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* Copyright (c) 1995, 2013, Oracle and/or its affiliates. All rights reserved.
* ORACLE PROPRIETARY/CONFIDENTIAL. Use is subject to license terms.
*
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*/
package java.lang;
import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.ByteArrayInputStream;
import java.io.FileDescriptor;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.util.Arrays;
import java.util.concurrent.Executors;
import java.util.concurrent.Executor;
import java.util.concurrent.ThreadFactory;
import java.util.concurrent.TimeUnit;
import java.security.AccessController;
import static java.security.AccessController.doPrivileged;
import java.security.PrivilegedAction;
import java.security.PrivilegedActionException;
import java.security.PrivilegedExceptionAction;
/**
* java.lang.Process subclass in the UNIX environment.
*
* @author Mario Wolczko and Ross Knippel.
* @author Konstantin Kladko (ported to Linux)
* @author Martin Buchholz
*/
final class UNIXProcess extends Process {
private static final sun.misc.JavaIOFileDescriptorAccess fdAccess
= sun.misc.SharedSecrets.getJavaIOFileDescriptorAccess();
private final int pid;
private int exitcode;
private boolean hasExited;
private /* final */ OutputStream stdin;
private /* final */ InputStream stdout;
private /* final */ InputStream stderr;
private static enum LaunchMechanism {
FORK(1),
VFORK(3);
private int value;
LaunchMechanism(int x) {value = x;}
};
/* default is VFORK on Linux */
private static final LaunchMechanism launchMechanism;
private static byte[] helperpath;
private static byte[] toCString(String s) {
if (s == null)
return null;
byte[] bytes = s.getBytes();
byte[] result = new byte[bytes.length + 1];
System.arraycopy(bytes, 0,
result, 0,
bytes.length);
result[result.length-1] = (byte)0;
return result;
}
static {
launchMechanism = AccessController.doPrivileged(
new PrivilegedAction<LaunchMechanism>()
{
public LaunchMechanism run() {
String javahome = System.getProperty("java.home");
String osArch = System.getProperty("os.arch");
helperpath = toCString(javahome + "/lib/" + osArch + "/jspawnhelper");
String s = System.getProperty(
"jdk.lang.Process.launchMechanism", "vfork");
try {
return LaunchMechanism.valueOf(s.toUpperCase());
} catch (IllegalArgumentException e) {
throw new Error(s + " is not a supported " +
"process launch mechanism on this platform.");
}
}
});
}
/* this is for the reaping thread */
private native int waitForProcessExit(int pid);
/**
* Create a process. Depending on the mode flag, this is done by
* one of the following mechanisms.
* - fork(2) and exec(2)
* - clone(2) and exec(2)
* - vfork(2) and exec(2)
*
* @param fds an array of three file descriptors.
* Indexes 0, 1, and 2 correspond to standard input,
* standard output and standard error, respectively. On
* input, a value of -1 means to create a pipe to connect
* child and parent processes. On output, a value which
* is not -1 is the parent pipe fd corresponding to the
* pipe which has been created. An element of this array
* is -1 on input if and only if it is <em>not</em> -1 on
* output.
* @return the pid of the subprocess
*/
private native int forkAndExec(int mode, byte[] helperpath,
byte[] prog,
byte[] argBlock, int argc,
byte[] envBlock, int envc,
byte[] dir,
int[] fds,
boolean redirectErrorStream)
throws IOException;
/**
* The thread factory used to create "process reaper" daemon threads.
*/
private static class ProcessReaperThreadFactory implements ThreadFactory {
private final static ThreadGroup group = getRootThreadGroup();
private static ThreadGroup getRootThreadGroup() {
return doPrivileged(new PrivilegedAction<ThreadGroup> () {
public ThreadGroup run() {
ThreadGroup root = Thread.currentThread().getThreadGroup();
while (root.getParent() != null)
root = root.getParent();
return root;
}});
}
public Thread newThread(Runnable grimReaper) {
// Our thread stack requirement is quite modest.
Thread t = new Thread(group, grimReaper, "process reaper", 32768);
t.setDaemon(true);
// A small attempt (probably futile) to avoid priority inversion
t.setPriority(Thread.MAX_PRIORITY);
return t;
}
}
/**
* The thread pool of "process reaper" daemon threads.
*/
private static final Executor processReaperExecutor =
doPrivileged(new PrivilegedAction<Executor>() {
public Executor run() {
return Executors.newCachedThreadPool
(new ProcessReaperThreadFactory());
}});
UNIXProcess(final byte[] prog,
final byte[] argBlock, final int argc,
final byte[] envBlock, final int envc,
final byte[] dir,
final int[] fds,
final boolean redirectErrorStream)
throws IOException {
pid = forkAndExec(launchMechanism.value,
helperpath,
prog,
argBlock, argc,
envBlock, envc,
dir,
fds,
redirectErrorStream);
try {
doPrivileged(new PrivilegedExceptionAction<Void>() {
public Void run() throws IOException {
initStreams(fds);
return null;
}});
} catch (PrivilegedActionException ex) {
throw (IOException) ex.getException();
}
}
static FileDescriptor newFileDescriptor(int fd) {
FileDescriptor fileDescriptor = new FileDescriptor();
fdAccess.set(fileDescriptor, fd);
return fileDescriptor;
}
void initStreams(int[] fds) throws IOException {
stdin = (fds[0] == -1) ?
