run-command.c

   1 #include "cache.h"
   2 #include "run-command.h"
   3 #include "exec_cmd.h"
   4 #include "sigchain.h"
   5 #include "argv-array.h"
   6 #include "thread-utils.h"
   7 #include "strbuf.h"
   8
   9 void child_process_init(struct child_process *child)
  10 {
  11         memset(child, 0, sizeof(*child));
  12         argv_array_init(&child->args);
  13         argv_array_init(&child->env_array);
  14 }
  15
  16 void child_process_clear(struct child_process *child)
  17 {
  18         argv_array_clear(&child->args);
  19         argv_array_clear(&child->env_array);
  20 }
  21
  22 struct child_to_clean {
  23         pid_t pid;
  24         struct child_process *process;
  25         struct child_to_clean *next;
  26 };
  27 static struct child_to_clean *children_to_clean;
  28 static int installed_child_cleanup_handler;
  29
  30 static void cleanup_children(int sig, int in_signal)
  31 {
  32         struct child_to_clean *children_to_wait_for = NULL;
  33
  34         while (children_to_clean) {
  35                 struct child_to_clean *p = children_to_clean;
  36                 children_to_clean = p->next;
  37
  38                 if (p->process && !in_signal) {
  39                         struct child_process *process = p->process;
  40                         if (process->clean_on_exit_handler) {
  41                                 trace_printf(
  42                                         "trace: run_command: running exit handler for pid %"
  43                                         PRIuMAX, (uintmax_t)p->pid
  44                                 );
  45                                 process->clean_on_exit_handler(process);
  46                         }
  47                 }
  48
  49                 kill(p->pid, sig);
  50
  51                 if (p->process && p->process->wait_after_clean) {
  52                         p->next = children_to_wait_for;
  53                         children_to_wait_for = p;
  54                 } else {
  55                         if (!in_signal)
  56                                 free(p);
  57                 }
  58         }
  59
  60         while (children_to_wait_for) {
  61                 struct child_to_clean *p = children_to_wait_for;
  62                 children_to_wait_for = p->next;
  63
  64                 while (waitpid(p->pid, NULL, 0) < 0 && errno == EINTR)
  65                         ; /* spin waiting for process exit or error */
  66
  67                 if (!in_signal)
  68                         free(p);
  69         }
  70 }
  71
  72 static void cleanup_children_on_signal(int sig)
  73 {
  74         cleanup_children(sig, 1);
  75         sigchain_pop(sig);
  76         raise(sig);
  77 }
  78
  79 static void cleanup_children_on_exit(void)
  80 {
  81         cleanup_children(SIGTERM, 0);
  82 }
  83
  84 static void mark_child_for_cleanup(pid_t pid, struct child_process *process)
  85 {
  86         struct child_to_clean *p = xmalloc(sizeof(*p));
  87         p->pid = pid;
  88         p->process = process;
  89         p->next = children_to_clean;
  90         children_to_clean = p;
  91
  92         if (!installed_child_cleanup_handler) {
  93                 atexit(cleanup_children_on_exit);
  94                 sigchain_push_common(cleanup_children_on_signal);
  95                 installed_child_cleanup_handler = 1;
  96         }
  97 }
  98
  99 static void clear_child_for_cleanup(pid_t pid)
 100 {
 101         struct child_to_clean **pp;
 102
 103         for (pp = &children_to_clean; *pp; pp = &(*pp)->next) {
 104                 struct child_to_clean *clean_me = *pp;
 105
 106                 if (clean_me->pid == pid) {
 107                         *pp = clean_me->next;
 108                         free(clean_me);
 109                         return;
 110                 }
 111         }
 112 }
 113
 114 static inline void close_pair(int fd[2])
 115 {
 116         close(fd[0]);
 117         close(fd[1]);
 118 }
 119
 120 static char *locate_in_PATH(const char *file)
 121 {
 122         const char *p = getenv("PATH");
 123         struct strbuf buf = STRBUF_INIT;
 124
 125         if (!p || !*p)
 126                 return NULL;
 127
 128         while (1) {
 129                 const char *end = strchrnul(p, ':');
 130
 131                 strbuf_reset(&buf);
 132
 133                 /* POSIX specifies an empty entry as the current directory. */
 134                 if (end != p) {
 135                         strbuf_add(&buf, p, end - p);
 136                         strbuf_addch(&buf, '/');
 137                 }
 138                 strbuf_addstr(&buf, file);
 139
 140                 if (!access(buf.buf, F_OK))
 141                         return strbuf_detach(&buf, NULL);
 142
 143                 if (!*end)
 144                         break;
 145                 p = end + 1;
 146         }
 147
 148         strbuf_release(&buf);
 149         return NULL;
 150 }
 151
 152 static int exists_in_PATH(const char *file)
 153 {
 154         char *r = locate_in_PATH(file);
 155         free(r);
 156         return r != NULL;
 157 }
 158
 159 int sane_execvp(const char *file, char * const argv[])
 160 {
 161         if (!execvp(file, argv))
 162                 return 0; /* cannot happen ;-) */
 163
 164         /*
 165          * When a command can't be found because one of the directories
 166          * listed in $PATH is unsearchable, execvp reports EACCES, but
 167          * careful usability testing (read: analysis of occasional bug
 168          * reports) reveals that "No such file or directory" is more
 169          * intuitive.
 170          *
 171          * We avoid commands with "/", because execvp will not do $PATH
 172          * lookups in that case.
 173          *
 174          * The reassignment of EACCES to errno looks like a no-op below,
 175          * but we need to protect against exists_in_PATH overwriting errno.
 176          */
 177         if (errno == EACCES && !strchr(file, '/'))
 178                 errno = exists_in_PATH(file) ? EACCES : ENOENT;
 179         else if (errno == ENOTDIR && !strchr(file, '/'))
 180                 errno = ENOENT;
 181         return -1;
 182 }
 183
 184 static const char **prepare_shell_cmd(struct argv_array *out, const char **argv)
 185 {
 186         if (!argv[0])
 187                 die("BUG: shell command is empty");
 188
 189         if (strcspn(argv[0], "|&;<>()$`\\\"' \t\n*?[#~=%") != strlen(argv[0])) {
 190 #ifndef GIT_WINDOWS_NATIVE
 191                 argv_array_push(out, SHELL_PATH);
 192 #else
 193                 argv_array_push(out, "sh");
 194 #endif
 195                 argv_array_push(out, "-c");
 196
 197                 /*
 198                  * If we have no extra arguments, we do not even need to
 199                  * bother with the "$@" magic.
