HBASE-2964 Deadlock when RS tries to RPC to itself inside SplitTransaction

git-svn-id: https://svn.apache.org/repos/asf/hbase/trunk@995151 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -506,6 +506,7 @@ Release 0.21.0 - Unreleased
    HBASE-2925  LRU of HConnectionManager.HBASE_INSTANCES breaks if
                HBaseConfiguration is changed
                (Robert Mahfoud via Stack)
+   HBASE-2964  Deadlock when RS tries to RPC to itself inside SplitTransaction
 
   IMPROVEMENTS
    HBASE-1760  Cleanup TODOs in HTable

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

@@ -214,7 +214,7 @@ public class HRegion implements HeapSize { // , Writable{
   final FlushRequester flushRequester;
   private final long blockingMemStoreSize;
   final long threadWakeFrequency;
-  // Used to guard splits and closes
+  // Used to guard closes
   final ReentrantReadWriteLock lock =
     new ReentrantReadWriteLock();
 

src/main/java/org/apache/hadoop/hbase/regionserver/SplitTransaction.java

@@ -61,6 +61,8 @@ import org.apache.zookeeper.KeeperException;
  *    }
  *  }
  * </Pre>
+ * <p>This class is not thread safe.  Caller needs ensure split is run by
+ * one thread only.
  */
 class SplitTransaction {
   private static final Log LOG = LogFactory.getLog(SplitTransaction.class);
@@ -127,16 +129,10 @@ class SplitTransaction {
   /**
    * Does checks on split inputs.
    * @return <code>true</code> if the region is splittable else
-   * <code>false</code> if it is not (e.g. its already closed, etc.). If we
-   * return <code>true</code>, we'll have taken out the parent's
-   * <code>splitsAndClosesLock</code> and only way to unlock is successful
-   * {@link #execute(OnlineRegions)} or {@link #rollback(OnlineRegions)}
+   * <code>false</code> if it is not (e.g. its already closed, etc.).
    */
   public boolean prepare() {
-    boolean prepared = false;
-    this.parent.lock.writeLock().lock();
-    try {
-      if (this.parent.isClosed() || this.parent.isClosing()) return prepared;
+    if (this.parent.isClosed() || this.parent.isClosing()) return false;
     HRegionInfo hri = this.parent.getRegionInfo();
     // Check splitrow.
     byte [] startKey = hri.getStartKey();
@@ -145,18 +141,14 @@ class SplitTransaction {
         !this.parent.getRegionInfo().containsRow(splitrow)) {
       LOG.info("Split row is not inside region key range or is equal to " +
           "startkey: " + Bytes.toString(this.splitrow));
-        return prepared;
+      return false;
     }
     long rid = getDaughterRegionIdTimestamp(hri);
     this.hri_a = new HRegionInfo(hri.getTableDesc(), startKey, this.splitrow,
       false, rid);
     this.hri_b = new HRegionInfo(hri.getTableDesc(), this.splitrow, endKey,
       false, rid);
-      prepared = true;
-    } finally {
-      if (!prepared) this.parent.lock.writeLock().unlock();
-    }
-    return prepared;
+    return true;
   }
 
   /**
@@ -188,9 +180,7 @@ class SplitTransaction {
       final RegionServerServices services)
   throws IOException {
     LOG.info("Starting split of region " + this.parent);
-    if (!this.parent.lock.writeLock().isHeldByCurrentThread()) {
-      throw new SplitAndCloseWriteLockNotHeld();
-    }
+    assert !this.parent.lock.writeLock().isHeldByCurrentThread() : "Unsafe to hold write lock while performing RPCs";
 
     // If true, no cluster to write meta edits into.
     boolean testing =
@@ -251,9 +241,6 @@ class SplitTransaction {
       }
     }
 
-    // Unlock if successful split.
-    this.parent.lock.writeLock().unlock();
-
     // Leaving here, the splitdir with its dross will be in place but since the
     // split was successful, just leave it; it'll be cleaned when parent is
     // deleted and cleaned up.
@@ -441,9 +428,6 @@ class SplitTransaction {
    * @throws IOException If thrown, rollback failed.  Take drastic action.
    */
   public void rollback(final OnlineRegions or) throws IOException {
-    if (!this.parent.lock.writeLock().isHeldByCurrentThread()) {
-      throw new SplitAndCloseWriteLockNotHeld();
-    }
     FileSystem fs = this.parent.getFilesystem();
     ListIterator<JournalEntry> iterator =
       this.journal.listIterator(this.journal.size());
@@ -481,16 +465,7 @@ class SplitTransaction {
         throw new RuntimeException("Unhandled journal entry: " + je);
       }
     }
-    if (this.parent.lock.writeLock().isHeldByCurrentThread()) {
-      this.parent.lock.writeLock().unlock();
   }
-  }
-
-  /**
-   * Thrown if lock not held.
-   */
-  @SuppressWarnings("serial")
-  public class SplitAndCloseWriteLockNotHeld extends IOException {}
 
   HRegionInfo getFirstDaughter() {
     return hri_a;

src/test/java/org/apache/hadoop/hbase/regionserver/TestSplitTransaction.java

@@ -95,8 +95,6 @@ public class TestSplitTransaction {
   private SplitTransaction prepareGOOD_SPLIT_ROW() {
     SplitTransaction st = new SplitTransaction(this.parent, GOOD_SPLIT_ROW);
     assertTrue(st.prepare());
-    // Assert the write lock is held on successful prepare as the javadoc asserts.
-    assertTrue(this.parent.lock.writeLock().isHeldByCurrentThread());
     return st;
   }