ProcessBuilder.NullOutputStream.INSTANCE :
new ProcessPipeOutputStream(fds[0]);
stdout = (fds[1] == -1) ?
ProcessBuilder.NullInputStream.INSTANCE :
new ProcessPipeInputStream(fds[1]);
stderr = (fds[2] == -1) ?
ProcessBuilder.NullInputStream.INSTANCE :
new ProcessPipeInputStream(fds[2]);
processReaperExecutor.execute(new Runnable() {
public void run() {
int exitcode = waitForProcessExit(pid);
UNIXProcess.this.processExited(exitcode);
}});
}
void processExited(int exitcode) {
synchronized (this) {
this.exitcode = exitcode;
hasExited = true;
notifyAll();
}
if (stdout instanceof ProcessPipeInputStream)
((ProcessPipeInputStream) stdout).processExited();
if (stderr instanceof ProcessPipeInputStream)
((ProcessPipeInputStream) stderr).processExited();
if (stdin instanceof ProcessPipeOutputStream)
((ProcessPipeOutputStream) stdin).processExited();
}
public OutputStream getOutputStream() {
return stdin;
}
public InputStream getInputStream() {
return stdout;
}
public InputStream getErrorStream() {
return stderr;
}
public synchronized int waitFor() throws InterruptedException {
while (!hasExited) {
wait();
}
return exitcode;
}
@Override
public synchronized boolean waitFor(long timeout, TimeUnit unit)
throws InterruptedException
{
if (hasExited) return true;
if (timeout <= 0) return false;
long timeoutAsNanos = unit.toNanos(timeout);
long startTime = System.nanoTime();
long rem = timeoutAsNanos;
while (!hasExited && (rem > 0)) {
wait(Math.max(TimeUnit.NANOSECONDS.toMillis(rem), 1));
rem = timeoutAsNanos - (System.nanoTime() - startTime);
}
return hasExited;
}
public synchronized int exitValue() {
if (!hasExited) {
throw new IllegalThreadStateException("process hasn't exited");
}
return exitcode;
}
private static native void destroyProcess(int pid, boolean force);
private void destroy(boolean force) {
// There is a risk that pid will be recycled, causing us to
// kill the wrong process! So we only terminate processes
// that appear to still be running. Even with this check,
// there is an unavoidable race condition here, but the window
// is very small, and OSes try hard to not recycle pids too
// soon, so this is quite safe.
synchronized (this) {
if (!hasExited)
destroyProcess(pid, force);
}
try { stdin.close(); } catch (IOException ignored) {}
try { stdout.close(); } catch (IOException ignored) {}
try { stderr.close(); } catch (IOException ignored) {}
}
public void destroy() {
destroy(false);
}
@Override
public Process destroyForcibly() {
destroy(true);
return this;
}
@Override
public synchronized boolean isAlive() {
return !hasExited;
}
private static native void init();
static {
init();
}
/**
* A buffered input stream for a subprocess pipe file descriptor
* that allows the underlying file descriptor to be reclaimed when
* the process exits, via the processExited hook.
*
* This is tricky because we do not want the user-level InputStream to be
* closed until the user invokes close(), and we need to continue to be
* able to read any buffered data lingering in the OS pipe buffer.
*/
static class ProcessPipeInputStream extends BufferedInputStream {
private final Object closeLock = new Object();
ProcessPipeInputStream(int fd) {
super(new FileInputStream(newFileDescriptor(fd)));
}
private static byte[] drainInputStream(InputStream in)
throws IOException {
int n = 0;
int j;
byte[] a = null;
while ((j = in.available()) > 0) {
a = (a == null) ? new byte[j] : Arrays.copyOf(a, n + j);
n += in.read(a, n, j);
}
return (a == null || n == a.length) ? a : Arrays.copyOf(a, n);
}
/** Called by the process reaper thread when the process exits. */
synchronized void processExited() {
synchronized (closeLock) {
try {
InputStream in = this.in;
// this stream is closed if and only if: in == null
if (in != null) {
byte[] stragglers = drainInputStream(in);
in.close();
this.in = (stragglers == null) ?
ProcessBuilder.NullInputStream.INSTANCE :
new ByteArrayInputStream(stragglers);
}
} catch (IOException ignored) {}
}
}
@Override
public void close() throws IOException {
// BufferedInputStream#close() is not synchronized unlike most other methods.
// Synchronizing helps avoid race with processExited().
synchronized (closeLock) {
super.close();
}
}
}
/**
* A buffered output stream for a subprocess pipe file descriptor
* that allows the underlying file descriptor to be reclaimed when
* the process exits, via the processExited hook.
*/
static class ProcessPipeOutputStream extends BufferedOutputStream {
ProcessPipeOutputStream(int fd) {
super(new FileOutputStream(newFileDescriptor(fd)));
}
/** Called by the process reaper thread when the process exits. */
synchronized void processExited() {
OutputStream out = this.out;
if (out != null) {
try {
out.close();
} catch (IOException ignored) {
// We know of no reason to get an IOException, but if
// we do, there's nothing else to do but carry on.
}
this.out = ProcessBuilder.NullOutputStream.INSTANCE;
}
}
}
}