git.oblomov.eu Git - git/blob - 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         /*
 541          * NOTE: In order to prevent deadlocking when using threads special
 542          * care should be taken with the function calls made in between the
 543          * fork() and exec() calls.  No calls should be made to functions which
 544          * require acquiring a lock (e.g. malloc) as the lock could have been
 545          * held by another thread at the time of forking, causing the lock to
 546          * never be released in the child process.  This means only
 547          * Async-Signal-Safe functions are permitted in the child.
 548          */
 549         cmd->pid = fork();
 550         failed_errno = errno;
 551         if (!cmd->pid) {
 552                 /*
 553                  * Ensure the default die/error/warn routines do not get
 554                  * called, they can take stdio locks and malloc.
 555                  */
 556                 set_die_routine(child_die_fn);
 557                 set_error_routine(child_error_fn);
 558                 set_warn_routine(child_warn_fn);
 559
 560                 close(notify_pipe[0]);
 561                 set_cloexec(notify_pipe[1]);
 562                 child_notifier = notify_pipe[1];
 563
 564                 if (cmd->no_stdin)
 565                         child_dup2(null_fd, 0);
 566                 else if (need_in) {
 567                         child_dup2(fdin[0], 0);
 568                         child_close_pair(fdin);
 569                 } else if (cmd->in) {
 570                         child_dup2(cmd->in, 0);
 571                         child_close(cmd->in);
 572                 }
 573
 574                 if (cmd->no_stderr)
 575                         child_dup2(null_fd, 2);
 576                 else if (need_err) {
 577                         child_dup2(fderr[1], 2);
 578                         child_close_pair(fderr);
 579                 } else if (cmd->err > 1) {
 580                         child_dup2(cmd->err, 2);
 581                         child_close(cmd->err);
 582                 }
 583
 584                 if (cmd->no_stdout)
 585                         child_dup2(null_fd, 1);
 586                 else if (cmd->stdout_to_stderr)
 587                         child_dup2(2, 1);
 588                 else if (need_out) {
 589                         child_dup2(fdout[1], 1);
 590                         child_close_pair(fdout);
 591                 } else if (cmd->out > 1) {
 592                         child_dup2(cmd->out, 1);
 593                         child_close(cmd->out);
 594                 }
 595
 596                 if (cmd->dir && chdir(cmd->dir))
 597                         child_die(CHILD_ERR_CHDIR);
 598
 599                 /*
 600                  * Attempt to exec using the command and arguments starting at
 601                  * argv.argv[1].  argv.argv[0] contains SHELL_PATH which will
 602                  * be used in the event exec failed with ENOEXEC at which point
 603                  * we will try to interpret the command using 'sh'.
 604                  */
 605                 execve(argv.argv[1], (char *const *) argv.argv + 1,
 606                        (char *const *) childenv);
 607                 if (errno == ENOEXEC)
 608                         execve(argv.argv[0], (char *const *) argv.argv,
 609                                (char *const *) childenv);
 610
 611                 if (errno == ENOENT) {
 612                         if (cmd->silent_exec_failure)
 613                                 child_die(CHILD_ERR_SILENT);
 614                         child_die(CHILD_ERR_ENOENT);
 615                 } else {
 616                         child_die(CHILD_ERR_ERRNO);
 617                 }
 618         }
 619         if (cmd->pid < 0)
 620                 error_errno("cannot fork() for %s", cmd->argv[0]);
 621         else if (cmd->clean_on_exit)
 622                 mark_child_for_cleanup(cmd->pid, cmd);
 623
 624         /*
 625          * Wait for child's exec. If the exec succeeds (or if fork()
 626          * failed), EOF is seen immediately by the parent. Otherwise, the
 627          * child process sends a child_err struct.
 628          * Note that use of this infrastructure is completely advisory,
 629          * therefore, we keep error checks minimal.
 630          */
 631         close(notify_pipe[1]);
 632         if (xread(notify_pipe[0], &cerr, sizeof(cerr)) == sizeof(cerr)) {
 633                 /*
 634                  * At this point we know that fork() succeeded, but exec()
 635                  * failed. Errors have been reported to our stderr.