 200                  */
 201                 if (!argv[1])
 202                         argv_array_push(out, argv[0]);
 203                 else
 204                         argv_array_pushf(out, "%s \"$@\"", argv[0]);
 205         }
 206
 207         argv_array_pushv(out, argv);
 208         return out->argv;
 209 }
 210
 211 #ifndef GIT_WINDOWS_NATIVE
 212 static int child_notifier = -1;
 213
 214 enum child_errcode {
 215         CHILD_ERR_CHDIR,
 216         CHILD_ERR_DUP2,
 217         CHILD_ERR_CLOSE,
 218         CHILD_ERR_ENOENT,
 219         CHILD_ERR_SILENT,
 220         CHILD_ERR_ERRNO
 221 };
 222
 223 struct child_err {
 224         enum child_errcode err;
 225         int syserr; /* errno */
 226 };
 227
 228 static void child_die(enum child_errcode err)
 229 {
 230         struct child_err buf;
 231
 232         buf.err = err;
 233         buf.syserr = errno;
 234
 235         /* write(2) on buf smaller than PIPE_BUF (min 512) is atomic: */
 236         xwrite(child_notifier, &buf, sizeof(buf));
 237         _exit(1);
 238 }
 239
 240 static void child_dup2(int fd, int to)
 241 {
 242         if (dup2(fd, to) < 0)
 243                 child_die(CHILD_ERR_DUP2);
 244 }
 245
 246 static void child_close(int fd)
 247 {
 248         if (close(fd))
 249                 child_die(CHILD_ERR_CLOSE);
 250 }
 251
 252 static void child_close_pair(int fd[2])
 253 {
 254         child_close(fd[0]);
 255         child_close(fd[1]);
 256 }
 257
 258 /*
 259  * parent will make it look like the child spewed a fatal error and died
 260  * this is needed to prevent changes to t0061.
 261  */
 262 static void fake_fatal(const char *err, va_list params)
 263 {
 264         vreportf("fatal: ", err, params);
 265 }
 266
 267 static void child_error_fn(const char *err, va_list params)
 268 {
 269         const char msg[] = "error() should not be called in child\n";
 270         xwrite(2, msg, sizeof(msg) - 1);
 271 }
 272
 273 static void child_warn_fn(const char *err, va_list params)
 274 {
 275         const char msg[] = "warn() should not be called in child\n";
 276         xwrite(2, msg, sizeof(msg) - 1);
 277 }
 278
 279 static void NORETURN child_die_fn(const char *err, va_list params)
 280 {
 281         const char msg[] = "die() should not be called in child\n";
 282         xwrite(2, msg, sizeof(msg) - 1);
 283         _exit(2);
 284 }
 285
 286 /* this runs in the parent process */
 287 static void child_err_spew(struct child_process *cmd, struct child_err *cerr)
 288 {
 289         static void (*old_errfn)(const char *err, va_list params);
 290
 291         old_errfn = get_error_routine();
 292         set_error_routine(fake_fatal);
 293         errno = cerr->syserr;
 294
 295         switch (cerr->err) {
 296         case CHILD_ERR_CHDIR:
 297                 error_errno("exec '%s': cd to '%s' failed",
 298                             cmd->argv[0], cmd->dir);
 299                 break;
 300         case CHILD_ERR_DUP2:
 301                 error_errno("dup2() in child failed");
 302                 break;
 303         case CHILD_ERR_CLOSE:
 304                 error_errno("close() in child failed");
 305                 break;
 306         case CHILD_ERR_ENOENT:
 307                 error_errno("cannot run %s", cmd->argv[0]);
 308                 break;
 309         case CHILD_ERR_SILENT:
 310                 break;
 311         case CHILD_ERR_ERRNO:
 312                 error_errno("cannot exec '%s'", cmd->argv[0]);
 313                 break;
 314         }
 315         set_error_routine(old_errfn);
 316 }
 317
 318 static void prepare_cmd(struct argv_array *out, const struct child_process *cmd)
 319 {
 320         if (!cmd->argv[0])
 321                 die("BUG: command is empty");
 322
 323         /*
 324          * Add SHELL_PATH so in the event exec fails with ENOEXEC we can
 325          * attempt to interpret the command with 'sh'.
 326          */
 327         argv_array_push(out, SHELL_PATH);
 328
 329         if (cmd->git_cmd) {
 330                 argv_array_push(out, "git");
 331                 argv_array_pushv(out, cmd->argv);
 332         } else if (cmd->use_shell) {
 333                 prepare_shell_cmd(out, cmd->argv);
 334         } else {
 335                 argv_array_pushv(out, cmd->argv);
 336         }
 337
 338         /*
 339          * If there are no '/' characters in the command then perform a path
 340          * lookup and use the resolved path as the command to exec.  If there
 341          * are no '/' characters or if the command wasn't found in the path,
 342          * have exec attempt to invoke the command directly.
