Java多執行緒（十二）：中斷機制
阿新 • • 發佈：2019-09-06
這裡詳細分析interrupt(),interrupted(),isInterrupted()三個方法
interrupt()
中斷這個執行緒，設定中斷標識位
public void interrupt() { if (this != Thread.currentThread()) checkAccess(); synchronized (blockerLock) { Interruptible b = blocker; if (b != null) { interrupt0(); // Just to set the interrupt flag b.interrupt(this); return; } } interrupt0(); }
我們來找下如何設定中斷標識位的
找到interrupt0()的原始碼，src/hotspot/share/prims/jvm.cpp
JVM_ENTRY(void, JVM_Interrupt(JNIEnv* env, jobject jthread))
...
if (is_alive) {
// jthread refers to a live JavaThread.
Thread::interrupt(receiver);
}
JVM_END呼叫了Thread::interrupt方法
src/hotspot/share/runtime/thread.cpp
void Thread::interrupt(Thread* thread) { ... os::interrupt(thread); }
os::interrupt方法，src/hotspot/os/posix/os_posix.cpp
void os::interrupt(Thread* thread) {
...
OSThread* osthread = thread->osthread();
if (!osthread->interrupted()) {
//設定中斷標識位
osthread->set_interrupted(true);
...
}
...
}isInterrupted()
測試執行緒是否被中斷，執行緒的中斷狀態不會改變
public boolean isInterrupted() { return isInterrupted(false); }
檢視native isInterrupted(boolean ClearInterrupted)原始碼，查詢方式同上
src/hotspot/os/posix/os_posix.cpp
bool os::is_interrupted(Thread* thread, bool clear_interrupted) {
debug_only(Thread::check_for_dangling_thread_pointer(thread);)
OSThread* osthread = thread->osthread();
// 檢視是否被中斷
bool interrupted = osthread->interrupted();
// 清除標識位後再設定false
if (interrupted && clear_interrupted) {
osthread->set_interrupted(false);
}
return interrupted;
}Java傳遞ClearInterrupted為false，對應C++的clear_interrupted
interrupted()
測試執行緒是否被中斷，清除中斷標識位
public static boolean interrupted() {
return currentThread().isInterrupted(true);
}簡單的例子
public class MyThread45 {
public static void main(String[] args) throws Exception
{
Runnable runnable = new Runnable()
{
public void run()
{
while (true)
{
if (Thread.currentThread().isInterrupted())
{
System.out.println("執行緒被中斷了");
return ;
}
else
{
System.out.println("執行緒沒有被中斷");
}
}
}
};
Thread t = new Thread(runnable);
t.start();
Thread.sleep(500);
t.interrupt();
System.out.println("執行緒中斷了，程式到這裡了");
}
}檢查執行緒是否中斷，中斷執行緒，執行結果如下
······
執行緒沒有被中斷
執行緒沒有被中斷
執行緒沒有被中斷
執行緒被中斷了
執行緒中斷了，程式到這裡了