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comparison src/tests/gov/nasa/jpf/test/mc/threads/ClinitTest.java @ 24:6774e2e08d37

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the fix I would have liked to avoid - apparently hotspot internally does nested locking during class init, which can lead to deadlocks such as described in http://ternarysearch.blogspot.ru/2013/07/static-initialization-deadlock.html. Actually, it's not a regular deadlock since core dumps still list the threads as runnable, althouth it doesn't seem to be a livelock either. In any case, it can be simulated by nested locking and clinit execution, and it is such a serious defect that we want to be able to catch it. The general mechanism is to replace the disparate (but properly ordered) direct clinit calls of the generic ClassInfo.initializeClass() with a single sythetic method that includes all required locking (bottom up), clinit calls / class status change (top down), and unlocking (top down). We also need to add a synthetic insn to defer changing the class status of classes that don't have clinits(), or otherwise the correct lock/unlock order will not amount to anything if the hierarchy is entered through one of the clinit-absent classes. Now we get proper deadlocks if there are concurrent cyclic dependencies during class resolution. However, this can be such a state exploder that we certainly don't want this as the default behavior, especially since it probably is hotspot specific. Nested class init locking is therefore controlled by jvm.nested_init and respective jvm.nested_init.include/exclude options. Added a NestedInitTest to demonstrate use. Thanks to Lilia Abdulina for bringing this long forgotten issue up In the wake of nested locks, there were a number of cases to fix that implicitly relied on absent clinits because clients were not properly checking for re-execution (most notably java.util.Exchanger). This mostly came in through MJIEnv.newObject/ElementInfo. We might turn ClinitRequired into a handled exception at some point, to catch such cases during compilation. Added a UnknownJPFClass exception (in analogy to ClinitRequired), to make clients aware of failed class load attempts/reasons. fixed Exchanger peer, which was not giving up the lock when timing out. This is an example of a lockfree wait op that can time out. Basically, ThreadInfo.isWaiting() needs to be complemented by a isWaitingOrTimedOut(), and ElementInfo.notifies0() has to be aware of it fixed NPE when setting report.probe_interval in tests, which was missing that it had to create a stat object
author Peter Mehlitz <Peter.C.Mehlitz@nasa.gov>
date Tue, 21 Apr 2015 00:34:15 -0700
parents 61d41facf527
children
comparison
equal deleted inserted replaced
23:db918c531e6d 24:6774e2e08d37
27 */ 27 */
28 public class ClinitTest extends TestJPF { 28 public class ClinitTest extends TestJPF {
29 29
30 static class X { 30 static class X {
31 static int x; 31 static int x;
32
32 static { 33 static {
33 Verify.threadPrintln("initializing X"); 34 Verify.threadPrintln("initializing X");
34 assertTrue( x == 0); 35 assertTrue(x == 0);
35 x++; 36 x++;
36 } 37 }
37 } 38 }
38 39
39 @Test 40 @Test
40 public void testNoConcurrentClinit () { 41 public void testNoConcurrentClinit() {
41 if (verifyNoPropertyViolation()) { 42 if (verifyNoPropertyViolation()) {
42 43
43 Runnable r = new Runnable() { 44 Runnable r = new Runnable() {
44 @Override 45 @Override
45 public void run() { 46 public void run() {
46 int x = X.x; 47 int x = X.x;
47 } 48 }
48 }; 49 };
49 Thread t = new Thread(r); 50 Thread t = new Thread(r);
50 t.start(); 51 t.start();
51 52
52 int x = X.x; 53 int x = X.x;
53 assertTrue( "x = " + x, x == 1); 54 assertTrue("x = " + x, x == 1);
54 } 55 }
55 } 56 }
56 57
57 58
58 static class Y { 59 static class Y {
59 static long y; 60 static long y;
60 61
61 static { 62 static {
62 Thread t = Thread.currentThread(); 63 Thread t = Thread.currentThread();
63 Verify.threadPrintln("initializing Y"); 64 Verify.threadPrintln("initializing Y");
64 y = t.getId(); 65 y = t.getId();
65 } 66 }
66 } 67 }
67 68
68 @Test 69 @Test
69 public void testClinitChoices() { 70 public void testClinitChoices() {
70 if (verifyAssertionErrorDetails("gotcha")) { 71 if (verifyAssertionErrorDetails("gotcha")) {
71 Runnable r = new Runnable() { 72 Runnable r = new Runnable() {
72 @Override 73 @Override
73 public void run() { 74 public void run() {
74 long y = Y.y; 75 long y = Y.y;
75 } 76 }
76 }; 77 };
77 Thread t = new Thread(r); 78 Thread t = new Thread(r);
78 t.start(); 79 t.start();
79 80
80 long y = Y.y; 81 long y = Y.y;
81 Thread tCur = Thread.currentThread(); 82 Thread tCur = Thread.currentThread();
82 Verify.threadPrintln("testing Y.y"); 83 Verify.threadPrintln("testing Y.y");
83 assertTrue( "gotcha", y == tCur.getId()); 84 assertTrue("gotcha", y == tCur.getId());
84 } 85 }
85 } 86 }
86 } 87 }