 636                  */
 637                 wait_or_whine(cmd->pid, cmd->argv[0], 0);
 638                 child_err_spew(cmd, &cerr);
 639                 failed_errno = errno;
 640                 cmd->pid = -1;
 641         }
 642         close(notify_pipe[0]);
 643
 644         if (null_fd >= 0)
 645                 close(null_fd);
 646         argv_array_clear(&argv);
 647         free(childenv);
 648 }
 649 #else
 650 {
 651         int fhin = 0, fhout = 1, fherr = 2;
 652         const char **sargv = cmd->argv;
 653         struct argv_array nargv = ARGV_ARRAY_INIT;
 654
 655         if (cmd->no_stdin)
 656                 fhin = open("/dev/null", O_RDWR);
 657         else if (need_in)
 658                 fhin = dup(fdin[0]);
 659         else if (cmd->in)
 660                 fhin = dup(cmd->in);
 661
 662         if (cmd->no_stderr)
 663                 fherr = open("/dev/null", O_RDWR);
 664         else if (need_err)
 665                 fherr = dup(fderr[1]);
 666         else if (cmd->err > 2)
 667                 fherr = dup(cmd->err);
 668
 669         if (cmd->no_stdout)
 670                 fhout = open("/dev/null", O_RDWR);
 671         else if (cmd->stdout_to_stderr)
 672                 fhout = dup(fherr);
 673         else if (need_out)
 674                 fhout = dup(fdout[1]);
 675         else if (cmd->out > 1)
 676                 fhout = dup(cmd->out);
 677
 678         if (cmd->git_cmd)
 679                 cmd->argv = prepare_git_cmd(&nargv, cmd->argv);
 680         else if (cmd->use_shell)
 681                 cmd->argv = prepare_shell_cmd(&nargv, cmd->argv);
 682
 683         cmd->pid = mingw_spawnvpe(cmd->argv[0], cmd->argv, (char**) cmd->env,
 684                         cmd->dir, fhin, fhout, fherr);
 685         failed_errno = errno;
 686         if (cmd->pid < 0 && (!cmd->silent_exec_failure || errno != ENOENT))
 687                 error_errno("cannot spawn %s", cmd->argv[0]);
 688         if (cmd->clean_on_exit && cmd->pid >= 0)
 689                 mark_child_for_cleanup(cmd->pid, cmd);
 690
 691         argv_array_clear(&nargv);
 692         cmd->argv = sargv;
 693         if (fhin != 0)
 694                 close(fhin);
 695         if (fhout != 1)
 696                 close(fhout);
 697         if (fherr != 2)
 698                 close(fherr);
 699 }
 700 #endif
 701
 702         if (cmd->pid < 0) {
 703                 if (need_in)
 704                         close_pair(fdin);
 705                 else if (cmd->in)
 706                         close(cmd->in);
 707                 if (need_out)
 708                         close_pair(fdout);
 709                 else if (cmd->out)
 710                         close(cmd->out);
 711                 if (need_err)
 712                         close_pair(fderr);
 713                 else if (cmd->err)
 714                         close(cmd->err);
 715                 child_process_clear(cmd);
 716                 errno = failed_errno;
 717                 return -1;
 718         }
 719
 720         if (need_in)
 721                 close(fdin[0]);
 722         else if (cmd->in)
 723                 close(cmd->in);
 724
 725         if (need_out)
 726                 close(fdout[1]);
 727         else if (cmd->out)
 728                 close(cmd->out);
 729
 730         if (need_err)
 731                 close(fderr[1]);
 732         else if (cmd->err)
 733                 close(cmd->err);
 734
 735         return 0;
 736 }
 737
 738 int finish_command(struct child_process *cmd)
 739 {
 740         int ret = wait_or_whine(cmd->pid, cmd->argv[0], 0);
 741         child_process_clear(cmd);
 742         return ret;
 743 }
 744
 745 int finish_command_in_signal(struct child_process *cmd)
 746 {
 747         return wait_or_whine(cmd->pid, cmd->argv[0], 1);
