1 /* 2 * Copyright (c) 1995, 2013, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. Oracle designates this 8 * particular file as subject to the "Classpath" exception as provided 9 * by Oracle in the LICENSE file that accompanied this code. 10 * 11 * This code is distributed in the hope that it will be useful, but WITHOUT 12 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 13 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 14 * version 2 for more details (a copy is included in the LICENSE file that 15 * accompanied this code). 16 * 17 * You should have received a copy of the GNU General Public License version 18 * 2 along with this work; if not, write to the Free Software Foundation, 19 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 20 * 21 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 22 * or visit www.oracle.com if you need additional information or have any 23 * questions. 24 */ 25 26 package java.lang; 27 28 import java.io.BufferedInputStream; 29 import java.io.BufferedOutputStream; 30 import java.io.ByteArrayInputStream; 31 import java.io.FileDescriptor; 32 import java.io.FileInputStream; 33 import java.io.FileOutputStream; 34 import java.io.IOException; 35 import java.io.InputStream; 36 import java.io.OutputStream; 37 import java.util.Arrays; 38 import java.util.concurrent.Executors; 39 import java.util.concurrent.Executor; 40 import java.util.concurrent.ThreadFactory; 41 import java.util.concurrent.TimeUnit; 42 import java.security.AccessController; 43 import static java.security.AccessController.doPrivileged; 44 import java.security.PrivilegedAction; 45 import java.security.PrivilegedActionException; 46 import java.security.PrivilegedExceptionAction; 47 48 /** 49 * java.lang.Process subclass in the UNIX environment. 50 * 51 * @author Mario Wolczko and Ross Knippel. 52 * @author Konstantin Kladko (ported to Linux) 53 * @author Martin Buchholz 54 * @author Volker Simonis (ported to AIX) 55 */ 56 final class UNIXProcess extends Process { 57 private static final sun.misc.JavaIOFileDescriptorAccess fdAccess 58 = sun.misc.SharedSecrets.getJavaIOFileDescriptorAccess(); 59 60 private final int pid; 61 private int exitcode; 62 private boolean hasExited; 63 64 private /* final */ OutputStream stdin; 65 private /* final */ InputStream stdout; 66 private /* final */ InputStream stderr; 67 68 private static enum LaunchMechanism { 69 FORK(1), 70 POSIX_SPAWN(2); 71 72 private int value; 73 LaunchMechanism(int x) {value = x;} 74 }; 75 76 /* On AIX, the default is to spawn */ 77 private static final LaunchMechanism launchMechanism; 78 private static byte[] helperpath; 79 80 private static byte[] toCString(String s) { 81 if (s == null) 82 return null; 83 byte[] bytes = s.getBytes(); 84 byte[] result = new byte[bytes.length + 1]; 85 System.arraycopy(bytes, 0, 86 result, 0, 87 bytes.length); 88 result[result.length-1] = (byte)0; 89 return result; 90 } 91 92 static { 93 launchMechanism = AccessController.doPrivileged( 94 new PrivilegedAction<LaunchMechanism>() 95 { 96 public LaunchMechanism run() { 97 String javahome = System.getProperty("java.home"); 98 String osArch = System.getProperty("os.arch"); 99 100 helperpath = toCString(javahome + "/lib/" + osArch + "/jspawnhelper"); 101 String s = System.getProperty( 102 "jdk.lang.Process.launchMechanism", "posix_spawn"); 103 104 try { 105 return LaunchMechanism.valueOf(s.toUpperCase()); 106 } catch (IllegalArgumentException e) { 107 throw new Error(s + " is not a supported " + 108 "process launch mechanism on this platform."); 109 } 110 } 111 }); 112 } 113 114 /* this is for the reaping thread */ 115 private native int waitForProcessExit(int pid); 116 117 /** 118 * Create a process. Depending on the mode flag, this is done by 119 * one of the following mechanisms. 