clebertsuconic commented on code in PR #5498:
URL: https://github.com/apache/activemq-artemis/pull/5498#discussion_r1959811848


##########
artemis-server/src/main/java/org/apache/activemq/artemis/core/paging/impl/PagingStoreImpl.java:
##########
@@ -1262,8 +1324,16 @@ private boolean writePage(Message message,
                              Transaction tx,
                              RouteContextList listCtx,
                              Function<Message, Message> pageDecorator) throws 
Exception {
-      lock.writeLock().lock();
-
+      if (timedWriter == null) {
+         // in case timedWriter is not being used, we need to guarantee a 
writeLock.
+         // because there's no way to upgrade from reading to writeLock
+         writeLock();
+      } else {
+         // if we are using a timedWritter, we can just use a readLock to 
guarantee paging is not changed
+         // this will issue the writer on a different thread, and we can just 
use a readLock
+         readLock();

Review Comment:
   I will improve the comment there.
   
   
   We need to keep a lock while we checked for isPaging... we need to make sure 
the system is paging for the entire duration of the method, hence the readLock.
   
   
   When timedWriter is null (which will only happen in tests), I still  need to 
hold the lock, however later on when moving to a different page a writeLock 
will be needed, and that would break things with a deadlock.
   



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