From fd240b3b8679c699808baf7f4c94263d0e8e0e9f Mon Sep 17 00:00:00 2001
From: rstoyanchev <rossen.stoyanchev@broadcom.com>
Date: Fri, 12 Jan 2024 17:15:06 +0000
Subject: [PATCH] Double-checked lock in ChannelSendOperator#request

Closes gh-31865
---
 .../handler/invocation/reactive/ChannelSendOperator.java      | 4 ++++
 .../http/server/reactive/ChannelSendOperator.java             | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/spring-messaging/src/main/java/org/springframework/messaging/handler/invocation/reactive/ChannelSendOperator.java b/spring-messaging/src/main/java/org/springframework/messaging/handler/invocation/reactive/ChannelSendOperator.java
index 108d149299..ddcf7e709c 100644
--- a/spring-messaging/src/main/java/org/springframework/messaging/handler/invocation/reactive/ChannelSendOperator.java
+++ b/spring-messaging/src/main/java/org/springframework/messaging/handler/invocation/reactive/ChannelSendOperator.java
@@ -281,6 +281,10 @@ class ChannelSendOperator<T> extends Mono<Void> implements Scannable {
 				return;
 			}
 			synchronized (this) {
+				if (this.state == State.READY_TO_WRITE) {
+					s.request(n);
+					return;
+				}
 				if (this.writeSubscriber != null) {
 					if (this.state == State.EMITTING_CACHED_SIGNALS) {
 						this.demandBeforeReadyToWrite = n;
diff --git a/spring-web/src/main/java/org/springframework/http/server/reactive/ChannelSendOperator.java b/spring-web/src/main/java/org/springframework/http/server/reactive/ChannelSendOperator.java
index da46443edc..6b5e409595 100644
--- a/spring-web/src/main/java/org/springframework/http/server/reactive/ChannelSendOperator.java
+++ b/spring-web/src/main/java/org/springframework/http/server/reactive/ChannelSendOperator.java
@@ -273,6 +273,10 @@ public class ChannelSendOperator<T> extends Mono<Void> implements Scannable {
 				return;
 			}
 			synchronized (this) {
+				if (this.state == State.READY_TO_WRITE) {
+					s.request(n);
+					return;
+				}
 				if (this.writeSubscriber != null) {
 					if (this.state == State.EMITTING_CACHED_SIGNALS) {
 						this.demandBeforeReadyToWrite = n;