 343          */
 344         if (!strchr(out->argv[1], '/')) {
 345                 char *program = locate_in_PATH(out->argv[1]);
 346                 if (program) {
 347                         free((char *)out->argv[1]);
 348                         out->argv[1] = program;
 349                 }
 350         }
 351 }
 352
 353 static char **prep_childenv(const char *const *deltaenv)
 354 {
 355         extern char **environ;
 356         char **childenv;
 357         struct string_list env = STRING_LIST_INIT_DUP;
 358         struct strbuf key = STRBUF_INIT;
 359         const char *const *p;
 360         int i;
 361
 362         /* Construct a sorted string list consisting of the current environ */
 363         for (p = (const char *const *) environ; p && *p; p++) {
 364                 const char *equals = strchr(*p, '=');
 365
 366                 if (equals) {
 367                         strbuf_reset(&key);
 368                         strbuf_add(&key, *p, equals - *p);
 369                         string_list_append(&env, key.buf)->util = (void *) *p;
 370                 } else {
 371                         string_list_append(&env, *p)->util = (void *) *p;
 372                 }
 373         }
 374         string_list_sort(&env);
 375
 376         /* Merge in 'deltaenv' with the current environ */
 377         for (p = deltaenv; p && *p; p++) {
 378                 const char *equals = strchr(*p, '=');
 379
 380                 if (equals) {
 381                         /* ('key=value'), insert or replace entry */
 382                         strbuf_reset(&key);
 383                         strbuf_add(&key, *p, equals - *p);
 384                         string_list_insert(&env, key.buf)->util = (void *) *p;
 385                 } else {
 386                         /* otherwise ('key') remove existing entry */
 387                         string_list_remove(&env, *p, 0);
 388                 }
 389         }
 390
 391         /* Create an array of 'char *' to be used as the childenv */
 392         childenv = xmalloc((env.nr + 1) * sizeof(char *));
 393         for (i = 0; i < env.nr; i++)
 394                 childenv[i] = env.items[i].util;
 395         childenv[env.nr] = NULL;
 396
 397         string_list_clear(&env, 0);
 398         strbuf_release(&key);
 399         return childenv;
 400 }
 401 #endif
 402
 403 static inline void set_cloexec(int fd)
 404 {
 405         int flags = fcntl(fd, F_GETFD);
 406         if (flags >= 0)
 407                 fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
 408 }
 409
 410 static int wait_or_whine(pid_t pid, const char *argv0, int in_signal)
 411 {
 412         int status, code = -1;
 413         pid_t waiting;
 414         int failed_errno = 0;
 415
 416         while ((waiting = waitpid(pid, &status, 0)) < 0 && errno == EINTR)
 417                 ;       /* nothing */
 418         if (in_signal)
 419                 return 0;
 420
 421         if (waiting < 0) {
 422                 failed_errno = errno;
 423                 error_errno("waitpid for %s failed", argv0);
 424         } else if (waiting != pid) {
 425                 error("waitpid is confused (%s)", argv0);
 426         } else if (WIFSIGNALED(status)) {
 427                 code = WTERMSIG(status);
 428                 if (code != SIGINT && code != SIGQUIT && code != SIGPIPE)
 429                         error("%s died of signal %d", argv0, code);
 430                 /*
 431                  * This return value is chosen so that code & 0xff
 432                  * mimics the exit code that a POSIX shell would report for
 433                  * a program that died from this signal.
 434                  */
 435                 code += 128;
 436         } else if (WIFEXITED(status)) {
 437                 code = WEXITSTATUS(status);
 438         } else {
 439                 error("waitpid is confused (%s)", argv0);
 440         }
 441
 442         clear_child_for_cleanup(pid);
 443
 444         errno = failed_errno;
 445         return code;
 446 }
 447
 448 int start_command(struct child_process *cmd)
 449 {
 450         int need_in, need_out, need_err;
 451         int fdin[2], fdout[2], fderr[2];
 452         int failed_errno;
 453         char *str;
 454
 455         if (!cmd->argv)
 456                 cmd->argv = cmd->args.argv;
 457         if (!cmd->env)
 458                 cmd->env = cmd->env_array.argv;
 459
 460         /*
 461          * In case of errors we must keep the promise to close FDs
 462          * that have been passed in via ->in and ->out.
 463          */
 464
 465         need_in = !cmd->no_stdin && cmd->in < 0;
 466         if (need_in) {
 467                 if (pipe(fdin) < 0) {
 468                         failed_errno = errno;
 469                         if (cmd->out > 0)
 470                                 close(cmd->out);
 471                         str = "standard input";
 472                         goto fail_pipe;
 473                 }
 474                 cmd->in = fdin[1];
 475         }
 476
 477         need_out = !cmd->no_stdout
 478                 && !cmd->stdout_to_stderr
 479                 && cmd->out < 0;
 480         if (need_out) {
 481                 if (pipe(fdout) < 0) {
 482                         failed_errno = errno;
 483                         if (need_in)
 484                                 close_pair(fdin);
 485                         else if (cmd->in)
 486                                 close(cmd->in);
 487                         str = "standard output";
 488                         goto fail_pipe;
 489                 }
 490                 cmd->out = fdout[0];
 491         }
 492
 493         need_err = !cmd->no_stderr && cmd->err < 0;
 494         if (need_err) {
 495                 if (pipe(fderr) < 0) {
 496                         failed_errno = errno;
 497                         if (need_in)
 498                                 close_pair(fdin);
 499                         else if (cmd->in)
 500                                 close(cmd->in);
 501                         if (need_out)
 502                                 close_pair(fdout);
 503                         else if (cmd->out)
 504                                 close(cmd->out);
 505                         str = "standard error";
 506 fail_pipe:
 507                         error("cannot create %s pipe for %s: %s",
 508                                 str, cmd->argv[0], strerror(failed_errno));
 509                         child_process_clear(cmd);
 510                         errno = failed_errno;
 511                         return -1;
 512                 }
 513                 cmd->err = fderr[0];
 514         }
 515
 516         trace_argv_printf(cmd->argv, "trace: run_command:");
 517         fflush(NULL);
 518
 519 #ifndef GIT_WINDOWS_NATIVE
 520 {
 521         int notify_pipe[2];
 522         int null_fd = -1;
 523         char **childenv;
 524         struct argv_array argv = ARGV_ARRAY_INIT;
 525         struct child_err cerr;
 526
 527         if (pipe(notify_pipe))
 528                 notify_pipe[0] = notify_pipe[1] = -1;
 529
 530         if (cmd->no_stdin || cmd->no_stdout || cmd->no_stderr) {
 531                 null_fd = open("/dev/null", O_RDWR | O_CLOEXEC);
 532                 if (null_fd < 0)
 533                         die_errno(_("open /dev/null failed"));
 534                 set_cloexec(null_fd);
 535         }
 536
 537         prepare_cmd(&argv, cmd);
 538         childenv = prep_childenv(cmd->env);
 539
 540         cmd->pid = fork();
 541         failed_errno = errno;
 542         if (!cmd->pid) {
 543                 /*
 544                  * Ensure the default die/error/warn routines do not get
 545                  * called, they can take stdio locks and malloc.