 748 }
 749
 750
 751 int run_command(struct child_process *cmd)
 752 {
 753         int code;
 754
 755         if (cmd->out < 0 || cmd->err < 0)
 756                 die("BUG: run_command with a pipe can cause deadlock");
 757
 758         code = start_command(cmd);
 759         if (code)
 760                 return code;
 761         return finish_command(cmd);
 762 }
 763
 764 int run_command_v_opt(const char **argv, int opt)
 765 {
 766         return run_command_v_opt_cd_env(argv, opt, NULL, NULL);
 767 }
 768
 769 int run_command_v_opt_cd_env(const char **argv, int opt, const char *dir, const char *const *env)
 770 {
 771         struct child_process cmd = CHILD_PROCESS_INIT;
 772         cmd.argv = argv;
 773         cmd.no_stdin = opt & RUN_COMMAND_NO_STDIN ? 1 : 0;
 774         cmd.git_cmd = opt & RUN_GIT_CMD ? 1 : 0;
 775         cmd.stdout_to_stderr = opt & RUN_COMMAND_STDOUT_TO_STDERR ? 1 : 0;
 776         cmd.silent_exec_failure = opt & RUN_SILENT_EXEC_FAILURE ? 1 : 0;
 777         cmd.use_shell = opt & RUN_USING_SHELL ? 1 : 0;
 778         cmd.clean_on_exit = opt & RUN_CLEAN_ON_EXIT ? 1 : 0;
 779         cmd.dir = dir;
 780         cmd.env = env;
 781         return run_command(&cmd);
 782 }
 783
 784 #ifndef NO_PTHREADS
 785 static pthread_t main_thread;
 786 static int main_thread_set;
 787 static pthread_key_t async_key;
 788 static pthread_key_t async_die_counter;
 789
 790 static void *run_thread(void *data)
 791 {
 792         struct async *async = data;
 793         intptr_t ret;
 794
 795         if (async->isolate_sigpipe) {
 796                 sigset_t mask;
 797                 sigemptyset(&mask);
 798                 sigaddset(&mask, SIGPIPE);
 799                 if (pthread_sigmask(SIG_BLOCK, &mask, NULL) < 0) {
 800                         ret = error("unable to block SIGPIPE in async thread");
 801                         return (void *)ret;
 802                 }
 803         }
 804
 805         pthread_setspecific(async_key, async);
 806         ret = async->proc(async->proc_in, async->proc_out, async->data);
 807         return (void *)ret;
 808 }
 809
 810 static NORETURN void die_async(const char *err, va_list params)
 811 {
 812         vreportf("fatal: ", err, params);
 813
 814         if (in_async()) {
 815                 struct async *async = pthread_getspecific(async_key);
 816                 if (async->proc_in >= 0)
 817                         close(async->proc_in);
 818                 if (async->proc_out >= 0)
 819                         close(async->proc_out);
 820                 pthread_exit((void *)128);
 821         }
 822
 823         exit(128);
 824 }
 825
 826 static int async_die_is_recursing(void)
 827 {
 828         void *ret = pthread_getspecific(async_die_counter);
 829         pthread_setspecific(async_die_counter, (void *)1);
 830         return ret != NULL;
 831 }
 832
 833 int in_async(void)
 834 {
 835         if (!main_thread_set)
 836                 return 0; /* no asyncs started yet */
 837         return !pthread_equal(main_thread, pthread_self());
 838 }
 839
 840 static void NORETURN async_exit(int code)
 841 {
 842         pthread_exit((void *)(intptr_t)code);
 843 }
 844
 845 #else
 846
 847 static struct {
 848         void (**handlers)(void);
 849         size_t nr;
 850         size_t alloc;
 851 } git_atexit_hdlrs;
 852
 853 static int git_atexit_installed;
 854
 855 static void git_atexit_dispatch(void)
 856 {
 857         size_t i;
 858
 859         for (i=git_atexit_hdlrs.nr ; i ; i--)
 860                 git_atexit_hdlrs.handlers[i-1]();
 861 }
 862
 863 static void git_atexit_clear(void)
 864 {
 865         free(git_atexit_hdlrs.handlers);
 866         memset(&git_atexit_hdlrs, 0, sizeof(git_atexit_hdlrs));
