Protect NewSymbols table from concurrent access when internalizing ne…

…w symbols

src/Collections-Strings/Symbol.class.st

@@ -106,8 +106,8 @@ Symbol class >> initialize [
 { #category : 'symbol table' }
 Symbol class >> intern: aStringOrSymbol [
 
-	^ (self findInterned: aStringOrSymbol) ifNil: [
-		  NewSymbols add: aStringOrSymbol createSymbol ]
+	SymbolTableSemaphore singleInstance critical: [
+		^ self rawIntern: aStringOrSymbol ]
 ]
 
 { #category : 'instance creation' }
@@ -156,6 +156,13 @@ Symbol class >> possibleSelectorsFor: misspelled [
 	^ best
 ]
 
+{ #category : 'symbol table' }
+Symbol class >> rawIntern: aStringOrSymbol [
+
+	^ (self findInterned: aStringOrSymbol) ifNil: [
+		  NewSymbols add: aStringOrSymbol createSymbol ]
+]
+
 { #category : 'instance creation' }
 Symbol class >> readFrom: strm [
 	"Symbol readFromString: '#abc'"

src/Collections-Strings/SymbolTableSemaphore.class.st

@@ -0,0 +1,19 @@
+"
+I am a semaphore to protect the NewSymbols table from concurrent access when new symbols are internalized. 
+I have a single instance 
+"
+Class {
+	#name : 'SymbolTableSemaphore',
+	#superclass : 'Semaphore',
+	#classVars : [
+		'SingleInstance'
+	],
+	#category : 'Collections-Strings-Base',
+	#package : 'Collections-Strings',
+	#tag : 'Base'
+}
+
+{ #category : 'instance creation' }
+SymbolTableSemaphore class >> singleInstance [
+	^ SingleInstance ifNil: [ SingleInstance := self forMutualExclusion ]
+]