1 /*
2 * Copyright (c) 1995, 2012, 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.*;
29 import java.util.concurrent.TimeUnit;
30
31 /* java.lang.Process subclass in the UNIX environment.
32 *
33 * @author Mario Wolczko and Ross Knippel.
34 */
35
36 final class UNIXProcess extends Process {
37 private static final sun.misc.JavaIOFileDescriptorAccess fdAccess
38 = sun.misc.SharedSecrets.getJavaIOFileDescriptorAccess();
39
40 private final int pid;
41 private int exitcode;
42 private boolean hasExited;
43
44 private OutputStream stdin_stream;
45 private InputStream stdout_stream;
46 private DeferredCloseInputStream stdout_inner_stream;
47 private InputStream stderr_stream;
48
49 /* this is for the reaping thread */
50 private native int waitForProcessExit(int pid);
51
52 /**
53 * Create a process using fork(2) and exec(2).
54 *
55 * @param std_fds array of file descriptors. Indexes 0, 1, and
56 * 2 correspond to standard input, standard output and
57 * standard error, respectively. On input, a value of -1
58 * means to create a pipe to connect child and parent
59 * processes. On output, a value which is not -1 is the
60 * parent pipe fd corresponding to the pipe which has
61 * been created. An element of this array is -1 on input
62 * if and only if it is <em>not</em> -1 on output.
63 * @return the pid of the subprocess
64 */
65 private native int forkAndExec(byte[] prog,
66 byte[] argBlock, int argc,
67 byte[] envBlock, int envc,
68 byte[] dir,
69 int[] std_fds,
70 boolean redirectErrorStream)
71 throws IOException;
72
73 UNIXProcess(final byte[] prog,
74 final byte[] argBlock, int argc,
75 final byte[] envBlock, int envc,
76 final byte[] dir,
77 final int[] std_fds,
78 final boolean redirectErrorStream)
79 throws IOException {
80 pid = forkAndExec(prog,
81 argBlock, argc,
82 envBlock, envc,
83 dir,
84 std_fds,
85 redirectErrorStream);
86
87 java.security.AccessController.doPrivileged(
88 new java.security.PrivilegedAction<Void>() { public Void run() {
89 if (std_fds[0] == -1)
90 stdin_stream = ProcessBuilder.NullOutputStream.INSTANCE;
91 else {
92 FileDescriptor stdin_fd = new FileDescriptor();
93 fdAccess.set(stdin_fd, std_fds[0]);
94 stdin_stream = new BufferedOutputStream(
95 new FileOutputStream(stdin_fd));
96 }
97
98 if (std_fds[1] == -1)
99 stdout_stream = ProcessBuilder.NullInputStream.INSTANCE;
100 else {
101 FileDescriptor stdout_fd = new FileDescriptor();
102 fdAccess.set(stdout_fd, std_fds[1]);
103 stdout_inner_stream = new DeferredCloseInputStream(stdout_fd);
104 stdout_stream = new BufferedInputStream(stdout_inner_stream);
105 }
106
107 if (std_fds[2] == -1)
108 stderr_stream = ProcessBuilder.NullInputStream.INSTANCE;
109 else {
110 FileDescriptor stderr_fd = new FileDescriptor();
111 fdAccess.set(stderr_fd, std_fds[2]);
112 stderr_stream = new DeferredCloseInputStream(stderr_fd);
113 }
114
115 return null; }});
116
117 /*
118 * For each subprocess forked a corresponding reaper thread
119 * is started. That thread is the only thread which waits
120 * for the subprocess to terminate and it doesn't hold any
121 * locks while doing so. This design allows waitFor() and
122 * exitStatus() to be safely executed in parallel (and they
123 * need no native code).