 546                  */
 547                 set_die_routine(child_die_fn);
 548                 set_error_routine(child_error_fn);
 549                 set_warn_routine(child_warn_fn);
 550
 551                 close(notify_pipe[0]);
 552                 set_cloexec(notify_pipe[1]);
 553                 child_notifier = notify_pipe[1];
 554
 555                 if (cmd->no_stdin)
 556                         child_dup2(null_fd, 0);
 557                 else if (need_in) {
 558                         child_dup2(fdin[0], 0);
 559                         child_close_pair(fdin);
 560                 } else if (cmd->in) {
 561                         child_dup2(cmd->in, 0);
 562                         child_close(cmd->in);
 563                 }
 564
 565                 if (cmd->no_stderr)
 566                         child_dup2(null_fd, 2);
 567                 else if (need_err) {
 568                         child_dup2(fderr[1], 2);
 569                         child_close_pair(fderr);
 570                 } else if (cmd->err > 1) {
 571                         child_dup2(cmd->err, 2);
 572                         child_close(cmd->err);
 573                 }
 574
 575                 if (cmd->no_stdout)
 576                         child_dup2(null_fd, 1);
 577                 else if (cmd->stdout_to_stderr)
 578                         child_dup2(2, 1);
 579                 else if (need_out) {
 580                         child_dup2(fdout[1], 1);
 581                         child_close_pair(fdout);
 582                 } else if (cmd->out > 1) {
 583                         child_dup2(cmd->out, 1);
 584                         child_close(cmd->out);
 585                 }
 586
 587                 if (cmd->dir && chdir(cmd->dir))
 588                         child_die(CHILD_ERR_CHDIR);
 589
 590                 /*
 591                  * Attempt to exec using the command and arguments starting at
 592                  * argv.argv[1].  argv.argv[0] contains SHELL_PATH which will
 593                  * be used in the event exec failed with ENOEXEC at which point
 594                  * we will try to interpret the command using 'sh'.
 595                  */
 596                 execve(argv.argv[1], (char *const *) argv.argv + 1,
 597                        (char *const *) childenv);
 598                 if (errno == ENOEXEC)
 599                         execve(argv.argv[0], (char *const *) argv.argv,
 600                                (char *const *) childenv);
 601
 602                 if (errno == ENOENT) {
 603                         if (cmd->silent_exec_failure)
 604                                 child_die(CHILD_ERR_SILENT);
 605                         child_die(CHILD_ERR_ENOENT);
 606                 } else {
 607                         child_die(CHILD_ERR_ERRNO);
 608                 }
 609         }
 610         if (cmd->pid < 0)
 611                 error_errno("cannot fork() for %s", cmd->argv[0]);
 612         else if (cmd->clean_on_exit)
 613                 mark_child_for_cleanup(cmd->pid, cmd);
 614
 615         /*
 616          * Wait for child's exec. If the exec succeeds (or if fork()
 617          * failed), EOF is seen immediately by the parent. Otherwise, the
 618          * child process sends a child_err struct.
 619          * Note that use of this infrastructure is completely advisory,
 620          * therefore, we keep error checks minimal.
 621          */
 622         close(notify_pipe[1]);
 623         if (xread(notify_pipe[0], &cerr, sizeof(cerr)) == sizeof(cerr)) {
 624                 /*
 625                  * At this point we know that fork() succeeded, but exec()
 626                  * failed. Errors have been reported to our stderr.
 627                  */
 628                 wait_or_whine(cmd->pid, cmd->argv[0], 0);
 629                 child_err_spew(cmd, &cerr);
 630                 failed_errno = errno;
 631                 cmd->pid = -1;
 632         }
 633         close(notify_pipe[0]);
 634
 635         if (null_fd >= 0)
 636                 close(null_fd);
 637         argv_array_clear(&argv);
 638         free(childenv);
 639 }
 640 #else
 641 {
 642         int fhin = 0, fhout = 1, fherr = 2;
 643         const char **sargv = cmd->argv;
 644         struct argv_array nargv = ARGV_ARRAY_INIT;
 645
 646         if (cmd->no_stdin)
 647                 fhin = open("/dev/null", O_RDWR);
 648         else if (need_in)
 649                 fhin = dup(fdin[0]);
 650         else if (cmd->in)
 651                 fhin = dup(cmd->in);
 652
 653         if (cmd->no_stderr)
 654                 fherr = open("/dev/null", O_RDWR);
 655         else if (need_err)
 656                 fherr = dup(fderr[1]);
 657         else if (cmd->err > 2)
 658                 fherr = dup(cmd->err);
 659
 660         if (cmd->no_stdout)
 661                 fhout = open("/dev/null", O_RDWR);
 662         else if (cmd->stdout_to_stderr)
 663                 fhout = dup(fherr);
 664         else if (need_out)
 665                 fhout = dup(fdout[1]);
 666         else if (cmd->out > 1)
 667                 fhout = dup(cmd->out);
 668
 669         if (cmd->git_cmd)
 670                 cmd->argv = prepare_git_cmd(&nargv, cmd->argv);
 671         else if (cmd->use_shell)
 672                 cmd->argv = prepare_shell_cmd(&nargv, cmd->argv);
 673
 674         cmd->pid = mingw_spawnvpe(cmd->argv[0], cmd->argv, (char**) cmd->env,
 675                         cmd->dir, fhin, fhout, fherr);
 676         failed_errno = errno;
 677         if (cmd->pid < 0 && (!cmd->silent_exec_failure || errno != ENOENT))
 678                 error_errno("cannot spawn %s", cmd->argv[0]);
 679         if (cmd->clean_on_exit && cmd->pid >= 0)
 680                 mark_child_for_cleanup(cmd->pid, cmd);
 681
 682         argv_array_clear(&nargv);
 683         cmd->argv = sargv;
 684         if (fhin != 0)
 685                 close(fhin);
 686         if (fhout != 1)
 687                 close(fhout);
 688         if (fherr != 2)
 689                 close(fherr);
 690 }
 691 #endif
 692
 693         if (cmd->pid < 0) {
 694                 if (need_in)
 695                         close_pair(fdin);
 696                 else if (cmd->in)
 697                         close(cmd->in);
 698                 if (need_out)
 699                         close_pair(fdout);
 700                 else if (cmd->out)
 701                         close(cmd->out);
 702                 if (need_err)
 703                         close_pair(fderr);
 704                 else if (cmd->err)
 705                         close(cmd->err);
 706                 child_process_clear(cmd);
 707                 errno = failed_errno;
 708                 return -1;
 709         }
 710
 711         if (need_in)
 712                 close(fdin[0]);
 713         else if (cmd->in)
 714                 close(cmd->in);
 715
 716         if (need_out)
 717                 close(fdout[1]);
 718         else if (cmd->out)
 719                 close(cmd->out);
 720
 721         if (need_err)
 722                 close(fderr[1]);
 723         else if (cmd->err)
 724                 close(cmd->err);
 725
 726         return 0;
 727 }
 728
 729 int finish_command(struct child_process *cmd)
 730 {
 731         int ret = wait_or_whine(cmd->pid, cmd->argv[0], 0);
 732         child_process_clear(cmd);
 733         return ret;
 734 }
 735
 736 int finish_command_in_signal(struct child_process *cmd)
 737 {
 738         return wait_or_whine(cmd->pid, cmd->argv[0], 1);
