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From "Egor Pasko (JIRA)" <j...@apache.org>
Subject [jira] Commented: (HARMONY-2092) [drlvm] Harmony works with volatile variables incorrectly
Date Wed, 08 Nov 2006 07:46:53 GMT
    [ http://issues.apache.org/jira/browse/HARMONY-2092?page=comments#action_12448065 ] 
            
Egor Pasko commented on HARMONY-2092:
-------------------------------------

If I get it right, volatile variables should be atomic regardless of their type (JVM Spec:
"8.7 Rules for volatile Variables"). 
There is a special exception for volatile variables of the types 'double' and 'long' (JVM
Spec: "8.4 Nonatomic Treatment of double and long Variables")

This bug should be fixed in several components (int, JET, OPT, VM). Extra synchronization
will decrease performance on some tests significantly. Any ideas for alternative solutions?

P.S.: I think, the test can be somewhat reduced.
P.P.S.: I would have changed the subject to "[drlvm][jit][int] non-atomic treatment of volatile
variables of type 'long'"


> [drlvm] Harmony works with volatile variables incorrectly
> ---------------------------------------------------------
>
>                 Key: HARMONY-2092
>                 URL: http://issues.apache.org/jira/browse/HARMONY-2092
>             Project: Harmony
>          Issue Type: Bug
>          Components: DRLVM
>         Environment: Windows and Linux
>            Reporter: Vera Petrashkova
>         Attachments: volatileTest.zip
>
>
> When Long_MAX_VALUE or Long.MIN_VALUE should be assigned to volatile variable then
> VM works incorrectly.
> Code for reproducing:
> ------------------volatileTest.java-----------------
> public class volatileTest  {
>     public static int delay = 5000;
>     private boolean interruptFlag = false;
>     long hi;
>     long lo;
>     volatile long v;
>     public static void main(String [] args ) {
>         int maxI = 20;
>         for (int i = 0; i < maxI; i++) {
>             int t = new volatileTest().test(delay);
>             System.out.println((t == 104 ? "Test passed: ": "Test failed: ") 
>                 + t + "  (step: " + i + ")");
>         }
>     }
>     public synchronized void interrupt() {
>         interruptFlag = true;
>     }
>     public synchronized boolean interrupted() {
>         return interruptFlag;
>     }
>     public volatileTest() {
>         super();
>         hi = Long.MAX_VALUE;
>         lo = Long.MIN_VALUE;
>         v = hi;              
>     }
>     public int test(int delay)  {        
>         boolean passed = true;
>         Thread_1_class  t1 = new Thread_1_class(this);
>         Thread_2_class t2 = new Thread_2_class(this);
>         Interruptor killer = new Interruptor(this, delay);
>         try {
>             t1.start();
>             t2.start();
>             killer.start();
>       
>             while (!interrupted()) {
>                 Thread.yield();
>                 long v3 = v;
>                 if (v3 != hi && v3 != lo) { 
>                     System.out.println(v3+"  "+hi +"  "+lo);
>                     passed = false;
>                     break;
>                 }            
>             }
>             t1.interrupt();
>             t2.interrupt();
>             return passed ? 104 : 105;
>        } catch (Throwable e) {
>            e.printStackTrace();
>            return 106;
>        }
>     }
> }
> class Thread_1_class extends Thread {
>    volatileTest thh;
>    public Thread_1_class (volatileTest t) {
>        super();
>        thh = t;
>    }
>    public void run() {
>        while (!isInterrupted()) {
>            thh.v = thh.lo;
>            thh.v = thh.hi;
>        }
>    }
> }
> class Thread_2_class extends Thread {
>    volatileTest thh;
>    public Thread_2_class (volatileTest t) {
>        super();
>        thh = t;
>    }
>    public void run() {
>        while (!isInterrupted()) {
>                 thh.v = thh.hi;
>                 thh.v = thh.lo;
>             }
>    }
> }
> class Interruptor extends Thread {
>     volatileTest t;
>     int delay;
>     public Interruptor(volatileTest t, int delay) {
>         this.t = t;
>         this.delay = delay;
>     }
>     public void run() {
