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From "Paulex Yang (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HARMONY-4081) [classlib][nio] FileChannel.write(ByteBuffer[]) sometimes works incorrectly
Date Thu, 16 Aug 2007 10:35:33 GMT

    [ https://issues.apache.org/jira/browse/HARMONY-4081?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#action_12520200
] 

Paulex Yang commented on HARMONY-4081:
--------------------------------------

Mikhail,

I agree the FileChannelImpl part of your patch, but I'm not sure I understand the modifications
on AbstractMemorySpy and MappedPlatformAddress, would you please explain a little more on
this? 

I'm a little confused on MappedPlatformAddress, because it actually holds a pointer to a mapped
memory(got from mmap() on Linux), and the native method unmap(osaddr, size) is right method
to free the native resource, for example on Linux, unmap() invokes munmap() system call. So
why to add another call to free()?  

About the AbstractMemorySpy, if the address is removed from memoryInUse, supposingly its relevant
native resource will be freed in next call to orphandMemory() after GC run. If the relevant
reference object is removed from refToShadow, the mechanism won't work, because the wrapper.shadow.free()
(Line.110, AbstractMemorySpy) cannot be reached any more.

Anything I missed? 

> [classlib][nio] FileChannel.write(ByteBuffer[]) sometimes works incorrectly
> ---------------------------------------------------------------------------
>
>                 Key: HARMONY-4081
>                 URL: https://issues.apache.org/jira/browse/HARMONY-4081
>             Project: Harmony
>          Issue Type: Bug
>          Components: Classlib
>         Environment: Windows
>            Reporter: Vera Petrashkova
>            Assignee: Alexei Zakharov
>            Priority: Minor
>         Attachments: H-4081_fix.patch, H-4081_temp_workaround.patch, SourceViewScreenshot-1.jpg
>
>
> According to J2SE specification
> "File channels are safe for use by multiple concurrent threads."
> But the following test demonstrates that FileChannel.write(ByteBuffer[]) sometimes works
incorrectly when
> some threads try to write bytes to the same channel.
> Not all data are written to the file.
> ---------------fchTest.java---------------
> import java.io.File;
> import java.io.IOException;
> import java.io.FileOutputStream;
> import java.io.FileInputStream;
> import java.nio.channels.FileChannel;
> import java.nio.ByteBuffer;
> public class fchTest {
>         
>     public static int N_TH = 20;
>     public static final int BUF_SIZE = 2000;
>     public static final int N_BUF = 20;
>     public static final int N_WRITES = 20;
>     boolean passed = true;
>   
>     String fileName = "FileChannel.file";
>     FileChannel outChannel = null;
>     FileChannel inChannel = null;
>     public static void main(String[] args) {
>         try {
>              if (args.length > 0) {
>                 N_TH = Integer.parseInt(args[0]);
>             }
>         } catch (Throwable e) {
>         }    
>         int res = new fchTest().test(args);
>         System.err.println(res == 104 ? "Test passed" : "Test failed");          
>     }
>     public int test(String[] params) {
>         File f = null;
>         passed = true;
>         try {
>             f = new File(fileName);
>             if (f.exists()) {
>                 f.delete();
>             }
>             outChannel = new FileOutputStream(f).getChannel();
>             inChannel = new FileInputStream(f).getChannel();
>             Thread[] t = new Thread[N_TH];
>             for (int i = 0; i < t.length; ++i) {
>                 t[i] = new thWriter(this); 
>                 t[i].start();
>             }
>             for (int i = 0; i < t.length; ++i) {
>                 t[i].join();
>             }
>         } catch (Throwable t) {
>             t.printStackTrace();
>             return 105;
>         } finally {
>             try {
>                 if (outChannel != null){
>                     outChannel.close();
>                 }
>                 if (inChannel != null){
>                     inChannel.close();
>                 }                    
>             } catch (Throwable t){
>                 t.printStackTrace();
>             }
>             if (f != null){
>                 f.delete();
>             }
>         }
>         return (passed ? 104 : 106);
>     }
> }
> class thWriter extends Thread {
>     FileChannel outChannel = null;
>     fchTest base = null;
>     
>     thWriter(fchTest base) {
>         this.outChannel = base.outChannel;
>         this.base = base;
>     }
> public void run () {
>         try {
>             long allW = 0;
>             long allC = 0;
>             for (int i = 0; i < fchTest.N_WRITES; ++i) {
>                 ByteBuffer[] bbb = createByteChunks();