120 * - fork(2) and exec(2) 121 * - clone(2) and exec(2) 122 * - vfork(2) and exec(2) 123 * 124 * @param fds an array of three file descriptors. 125 * Indexes 0, 1, and 2 correspond to standard input, 126 * standard output and standard error, respectively. On 127 * input, a value of -1 means to create a pipe to connect 128 * child and parent processes. On output, a value which 129 * is not -1 is the parent pipe fd corresponding to the 130 * pipe which has been created. An element of this array 131 * is -1 on input if and only if it is <em>not</em> -1 on 132 * output. 133 * @return the pid of the subprocess 134 */ 135 private native int forkAndExec(int mode, byte[] helperpath, 136 byte[] prog, 137 byte[] argBlock, int argc, 138 byte[] envBlock, int envc, 139 byte[] dir, 140 int[] fds, 141 boolean redirectErrorStream) 142 throws IOException; 143 144 /** 145 * The thread factory used to create "process reaper" daemon threads. 146 */ 147 private static class ProcessReaperThreadFactory implements ThreadFactory { 148 private final static ThreadGroup group = getRootThreadGroup(); 149 150 private static ThreadGroup getRootThreadGroup() { 151 return doPrivileged(new PrivilegedAction<ThreadGroup> () { 152 public ThreadGroup run() { 153 ThreadGroup root = Thread.currentThread().getThreadGroup(); 154 while (root.getParent() != null) 155 root = root.getParent(); 156 return root; 157 }}); 158 } 159 160 public Thread newThread(Runnable grimReaper) { 161 // Our thread stack requirement is quite modest. 162 Thread t = new Thread(group, grimReaper, "process reaper", 32768); 163 t.setDaemon(true); 164 // A small attempt (probably futile) to avoid priority inversion 165 t.setPriority(Thread.MAX_PRIORITY); 166 return t; 167 } 168 } 169 170 /** 171 * The thread pool of "process reaper" daemon threads. 172 */ 173 private static final Executor processReaperExecutor = 174 doPrivileged(new PrivilegedAction<Executor>() { 175 public Executor run() { 176 return Executors.newCachedThreadPool 177 (new ProcessReaperThreadFactory()); 178 }}); 179 180 UNIXProcess(final byte[] prog, 181 final byte[] argBlock, final int argc, 182 final byte[] envBlock, final int envc, 183 final byte[] dir, 184 final int[] fds, 185 final boolean redirectErrorStream) 186 throws IOException { 187 188 pid = forkAndExec(launchMechanism.value, 189 helperpath, 190 prog, 191 argBlock, argc, 192 envBlock, envc, 193 dir, 194 fds, 195 redirectErrorStream); 196 197 try { 198 doPrivileged(new PrivilegedExceptionAction<Void>() { 199 public Void run() throws IOException { 200 initStreams(fds); 201 return null; 202 }}); 203 } catch (PrivilegedActionException ex) { 204 throw (IOException) ex.getException(); 205 } 206 } 207 208 static FileDescriptor newFileDescriptor(int fd) { 209 FileDescriptor fileDescriptor = new FileDescriptor(); 210 fdAccess.set(fileDescriptor, fd); 211 return fileDescriptor; 212 } 213 214 void initStreams(int[] fds) throws IOException { 215 stdin = (fds[0] == -1) ? 216 ProcessBuilder.NullOutputStream.INSTANCE : 217 new ProcessPipeOutputStream(fds[0]); 218 219 stdout = (fds[1] == -1) ? 220 ProcessBuilder.NullInputStream.INSTANCE : 221 new ProcessPipeInputStream(fds[1]); 222 223 stderr = (fds[2] == -1) ? 