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1 package com.quadcap.sql.lock;
2
3
40
41 import com.quadcap.util.collections.ArrayQueue;
42
43 import com.quadcap.util.Debug;
44
45
50 public class Lock implements Comparable  {
51 static Lock tombstone = new Lock();
52
53 String name;
54 final int[] heldCount = new int[LockMode.MAX];
55 int refCount = 0;
56 private Lock parent = null;
57 ArrayQueue waitQueue = null;
58 Object sync = new Object ();
59
60
63 protected Lock() {}
64
65
68 public void init(Lock parent, String name) {
69 this.parent = parent;
70 this.name = name;
71 }
72
73
76 final String getName() { return name; }
77
78 final int getHeldCount(int mode) {
79 return heldCount[mode];
80 }
81
82 final int incrHeldCount(int mode) {
83 return ++heldCount[mode];
84 }
85 final int decrHeldCount(int mode) {
86 return --heldCount[mode];
87 }
88
89 final int getHeldCount() {
90 int sum = 0;
91 for (int i = 0; i < LockMode.MAX; i++) sum += heldCount[i];
92 return sum;
93 }
94
95 final void addWaitQueue(Transaction t) {
96 synchronized (sync) {
97 if (waitQueue == null) waitQueue = new ArrayQueue(2, -1);
98 waitQueue.addBack(t);
99 }
100 }
101
102 final boolean hasWaiters() {
103 synchronized (sync) {
104 return waitQueue == null ? false : waitQueue.size() > 0;
105 }
106 }
107
108 final Transaction popWaitQueue() {
109 Transaction ret = null;
110 synchronized (sync) {
111 if (waitQueue != null) ret = (Transaction)waitQueue.popFront();
112 }
113 return ret;
114 }
115
116 final Transaction headWaitQueue() {
117 Transaction ret = null;
118 synchronized (sync) {
119 if (waitQueue != null) ret = (Transaction)waitQueue.head();
120 }
121 return ret;
122 }
123
124 final boolean couldLock(int mode) {
125 switch (mode) {
126 case LockMode.S:
127 return (heldCount[LockMode.X] == 0 &&
128 heldCount[LockMode.IX] == 0 &&
129 heldCount[LockMode.SIX] == 0);
130 case LockMode.IS:
131 return heldCount[LockMode.X] == 0;
132 case LockMode.X:
133 return (heldCount[LockMode.X] == 0 &&
134 heldCount[LockMode.IX] == 0 &&
135 heldCount[LockMode.SIX] == 0 &&
136 heldCount[LockMode.IS] == 0 &&
137 heldCount[LockMode.S] == 0);
138 case LockMode.IX:
139 return (heldCount[LockMode.X] == 0 &&
140 heldCount[LockMode.S] == 0 &&
141 heldCount[LockMode.SIX] == 0);
142 case LockMode.SIX:
143 return (heldCount[LockMode.X] == 0 &&
144 heldCount[LockMode.S] == 0 &&
145 heldCount[LockMode.IX] == 0 &&
146 heldCount[LockMode.SIX] == 0);
147 default:
148 throw new RuntimeException ("Bad lock mode: " + mode);
149 }
150 }
151
152 final boolean couldPromote(int fromMode, int toMode) {
153 int savc = heldCount[fromMode];
154 heldCount[fromMode] = 0;
155 boolean could = couldLock(toMode);
156 heldCount[fromMode] = savc;
157 return could;
158 }
159
160 public int compareTo(Object obj) {
161 return name.compareTo(((Lock)obj).name);
162 }
163
164 public boolean equals(Object obj) {
165 return 0 == compareTo(obj);
166 }
167
168 public int hashCode() {
169 return name.hashCode();
170 }
171
172 public Lock getParent() { return parent; }
173
174 public String toString() {
176 return dump();
177 }
178
179 public String dump() {
180 StringBuffer sb = new StringBuffer ();
181 sb.append(name);
182 sb.append(": ");
183 for (int i = 0; i < LockMode.MAX; i++) {
184 if (heldCount[i] > 0) {
185 sb.append("{");
186 sb.append(LockMode.toString(i));
187 sb.append(",");
188 sb.append(Integer.toString(heldCount[i]));
189 sb.append("} ");
190 }
191 }
192 Transaction t = headWaitQueue();
193 if (t != null) {
194 sb.append("wait=T:");
195 sb.append(String.valueOf(t.getTransactionId()));
196 if (waitQueue.size() > 1) {
197 sb.append(" + ");
198 sb.append(waitQueue.size() - 1);
199 sb.append(" other");
200 if (waitQueue.size() > 2) sb.append('s');
201 }
202 }
203 return sb.toString();
204 }
205 }
207 |
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