活锁的好例子？
我理解livelock是什么，但我想知道是否有人有一个很好的基于代码的例子呢？而基于代码的，我并不是说“两个人试图在走廊里相互过去”。如果我再读一遍，我会失去午餐。
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誓猎贰
public class Livelock { static class Spoon { private Diner owner; public Spoon(Diner d) { owner = d; } public Diner getOwner() { return owner; } public synchronized void setOwner(Diner d) { owner = d; } public synchronized void use() { System.out.printf("%s has eaten!", owner.name); } } static class Diner { private String name; private boolean isHungry; public Diner(String n) { name = n; isHungry = true; } public String getName() { return name; } public boolean isHungry() { return isHungry; } public void eatWith(Spoon spoon, Diner spouse) { while (isHungry) { // Don't have the spoon, so wait patiently for spouse. if (spoon.owner != this) { try { Thread.sleep(1); } catch(InterruptedException e) { continue; } continue; } // If spouse is hungry, insist upon passing the spoon. if (spouse.isHungry()) { System.out.printf( "%s: You eat first my darling %s!%n", name, spouse.getName()); spoon.setOwner(spouse); continue; } // Spouse wasn't hungry, so finally eat spoon.use(); isHungry = false; System.out.printf( "%s: I am stuffed, my darling %s!%n", name, spouse.getName()); spoon.setOwner(spouse); } } } public static void main(String[] args) { final Diner husband = new Diner("Bob"); final Diner wife = new Diner("Alice"); final Spoon s = new Spoon(husband); new Thread(new Runnable() { public void run() { husband.eatWith(s, wife); } }).start(); new Thread(new Runnable() { public void run() { wife.eatWith(s, husband); } }).start(); } }抢垢洛韧
// thread 1 getLocks12(lock1, lock2) { lock1.lock(); while (lock2.locked()) { // attempt to step aside for the other thread lock1.unlock(); wait(); lock1.lock(); } lock2.lock(); } // thread 2 getLocks21(lock1, lock2) { lock2.lock(); while (lock1.locked()) { // attempt to step aside for the other thread lock2.unlock(); wait(); lock2.lock(); } lock1.lock(); }吞睫素
private Integer getMaterial(final Ingredient ingredient) throws Exception{ : container.lock(); while (!container.getIngredient(quantity)) { container.empty.await(1000, TimeUnit.MILLISECONDS); //Thread.sleep(500); //For deadlock } container.unlock(); : }public boolean getIngredient(int n) throws Exception { : lock(); if (quantityHeld >= n) { TimeUnit.SECONDS.sleep(2); quantityHeld -= n; unlock(); return true; } unlock(); return false; }你会注意到子线程并改变它们的状态并等待。羔磺
峨躬坎抬焚
using System; using System.Runtime.CompilerServices; using System.Threading; using System.Threading.Tasks; namespace LiveLockExample { static class Program { public static void Main(string[] args) { var husband = new Diner("Bob"); var wife = new Diner("Alice"); var s = new Spoon(husband); Task.WaitAll( Task.Run(() => husband.EatWith(s, wife)), Task.Run(() => wife.EatWith(s, husband)) ); } public class Spoon { public Spoon(Diner diner) { Owner = diner; } public Diner Owner { get; private set; } [MethodImpl(MethodImplOptions.Synchronized)] public void SetOwner(Diner d) { Owner = d; } [MethodImpl(MethodImplOptions.Synchronized)] public void Use() { Console.WriteLine("{0} has eaten!", Owner.Name); } } public class Diner { public Diner(string n) { Name = n; IsHungry = true; } public string Name { get; private set; } private bool IsHungry { get; set; } public void EatWith(Spoon spoon, Diner spouse) { while (IsHungry) { // Don't have the spoon, so wait patiently for spouse. if (spoon.Owner != this) { try { Thread.Sleep(1); } catch (ThreadInterruptedException e) { } continue; } // If spouse is hungry, insist upon passing the spoon. if (spouse.IsHungry) { Console.WriteLine("{0}: You eat first my darling {1}!", Name, spouse.Name); spoon.SetOwner(spouse); continue; } // Spouse wasn't hungry, so finally eat spoon.Use(); IsHungry = false; Console.WriteLine("{0}: I am stuffed, my darling {1}!", Name, spouse.Name); spoon.SetOwner(spouse); } } } } }屠创氓读叔
boolean tryLockAll(Collection<Lock> locks) { boolean grabbedAllLocks = false; for(int i=0; i<locks.size(); i++) { Lock lock = locks.get(i); if(!lock.tryLock(5, TimeUnit.SECONDS)) { grabbedAllLocks = false; // undo the locks I already took in reverse order for(int j=i-1; j >= 0; j--) { lock.unlock(); } } } }曝匿弄罚
public class LiveLock { public static void main(String[] args) throws InterruptedException { Object left = new Object(); Object right = new Object(); Pedestrian one = new Pedestrian(left, right, 0); //one's left is one's left Pedestrian two = new Pedestrian(right, left, 1); //one's left is two's right, so have to swap order one.setOther(two); two.setOther(one); one.start(); two.start(); } } class Pedestrian extends Thread { private Object l; private Object r; private Pedestrian other; private Object current; Pedestrian (Object left, Object right, int firstDirection) { l = left; r = right; if (firstDirection==0) { current = l; } else { current = r; } } void setOther(Pedestrian otherP) { other = otherP; } Object getDirection() { return current; } Object getOppositeDirection() { if (current.equals(l)) { return r; } else { return l; } } void switchDirection() throws InterruptedException { Thread.sleep(100); current = getOppositeDirection(); System.out.println(Thread.currentThread().getName() + " is stepping aside."); } public void run() { while (getDirection().equals(other.getDirection())) { try { switchDirection(); Thread.sleep(100); } catch (InterruptedException e) {} } } }磐乓铝举