 867         git_atexit_installed = 0;
 868 }
 869
 870 #undef atexit
 871 int git_atexit(void (*handler)(void))
 872 {
 873         ALLOC_GROW(git_atexit_hdlrs.handlers, git_atexit_hdlrs.nr + 1, git_atexit_hdlrs.alloc);
 874         git_atexit_hdlrs.handlers[git_atexit_hdlrs.nr++] = handler;
 875         if (!git_atexit_installed) {
 876                 if (atexit(&git_atexit_dispatch))
 877                         return -1;
 878                 git_atexit_installed = 1;
 879         }
 880         return 0;
 881 }
 882 #define atexit git_atexit
 883
 884 static int process_is_async;
 885 int in_async(void)
 886 {
 887         return process_is_async;
 888 }
 889
 890 static void NORETURN async_exit(int code)
 891 {
 892         exit(code);
 893 }
 894
 895 #endif
 896
 897 void check_pipe(int err)
 898 {
 899         if (err == EPIPE) {
 900                 if (in_async())
 901                         async_exit(141);
 902
 903                 signal(SIGPIPE, SIG_DFL);
 904                 raise(SIGPIPE);
 905                 /* Should never happen, but just in case... */
 906                 exit(141);
 907         }
 908 }
 909
 910 int start_async(struct async *async)
 911 {
 912         int need_in, need_out;
 913         int fdin[2], fdout[2];
 914         int proc_in, proc_out;
 915
 916         need_in = async->in < 0;
 917         if (need_in) {
 918                 if (pipe(fdin) < 0) {
 919                         if (async->out > 0)
 920                                 close(async->out);
 921                         return error_errno("cannot create pipe");
 922                 }
 923                 async->in = fdin[1];
 924         }
 925
 926         need_out = async->out < 0;
 927         if (need_out) {
 928                 if (pipe(fdout) < 0) {
 929                         if (need_in)
 930                                 close_pair(fdin);
 931                         else if (async->in)
 932                                 close(async->in);
 933                         return error_errno("cannot create pipe");
 934                 }
 935                 async->out = fdout[0];
 936         }
 937
 938         if (need_in)
 939                 proc_in = fdin[0];
 940         else if (async->in)
 941                 proc_in = async->in;
 942         else
 943                 proc_in = -1;
 944
 945         if (need_out)
 946                 proc_out = fdout[1];
 947         else if (async->out)
 948                 proc_out = async->out;
 949         else
 950                 proc_out = -1;
 951
 952 #ifdef NO_PTHREADS
 953         /* Flush stdio before fork() to avoid cloning buffers */
 954         fflush(NULL);
 955
 956         async->pid = fork();
 957         if (async->pid < 0) {
 958                 error_errno("fork (async) failed");
 959                 goto error;
 960         }
 961         if (!async->pid) {
 962                 if (need_in)
 963                         close(fdin[1]);
 964                 if (need_out)
 965                         close(fdout[0]);
 966                 git_atexit_clear();
 967                 process_is_async = 1;
 968                 exit(!!async->proc(proc_in, proc_out, async->data));
 969         }
 970
 971         mark_child_for_cleanup(async->pid, NULL);
 972
 973         if (need_in)
 974                 close(fdin[0]);
 975         else if (async->in)
 976                 close(async->in);
 977
 978         if (need_out)
 979                 close(fdout[1]);
 980         else if (async->out)
 981                 close(async->out);
 982 #else
 983         if (!main_thread_set) {
 984                 /*
 985                  * We assume that the first time that start_async is called
 986                  * it is from the main thread.
