[GitHub] [hbase] markrmiller commented on issue #1261: HBASE-23952: Address thread safety issue with Map used in BufferCallB…

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markrmiller commented on issue #1261: HBASE-23952: Address thread safety issue with Map used in BufferCallB…
URL: https://github.com/apache/hbase/pull/1261#issuecomment-596869131
 
 
   I think the issue is that Netty can use different threads to access this data structure, ie:
   
   `    
   static void invokeUserEventTriggered(final AbstractChannelHandlerContext next, final Object event) {
           ObjectUtil.checkNotNull(event, "event");
           EventExecutor executor = next.executor();
           if (executor.inEventLoop()) {
               next.invokeUserEventTriggered(event);
           } else {
               executor.execute(new Runnable() {
                   @Override
                   public void run() {
                       next.invokeUserEventTriggered(event);
                   }
               });
           }
       }
   `
   
   If more than one thread is going to access a shared field, you have to publish it properly - either with memory barriers or it has to be final or effectively final. It seems very difficult to ensure that this is thread safe or will remain thread safe over time.

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