94 lines
2.8 KiB
Java
94 lines
2.8 KiB
Java
import java.util.Map;
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public class Main {
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static public void main(String[] args) throws Exception {
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checkManager();
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// Warm up the reaper so that there are no issues with scheduling because of static
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// initialization.
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{
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ProcessBuilder pb = new ProcessBuilder("sleep", "0");
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Process proc = pb.start();
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proc.waitFor();
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waitForReaperTimedWaiting(true /* reaperMustExist */);
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}
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for (int i = 1; i <= 2; i++) {
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System.out.println("\nspawning child #" + i);
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child();
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Thread.sleep(2000);
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checkManager();
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}
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System.out.println("\ndone!");
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}
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static private void child() throws Exception {
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System.out.println("spawning child");
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ProcessBuilder pb = new ProcessBuilder("sleep", "5");
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Process proc = pb.start();
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Thread.sleep(250);
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checkManager();
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proc.waitFor();
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System.out.println("child died");
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}
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private static boolean isReaperThread(Thread t) {
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String name = t.getName();
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return name.indexOf("process reaper") >= 0;
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}
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static private void checkManager() {
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Map<Thread, StackTraceElement[]> traces = Thread.getAllStackTraces();
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boolean found = false;
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for (Map.Entry<Thread, StackTraceElement[]> entry :
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traces.entrySet()) {
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Thread t = entry.getKey();
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if (isReaperThread(t)) {
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Thread.State state = t.getState();
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System.out.println("process manager: " + state);
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if (state != Thread.State.RUNNABLE && state != Thread.State.TIMED_WAITING) {
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for (StackTraceElement e : entry.getValue()) {
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System.out.println(" " + e);
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}
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}
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found = true;
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}
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}
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if (! found) {
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System.out.println("process manager: nonexistent");
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}
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}
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private static void waitForReaperTimedWaiting(boolean reaperMustExist) {
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for (;;) {
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Map<Thread, StackTraceElement[]> traces = Thread.getAllStackTraces();
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boolean ok = true;
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boolean found = false;
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for (Thread t : traces.keySet()) {
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if (isReaperThread(t)) {
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found = true;
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Thread.State state = t.getState();
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if (state != Thread.State.TIMED_WAITING) {
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ok = false;
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break;
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}
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}
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}
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if (ok && (!reaperMustExist || found)) {
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return;
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}
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try {
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Thread.sleep(100);
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} catch (Exception e) {
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// Ignore.
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}
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}
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}
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}
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