2 * Copyright (c) 2008, 2009, 2010, 2011, 2012, 2013 Nicira, Inc.
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at:
8 * http://www.apache.org/licenses/LICENSE-2.0
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
28 #include "dynamic-string.h"
29 #include "fatal-signal.h"
31 #include "poll-loop.h"
33 #include "socket-util.h"
37 VLOG_DEFINE_THIS_MODULE(process);
39 COVERAGE_DEFINE(process_sigchld);
40 COVERAGE_DEFINE(process_start);
47 /* Modified by signal handler. */
52 /* Pipe used to signal child termination. */
56 static struct list all_processes = LIST_INITIALIZER(&all_processes);
58 static bool sigchld_is_blocked(void);
59 static void block_sigchld(sigset_t *);
60 static void unblock_sigchld(const sigset_t *);
61 static void sigchld_handler(int signr OVS_UNUSED);
63 /* Initializes the process subsystem (if it is not already initialized). Calls
64 * exit() if initialization fails.
66 * Calling this function is optional; it will be called automatically by
67 * process_start() if necessary. Calling it explicitly allows the client to
68 * prevent the process from exiting at an unexpected time. */
80 /* Create notification pipe. */
81 xpipe_nonblocking(fds);
83 /* Set up child termination signal handler. */
84 memset(&sa, 0, sizeof sa);
85 sa.sa_handler = sigchld_handler;
86 sigemptyset(&sa.sa_mask);
87 sa.sa_flags = SA_NOCLDSTOP | SA_RESTART;
88 xsigaction(SIGCHLD, &sa, NULL);
92 process_escape_args(char **argv)
94 struct ds ds = DS_EMPTY_INITIALIZER;
96 for (argp = argv; *argp; argp++) {
97 const char *arg = *argp;
100 ds_put_char(&ds, ' ');
102 if (arg[strcspn(arg, " \t\r\n\v\\\'\"")]) {
103 ds_put_char(&ds, '"');
104 for (p = arg; *p; p++) {
105 if (*p == '\\' || *p == '\"') {
106 ds_put_char(&ds, '\\');
108 ds_put_char(&ds, *p);
110 ds_put_char(&ds, '"');
112 ds_put_cstr(&ds, arg);
118 /* Prepare to start a process whose command-line arguments are given by the
119 * null-terminated 'argv' array. Returns 0 if successful, otherwise a
120 * positive errno value. */
122 process_prestart(char **argv)
128 /* Log the process to be started. */
129 if (VLOG_IS_DBG_ENABLED()) {
130 char *args = process_escape_args(argv);
131 VLOG_DBG("starting subprocess: %s", args);
135 /* execvp() will search PATH too, but the error in that case is more
136 * obscure, since it is only reported post-fork. */
137 binary = process_search_path(argv[0]);
139 VLOG_ERR("%s not found in PATH", argv[0]);
147 /* Creates and returns a new struct process with the specified 'name' and
150 * This is racy unless SIGCHLD is blocked (and has been blocked since before
151 * the fork()) that created the subprocess. */
152 static struct process *
153 process_register(const char *name, pid_t pid)
158 ovs_assert(sigchld_is_blocked());
160 p = xzalloc(sizeof *p);
162 slash = strrchr(name, '/');
163 p->name = xstrdup(slash ? slash + 1 : name);
166 list_push_back(&all_processes, &p->node);
171 /* Starts a subprocess with the arguments in the null-terminated argv[] array.
172 * argv[0] is used as the name of the process. Searches the PATH environment
173 * variable to find the program to execute.
