[GitHub] [hadoop] steveloughran commented on a diff in pull request #5675: HADOOP-18740. S3A prefetch cache blocks should be accessed by RW locks

["steveloughran (via GitHub)" <gi...@apache.org>]

steveloughran commented on code in PR #5675:
URL: https://github.com/apache/hadoop/pull/5675#discussion_r1213038983


##########
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/impl/prefetch/SingleFilePerBlockCache.java:
##########
@@ -310,7 +333,12 @@ public void close() throws IOException {
     int numFilesDeleted = 0;
 
     for (Entry entry : blocks.values()) {
-      entry.takeLock(Entry.LockType.WRITE);
+      boolean lockAcquired = entry.takeLock(Entry.LockType.WRITE, 5, TimeUnit.SECONDS);

Review Comment:
   pull the number into a constant. Know that I automatically -1 all inline constants in production code and save time all round.



##########
hadoop-common-project/hadoop-common/src/main/java/org/apache/hadoop/fs/impl/prefetch/SingleFilePerBlockCache.java:
##########
@@ -127,11 +128,33 @@ void takeLock(LockType lockType) {
      */
     void releaseLock(LockType lockType) {
       if (LockType.READ == lockType) {
-        this.lock.readLock().unlock();
+        lock.readLock().unlock();
       } else if (LockType.WRITE == lockType) {
-        this.lock.writeLock().unlock();
+        lock.writeLock().unlock();
       }
     }
+
+    /**
+     * Try to take the read or write lock within the given timeout.
+     *
+     * @param lockType type of the lock.
+     * @param timeout the time to wait for the given lock.
+     * @param unit the time unit of the timeout argument.
+     * @return true if the lock of the given lock type was acquired.
+     */
+    boolean takeLock(LockType lockType, long timeout, TimeUnit unit) {

Review Comment:
   should this and the others be private? you don't want other classes playing with your lock code...



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