 739 }
 740
 741
 742 int run_command(struct child_process *cmd)
 743 {
 744         int code;
 745
 746         if (cmd->out < 0 || cmd->err < 0)
 747                 die("BUG: run_command with a pipe can cause deadlock");
 748
 749         code = start_command(cmd);
 750         if (code)
 751                 return code;
 752         return finish_command(cmd);
 753 }
 754
 755 int run_command_v_opt(const char **argv, int opt)
 756 {
 757         return run_command_v_opt_cd_env(argv, opt, NULL, NULL);
 758 }
 759
 760 int run_command_v_opt_cd_env(const char **argv, int opt, const char *dir, const char *const *env)
 761 {
 762         struct child_process cmd = CHILD_PROCESS_INIT;
 763         cmd.argv = argv;
 764         cmd.no_stdin = opt & RUN_COMMAND_NO_STDIN ? 1 : 0;
 765         cmd.git_cmd = opt & RUN_GIT_CMD ? 1 : 0;
 766         cmd.stdout_to_stderr = opt & RUN_COMMAND_STDOUT_TO_STDERR ? 1 : 0;
 767         cmd.silent_exec_failure = opt & RUN_SILENT_EXEC_FAILURE ? 1 : 0;
 768         cmd.use_shell = opt & RUN_USING_SHELL ? 1 : 0;
 769         cmd.clean_on_exit = opt & RUN_CLEAN_ON_EXIT ? 1 : 0;
 770         cmd.dir = dir;
 771         cmd.env = env;
 772         return run_command(&cmd);
 773 }
 774
 775 #ifndef NO_PTHREADS
 776 static pthread_t main_thread;
 777 static int main_thread_set;
 778 static pthread_key_t async_key;
 779 static pthread_key_t async_die_counter;
 780
 781 static void *run_thread(void *data)
 782 {
 783         struct async *async = data;
 784         intptr_t ret;
 785
 786         if (async->isolate_sigpipe) {
 787                 sigset_t mask;
 788                 sigemptyset(&mask);
 789                 sigaddset(&mask, SIGPIPE);
 790                 if (pthread_sigmask(SIG_BLOCK, &mask, NULL) < 0) {
 791                         ret = error("unable to block SIGPIPE in async thread");
 792                         return (void *)ret;
 793                 }
 794         }
 795
 796         pthread_setspecific(async_key, async);
 797         ret = async->proc(async->proc_in, async->proc_out, async->data);
 798         return (void *)ret;
 799 }
 800
 801 static NORETURN void die_async(const char *err, va_list params)
 802 {
 803         vreportf("fatal: ", err, params);
 804
 805         if (in_async()) {
 806                 struct async *async = pthread_getspecific(async_key);
 807                 if (async->proc_in >= 0)
 808                         close(async->proc_in);
 809                 if (async->proc_out >= 0)
 810                         close(async->proc_out);
 811                 pthread_exit((void *)128);
 812         }
 813
 814         exit(128);
 815 }
 816
 817 static int async_die_is_recursing(void)
 818 {
 819         void *ret = pthread_getspecific(async_die_counter);
 820         pthread_setspecific(async_die_counter, (void *)1);
 821         return ret != NULL;
 822 }
 823
 824 int in_async(void)
 825 {
 826         if (!main_thread_set)
 827                 return 0; /* no asyncs started yet */
 828         return !pthread_equal(main_thread, pthread_self());
 829 }
 830
 831 static void NORETURN async_exit(int code)
 832 {
 833         pthread_exit((void *)(intptr_t)code);
 834 }
 835
 836 #else
 837
 838 static struct {
 839         void (**handlers)(void);
 840         size_t nr;
 841         size_t alloc;
 842 } git_atexit_hdlrs;
 843
 844 static int git_atexit_installed;
 845
 846 static void git_atexit_dispatch(void)
 847 {
 848         size_t i;
 849
 850         for (i=git_atexit_hdlrs.nr ; i ; i--)
 851                 git_atexit_hdlrs.handlers[i-1]();
 852 }
 853
 854 static void git_atexit_clear(void)
 855 {
 856         free(git_atexit_hdlrs.handlers);
 857         memset(&git_atexit_hdlrs, 0, sizeof(git_atexit_hdlrs));
 858         git_atexit_installed = 0;
 859 }
 860
 861 #undef atexit
 862 int git_atexit(void (*handler)(void))
 863 {
 864         ALLOC_GROW(git_atexit_hdlrs.handlers, git_atexit_hdlrs.nr + 1, git_atexit_hdlrs.alloc);
 865         git_atexit_hdlrs.handlers[git_atexit_hdlrs.nr++] = handler;
 866         if (!git_atexit_installed) {
 867                 if (atexit(&git_atexit_dispatch))
 868                         return -1;
 869                 git_atexit_installed = 1;
 870         }
 871         return 0;
 872 }
 873 #define atexit git_atexit
 874
 875 static int process_is_async;
 876 int in_async(void)
 877 {
 878         return process_is_async;
 879 }
 880
 881 static void NORETURN async_exit(int code)
 882 {
 883         exit(code);
 884 }
 885
 886 #endif
 887
 888 void check_pipe(int err)
 889 {
 890         if (err == EPIPE) {
 891                 if (in_async())
 892                         async_exit(141);
 893
 894                 signal(SIGPIPE, SIG_DFL);
 895                 raise(SIGPIPE);
 896                 /* Should never happen, but just in case... */
 897                 exit(141);
 898         }
 899 }
 900
 901 int start_async(struct async *async)
 902 {
 903         int need_in, need_out;
 904         int fdin[2], fdout[2];
 905         int proc_in, proc_out;
 906
 907         need_in = async->in < 0;
 908         if (need_in) {
 909                 if (pipe(fdin) < 0) {
 910                         if (async->out > 0)
 911                                 close(async->out);
 912                         return error_errno("cannot create pipe");
 913                 }
 914                 async->in = fdin[1];
 915         }
 916
 917         need_out = async->out < 0;
 918         if (need_out) {
 919                 if (pipe(fdout) < 0) {
 920                         if (need_in)
 921                                 close_pair(fdin);
 922                         else if (async->in)
 923                                 close(async->in);
 924                         return error_errno("cannot create pipe");
 925                 }
 926                 async->out = fdout[0];
 927         }
 928
 929         if (need_in)
 930                 proc_in = fdin[0];
 931         else if (async->in)
 932                 proc_in = async->in;
 933         else
 934                 proc_in = -1;
 935
 936         if (need_out)
 937                 proc_out = fdout[1];
 938         else if (async->out)
 939                 proc_out = async->out;
 940         else
 941                 proc_out = -1;
 942
 943 #ifdef NO_PTHREADS
 944         /* Flush stdio before fork() to avoid cloning buffers */
 945         fflush(NULL);
 946
 947         async->pid = fork();
 948         if (async->pid < 0) {
 949                 error_errno("fork (async) failed");
 950                 goto error;
 951         }
 952         if (!async->pid) {
 953                 if (need_in)
 954                         close(fdin[1]);
 955                 if (need_out)
 956                         close(fdout[0]);
 957                 git_atexit_clear();
 958                 process_is_async = 1;
 959                 exit(!!async->proc(proc_in, proc_out, async->data));
 960         }
 961
 962         mark_child_for_cleanup(async->pid, NULL);
 963
 964         if (need_in)
 965                 close(fdin[0]);
 966         else if (async->in)
 967                 close(async->in);
 968
 969         if (need_out)
 970                 close(fdout[1]);
 971         else if (async->out)
 972                 close(async->out);
 973 #else
 974         if (!main_thread_set) {
 975                 /*
 976                  * We assume that the first time that start_async is called
 977                  * it is from the main thread.
