misc-utils/waitpid.c

   1 /*
   2  * waitpid(1) - wait for process termination
   3  *
   4  * Copyright (C) 2022 Thomas Weißschuh <thomas@t-8ch.de>
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it would be useful,
  12  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  * GNU General Public License for more details.
  15  *
  16  * You should have received a copy of the GNU General Public License along
  17  * with this program; if not, write to the Free Software Foundation, Inc.,
  18  * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
  19  */
  20
  21 #include <sys/epoll.h>
  22 #include <sys/timerfd.h>
  23 #include <assert.h>
  24 #include <stdlib.h>
  25 #include <errno.h>
  26 #include <string.h>
  27 #include <unistd.h>
  28 #include <stdbool.h>
  29 #include <getopt.h>
  30
  31 #include "pidfd-utils.h"
  32 #include "c.h"
  33 #include "nls.h"
  34 #include "xalloc.h"
  35 #include "strutils.h"
  36 #include "exitcodes.h"
  37 #include "timeutils.h"
  38
  39 #define EXIT_TIMEOUT_EXPIRED 3
  40
  41 #define TIMEOUT_SOCKET_IDX UINT64_MAX
  42
  43 #define err_nosys(exitcode, ...) \
  44         err(errno == ENOSYS ? EXIT_NOTSUPP : exitcode, __VA_ARGS__)
  45
  46 static bool verbose = false;
  47 static struct timespec timeout;
  48 static bool allow_exited = false;
  49
  50 static pid_t *parse_pids(size_t n_strings, char * const *strings)
  51 {
  52         pid_t *pids = xcalloc(n_strings, sizeof(*pids));
  53
  54         for (size_t i = 0; i < n_strings; i++)
  55                 pids[i] = strtopid_or_err(strings[i], _("failed to parse pid"));
  56
  57         return pids;
  58 }
  59
  60 static int *open_pidfds(size_t n_pids, pid_t *pids)
  61 {
  62         int *pidfds = xcalloc(n_pids, sizeof(*pidfds));
  63
  64         for (size_t i = 0; i < n_pids; i++) {
  65                 pidfds[i] = pidfd_open(pids[i], 0);
  66                 if (pidfds[i] == -1) {
  67                         if (allow_exited && errno == ESRCH) {
  68                                 warnx(_("PID %d has exited, skipping"), pids[i]);
  69                                 continue;
  70                         }
  71                         err_nosys(EXIT_FAILURE, _("could not open pid %u"), pids[i]);
  72                 }
  73         }
  74
  75         return pidfds;
  76 }
  77
  78 static int open_timeoutfd(void)
  79 {
  80         int fd;
  81         struct itimerspec timer = {};
  82
  83         if (!timeout.tv_sec && !timeout.tv_nsec)
  84                 return -1;
  85
  86         timer.it_value = timeout;
  87
  88         fd = timerfd_create(CLOCK_MONOTONIC, TFD_CLOEXEC);
  89         if (fd == -1)
  90                 err_nosys(EXIT_FAILURE, _("could not create timerfd"));
  91
  92         if (timerfd_settime(fd, 0, &timer, NULL))
  93                 err_nosys(EXIT_FAILURE, _("could not set timer"));
  94
  95         return fd;
  96
  97 }
  98
  99 static size_t add_listeners(int epll, size_t n_pids, int * const pidfds, int timeoutfd)
 100 {
 101         size_t skipped = 0;
 102         struct epoll_event evt = {
 103                 .events = EPOLLIN,
 104         };
 105
 106         if (timeoutfd != -1) {
 107                 evt.data.u64 = TIMEOUT_SOCKET_IDX;
 108                 if (epoll_ctl(epll, EPOLL_CTL_ADD, timeoutfd, &evt))
 109                         err_nosys(EXIT_FAILURE, _("could not add timerfd"));
 110         }
 111
 112         for (size_t i = 0; i < n_pids; i++) {
 113                 if (pidfds[i] == -1) {
 114                         skipped++;
 115                         continue;
 116                 }
 117                 evt.data.u64 = i;
 118                 if (epoll_ctl(epll, EPOLL_CTL_ADD, pidfds[i], &evt))
 119                         err_nosys(EXIT_FAILURE, _("could not add listener"));
 120         }
 121
 122         return n_pids - skipped;
 123 }
 124
 125 static void wait_for_exits(int epll, size_t active_pids, pid_t * const pids,
 126                            int * const pidfds)
 127 {
 128         while (active_pids) {
