https://github.com/spring-projects/spring-framework/issues/30996 fixed thread pinning issue. But only for SSEEmitter. Still there are several synchronized block in ResponseBodyEmitter.
https://github.com/spring-projects/spring-framework/blob/e5b58effa3b74569ca6d3b091fa44f47bdc6ccea/spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/ResponseBodyEmitter.java#L183
https://github.com/spring-projects/spring-framework/blob/e5b58effa3b74569ca6d3b091fa44f47bdc6ccea/spring-webmvc/src/main/java/org/springframework/web/servlet/mvc/method/annotation/ResponseBodyEmitter.java#L211
To prevent thread pinning when using virtual thread, it have to replaced with ReentrantLock.
Many of us cannot move to JDK 24 yet (which reduces synchronized pinning), so we need a framework-level mitigation.
Comment From: bclozel
Superseded by #35423