diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/FunctionRegistry.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/FunctionRegistry.scala
index 3a418497fa537..a52feaa41acf9 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/FunctionRegistry.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/FunctionRegistry.scala
@@ -18,9 +18,9 @@
 package org.apache.spark.sql.catalyst.analysis
 
 import java.util.Locale
-import javax.annotation.concurrent.GuardedBy
+import java.util.concurrent.ConcurrentHashMap
 
-import scala.collection.mutable
+import scala.jdk.CollectionConverters._
 import scala.reflect.ClassTag
 
 import org.apache.spark.SparkUnsupportedOperationException
@@ -195,9 +195,8 @@ object FunctionRegistryBase {
 
 trait SimpleFunctionRegistryBase[T] extends FunctionRegistryBase[T] with Logging {
 
-  @GuardedBy("this")
   protected val functionBuilders =
-    new mutable.HashMap[FunctionIdentifier, (ExpressionInfo, FunctionBuilder)]
+    new ConcurrentHashMap[FunctionIdentifier, (ExpressionInfo, FunctionBuilder)]
 
   // Resolution of the function name is always case insensitive, but the database name
   // depends on the caller
@@ -220,10 +219,10 @@ trait SimpleFunctionRegistryBase[T] extends FunctionRegistryBase[T] with Logging
   def internalRegisterFunction(
       name: FunctionIdentifier,
       info: ExpressionInfo,
-      builder: FunctionBuilder): Unit = synchronized {
+      builder: FunctionBuilder): Unit = {
     val newFunction = (info, builder)
     functionBuilders.put(name, newFunction) match {
-      case Some(previousFunction) if previousFunction != newFunction =>
+      case previousFunction if previousFunction != newFunction =>
         logWarning(log"The function ${MDC(FUNCTION_NAME, name)} replaced a " +
           log"previously registered function.")
       case _ =>
@@ -231,34 +230,25 @@ trait SimpleFunctionRegistryBase[T] extends FunctionRegistryBase[T] with Logging
   }
 
   override def lookupFunction(name: FunctionIdentifier, children: Seq[Expression]): T = {
-    val func = synchronized {
-      functionBuilders.get(normalizeFuncName(name)).map(_._2).getOrElse {
-        throw QueryCompilationErrors.unresolvedRoutineError(name, Seq("system.builtin"))
-      }
+    val func = Option(functionBuilders.get(normalizeFuncName(name))).map(_._2).getOrElse {
+      throw QueryCompilationErrors.unresolvedRoutineError(name, Seq("system.builtin"))
     }
     func(children)
   }
 
-  override def listFunction(): Seq[FunctionIdentifier] = synchronized {
-    functionBuilders.iterator.map(_._1).toList
-  }
+  override def listFunction(): Seq[FunctionIdentifier] =
+    functionBuilders.keys().asScala.toSeq
 
-  override def lookupFunction(name: FunctionIdentifier): Option[ExpressionInfo] = synchronized {
-    functionBuilders.get(normalizeFuncName(name)).map(_._1)
-  }
+  override def lookupFunction(name: FunctionIdentifier): Option[ExpressionInfo] =
+    Option(functionBuilders.get(normalizeFuncName(name))).map(_._1)
 
-  override def lookupFunctionBuilder(
-      name: FunctionIdentifier): Option[FunctionBuilder] = synchronized {
-    functionBuilders.get(normalizeFuncName(name)).map(_._2)
-  }
+  override def lookupFunctionBuilder(name: FunctionIdentifier): Option[FunctionBuilder] =
+    Option(functionBuilders.get(normalizeFuncName(name))).map(_._2)
 
-  override def dropFunction(name: FunctionIdentifier): Boolean = synchronized {
-    functionBuilders.remove(normalizeFuncName(name)).isDefined
-  }
+  override def dropFunction(name: FunctionIdentifier): Boolean =
+    Option(functionBuilders.remove(normalizeFuncName(name))).isDefined
 
-  override def clear(): Unit = synchronized {
-    functionBuilders.clear()
-  }
+  override def clear(): Unit = functionBuilders.clear()
 }
 
 /**
@@ -308,7 +298,11 @@ class SimpleFunctionRegistry
 
   override def clone(): SimpleFunctionRegistry = synchronized {
     val registry = new SimpleFunctionRegistry
-    functionBuilders.iterator.foreach { case (name, (info, builder)) =>
+    val iterator = functionBuilders.entrySet().iterator()
+    while (iterator.hasNext) {
+      val entry = iterator.next()
+      val name = entry.getKey
+      val (info, builder) = entry.getValue
       registry.internalRegisterFunction(name, info, builder)
     }
     registry
@@ -1036,7 +1030,11 @@ class SimpleTableFunctionRegistry extends SimpleFunctionRegistryBase[LogicalPlan
 
   override def clone(): SimpleTableFunctionRegistry = synchronized {
     val registry = new SimpleTableFunctionRegistry
-    functionBuilders.iterator.foreach { case (name, (info, builder)) =>
+    val iterator = functionBuilders.entrySet().iterator()
+    while (iterator.hasNext) {
+      val entry = iterator.next()
+      val name = entry.getKey
+      val (info, builder) = entry.getValue
       registry.internalRegisterFunction(name, info, builder)
     }
     registry