0b..e7a3cdc9ab6 100644
--- a/pkg/types/set.go
+++ b/pkg/types/set.go
@@ -148,6 +148,14 @@ func (ts *tsafeSet) Contains(value string) (exists bool) {
 func (ts *tsafeSet) Equals(other Set) bool {
 	ts.m.RLock()
 	defer ts.m.RUnlock()
+
+	// If ts and other represent the same variable, avoid calling
+	// ts.us.Equals(other), to avoid double RLock bug
+	if _other, ok := other.(*tsafeSet); ok {
+		if _other == ts {
+			return true
+		}
+	}
 	return ts.us.Equals(other)
 }
 
@@ -173,6 +181,15 @@ func (ts *tsafeSet) Copy() Set {
 func (ts *tsafeSet) Sub(other Set) Set {
 	ts.m.RLock()
 	defer ts.m.RUnlock()
+
+	// If ts and other represent the same variable, avoid calling
+	// ts.us.Sub(other), to avoid double RLock bug
+	if _other, ok := other.(*tsafeSet); ok {
+		if _other == ts {
+			usResult := NewUnsafeSet()
+			return &tsafeSet{usResult, sync.RWMutex{}}
+		}
+	}
 	usResult := ts.us.Sub(other).(*unsafeSet)
 	return &tsafeSet{usResult, sync.RWMutex{}}
 }