 978                  */
 979                 main_thread_set = 1;
 980                 main_thread = pthread_self();
 981                 pthread_key_create(&async_key, NULL);
 982                 pthread_key_create(&async_die_counter, NULL);
 983                 set_die_routine(die_async);
 984                 set_die_is_recursing_routine(async_die_is_recursing);
 985         }
 986
 987         if (proc_in >= 0)
 988                 set_cloexec(proc_in);
 989         if (proc_out >= 0)
 990                 set_cloexec(proc_out);
 991         async->proc_in = proc_in;
 992         async->proc_out = proc_out;
 993         {
 994                 int err = pthread_create(&async->tid, NULL, run_thread, async);
 995                 if (err) {
 996                         error_errno("cannot create thread");
 997                         goto error;
 998                 }
 999         }
1000 #endif
1001         return 0;
1002
1003 error:
1004         if (need_in)
1005                 close_pair(fdin);
1006         else if (async->in)
1007                 close(async->in);
1008
1009         if (need_out)
1010                 close_pair(fdout);
1011         else if (async->out)
1012                 close(async->out);
1013         return -1;
1014 }
1015
1016 int finish_async(struct async *async)
1017 {
1018 #ifdef NO_PTHREADS
1019         return wait_or_whine(async->pid, "child process", 0);
1020 #else
1021         void *ret = (void *)(intptr_t)(-1);
1022
1023         if (pthread_join(async->tid, &ret))
1024                 error("pthread_join failed");
1025         return (int)(intptr_t)ret;
1026 #endif
1027 }
1028
1029 const char *find_hook(const char *name)
1030 {
1031         static struct strbuf path = STRBUF_INIT;
1032
1033         strbuf_reset(&path);
1034         strbuf_git_path(&path, "hooks/%s", name);
1035         if (access(path.buf, X_OK) < 0) {
1036 #ifdef STRIP_EXTENSION
1037                 strbuf_addstr(&path, STRIP_EXTENSION);
1038                 if (access(path.buf, X_OK) >= 0)
1039                         return path.buf;
1040 #endif
1041                 return NULL;
1042         }
1043         return path.buf;
1044 }
1045
1046 int run_hook_ve(const char *const *env, const char *name, va_list args)
1047 {
1048         struct child_process hook = CHILD_PROCESS_INIT;
1049         const char *p;
1050
1051         p = find_hook(name);
1052         if (!p)
1053                 return 0;
1054
1055         argv_array_push(&hook.args, p);
1056         while ((p = va_arg(args, const char *)))
1057                 argv_array_push(&hook.args, p);
1058         hook.env = env;
1059         hook.no_stdin = 1;
1060         hook.stdout_to_stderr = 1;
1061
1062         return run_command(&hook);
1063 }
1064
1065 int run_hook_le(const char *const *env, const char *name, ...)
1066 {
1067         va_list args;
1068         int ret;
1069
1070         va_start(args, name);
1071         ret = run_hook_ve(env, name, args);
1072         va_end(args);
1073
1074         return ret;
1075 }
1076
1077 struct io_pump {
1078         /* initialized by caller */
1079         int fd;
1080         int type; /* POLLOUT or POLLIN */
1081         union {
1082                 struct {
1083                         const char *buf;
1084                         size_t len;
1085                 } out;
1086                 struct {
1087                         struct strbuf *buf;
1088                         size_t hint;
1089                 } in;
1090         } u;
1091
1092         /* returned by pump_io */
1093         int error; /* 0 for success, otherwise errno */
1094
1095         /* internal use */
1096         struct pollfd *pfd;
1097 };
1098
1099 static int pump_io_round(struct io_pump *slots, int nr, struct pollfd *pfd)
1100 {
1101         int pollsize = 0;
1102         int i;
1103
1104         for (i = 0; i < nr; i++) {
1105                 struct io_pump *io = &slots[i];
1106                 if (io->fd < 0)
1107                         continue;
1108                 pfd[pollsize].fd = io->fd;
1109                 pfd[pollsize].events = io->type;
1110                 io->pfd = &pfd[pollsize++];
1111         }
1112
1113         if (!pollsize)
1114                 return 0;
1115
1116         if (poll(pfd, pollsize, -1) < 0) {
1117                 if (errno == EINTR)
1118                         return 1;
1119                 die_errno("poll failed");
1120         }
1121
1122         for (i = 0; i < nr; i++) {
1123                 struct io_pump *io = &slots[i];
1124
1125                 if (io->fd < 0)
1126                         continue;
1127
1128                 if (!(io->pfd->revents & (POLLOUT|POLLIN|POLLHUP|POLLERR|POLLNVAL)))
1129                         continue;
1130
1131                 if (io->type == POLLOUT) {
1132                         ssize_t len = xwrite(io->fd,
1133                                              io->u.out.buf, io->u.out.len);
1134                         if (len < 0) {
1135                                 io->error = errno;
1136                                 close(io->fd);
1137                                 io->fd = -1;
1138                         } else {
1139                                 io->u.out.buf += len;
1140                                 io->u.out.len -= len;
1141                                 if (!io->u.out.len) {
1142                                         close(io->fd);
1143                                         io->fd = -1;
1144                                 }
1145                         }
1146                 }
1147
1148                 if (io->type == POLLIN) {
1149                         ssize_t len = strbuf_read_once(io->u.in.buf,
1150                                                        io->fd, io->u.in.hint);
1151                         if (len < 0)
1152                                 io->error = errno;
1153                         if (len <= 0) {
1154                                 close(io->fd);
1155                                 io->fd = -1;
1156                         }
1157                 }
1158         }
1159
1160         return 1;
1161 }
1162
1163 static int pump_io(struct io_pump *slots, int nr)
1164 {
1165         struct pollfd *pfd;
1166         int i;
1167
1168         for (i = 0; i < nr; i++)
1169                 slots[i].error = 0;
1170