>         try {
>             Thread.sleep(delay);
>         } catch (InterruptedException e) {
>         }
>         t.interrupt();
>     }
> }
> ----------------------------
> 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)
> Test passed: 104  (step: 0)
> Test passed: 104  (step: 1)
> Test passed: 104  (step: 2)
> Test passed: 104  (step: 3)
> Test passed: 104  (step: 4)
> Test passed: 104  (step: 5)
> Test passed: 104  (step: 6)
> Test passed: 104  (step: 7)
> Test passed: 104  (step: 8)
> Test passed: 104  (step: 9)
> Test passed: 104  (step: 10)
> Test passed: 104  (step: 11)
> Test passed: 104  (step: 12)
> Test passed: 104  (step: 13)
> Test passed: 104  (step: 14)
> Test passed: 104  (step: 15)
> Test passed: 104  (step: 16)
> Test passed: 104  (step: 17)
> Test passed: 104  (step: 18)
> Test passed: 104  (step: 19)
> Output on Harmony:
> ====================
> 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 = r471468, (Nov  7 2006), Windows/ia32/msvc 1310, release build
> http://incubator.apache.org/harmony
> Test passed: 104  (step: 0)
> Test passed: 104  (step: 1)
> Test passed: 104  (step: 2)
> Test passed: 104  (step: 3)
> Test passed: 104  (step: 4)
> Test passed: 104  (step: 5)
> Test passed: 104  (step: 6)
> Test passed: 104  (step: 7)
> Test passed: 104  (step: 8)
> Test passed: 104  (step: 9)
> Test passed: 104  (step: 10)
> 9223372032559808512  9223372036854775807  -9223372036854775808
> Test failed: 105  (step: 11)
> Test passed: 104  (step: 12)
> 9223372032559808512  9223372036854775807  -9223372036854775808
> Test failed: 105  (step: 13)
> Test passed: 104  (step: 14)
> Test passed: 104  (step: 15)
> -9223372032559808513  9223372036854775807  -9223372036854775808
> Test failed: 105  (step: 16)
> -9223372032559808513  9223372036854775807  -9223372036854775808
> Test failed: 105  (step: 17)
> Test passed: 104  (step: 18)
> Test passed: 104  (step: 19)
> 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 = r471468, (Nov  7 2006), Linux/ia32/gcc 3.3.3, release build
> http://incubator.apache.org/harmony
> -9223372032559808513  9223372036854775807  -9223372036854775808
> Test failed: 105  (step: 0)
> 9223372032559808512  9223372036854775807  -9223372036854775808
> Test failed: 105  (step: 1)
> 9223372032559808512  9223372036854775807  -9223372036854775808
> Test failed: 105  (step: 2)
> 9223372032559808512  9223372036854775807  -9223372036854775808
> Test failed: 105  (step: 3)
> 9223372032559808512  9223372036854775807  -9223372036854775808
> Test failed: 105  (step: 4)
> -9223372032559808513  9223372036854775807  -9223372036854775808
> Test failed: 105  (step: 5)
> 9223372032559808512  9223372036854775807  -9223372036854775808
> Test failed: 105  (step: 6)
> 9223372032559808512  9223372036854775807  -9223372036854775808
> Test failed: 105  (step: 7)
> -9223372032559808513  9223372036854775807  -9223372036854775808
> Test failed: 105  (step: 8)
> 9223372032559808512  9223372036854775807  -9223372036854775808
> Test failed: 105  (step: 9)
> 9223372032559808512  9223372036854775807  -9223372036854775808
> Test failed: 105  (step: 10)
> -9223372032559808513  9223372036854775807  -9223372036854775808
> Test failed: 105  (step: 11)
> -9223372032559808513  9223372036854775807  -9223372036854775808
> Test failed: 105  (step: 12)
> 9223372032559808512  9223372036854775807  -9223372036854775808
> Test failed: 105  (step: 13)
> -9223372032559808513  9223372036854775807  -9223372036854775808
> Test failed: 105  (step: 14)
> -9223372032559808513  9223372036854775807  -9223372036854775808
> Test failed: 105  (step: 15)
> 9223372032559808512  9223372036854775807  -9223372036854775808
> Test failed: 105  (step: 16)
> 9223372032559808512  9223372036854775807  -9223372036854775808
> Test failed: 105  (step: 17)
> -9223372032559808513  9223372036854775807  -9223372036854775808
> Test failed: 105  (step: 18)
> 9223372032559808512  9223372036854775807  -9223372036854775808
> Test failed: 105  (step: 19)
> This bug is reproducible on Jitrino (JET/OPT) and on interpreter:
> java -cp . volatileTest
> java -cp . -Xint volatileTest
> java -cp . -Xem:opt volatileTest

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