 987                  */
 988                 main_thread_set = 1;
 989                 main_thread = pthread_self();
 990                 pthread_key_create(&async_key, NULL);
 991                 pthread_key_create(&async_die_counter, NULL);
 992                 set_die_routine(die_async);
 993                 set_die_is_recursing_routine(async_die_is_recursing);
 994         }
 995
 996         if (proc_in >= 0)
 997                 set_cloexec(proc_in);
 998         if (proc_out >= 0)
 999                 set_cloexec(proc_out);
1000         async->proc_in = proc_in;
1001         async->proc_out = proc_out;
1002         {
1003                 int err = pthread_create(&async->tid, NULL, run_thread, async);
1004                 if (err) {
1005                         error_errno("cannot create thread");
1006                         goto error;
1007                 }
1008         }
1009 #endif
1010         return 0;
1011
1012 error:
1013         if (need_in)
1014                 close_pair(fdin);
1015         else if (async->in)
1016                 close(async->in);
1017
1018         if (need_out)
1019                 close_pair(fdout);
1020         else if (async->out)
1021                 close(async->out);
1022         return -1;
1023 }
1024
1025 int finish_async(struct async *async)
1026 {
1027 #ifdef NO_PTHREADS
1028         return wait_or_whine(async->pid, "child process", 0);
1029 #else
1030         void *ret = (void *)(intptr_t)(-1);
1031
1032         if (pthread_join(async->tid, &ret))
1033                 error("pthread_join failed");
1034         return (int)(intptr_t)ret;
1035 #endif
1036 }
1037
1038 const char *find_hook(const char *name)
1039 {
1040         static struct strbuf path = STRBUF_INIT;
1041
1042         strbuf_reset(&path);
1043         strbuf_git_path(&path, "hooks/%s", name);
1044         if (access(path.buf, X_OK) < 0) {
1045 #ifdef STRIP_EXTENSION
1046                 strbuf_addstr(&path, STRIP_EXTENSION);
1047                 if (access(path.buf, X_OK) >= 0)
1048                         return path.buf;
1049 #endif
1050                 return NULL;
1051         }
1052         return path.buf;
1053 }
1054
1055 int run_hook_ve(const char *const *env, const char *name, va_list args)
1056 {
1057         struct child_process hook = CHILD_PROCESS_INIT;
1058         const char *p;
1059
1060         p = find_hook(name);
1061         if (!p)
1062                 return 0;
1063
1064         argv_array_push(&hook.args, p);
1065         while ((p = va_arg(args, const char *)))
1066                 argv_array_push(&hook.args, p);
1067         hook.env = env;
1068         hook.no_stdin = 1;
1069         hook.stdout_to_stderr = 1;
1070
1071         return run_command(&hook);
1072 }
1073
1074 int run_hook_le(const char *const *env, const char *name, ...)
1075 {
1076         va_list args;
1077         int ret;
1078
1079         va_start(args, name);
1080         ret = run_hook_ve(env, name, args);
1081         va_end(args);
1082
1083         return ret;
1084 }
1085
1086 struct io_pump {
1087         /* initialized by caller */
1088         int fd;
1089         int type; /* POLLOUT or POLLIN */
1090         union {
1091                 struct {
1092                         const char *buf;
1093                         size_t len;
1094                 } out;
1095                 struct {
1096                         struct strbuf *buf;
1097                         size_t hint;
1098                 } in;
1099         } u;
1100
1101         /* returned by pump_io */
1102         int error; /* 0 for success, otherwise errno */
1103
1104         /* internal use */
1105         struct pollfd *pfd;
1106 };
1107
1108 static int pump_io_round(struct io_pump *slots, int nr, struct pollfd *pfd)
1109 {
1110         int pollsize = 0;
1111         int i;
1112
1113         for (i = 0; i < nr; i++) {
1114                 struct io_pump *io = &slots[i];
1115                 if (io->fd < 0)
1116                         continue;
1117                 pfd[pollsize].fd = io->fd;
1118                 pfd[pollsize].events = io->type;
1119                 io->pfd = &pfd[pollsize++];
1120         }
1121
1122         if (!pollsize)
1123                 return 0;
1124
1125         if (poll(pfd, pollsize, -1) < 0) {
1126                 if (errno == EINTR)
1127                         return 1;
1128                 die_errno("poll failed");
1129         }
1130
1131         for (i = 0; i < nr; i++) {
1132                 struct io_pump *io = &slots[i];
1133