224 ProcessBuilder.NullInputStream.INSTANCE : 225 new ProcessPipeInputStream(fds[2]); 226 227 processReaperExecutor.execute(new Runnable() { 228 public void run() { 229 int exitcode = waitForProcessExit(pid); 230 UNIXProcess.this.processExited(exitcode); 231 }}); 232 } 233 234 void processExited(int exitcode) { 235 synchronized (this) { 236 this.exitcode = exitcode; 237 hasExited = true; 238 notifyAll(); 239 } 240 241 if (stdout instanceof ProcessPipeInputStream) 242 ((ProcessPipeInputStream) stdout).processExited(); 243 244 if (stderr instanceof ProcessPipeInputStream) 245 ((ProcessPipeInputStream) stderr).processExited(); 246 247 if (stdin instanceof ProcessPipeOutputStream) 248 ((ProcessPipeOutputStream) stdin).processExited(); 249 } 250 251 public OutputStream getOutputStream() { 252 return stdin; 253 } 254 255 public InputStream getInputStream() { 256 return stdout; 257 } 258 259 public InputStream getErrorStream() { 260 return stderr; 261 } 262 263 public synchronized int waitFor() throws InterruptedException { 264 while (!hasExited) { 265 wait(); 266 } 267 return exitcode; 268 } 269 270 @Override 271 public synchronized boolean waitFor(long timeout, TimeUnit unit) 272 throws InterruptedException 273 { 274 if (hasExited) return true; 275 if (timeout <= 0) return false; 276 277 long timeoutAsNanos = unit.toNanos(timeout); 278 long startTime = System.nanoTime(); 279 long rem = timeoutAsNanos; 280 281 while (!hasExited && (rem > 0)) { 282 wait(Math.max(TimeUnit.NANOSECONDS.toMillis(rem), 1)); 283 rem = timeoutAsNanos - (System.nanoTime() - startTime); 284 } 285 return hasExited; 286 } 287 288 public synchronized int exitValue() { 289 if (!hasExited) { 290 throw new IllegalThreadStateException("process hasn't exited"); 291 } 292 return exitcode; 293 } 294 295 private static native void destroyProcess(int pid, boolean force); 296 private void destroy(boolean force) { 297 // There is a risk that pid will be recycled, causing us to 298 // kill the wrong process! So we only terminate processes 299 // that appear to still be running. Even with this check, 300 // there is an unavoidable race condition here, but the window 301 // is very small, and OSes try hard to not recycle pids too 302 // soon, so this is quite safe. 303 synchronized (this) { 304 if (!hasExited) 305 destroyProcess(pid, force); 306 } 307 try { stdin.close(); } catch (IOException ignored) {} 308 try { stdout.close(); } catch (IOException ignored) {} 309 try { stderr.close(); } catch (IOException ignored) {} 310 } 311 312 public void destroy() { 313 destroy(false); 314 } 315 316 @Override 317 public Process destroyForcibly() { 318 destroy(true); 319 return this; 320 } 321 322 @Override 323 public synchronized boolean isAlive() { 324 return !hasExited; 325 } 326 327 private static native void init(); 328 329 static { 330 init(); 331 } 332 333 /** 334 * A buffered input stream for a subprocess pipe file descriptor 335 * that allows the underlying file descriptor to be reclaimed when 336 * the process exits, via the processExited hook. 337 * 338 * This is tricky because we do not want the user-level InputStream to be 339 * closed until the user invokes close(), and we need to continue to be 340 * able to read any buffered data lingering in the OS pipe buffer. 341 * 342 * On AIX this is especially tricky, because the 'close()' system call 343 * will block if another thread is at the same time blocked in a file 344 * operation (e.g. 'read()') on the same file descriptor. We therefore 345 * combine this 'ProcessPipeInputStream' with the DeferredCloseInputStream 346 * approach used on Solaris (see "UNIXProcess.java.solaris"). This means 347 * that every potentially blocking operation on the file descriptor 348 * increments a counter before it is executed and decrements it once it 349 * finishes. The 'close()' operation will only be executed if there are 350 * no pending operations. Otherwise it is deferred after the last pending 351 * operation has finished. 