 129                 struct epoll_event evt;
 130                 int ret, fd;
 131
 132                 ret = epoll_wait(epll, &evt, 1, -1);
 133                 if (ret == -1) {
 134                         if (errno == EINTR)
 135                                 continue;
 136                         else
 137                                 err_nosys(EXIT_FAILURE, _("failure during wait"));
 138                 }
 139                 if (evt.data.u64 == TIMEOUT_SOCKET_IDX) {
 140                         if (verbose)
 141                                 printf(_("Timeout expired\n"));
 142                         exit(EXIT_TIMEOUT_EXPIRED);
 143                 }
 144                 if (verbose)
 145                         printf(_("PID %d finished\n"), pids[evt.data.u64]);
 146                 assert((size_t) ret <= active_pids);
 147                 fd = pidfds[evt.data.u64];
 148                 epoll_ctl(epll, EPOLL_CTL_DEL, fd, NULL);
 149                 active_pids -= ret;
 150         }
 151 }
 152
 153 static void __attribute__((__noreturn__)) usage(void)
 154 {
 155         FILE *out = stdout;
 156
 157         fputs(USAGE_HEADER, out);
 158         fprintf(out, _(" %s [options] pid...\n"), program_invocation_short_name);
 159
 160         fputs(USAGE_OPTIONS, out);
 161         fputs(_(" -v, --verbose           be more verbose\n"), out);
 162         fputs(_(" -t, --timeout=<timeout> wait at most timeout seconds\n"), out);
 163         fputs(_(" -e, --exited            allow exited PIDs\n"), out);
 164
 165         fputs(USAGE_SEPARATOR, out);
 166         fprintf(out, USAGE_HELP_OPTIONS(25));
 167
 168         fprintf(out, USAGE_MAN_TAIL("waitpid(1)"));
 169
 170         exit(EXIT_SUCCESS);
 171 }
 172
 173 static int parse_options(int argc, char **argv)
 174 {
 175         int c;
 176         static const struct option longopts[] = {
 177                 { "verbose", no_argument,       NULL, 'v' },
 178                 { "timeout", required_argument, NULL, 't' },
 179                 { "exited",  no_argument,       NULL, 'e' },
 180                 { "version", no_argument,       NULL, 'V' },
 181                 { "help",    no_argument,       NULL, 'h' },
 182                 { NULL, 0, NULL, 0 },
 183         };
 184
 185         while ((c = getopt_long (argc, argv, "vVht:e", longopts, NULL)) != -1) {
 186                 switch (c) {
 187                 case 'v':
 188                         verbose = true;
 189                         break;
 190                 case 't':
 191                         strtotimespec_or_err(optarg, &timeout,
 192                                              _("Could not parse timeout"));
 193                         break;
 194                 case 'e':
 195                         allow_exited = true;
 196                         break;
 197                 case 'V':
 198                         print_version(EXIT_SUCCESS);
 199                 case 'h':
 200                         usage();
 201                 default:
 202                         errtryhelp(EXIT_FAILURE);
 203                 }
 204         }
 205
 206         return optind;
 207 }
 208
 209 int main(int argc, char **argv)
 210 {
 211         int pid_idx, epoll, timeoutfd, *pidfds;
 212         size_t n_pids, active_pids;
 213
 214         setlocale(LC_ALL, "");
 215         bindtextdomain(PACKAGE, LOCALEDIR);
 216         textdomain(PACKAGE);
 217
 218         pid_idx = parse_options(argc, argv);
 219         n_pids = argc - pid_idx;
 220         if (!n_pids)
 221                 errx(EXIT_FAILURE, _("no PIDs specified"));
 222
 223         pid_t *pids = parse_pids(argc - pid_idx, argv + pid_idx);
 224
 225         pidfds = open_pidfds(n_pids, pids);
 226         timeoutfd = open_timeoutfd();
 227         epoll = epoll_create(n_pids);
 228         if (epoll == -1)
 229                 err_nosys(EXIT_FAILURE, _("could not create epoll"));
 230
 231         active_pids = add_listeners(epoll, n_pids, pidfds, timeoutfd);
 232         wait_for_exits(epoll, active_pids, pids, pidfds);
 233 }