1171         ALLOC_ARRAY(pfd, nr);
1172         while (pump_io_round(slots, nr, pfd))
1173                 ; /* nothing */
1174         free(pfd);
1175
1176         /* There may be multiple errno values, so just pick the first. */
1177         for (i = 0; i < nr; i++) {
1178                 if (slots[i].error) {
1179                         errno = slots[i].error;
1180                         return -1;
1181                 }
1182         }
1183         return 0;
1184 }
1185
1186
1187 int pipe_command(struct child_process *cmd,
1188                  const char *in, size_t in_len,
1189                  struct strbuf *out, size_t out_hint,
1190                  struct strbuf *err, size_t err_hint)
1191 {
1192         struct io_pump io[3];
1193         int nr = 0;
1194
1195         if (in)
1196                 cmd->in = -1;
1197         if (out)
1198                 cmd->out = -1;
1199         if (err)
1200                 cmd->err = -1;
1201
1202         if (start_command(cmd) < 0)
1203                 return -1;
1204
1205         if (in) {
1206                 io[nr].fd = cmd->in;
1207                 io[nr].type = POLLOUT;
1208                 io[nr].u.out.buf = in;
1209                 io[nr].u.out.len = in_len;
1210                 nr++;
1211         }
1212         if (out) {
1213                 io[nr].fd = cmd->out;
1214                 io[nr].type = POLLIN;
1215                 io[nr].u.in.buf = out;
1216                 io[nr].u.in.hint = out_hint;
1217                 nr++;
1218         }
1219         if (err) {
1220                 io[nr].fd = cmd->err;
1221                 io[nr].type = POLLIN;
1222                 io[nr].u.in.buf = err;
1223                 io[nr].u.in.hint = err_hint;
1224                 nr++;
1225         }
1226
1227         if (pump_io(io, nr) < 0) {
1228                 finish_command(cmd); /* throw away exit code */
1229                 return -1;
1230         }
1231
1232         return finish_command(cmd);
1233 }
1234
1235 enum child_state {
1236         GIT_CP_FREE,
1237         GIT_CP_WORKING,
1238         GIT_CP_WAIT_CLEANUP,
1239 };
1240
1241 struct parallel_processes {
1242         void *data;
1243
1244         int max_processes;
1245         int nr_processes;
1246
1247         get_next_task_fn get_next_task;
1248         start_failure_fn start_failure;
1249         task_finished_fn task_finished;
1250
1251         struct {
1252                 enum child_state state;
1253                 struct child_process process;
1254                 struct strbuf err;
1255                 void *data;
1256         } *children;
1257         /*
1258          * The struct pollfd is logically part of *children,
1259          * but the system call expects it as its own array.
1260          */
1261         struct pollfd *pfd;
1262
1263         unsigned shutdown : 1;
1264
1265         int output_owner;
1266         struct strbuf buffered_output; /* of finished children */
1267 };
1268
1269 static int default_start_failure(struct strbuf *out,
1270                                  void *pp_cb,
1271                                  void *pp_task_cb)
1272 {
1273         return 0;
1274 }
1275
1276 static int default_task_finished(int result,
1277                                  struct strbuf *out,
1278                                  void *pp_cb,
1279                                  void *pp_task_cb)
1280 {
1281         return 0;
1282 }
1283
1284 static void kill_children(struct parallel_processes *pp, int signo)
1285 {
1286         int i, n = pp->max_processes;
1287
1288         for (i = 0; i < n; i++)
1289                 if (pp->children[i].state == GIT_CP_WORKING)
1290                         kill(pp->children[i].process.pid, signo);
1291 }
1292
1293 static struct parallel_processes *pp_for_signal;
1294
1295 static void handle_children_on_signal(int signo)
1296 {
1297         kill_children(pp_for_signal, signo);
1298         sigchain_pop(signo);
1299         raise(signo);
1300 }
1301
1302 static void pp_init(struct parallel_processes *pp,
1303                     int n,
1304                     get_next_task_fn get_next_task,
1305                     start_failure_fn start_failure,
1306                     task_finished_fn task_finished,
1307                     void *data)
1308 {
1309         int i;
1310
1311         if (n < 1)
1312                 n = online_cpus();
1313
1314         pp->max_processes = n;
1315
1316         trace_printf("run_processes_parallel: preparing to run up to %d tasks", n);
1317
1318         pp->data = data;
1319         if (!get_next_task)
1320                 die("BUG: you need to specify a get_next_task function");
1321         pp->get_next_task = get_next_task;
1322
1323         pp->start_failure = start_failure ? start_failure : default_start_failure;
1324         pp->task_finished = task_finished ? task_finished : default_task_finished;
1325
1326         pp->nr_processes = 0;
1327         pp->output_owner = 0;
1328         pp->shutdown = 0;
1329         pp->children = xcalloc(n, sizeof(*pp->children));
1330         pp->pfd = xcalloc(n, sizeof(*pp->pfd));
1331         strbuf_init(&pp->buffered_output, 0);
1332
1333         for (i = 0; i < n; i++) {
1334                 strbuf_init(&pp->children[i].err, 0);
1335                 child_process_init(&pp->children[i].process);
1336                 pp->pfd[i].events = POLLIN | POLLHUP;
1337                 pp->pfd[i].fd = -1;
1338         }
1339
1340         pp_for_signal = pp;
1341         sigchain_push_common(handle_children_on_signal);
1342 }
1343
1344 static void pp_cleanup(struct parallel_processes *pp)
1345 {
1346         int i;
1347
1348         trace_printf("run_processes_parallel: done");
1349         for (i = 0; i < pp->max_processes; i++) {
1350                 strbuf_release(&pp->children[i].err);
1351                 child_process_clear(&pp->children[i].process);
1352         }
1353
1354         free(pp->children);
1355         free(pp->pfd);
1356
1357         /*
1358          * When get_next_task added messages to the buffer in its last
1359          * iteration, the buffered output is non empty.
1360          */
1361         strbuf_write(&pp->buffered_output, stderr);
1362         strbuf_release(&pp->buffered_output);
1363
1364         sigchain_pop_common();
1365 }
1366
1367 /* returns
1368  *  0 if a new task was started.
