test/loops/ReadHoldingWriteLock.java

/*
 * Written by Doug Lea with assistance from members of JCP JSR-166
 * Expert Group and released to the public domain, as explained at
 * http://creativecommons.org/publicdomain/zero/1.0/
 */
import java.util.concurrent.locks.*;

class ReadHoldingWriteLock {

    public static void main(String[] args) throws Exception {
        ReadHoldingWriteLock t = new ReadHoldingWriteLock();
        t.testReadAfterWriteLock();
        t.testReadHoldingWriteLock();
        t.testReadHoldingWriteLock2();
        t.testReadHoldingWriteLockFair();
        t.testReadHoldingWriteLockFair2();
    }

    static final long SHORT_DELAY_MS = 50;
    static final long MEDIUM_DELAY_MS = 200;

    void assertTrue(boolean b) {
        if (!b) throw new Error();
    }

    /**
     * Readlocks succeed after a writing thread unlocks
     */
    public void testReadAfterWriteLock() throws Exception {
        final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
        lock.writeLock().lock();
        Thread t1 = new Thread(new Runnable() {
                public void run() {
                    lock.readLock().lock();
                    lock.readLock().unlock();
                }
            });
        Thread t2 = new Thread(new Runnable() {
                public void run() {
                    lock.readLock().lock();
                    lock.readLock().unlock();
                }
            });

        t1.start();
        t2.start();
        Thread.sleep(SHORT_DELAY_MS);
        lock.writeLock().unlock();
        t1.join(MEDIUM_DELAY_MS);
        t2.join(MEDIUM_DELAY_MS);
        assertTrue(!t1.isAlive());
        assertTrue(!t2.isAlive());
    }

    /**
     * Read trylock succeeds if write locked by current thread
     */
    public void testReadHoldingWriteLock()throws Exception {
        final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
        lock.writeLock().lock();
        assertTrue(lock.readLock().tryLock());
        lock.readLock().unlock();
        lock.writeLock().unlock();
    }

    /**
     * Read lock succeeds if write locked by current thread even if
     * other threads are waiting
     */
    public void testReadHoldingWriteLock2() throws Exception {
        final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
        lock.writeLock().lock();
        Thread t1 = new Thread(new Runnable() {
                public void run() {
                    lock.readLock().lock();
                    lock.readLock().unlock();
                }
            });
        Thread t2 = new Thread(new Runnable() {
                public void run() {
                    lock.readLock().lock();
                    lock.readLock().unlock();
                }
            });

        t1.start();
        t2.start();
        lock.readLock().lock();
        lock.readLock().unlock();
        Thread.sleep(SHORT_DELAY_MS);
        lock.readLock().lock();
        lock.readLock().unlock();
        lock.writeLock().unlock();
        t1.join(MEDIUM_DELAY_MS);
        t2.join(MEDIUM_DELAY_MS);
        assertTrue(!t1.isAlive());
        assertTrue(!t2.isAlive());
    }

    /**
     * Fair Read trylock succeeds if write locked by current thread
     */
    public void testReadHoldingWriteLockFair() throws Exception {
        final ReentrantReadWriteLock lock = new ReentrantReadWriteLock(true);
        lock.writeLock().lock();
        assertTrue(lock.readLock().tryLock());
        lock.readLock().unlock();
        lock.writeLock().unlock();
    }

    /**
     * Fair Read lock succeeds if write locked by current thread even if
     * other threads are waiting
     */
    public void testReadHoldingWriteLockFair2() throws Exception {
        final ReentrantReadWriteLock lock = new ReentrantReadWriteLock(true);
        lock.writeLock().lock();
        Thread t1 = new Thread(new Runnable() {
                public void run() {
                    lock.readLock().lock();
                    lock.readLock().unlock();
                }
            });
        Thread t2 = new Thread(new Runnable() {
                public void run() {
                    lock.readLock().lock();
                    lock.readLock().unlock();
                }
            });