import threading import time lock = threading.Lock() class Spoon: def __init__(self, diner): self.owner = diner def setOwner(self, diner): with lock: self.owner = diner def use(self): with lock: "{0} has eaten".format(self.owner) class Diner: def __init__(self, name): self.name = name self.hungry = True def eatsWith(self, spoon, spouse): while(self.hungry): if self != spoon.owner: time.sleep(1) # blocks thread, not process continue if spouse.hungry: print "{0}: you eat first, {1}".format(self.name, spouse.name) spoon.setOwner(spouse) continue # Spouse was not hungry, eat spoon.use() print "{0}: I'm stuffed, {1}".format(self.name, spouse.name) spoon.setOwner(spouse) def main(): husband = Diner("Bob") wife = Diner("Alice") spoon = Spoon(husband) t0 = threading.Thread(target=husband.eatsWith, args=(spoon, wife)) t1 = threading.Thread(target=wife.eatsWith, args=(spoon, husband)) t0.start() t1.start() t0.join() t1.join() if __name__ == "__main__": main()梦砍废么
public class LiveLock { static class Spoon { Diner owner; public String getOwnerName() { return owner.getName(); } public void setOwner(Diner diner) { this.owner = diner; } public Spoon(Diner diner) { this.owner = diner; } public void use() { System.out.println(owner.getName() + " use this spoon and finish eat."); } } static class Diner { public Diner(boolean isHungry, String name) { this.isHungry = isHungry; this.name = name; } private boolean isHungry; private String name; public String getName() { return name; } public void eatWith(Diner spouse, Spoon sharedSpoon) { try { synchronized (sharedSpoon) { while (isHungry) { while (!sharedSpoon.getOwnerName().equals(name)) { sharedSpoon.wait(); //System.out.println("sharedSpoon belongs to" + sharedSpoon.getOwnerName()) } if (spouse.isHungry) { System.out.println(spouse.getName() + "is hungry,I should give it to him(her)."); sharedSpoon.setOwner(spouse); sharedSpoon.notifyAll(); } else { sharedSpoon.use(); sharedSpoon.setOwner(spouse); isHungry = false; } Thread.sleep(500); } } } catch (InterruptedException e) { System.out.println(name + " is interrupted."); } } } public static void main(String[] args) { final Diner husband = new Diner(true, "husband"); final Diner wife = new Diner(true, "wife"); final Spoon sharedSpoon = new Spoon(wife); Thread h = new Thread() { @Override public void run() { husband.eatWith(wife, sharedSpoon); } }; h.start(); Thread w = new Thread() { @Override public void run() { wife.eatWith(husband, sharedSpoon); } }; w.start(); try { Thread.sleep(10000); } catch (InterruptedException e) { e.printStackTrace(); } h.interrupt(); w.interrupt(); try { h.join(); w.join(); } catch (InterruptedException e) { e.printStackTrace(); } } }街茬
package concurrently.deadlock; import static java.lang.System.out; /* This is an example of livelock */ public class Dinner { public static void main(String[] args) { Spoon spoon = new Spoon(); Dish dish = new Dish(); new Thread(new Husband(spoon, dish)).start(); new Thread(new Wife(spoon, dish)).start(); } } class Spoon { boolean isLocked; } class Dish { boolean isLocked; } class Husband implements Runnable { Spoon spoon; Dish dish; Husband(Spoon spoon, Dish dish) { this.spoon = spoon; this.dish = dish; } @Override public void run() { while (true) { synchronized (spoon) { spoon.isLocked = true; out.println("husband get spoon"); try { Thread.sleep(2000); } catch (InterruptedException e) {} if (dish.isLocked == true) { spoon.isLocked = false; // give away spoon out.println("husband pass away spoon"); continue; } synchronized (dish) { dish.isLocked = true; out.println("Husband is eating!"); } dish.isLocked = false; } spoon.isLocked = false; } } } class Wife implements Runnable { Spoon spoon; Dish dish; Wife(Spoon spoon, Dish dish) { this.spoon = spoon; this.dish = dish; } @Override public void run() { while (true) { synchronized (dish) { dish.isLocked = true; out.println("wife get dish"); try { Thread.sleep(2000); } catch (InterruptedException e) {} if (spoon.isLocked == true) { dish.isLocked = false; // give away dish out.println("wife pass away dish"); continue; } synchronized (spoon) { spoon.isLocked = true; out.println("Wife is eating!"); } spoon.isLocked = false; } dish.isLocked = false; } } }