1369  *  1 if no new jobs was started (get_next_task ran out of work, non critical
1370  *    problem with starting a new command)
1371  * <0 no new job was started, user wishes to shutdown early. Use negative code
1372  *    to signal the children.
1373  */
1374 static int pp_start_one(struct parallel_processes *pp)
1375 {
1376         int i, code;
1377
1378         for (i = 0; i < pp->max_processes; i++)
1379                 if (pp->children[i].state == GIT_CP_FREE)
1380                         break;
1381         if (i == pp->max_processes)
1382                 die("BUG: bookkeeping is hard");
1383
1384         code = pp->get_next_task(&pp->children[i].process,
1385                                  &pp->children[i].err,
1386                                  pp->data,
1387                                  &pp->children[i].data);
1388         if (!code) {
1389                 strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1390                 strbuf_reset(&pp->children[i].err);
1391                 return 1;
1392         }
1393         pp->children[i].process.err = -1;
1394         pp->children[i].process.stdout_to_stderr = 1;
1395         pp->children[i].process.no_stdin = 1;
1396
1397         if (start_command(&pp->children[i].process)) {
1398                 code = pp->start_failure(&pp->children[i].err,
1399                                          pp->data,
1400                                          &pp->children[i].data);
1401                 strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1402                 strbuf_reset(&pp->children[i].err);
1403                 if (code)
1404                         pp->shutdown = 1;
1405                 return code;
1406         }
1407
1408         pp->nr_processes++;
1409         pp->children[i].state = GIT_CP_WORKING;
1410         pp->pfd[i].fd = pp->children[i].process.err;
1411         return 0;
1412 }
1413
1414 static void pp_buffer_stderr(struct parallel_processes *pp, int output_timeout)
1415 {
1416         int i;
1417
1418         while ((i = poll(pp->pfd, pp->max_processes, output_timeout)) < 0) {
1419                 if (errno == EINTR)
1420                         continue;
1421                 pp_cleanup(pp);
1422                 die_errno("poll");
1423         }
1424
1425         /* Buffer output from all pipes. */
1426         for (i = 0; i < pp->max_processes; i++) {
1427                 if (pp->children[i].state == GIT_CP_WORKING &&
1428                     pp->pfd[i].revents & (POLLIN | POLLHUP)) {
1429                         int n = strbuf_read_once(&pp->children[i].err,
1430                                                  pp->children[i].process.err, 0);
1431                         if (n == 0) {
1432                                 close(pp->children[i].process.err);
1433                                 pp->children[i].state = GIT_CP_WAIT_CLEANUP;
1434                         } else if (n < 0)
1435                                 if (errno != EAGAIN)
1436                                         die_errno("read");
1437                 }
1438         }
1439 }
1440
1441 static void pp_output(struct parallel_processes *pp)
1442 {
1443         int i = pp->output_owner;
1444         if (pp->children[i].state == GIT_CP_WORKING &&
1445             pp->children[i].err.len) {
1446                 strbuf_write(&pp->children[i].err, stderr);
1447                 strbuf_reset(&pp->children[i].err);
1448         }
1449 }
1450
1451 static int pp_collect_finished(struct parallel_processes *pp)
1452 {
1453         int i, code;
1454         int n = pp->max_processes;
1455         int result = 0;
1456
1457         while (pp->nr_processes > 0) {
1458                 for (i = 0; i < pp->max_processes; i++)
1459                         if (pp->children[i].state == GIT_CP_WAIT_CLEANUP)
1460                                 break;
1461                 if (i == pp->max_processes)
1462                         break;
1463
1464                 code = finish_command(&pp->children[i].process);
1465
1466                 code = pp->task_finished(code,
1467                                          &pp->children[i].err, pp->data,
1468                                          &pp->children[i].data);
1469
1470                 if (code)
1471                         result = code;
1472                 if (code < 0)
1473                         break;
1474
1475                 pp->nr_processes--;
1476                 pp->children[i].state = GIT_CP_FREE;
1477                 pp->pfd[i].fd = -1;
1478                 child_process_init(&pp->children[i].process);
1479
1480                 if (i != pp->output_owner) {
1481                         strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1482                         strbuf_reset(&pp->children[i].err);
1483                 } else {
1484                         strbuf_write(&pp->children[i].err, stderr);
1485                         strbuf_reset(&pp->children[i].err);
1486
1487                         /* Output all other finished child processes */
1488                         strbuf_write(&pp->buffered_output, stderr);
1489                         strbuf_reset(&pp->buffered_output);
1490
1491                         /*
1492                          * Pick next process to output live.
1493                          * NEEDSWORK:
1494                          * For now we pick it randomly by doing a round
1495                          * robin. Later we may want to pick the one with
1496                          * the most output or the longest or shortest
1497                          * running process time.
1498                          */
1499                         for (i = 0; i < n; i++)
1500                                 if (pp->children[(pp->output_owner + i) % n].state == GIT_CP_WORKING)
1501                                         break;
1502                         pp->output_owner = (pp->output_owner + i) % n;
1503                 }
1504         }
1505         return result;
1506 }
1507
1508 int run_processes_parallel(int n,
1509                            get_next_task_fn get_next_task,
1510                            start_failure_fn start_failure,
1511                            task_finished_fn task_finished,
1512                            void *pp_cb)
1513 {
1514         int i, code;
1515         int output_timeout = 100;
1516         int spawn_cap = 4;
1517         struct parallel_processes pp;
1518
1519         pp_init(&pp, n, get_next_task, start_failure, task_finished, pp_cb);
1520         while (1) {
1521                 for (i = 0;
1522                     i < spawn_cap && !pp.shutdown &&
1523                     pp.nr_processes < pp.max_processes;
1524                     i++) {
1525                         code = pp_start_one(&pp);
1526                         if (!code)
1527                                 continue;
1528                         if (code < 0) {
1529                                 pp.shutdown = 1;
1530                                 kill_children(&pp, -code);
1531                         }
1532                         break;
1533                 }
1534                 if (!pp.nr_processes)
1535                         break;
1536                 pp_buffer_stderr(&pp, output_timeout);
1537                 pp_output(&pp);
1538                 code = pp_collect_finished(&pp);
1539                 if (code) {
1540                         pp.shutdown = 1;
1541                         if (code < 0)
1542                                 kill_children(&pp, -code);
1543                 }
1544         }
1545
1546         pp_cleanup(&pp);
1547         return 0;
1548 }