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