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:	1.5
Committed:	Tue Mar 15 19:47:05 2011 UTC (13 years, 1 month ago) by jsr166
Branch:	MAIN
CVS Tags:	release-1_7_0
Changes since 1.4:	+1 -1 lines
Log Message:	Update Creative Commons license URL in legal notices
#	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			}
55	dl	1.1
56			/**
57			* Read trylock succeeds if write locked by current thread
58			*/
59	jsr166	1.3	public void testReadHoldingWriteLock()throws Exception {
60	jsr166	1.4	final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
61			lock.writeLock().lock();
62	dl	1.1	assertTrue(lock.readLock().tryLock());
63			lock.readLock().unlock();
64			lock.writeLock().unlock();
65	jsr166	1.3	}
66	dl	1.1
67			/**
68			* Read lock succeeds if write locked by current thread even if
69			* other threads are waiting
70			*/
71	jsr166	1.3	public void testReadHoldingWriteLock2() throws Exception{
72	jsr166	1.4	final ReentrantReadWriteLock lock = new ReentrantReadWriteLock();
73			lock.writeLock().lock();
74			Thread t1 = new Thread(new Runnable() {
75	dl	1.1	public void run() {
76			lock.readLock().lock();
77			lock.readLock().unlock();
78	jsr166	1.4	}
79			});
80			Thread t2 = new Thread(new Runnable() {
81	dl	1.1	public void run() {
82			lock.readLock().lock();
83			lock.readLock().unlock();
84	jsr166	1.4	}
85			});
86	jsr166	1.3
87	dl	1.1	t1.start();
88			t2.start();
89			lock.readLock().lock();
90			lock.readLock().unlock();
91			Thread.sleep(SHORT_DELAY_MS);
92			lock.readLock().lock();
93			lock.readLock().unlock();
94			lock.writeLock().unlock();
95			t1.join(MEDIUM_DELAY_MS);
96			t2.join(MEDIUM_DELAY_MS);
97			assertTrue(!t1.isAlive());
98			assertTrue(!t2.isAlive());
99	jsr166	1.3	}
100	dl	1.1
101			/**
102			* Fair Read trylock succeeds if write locked by current thread
103			*/
104	jsr166	1.3	public void testReadHoldingWriteLockFair() throws Exception{
105	jsr166	1.4	final ReentrantReadWriteLock lock = new ReentrantReadWriteLock(true);
106			lock.writeLock().lock();
107	dl	1.1	assertTrue(lock.readLock().tryLock());
108			lock.readLock().unlock();
109			lock.writeLock().unlock();
110	jsr166	1.3	}
111	dl	1.1
112			/**
113			* Fair Read lock succeeds if write locked by current thread even if
114			* other threads are waiting
115			*/
116	jsr166	1.3	public void testReadHoldingWriteLockFair2() throws Exception {
117	jsr166	1.4	final ReentrantReadWriteLock lock = new ReentrantReadWriteLock(true);
118			lock.writeLock().lock();
119			Thread t1 = new Thread(new Runnable() {
120	dl	1.1	public void run() {
121			lock.readLock().lock();
122			lock.readLock().unlock();
123	jsr166	1.4	}
124			});
125			Thread t2 = new Thread(new Runnable() {
126	dl	1.1	public void run() {
127			lock.readLock().lock();
128			lock.readLock().unlock();
129	jsr166	1.4	}
130			});
131	dl	1.1
132			t1.start();
133			t2.start();
134			lock.readLock().lock();
135			lock.readLock().unlock();
136			Thread.sleep(SHORT_DELAY_MS);
137			lock.readLock().lock();
138			lock.readLock().unlock();
139			lock.writeLock().unlock();
140			t1.join(MEDIUM_DELAY_MS);
141			t2.join(MEDIUM_DELAY_MS);
142			assertTrue(!t1.isAlive());
143			assertTrue(!t2.isAlive());
144
145	jsr166	1.3
146			}
147	dl	1.1	}