Repository: hbase
Updated Branches:
  refs/heads/branch-2 4a609db30 -> ca1b5503e


HBASE-21292 IdLock.getLockEntry() may hang if interrupted


Project: http://git-wip-us.apache.org/repos/asf/hbase/repo
Commit: http://git-wip-us.apache.org/repos/asf/hbase/commit/ca1b5503
Tree: http://git-wip-us.apache.org/repos/asf/hbase/tree/ca1b5503
Diff: http://git-wip-us.apache.org/repos/asf/hbase/diff/ca1b5503

Branch: refs/heads/branch-2
Commit: ca1b5503e15c7781d229c58e81ade078285820dc
Parents: 4a609db
Author: Allan Yang <[email protected]>
Authored: Thu Oct 18 14:40:38 2018 -0700
Committer: Michael Stack <[email protected]>
Committed: Thu Oct 18 14:41:42 2018 -0700

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 .../java/org/apache/hadoop/hbase/util/IdLock.java  | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)
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http://git-wip-us.apache.org/repos/asf/hbase/blob/ca1b5503/hbase-common/src/main/java/org/apache/hadoop/hbase/util/IdLock.java
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diff --git 
a/hbase-common/src/main/java/org/apache/hadoop/hbase/util/IdLock.java 
b/hbase-common/src/main/java/org/apache/hadoop/hbase/util/IdLock.java
index 414cc66..c4adfbf 100644
--- a/hbase-common/src/main/java/org/apache/hadoop/hbase/util/IdLock.java
+++ b/hbase-common/src/main/java/org/apache/hadoop/hbase/util/IdLock.java
@@ -81,6 +81,17 @@ public class IdLock {
               existing.wait();
             } catch (InterruptedException e) {
               --existing.numWaiters;  // Remove ourselves from waiters.
+              // HBASE-21292
+              // There is a rare case that interrupting and the lock owner 
thread call
+              // releaseLockEntry at the same time. Since the owner thread 
found there
+              // still one waiting, it won't remove the entry from the map. If 
the interrupted
+              // thread is the last one waiting on the lock, and since an 
exception is thrown,
+              // the 'existing' entry will stay in the map forever. Later 
threads which try to
+              // get this lock will stuck in a infinite loop because
+              // existing = map.putIfAbsent(entry.id, entry)) != null and 
existing.locked=false.
+              if (!existing.locked && existing.numWaiters == 0) {
+                map.remove(existing.id);
+              }
               throw new InterruptedIOException(
                   "Interrupted waiting to acquire sparse lock");
             }
@@ -135,6 +146,12 @@ public class IdLock {
 
             }
           } catch (InterruptedException e) {
+            // HBASE-21292
+            // Please refer to the comments in getLockEntry()
+            // the difference here is that we decrease numWaiters in finally 
block
+            if (!existing.locked && existing.numWaiters == 1) {
+              map.remove(existing.id);
+            }
             throw new InterruptedIOException(
                 "Interrupted waiting to acquire sparse lock");
           } finally {

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