HBASE-25749 Improved logging when interrupting active RPC handlers holding the region close lock

We should add the thread to regionlockholders map to make sure we have can track the threads holding a lock even if it is not interuuptable. When calling interrupt we will not interrupt such threads but will print warn with thread name to help with debugging

Author: mnpoonia

hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/HRegion.java

@@ -8441,9 +8441,9 @@ public void startRegionOperation(Operation op) throws IOException {
     // Update regionLockHolders ONLY for any startRegionOperation call that is invoked from
     // an RPC handler
     Thread thisThread = Thread.currentThread();
-    if (isInterruptableOp) {
-      regionLockHolders.put(thisThread, true);
-    }
+
+    regionLockHolders.put(thisThread, isInterruptableOp);
+
     if (this.closed.get()) {
       lock.readLock().unlock();
       throw new NotServingRegionException(getRegionInfo().getRegionNameAsString() + " is closed");
@@ -8458,11 +8458,7 @@ public void startRegionOperation(Operation op) throws IOException {
         coprocessorHost.postStartRegionOperation(op);
       }
     } catch (Exception e) {
-      if (isInterruptableOp) {
-        // would be harmless to remove what we didn't add but we know by 'isInterruptableOp'
-        // if we added this thread to regionLockHolders
-        regionLockHolders.remove(thisThread);
-      }
+      regionLockHolders.remove(thisThread);
       lock.readLock().unlock();
       throw new IOException(e);
     }
@@ -8702,8 +8698,13 @@ private void interruptRegionOperations() {
     for (Map.Entry<Thread, Boolean> entry : regionLockHolders.entrySet()) {
       // An entry in this map will have a boolean value indicating if it is currently
       // eligible for interrupt; if so, we should interrupt it.
+      Thread key = entry.getKey();
       if (entry.getValue().booleanValue()) {
-        entry.getKey().interrupt();
+        key.interrupt();
+      } else {
+        String s = Threads.printStackTrace(key);
+        LOG.warn("Can't interrupt thread {} : holding lock. Stack trace : {}", key, s);
+
       }
     }
   }