352 * 353 */ 354 static class ProcessPipeInputStream extends BufferedInputStream { 355 private final Object closeLock = new Object(); 356 private int useCount = 0; 357 private boolean closePending = false; 358 359 ProcessPipeInputStream(int fd) { 360 super(new FileInputStream(newFileDescriptor(fd))); 361 } 362 363 private InputStream drainInputStream(InputStream in) 364 throws IOException { 365 int n = 0; 366 int j; 367 byte[] a = null; 368 synchronized (closeLock) { 369 if (buf == null) // asynchronous close()? 370 return null; // discard 371 j = in.available(); 372 } 373 while (j > 0) { 374 a = (a == null) ? new byte[j] : Arrays.copyOf(a, n + j); 375 synchronized (closeLock) { 376 if (buf == null) // asynchronous close()? 377 return null; // discard 378 n += in.read(a, n, j); 379 j = in.available(); 380 } 381 } 382 return (a == null) ? 383 ProcessBuilder.NullInputStream.INSTANCE : 384 new ByteArrayInputStream(n == a.length ? a : Arrays.copyOf(a, n)); 385 } 386 387 /** Called by the process reaper thread when the process exits. */ 388 synchronized void processExited() { 389 try { 390 InputStream in = this.in; 391 if (in != null) { 392 InputStream stragglers = drainInputStream(in); 393 in.close(); 394 this.in = stragglers; 395 } 396 } catch (IOException ignored) { } 397 } 398 399 private void raise() { 400 synchronized (closeLock) { 401 useCount++; 402 } 403 } 404 405 private void lower() throws IOException { 406 synchronized (closeLock) { 407 useCount--; 408 if (useCount == 0 && closePending) { 409 closePending = false; 410 super.close(); 411 } 412 } 413 } 414 415 @Override 416 public int read() throws IOException { 417 raise(); 418 try { 419 return super.read(); 420 } finally { 421 lower(); 422 } 423 } 424 425 @Override 426 public int read(byte[] b) throws IOException { 427 raise(); 428 try { 429 return super.read(b); 430 } finally { 431 lower(); 432 } 433 } 434 435 @Override 436 public int read(byte[] b, int off, int len) throws IOException { 437 raise(); 438 try { 439 return super.read(b, off, len); 440 } finally { 441 lower(); 442 } 443 } 444 445 @Override 446 public long skip(long n) throws IOException { 447 raise(); 448 try { 449 return super.skip(n); 450 } finally { 451 lower(); 452 } 453 } 454 455 @Override 456 public int available() throws IOException { 457 raise(); 458 try { 459 return super.available(); 460 } finally { 461 lower(); 462 } 463 } 464 465 @Override 466 public void close() throws IOException { 467 // BufferedInputStream#close() is not synchronized unlike most other methods. 468 // Synchronizing helps avoid racing with drainInputStream(). 469 synchronized (closeLock) { 470 if (useCount == 0) { 471 super.close(); 472 } 473 else { 474 closePending = true; 475 } 476 } 477 } 478 } 479 480 /** 481 * A buffered output stream for a subprocess pipe file descriptor 482 * that allows the underlying file descriptor to be reclaimed when 483 * the process exits, via the processExited hook. 484 */ 485 static class ProcessPipeOutputStream extends BufferedOutputStream { 486 ProcessPipeOutputStream(int fd) { 487 super(new FileOutputStream(newFileDescriptor(fd))); 488 } 489 490 /** Called by the process reaper thread when the process exits. */ 491 synchronized void processExited() { 492 OutputStream out = this.out; 493 if (out != null) { 494 try { 495 out.close(); 496 } catch (IOException ignored) { 497 // We know of no reason to get an IOException, but if 498 // we do, there's nothing else to do but carry on. 499 } 500 this.out = ProcessBuilder.NullOutputStream.INSTANCE; 501 } 502 } 503 } 504 }