並行処理プログラミングの深淵~Java仮想マシン仕様スレッドとロック~

stopRequested

Java HotSpot

while(!stopRequested){ if(!stopRequested){
i++; while(true){
} i++;
}
}

Java

synchronized

volatile

synchronized

synchronized

synchronized

private ﬁnal Object lock = new Object();
private List<String> list;

public void add(String text){
synchronized (lock){
listadd(text);
}
}


listadd(text); lock
}
}


public String get(int index){
return list.get(index);
}
}


return list.get(index); list
}
}


list.add(text);
}
}

}


list.add(text);
list
}
}
IllegalArgumentException

}

1
2
3
Java

null ( )

3

V T A

P

V T
B
Q

3

(1)P Q
P
(2)Q
(3)Q
(4)P


private String get(int index){
}
}


private String get(int index){
return list.get(index); list
}
}

volatile 1

V T V
T

V T V
T

volatile 2

V T V
T

V T V
T

volatile 3

volatile (reordering)

private int num = 0;
private volatile boolean initialized;

public void run(){
num = 100;
initialized = true;
}

volatile 3

volatile (reordering)

private int num = 0;
private volatile boolean initialized;

public void run(){
num = 100; num
initialized = true;
}

並行処理プログラミングの深淵~Java仮想マシン仕様スレッドとロック~

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