        t1.start();
        t2.start();
        lock.readLock().lock();
        lock.readLock().unlock();
        Thread.sleep(SHORT_DELAY_MS);
        lock.readLock().lock();
        lock.readLock().unlock();
        lock.writeLock().unlock();
        t1.join(MEDIUM_DELAY_MS);
        t2.join(MEDIUM_DELAY_MS);
        assertTrue(!t1.isAlive());
        assertTrue(!t2.isAlive());
    }
}
Revision:	1.8
Committed:	Mon Aug 10 03:13:33 2015 UTC (8 years, 8 months ago) by jsr166
Branch:	MAIN
CVS Tags:	HEAD
Changes since 1.7:	+0 -1 lines
Log Message:	delete unwanted blank lines
#	User	Rev	Content
1	dl	1.2	/*
2			* Written by Doug Lea with assistance from members of JCP JSR-166
3			* Expert Group and released to the public domain, as explained at
4	jsr166	1.5	* http://creativecommons.org/publicdomain/zero/1.0/
5	dl	1.2	*/
6	dl	1.1	import java.util.concurrent.locks.*;
7
8			class ReadHoldingWriteLock {
9
10			public static void main(String[] args) throws Exception {
11			ReadHoldingWriteLock t = new ReadHoldingWriteLock();
12			t.testReadAfterWriteLock();
13			t.testReadHoldingWriteLock();
14			t.testReadHoldingWriteLock2();
15			t.testReadHoldingWriteLockFair();
16			t.testReadHoldingWriteLockFair2();
17			}
18
19			static final long SHORT_DELAY_MS = 50;
20			static final long MEDIUM_DELAY_MS = 200;
21
22			void assertTrue(boolean b) {
23			if (!b) throw new Error();
24			}
25
26			/**
27			* Readlocks succeed after a writing thread unlocks
28			*/
29	jsr166	1.3	public void testReadAfterWriteLock() throws Exception {
30	jsr166	1.4	final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
31			lock.writeLock().lock();
32			Thread t1 = new Thread(new Runnable() {
33	dl	1.1	public void run() {
34			lock.readLock().lock();
35			lock.readLock().unlock();
36	jsr166	1.4	}
37			});
38			Thread t2 = new Thread(new Runnable() {
39	dl	1.1	public void run() {
40			lock.readLock().lock();
41			lock.readLock().unlock();
42	jsr166	1.4	}
43			});
44	dl	1.1
45			t1.start();
46			t2.start();
47			Thread.sleep(SHORT_DELAY_MS);
48			lock.writeLock().unlock();
49			t1.join(MEDIUM_DELAY_MS);
50			t2.join(MEDIUM_DELAY_MS);
51			assertTrue(!t1.isAlive());
52			assertTrue(!t2.isAlive());
53	jsr166	1.3	}
54	dl	1.1
55			/**
56			* Read trylock succeeds if write locked by current thread
57			*/
58	jsr166	1.3	public void testReadHoldingWriteLock()throws Exception {
59	jsr166	1.4	final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
60			lock.writeLock().lock();
61	dl	1.1	assertTrue(lock.readLock().tryLock());
62			lock.readLock().unlock();
63			lock.writeLock().unlock();
64	jsr166	1.3	}
65	dl	1.1
66			/**
67			* Read lock succeeds if write locked by current thread even if
68			* other threads are waiting
69			*/
70	jsr166	1.6	public void testReadHoldingWriteLock2() throws Exception {
71	jsr166	1.4	final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
72			lock.writeLock().lock();
73			Thread t1 = new Thread(new Runnable() {
74	dl	1.1	public void run() {
75			lock.readLock().lock();
76			lock.readLock().unlock();
77	jsr166	1.4	}
78			});
79			Thread t2 = new Thread(new Runnable() {
80	dl	1.1	public void run() {
81			lock.readLock().lock();
82			lock.readLock().unlock();
83	jsr166	1.4	}
84			});
85	jsr166	1.3
86	dl	1.1	t1.start();
87			t2.start();
88			lock.readLock().lock();
89			lock.readLock().unlock();
90			Thread.sleep(SHORT_DELAY_MS);
91			lock.readLock().lock();
92			lock.readLock().unlock();
93			lock.writeLock().unlock();
94			t1.join(MEDIUM_DELAY_MS);
95			t2.join(MEDIUM_DELAY_MS);
96			assertTrue(!t1.isAlive());
97			assertTrue(!t2.isAlive());
98	jsr166	1.3	}
99	dl	1.1
100			/**
101			* Fair Read trylock succeeds if write locked by current thread
102			*/
103	jsr166	1.6	public void testReadHoldingWriteLockFair() throws Exception {
104	jsr166	1.4	final ReentrantReadWriteLock lock = new ReentrantReadWriteLock(true);
105			lock.writeLock().lock();
106	dl	1.1	assertTrue(lock.readLock().tryLock());
107			lock.readLock().unlock();
108			lock.writeLock().unlock();
109	jsr166	1.3	}
110	dl	1.1
111			/**
112			* Fair Read lock succeeds if write locked by current thread even if
113			* other threads are waiting
114			*/
115	jsr166	1.3	public void testReadHoldingWriteLockFair2() throws Exception {
116	jsr166	1.4	final ReentrantReadWriteLock lock = new ReentrantReadWriteLock(true);
117			lock.writeLock().lock();
118			Thread t1 = new Thread(new Runnable() {
119	dl	1.1	public void run() {
120			lock.readLock().lock();
121			lock.readLock().unlock();
122	jsr166	1.4	}
123			});
124			Thread t2 = new Thread(new Runnable() {
125	dl	1.1	public void run() {
126			lock.readLock().lock();
127			lock.readLock().unlock();
128	jsr166	1.4	}
129			});
130	dl	1.1
131			t1.start();
132			t2.start();
133			lock.readLock().lock();
134			lock.readLock().unlock();
135			Thread.sleep(SHORT_DELAY_MS);
136			lock.readLock().lock();
137			lock.readLock().unlock();
138			lock.writeLock().unlock();
139			t1.join(MEDIUM_DELAY_MS);
140			t2.join(MEDIUM_DELAY_MS);
141			assertTrue(!t1.isAlive());
142			assertTrue(!t2.isAlive());
143	jsr166	1.3	}
144	dl	1.1	}