1134                 if (io->fd < 0)
1135                         continue;
1136
1137                 if (!(io->pfd->revents & (POLLOUT|POLLIN|POLLHUP|POLLERR|POLLNVAL)))
1138                         continue;
1139
1140                 if (io->type == POLLOUT) {
1141                         ssize_t len = xwrite(io->fd,
1142                                              io->u.out.buf, io->u.out.len);
1143                         if (len < 0) {
1144                                 io->error = errno;
1145                                 close(io->fd);
1146                                 io->fd = -1;
1147                         } else {
1148                                 io->u.out.buf += len;
1149                                 io->u.out.len -= len;
1150                                 if (!io->u.out.len) {
1151                                         close(io->fd);
1152                                         io->fd = -1;
1153                                 }
1154                         }
1155                 }
1156
1157                 if (io->type == POLLIN) {
1158                         ssize_t len = strbuf_read_once(io->u.in.buf,
1159                                                        io->fd, io->u.in.hint);
1160                         if (len < 0)
1161                                 io->error = errno;
1162                         if (len <= 0) {
1163                                 close(io->fd);
1164                                 io->fd = -1;
1165                         }
1166                 }
1167         }
1168
1169         return 1;
1170 }
1171
1172 static int pump_io(struct io_pump *slots, int nr)
1173 {
1174         struct pollfd *pfd;
1175         int i;
1176
1177         for (i = 0; i < nr; i++)
1178                 slots[i].error = 0;
1179
1180         ALLOC_ARRAY(pfd, nr);
1181         while (pump_io_round(slots, nr, pfd))
1182                 ; /* nothing */
1183         free(pfd);
1184
1185         /* There may be multiple errno values, so just pick the first. */
1186         for (i = 0; i < nr; i++) {
1187                 if (slots[i].error) {
1188                         errno = slots[i].error;
1189                         return -1;
1190                 }
1191         }
1192         return 0;
1193 }
1194
1195
1196 int pipe_command(struct child_process *cmd,
1197                  const char *in, size_t in_len,
1198                  struct strbuf *out, size_t out_hint,
1199                  struct strbuf *err, size_t err_hint)
1200 {
1201         struct io_pump io[3];
1202         int nr = 0;
1203
1204         if (in)
1205                 cmd->in = -1;
1206         if (out)
1207                 cmd->out = -1;
1208         if (err)
1209                 cmd->err = -1;
1210
1211         if (start_command(cmd) < 0)
1212                 return -1;
1213
1214         if (in) {
1215                 io[nr].fd = cmd->in;
1216                 io[nr].type = POLLOUT;
1217                 io[nr].u.out.buf = in;
1218                 io[nr].u.out.len = in_len;
1219                 nr++;
1220         }
1221         if (out) {
1222                 io[nr].fd = cmd->out;
1223                 io[nr].type = POLLIN;
1224                 io[nr].u.in.buf = out;
1225                 io[nr].u.in.hint = out_hint;
1226                 nr++;
1227         }
1228         if (err) {
1229                 io[nr].fd = cmd->err;
1230                 io[nr].type = POLLIN;
1231                 io[nr].u.in.buf = err;
1232                 io[nr].u.in.hint = err_hint;
1233                 nr++;
1234         }
1235
1236         if (pump_io(io, nr) < 0) {
1237                 finish_command(cmd); /* throw away exit code */
1238                 return -1;
1239         }
1240
1241         return finish_command(cmd);
1242 }
1243
1244 enum child_state {
1245         GIT_CP_FREE,
1246         GIT_CP_WORKING,
1247         GIT_CP_WAIT_CLEANUP,
1248 };
1249
1250 struct parallel_processes {
1251         void *data;
1252
1253         int max_processes;
1254         int nr_processes;
1255
1256         get_next_task_fn get_next_task;
1257         start_failure_fn start_failure;
1258         task_finished_fn task_finished;
1259
1260         struct {
1261                 enum child_state state;
1262                 struct child_process process;
1263                 struct strbuf err;
1264                 void *data;
1265         } *children;
1266         /*
1267          * The struct pollfd is logically part of *children,
1268          * but the system call expects it as its own array.