>                 for (int t = 0; t < bbb.length; t++)  {
>                     allC += bbb[i].capacity();
>                 }
>                 long written = outChannel.write(bbb);
>                 if (written != (long)((fchTest.BUF_SIZE)*fchTest.N_BUF)) {
>                     System.err.println(this+"  Written: "+written+"  should be "+ fchTest.BUF_SIZE*fchTest.N_BUF+"
outChannel position: "+outChannel.position());
>                     base.passed = false;
>                 }
>                 allW+=written;
>                 Thread.yield();
>                 Thread.sleep(10);
>             }
>             System.err.println(this+" - after write: "+allW+"  "+allC);
>             if (allW != allC) {
>                 base.passed = false;
>             }
>             outChannel.force(false);
>         } catch (Throwable e){
>             System.err.println(this+" unexpected exception " + e);
>             e.printStackTrace();
>             base.passed = false;
>         }
>     }
>     ByteBuffer[] createByteChunks() {
>         ByteBuffer[] bb_arr = new ByteBuffer[fchTest.N_BUF];
>         byte [] bb = new byte[fchTest.BUF_SIZE];    
>         for (int i = 0; i < bb.length; i++) {
>             bb[i] = (byte)i;
>         }
>         for (int i = 0; i < bb_arr.length; ++i) {
>             bb_arr[i] = ByteBuffer.allocateDirect(bb.length).wrap(bb);
>         }       
>         return bb_arr;
>     }
> }
> ----------------------------------------------------
> Run this test several times and change the number of created threads
> java fchTest
> java fchTest 30
> Output on RI:
> ==============
> java version "1.5.0_06"
> Java(TM) 2 Runtime Environment, Standard Edition (build 1.5.0_06-b05)
> Java HotSpot(TM) Client VM (build 1.5.0_06-b05, mixed mode)
> Thread[Thread-1,5,main] - after write: 800000  800000
> Thread[Thread-11,5,main] - after write: 800000  800000
> Thread[Thread-19,5,main] - after write: 800000  800000
> Thread[Thread-17,5,main] - after write: 800000  800000
> Thread[Thread-9,5,main] - after write: 800000  800000
> Thread[Thread-13,5,main] - after write: 800000  800000
> Thread[Thread-15,5,main] - after write: 800000  800000
> Thread[Thread-7,5,main] - after write: 800000  800000
> Thread[Thread-3,5,main] - after write: 800000  800000
> Thread[Thread-0,5,main] - after write: 800000  800000
> Thread[Thread-5,5,main] - after write: 800000  800000
> Thread[Thread-16,5,main] - after write: 800000  800000
> Thread[Thread-6,5,main] - after write: 800000  800000
> Thread[Thread-12,5,main] - after write: 800000  800000
> Thread[Thread-2,5,main] - after write: 800000  800000
> Thread[Thread-8,5,main] - after write: 800000  800000
> Thread[Thread-10,5,main] - after write: 800000  800000
> Thread[Thread-4,5,main] - after write: 800000  800000
> Thread[Thread-14,5,main] - after write: 800000  800000
> Thread[Thread-18,5,main] - after write: 800000  800000
> Test passed
> Output on DRLVM:
> ==============
> Apache Harmony Launcher : (c) Copyright 1991, 2006 The Apache Software Foundation or
its licensors, as applicable.
> java version "1.5.0"
> pre-alpha : not complete or compatible
> svn = r544707, (Jun  6 2007), Windows/ia32/msvc 1310, release build
> http://harmony.apache.org
> The GC did not provide gc_add_weak_root_set_entry()
> Thread[Thread-9,5,main]  Written: 33100  should be 40000 outChannel position: 6874000
> Thread[Thread-20,5,main] - after write: 800000  800000
> Thread[Thread-16,5,main] - after write: 800000  800000
> Thread[Thread-8,5,main] - after write: 800000  800000
> Thread[Thread-12,5,main] - after write: 800000  800000
> Thread[Thread-22,5,main] - after write: 800000  800000
> Thread[Thread-14,5,main] - after write: 800000  800000
> Thread[Thread-18,5,main] - after write: 800000  800000
> Thread[Thread-23,5,main] - after write: 800000  800000
> Thread[Thread-11,5,main] - after write: 800000  800000
> Thread[Thread-10,5,main] - after write: 800000  800000
> Thread[Thread-24,5,main] - after write: 800000  800000
> Thread[Thread-7,5,main] - after write: 800000  800000
> Thread[Thread-15,5,main] - after write: 800000  800000
> Thread[Thread-9,5,main] - after write: 793100  800000
> Thread[Thread-6,5,main] - after write: 800000  800000
> Thread[Thread-25,5,main] - after write: 800000  800000
> Thread[Thread-17,5,main] - after write: 800000  800000
> Thread[Thread-13,5,main]  Written: 37700  should be 40000 outChannel position: 15872000
> Thread[Thread-19,5,main] - after write: 800000  800000
> Thread[Thread-13,5,main] - after write: 797700  800000
> Thread[Thread-21,5,main] - after write: 800000  800000
> Test failed
> This bug causes the failure of the test
>     api.nio.channels.filechannel.FileChannelThrSafetyTest
> from Reliability test suite https://issues.apache.org/jira/browse/HARMONY-2918

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