124 */
125
126 java.security.AccessController.doPrivileged(
127 new java.security.PrivilegedAction<Void>() { public Void run() {
128 Thread t = new Thread("process reaper") {
129 public void run() {
130 int res = waitForProcessExit(pid);
131 synchronized (UNIXProcess.this) {
132 hasExited = true;
133 exitcode = res;
134 UNIXProcess.this.notifyAll();
135 }
136 }
137 };
138 t.setDaemon(true);
139 t.start();
140 return null; }});
141 }
142
143 public OutputStream getOutputStream() {
144 return stdin_stream;
145 }
146
147 public InputStream getInputStream() {
148 return stdout_stream;
149 }
150
151 public InputStream getErrorStream() {
152 return stderr_stream;
153 }
154
155 public synchronized int waitFor() throws InterruptedException {
156 while (!hasExited) {
157 wait();
158 }
159 return exitcode;
160 }
161
162 @Override
163 public synchronized boolean waitFor(long timeout, TimeUnit unit)
164 throws InterruptedException
165 {
166 if (hasExited) return true;
167 if (timeout <= 0) return false;
168
169 long timeoutAsNanos = unit.toNanos(timeout);
170 long startTime = System.nanoTime();
171 long rem = timeoutAsNanos;
172
173 while (!hasExited && (rem > 0)) {
174 wait(Math.max(TimeUnit.NANOSECONDS.toMillis(rem), 1));
175 rem = timeoutAsNanos - (System.nanoTime() - startTime);
176 }
177 return hasExited;
178 }
179
180 public synchronized int exitValue() {
181 if (!hasExited) {
182 throw new IllegalThreadStateException("process hasn't exited");
183 }
184 return exitcode;
185 }
186
187 private static native void destroyProcess(int pid, boolean force);
188 private synchronized void destroy(boolean force) {
189 // There is a risk that pid will be recycled, causing us to
190 // kill the wrong process! So we only terminate processes
191 // that appear to still be running. Even with this check,
192 // there is an unavoidable race condition here, but the window
193 // is very small, and OSes try hard to not recycle pids too
194 // soon, so this is quite safe.
195 if (!hasExited)
196 destroyProcess(pid, force);
197 try {
198 stdin_stream.close();
199 if (stdout_inner_stream != null)
200 stdout_inner_stream.closeDeferred(stdout_stream);
201 if (stderr_stream instanceof DeferredCloseInputStream)
202 ((DeferredCloseInputStream) stderr_stream)
203 .closeDeferred(stderr_stream);
204 } catch (IOException e) {
205 // ignore
206 }
207 }
208
209 public void destroy() {
210 destroy(false);
211 }
212
213 @Override
214 public Process destroyForcibly() {
215 destroy(true);
216 return this;
217 }
218
219 @Override
220 public synchronized boolean isAlive() {
221 return !hasExited;
222 }
223
224 // A FileInputStream that supports the deferment of the actual close
225 // operation until the last pending I/O operation on the stream has
226 // finished. This is required on Solaris because we must close the stdin
227 // and stdout streams in the destroy method in order to reclaim the
228 // underlying file descriptors. Doing so, however, causes any thread
229 // currently blocked in a read on one of those streams to receive an
230 // IOException("Bad file number"), which is incompatible with historical
231 // behavior. By deferring the close we allow any pending reads to see -1
232 // (EOF) as they did before.
233 //
234 private static class DeferredCloseInputStream
235 extends FileInputStream
236 {
237
238 private DeferredCloseInputStream(FileDescriptor fd) {
239 super(fd);
240 }
241
242 private Object lock = new Object(); // For the following fields
243 private boolean closePending = false;
244 private int useCount = 0;
245 private InputStream streamToClose;
246
247 private void raise() {
248 synchronized (lock) {
249 useCount++;
250 }
251 }
252
253 private void lower() throws IOException {
254 synchronized (lock) {
255 useCount--;
256 if (useCount == 0 && closePending) {
257 streamToClose.close();
258 }
259 }
260 }
261
262 // stc is the actual stream to be closed; it might be this object, or
263 // it might be an upstream object for which this object is downstream.
264 //
265 private void closeDeferred(InputStream stc) throws IOException {
266 synchronized (lock) {
267 if (useCount == 0) {
268 stc.close();
269 } else {
270 closePending = true;
271 streamToClose = stc;
272 }
273 }
274 }
275
276 public void close() throws IOException {
277 synchronized (lock) {
278 useCount = 0;
279 closePending = false;
280 }
281 super.close();
282 }
283
284 public int read() throws IOException {
285 raise();
286 try {
287 return super.read();
288 } finally {
289 lower();
290 }
291 }
292
293 public int read(byte[] b) throws IOException {
294 raise();
295 try {
296 return super.read(b);
297 } finally {
298 lower();
299 }
300 }
301
302 public int read(byte[] b, int off, int len) throws IOException {
303 raise();
304 try {
305 return super.read(b, off, len);
306 } finally {
307 lower();
308 }
309 }
310
311 public long skip(long n) throws IOException {
312 raise();
313 try {
314 return super.skip(n);
315 } finally {
316 lower();
317 }
318 }
319
320 public int available() throws IOException {
321 raise();
322 try {
323 return super.available();
324 } finally {
325 lower();
326 }
327 }
328
329 }
330
331 /* This routine initializes JNI field offsets for the class */
332 private static native void initIDs();
333
334 static {
335 initIDs();
336 }
337 }