1269          */
1270         struct pollfd *pfd;
1271
1272         unsigned shutdown : 1;
1273
1274         int output_owner;
1275         struct strbuf buffered_output; /* of finished children */
1276 };
1277
1278 static int default_start_failure(struct strbuf *out,
1279                                  void *pp_cb,
1280                                  void *pp_task_cb)
1281 {
1282         return 0;
1283 }
1284
1285 static int default_task_finished(int result,
1286                                  struct strbuf *out,
1287                                  void *pp_cb,
1288                                  void *pp_task_cb)
1289 {
1290         return 0;
1291 }
1292
1293 static void kill_children(struct parallel_processes *pp, int signo)
1294 {
1295         int i, n = pp->max_processes;
1296
1297         for (i = 0; i < n; i++)
1298                 if (pp->children[i].state == GIT_CP_WORKING)
1299                         kill(pp->children[i].process.pid, signo);
1300 }
1301
1302 static struct parallel_processes *pp_for_signal;
1303
1304 static void handle_children_on_signal(int signo)
1305 {
1306         kill_children(pp_for_signal, signo);
1307         sigchain_pop(signo);
1308         raise(signo);
1309 }
1310
1311 static void pp_init(struct parallel_processes *pp,
1312                     int n,
1313                     get_next_task_fn get_next_task,
1314                     start_failure_fn start_failure,
1315                     task_finished_fn task_finished,
1316                     void *data)
1317 {
1318         int i;
1319
1320         if (n < 1)
1321                 n = online_cpus();
1322
1323         pp->max_processes = n;
1324
1325         trace_printf("run_processes_parallel: preparing to run up to %d tasks", n);
1326
1327         pp->data = data;
1328         if (!get_next_task)
1329                 die("BUG: you need to specify a get_next_task function");
1330         pp->get_next_task = get_next_task;
1331
1332         pp->start_failure = start_failure ? start_failure : default_start_failure;
1333         pp->task_finished = task_finished ? task_finished : default_task_finished;
1334
1335         pp->nr_processes = 0;
1336         pp->output_owner = 0;
1337         pp->shutdown = 0;
1338         pp->children = xcalloc(n, sizeof(*pp->children));
1339         pp->pfd = xcalloc(n, sizeof(*pp->pfd));
1340         strbuf_init(&pp->buffered_output, 0);
1341
1342         for (i = 0; i < n; i++) {
1343                 strbuf_init(&pp->children[i].err, 0);
1344                 child_process_init(&pp->children[i].process);
1345                 pp->pfd[i].events = POLLIN | POLLHUP;
1346                 pp->pfd[i].fd = -1;
1347         }
1348
1349         pp_for_signal = pp;
1350         sigchain_push_common(handle_children_on_signal);
1351 }
1352
1353 static void pp_cleanup(struct parallel_processes *pp)
1354 {
1355         int i;
1356
1357         trace_printf("run_processes_parallel: done");
1358         for (i = 0; i < pp->max_processes; i++) {
1359                 strbuf_release(&pp->children[i].err);
1360                 child_process_clear(&pp->children[i].process);
1361         }
1362
1363         free(pp->children);
1364         free(pp->pfd);
1365
1366         /*
1367          * When get_next_task added messages to the buffer in its last
1368          * iteration, the buffered output is non empty.
1369          */
1370         strbuf_write(&pp->buffered_output, stderr);
1371         strbuf_release(&pp->buffered_output);
1372
1373         sigchain_pop_common();
1374 }
1375
1376 /* returns
1377  *  0 if a new task was started.
1378  *  1 if no new jobs was started (get_next_task ran out of work, non critical
1379  *    problem with starting a new command)
1380  * <0 no new job was started, user wishes to shutdown early. Use negative code
1381  *    to signal the children.
1382  */
1383 static int pp_start_one(struct parallel_processes *pp)
1384 {
1385         int i, code;
1386
1387         for (i = 0; i < pp->max_processes; i++)
1388                 if (pp->children[i].state == GIT_CP_FREE)
1389                         break;
1390         if (i == pp->max_processes)
1391                 die("BUG: bookkeeping is hard");
1392
1393         code = pp->get_next_task(&pp->children[i].process,
1394                                  &pp->children[i].err,
1395                                  pp->data,
1396                                  &pp->children[i].data);
1397         if (!code) {
1398                 strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1399                 strbuf_reset(&pp->children[i].err);
1400                 return 1;
1401         }
1402         pp->children[i].process.err = -1;
1403         pp->children[i].process.stdout_to_stderr = 1;
1404         pp->children[i].process.no_stdin = 1;
1405
1406         if (start_command(&pp->children[i].process)) {
1407                 code = pp->start_failure(&pp->children[i].err,
1408                                          pp->data,
1409                                          &pp->children[i].data);
1410                 strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1411                 strbuf_reset(&pp->children[i].err);
1412                 if (code)
1413                         pp->shutdown = 1;
1414                 return code;