175 * All file descriptors are closed before executing the subprocess, except for
178 * Returns 0 if successful, otherwise a positive errno value indicating the
179 * error. If successful, '*pp' is assigned a new struct process that may be
180 * used to query the process's status. On failure, '*pp' is set to NULL. */
182 process_start(char **argv, struct process **pp)
189 COVERAGE_INC(process_start);
190 error = process_prestart(argv);
195 block_sigchld(&oldsigs);
198 unblock_sigchld(&oldsigs);
199 VLOG_WARN("fork failed: %s", strerror(errno));
202 /* Running in parent process. */
203 *pp = process_register(argv[0], pid);
204 unblock_sigchld(&oldsigs);
207 /* Running in child process. */
208 int fd_max = get_max_fds();
212 unblock_sigchld(&oldsigs);
213 for (fd = 3; fd < fd_max; fd++) {
216 execvp(argv[0], argv);
217 fprintf(stderr, "execvp(\"%s\") failed: %s\n",
218 argv[0], strerror(errno));
223 /* Destroys process 'p'. */
225 process_destroy(struct process *p)
230 block_sigchld(&oldsigs);
231 list_remove(&p->node);
232 unblock_sigchld(&oldsigs);
239 /* Sends signal 'signr' to process 'p'. Returns 0 if successful, otherwise a
240 * positive errno value. */
242 process_kill(const struct process *p, int signr)
244 return (p->exited ? ESRCH
245 : !kill(p->pid, signr) ? 0
249 /* Returns the pid of process 'p'. */
251 process_pid(const struct process *p)
256 /* Returns the name of process 'p' (the name passed to process_start() with any
257 * leading directories stripped). */
259 process_name(const struct process *p)
264 /* Returns true if process 'p' has exited, false otherwise. */
266 process_exited(struct process *p)
271 char buf[_POSIX_PIPE_BUF];
272 ignore(read(fds[0], buf, sizeof buf));
277 /* Returns process 'p''s exit status, as reported by waitpid(2).
278 * process_status(p) may be called only after process_exited(p) has returned
281 process_status(const struct process *p)
283 ovs_assert(p->exited);
287 /* Given 'status', which is a process status in the form reported by waitpid(2)
288 * and returned by process_status(), returns a string describing how the
289 * process terminated. The caller is responsible for freeing the string when
290 * it is no longer needed. */
292 process_status_msg(int status)
294 struct ds ds = DS_EMPTY_INITIALIZER;
295 if (WIFEXITED(status)) {
296 ds_put_format(&ds, "exit status %d", WEXITSTATUS(status));
297 } else if (WIFSIGNALED(status)) {
298 char namebuf[SIGNAL_NAME_BUFSIZE];
300 ds_put_format(&ds, "killed (%s)",
301 signal_name(WTERMSIG(status), namebuf, sizeof namebuf));
302 } else if (WIFSTOPPED(status)) {
303 char namebuf[SIGNAL_NAME_BUFSIZE];
305 ds_put_format(&ds, "stopped (%s)",
306 signal_name(WSTOPSIG(status), namebuf, sizeof namebuf));
308 ds_put_format(&ds, "terminated abnormally (%x)", status);
310 if (WCOREDUMP(status)) {
311 ds_put_cstr(&ds, ", core dumped");
316 /* Causes the next call to poll_block() to wake up when process 'p' has
319 process_wait(struct process *p)
322 poll_immediate_wake();
324 poll_fd_wait(fds[0], POLLIN);
329 process_search_path(const char *name)
331 char *save_ptr = NULL;
335 if (strchr(name, '/') || !getenv("PATH")) {
336 return stat(name, &s) == 0 ? xstrdup(name) : NULL;
339 path = xstrdup(getenv("PATH"));
340 for (dir = strtok_r(path, ":", &save_ptr); dir;
341 dir = strtok_r(NULL, ":", &save_ptr)) {
342 char *file = xasprintf("%s/%s", dir, name);
343 if (stat(file, &s) == 0) {
354 sigchld_handler(int signr OVS_UNUSED)
358 COVERAGE_INC(process_sigchld);
359 LIST_FOR_EACH (p, node, &all_processes) {
363 retval = waitpid(p->pid, &status, WNOHANG);
364 } while (retval == -1 && errno == EINTR);
365 if (retval == p->pid) {
368 } else if (retval < 0) {
369 /* XXX We want to log something but we're in a signal
376 ignore(write(fds[1], "", 1));
380 sigchld_is_blocked(void)
384 xpthread_sigmask(SIG_SETMASK, NULL, &sigs);
385 return sigismember(&sigs, SIGCHLD);
389 block_sigchld(sigset_t *oldsigs)
393 sigemptyset(&sigchld);
394 sigaddset(&sigchld, SIGCHLD);
395 xpthread_sigmask(SIG_BLOCK, &sigchld, oldsigs);
399 unblock_sigchld(const sigset_t *oldsigs)
401 xpthread_sigmask(SIG_SETMASK, oldsigs, NULL);