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1
4 package com.tc.objectserver.lockmanager.impl;
5
6 import com.tc.objectserver.lockmanager.api.DeadlockResults;
7
8 import java.util.ArrayList  ;
9 import java.util.Collection ;
10 import java.util.HashSet ;
11 import java.util.Iterator ;
12 import java.util.List ;
13 import java.util.Set ;
14
15 class DeadlockDetector {
16 private static final ServerThreadContext[] EMPTY_TXN_ARRAY = new ServerThreadContext[] {};
17
18 private final DeadlockResults listener;
19 private final Set inDeadlock = new HashSet ();
20
21 DeadlockDetector(DeadlockResults listener) {
22 this.listener = listener;
23 }
24
25 void detect(Iterator openTransactions) {
26 while (openTransactions.hasNext()) {
27 ServerThreadContext txn = (ServerThreadContext) openTransactions.next();
28 txn.setCycle(null);
30 if (!inDeadlock.contains(txn)) {
31 visit(txn);
32 }
33 }
34 }
35
36 private void visit(final ServerThreadContext me) {
37 if (!me.isWaiting()) return;
38
39 final Lock waitingOn = me.getWaitingOn();
40 final Collection holders = waitingOn.getHoldersCollection();
41
42 for (final Iterator iter = holders.iterator(); iter.hasNext();) {
43 Holder holder = (Holder) iter.next();
44 ServerThreadContext them = holder.getThreadContext();
45
46 if (!them.equals(me)) {
47 if (them.isWaiting()) {
48 me.setCycle(them);
49 if (them.getCycle() != null) {
50 handleDeadlock(me, them);
51 } else {
52 visit(them);
53 }
54 me.setCycle(null);
55 }
56 }
57 }
58 }
59
60 private void handleDeadlock(ServerThreadContext me, ServerThreadContext them) {
61 List txnList = getTransactionsInCycle(me, them);
62 inDeadlock.addAll(txnList);
63
64 DeadlockChainImpl head = null;
65 DeadlockChainImpl link = null;
66
67 ServerThreadContext[] txnArray = (ServerThreadContext[]) txnList.toArray(EMPTY_TXN_ARRAY);
68 for (int i = 0, n = txnArray.length; i < n; i++) {
69 ServerThreadContext txn = txnArray[i];
70 DeadlockChainImpl tmp = new DeadlockChainImpl(txn.getId(), txn.getWaitingOn().getLockID());
71
72 if (head == null) {
73 head = tmp;
74 }
75
76 if (link != null) {
77 link.setNextLink(tmp);
78 }
79
80 link = tmp;
81 }
82
83 link.setNextLink(head);
84
85 listener.foundDeadlock(head);
86 }
87
88 private static List getTransactionsInCycle(ServerThreadContext me, ServerThreadContext them) {
89 List txns = new ArrayList ();
90 txns.add(me);
91
92 do {
93 txns.add(them);
94 them = them.getCycle();
95 } while (!them.equals(me));
96
97 return txns;
98 }
99 }
100 |
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