1415         }
1416
1417         pp->nr_processes++;
1418         pp->children[i].state = GIT_CP_WORKING;
1419         pp->pfd[i].fd = pp->children[i].process.err;
1420         return 0;
1421 }
1422
1423 static void pp_buffer_stderr(struct parallel_processes *pp, int output_timeout)
1424 {
1425         int i;
1426
1427         while ((i = poll(pp->pfd, pp->max_processes, output_timeout)) < 0) {
1428                 if (errno == EINTR)
1429                         continue;
1430                 pp_cleanup(pp);
1431                 die_errno("poll");
1432         }
1433
1434         /* Buffer output from all pipes. */
1435         for (i = 0; i < pp->max_processes; i++) {
1436                 if (pp->children[i].state == GIT_CP_WORKING &&
1437                     pp->pfd[i].revents & (POLLIN | POLLHUP)) {
1438                         int n = strbuf_read_once(&pp->children[i].err,
1439                                                  pp->children[i].process.err, 0);
1440                         if (n == 0) {
1441                                 close(pp->children[i].process.err);
1442                                 pp->children[i].state = GIT_CP_WAIT_CLEANUP;
1443                         } else if (n < 0)
1444                                 if (errno != EAGAIN)
1445                                         die_errno("read");
1446                 }
1447         }
1448 }
1449
1450 static void pp_output(struct parallel_processes *pp)
1451 {
1452         int i = pp->output_owner;
1453         if (pp->children[i].state == GIT_CP_WORKING &&
1454             pp->children[i].err.len) {
1455                 strbuf_write(&pp->children[i].err, stderr);
1456                 strbuf_reset(&pp->children[i].err);
1457         }
1458 }
1459
1460 static int pp_collect_finished(struct parallel_processes *pp)
1461 {
1462         int i, code;
1463         int n = pp->max_processes;
1464         int result = 0;
1465
1466         while (pp->nr_processes > 0) {
1467                 for (i = 0; i < pp->max_processes; i++)
1468                         if (pp->children[i].state == GIT_CP_WAIT_CLEANUP)
1469                                 break;
1470                 if (i == pp->max_processes)
1471                         break;
1472
1473                 code = finish_command(&pp->children[i].process);
1474
1475                 code = pp->task_finished(code,
1476                                          &pp->children[i].err, pp->data,
1477                                          &pp->children[i].data);
1478
1479                 if (code)
1480                         result = code;
1481                 if (code < 0)
1482                         break;
1483
1484                 pp->nr_processes--;
1485                 pp->children[i].state = GIT_CP_FREE;
1486                 pp->pfd[i].fd = -1;
1487                 child_process_init(&pp->children[i].process);
1488
1489                 if (i != pp->output_owner) {
1490                         strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1491                         strbuf_reset(&pp->children[i].err);
1492                 } else {
1493                         strbuf_write(&pp->children[i].err, stderr);
1494                         strbuf_reset(&pp->children[i].err);
1495
1496                         /* Output all other finished child processes */
1497                         strbuf_write(&pp->buffered_output, stderr);
1498                         strbuf_reset(&pp->buffered_output);
1499
1500                         /*
1501                          * Pick next process to output live.
1502                          * NEEDSWORK:
1503                          * For now we pick it randomly by doing a round
1504                          * robin. Later we may want to pick the one with
1505                          * the most output or the longest or shortest
1506                          * running process time.
1507                          */
1508                         for (i = 0; i < n; i++)
1509                                 if (pp->children[(pp->output_owner + i) % n].state == GIT_CP_WORKING)
1510                                         break;
1511                         pp->output_owner = (pp->output_owner + i) % n;
1512                 }
1513         }
1514         return result;
1515 }
1516
1517 int run_processes_parallel(int n,
1518                            get_next_task_fn get_next_task,
1519                            start_failure_fn start_failure,
1520                            task_finished_fn task_finished,
1521                            void *pp_cb)
1522 {
1523         int i, code;
1524         int output_timeout = 100;
1525         int spawn_cap = 4;
1526         struct parallel_processes pp;
1527
1528         pp_init(&pp, n, get_next_task, start_failure, task_finished, pp_cb);
1529         while (1) {
1530                 for (i = 0;
1531                     i < spawn_cap && !pp.shutdown &&
1532                     pp.nr_processes < pp.max_processes;
1533                     i++) {
1534                         code = pp_start_one(&pp);
1535                         if (!code)
1536                                 continue;
1537                         if (code < 0) {
1538                                 pp.shutdown = 1;
1539                                 kill_children(&pp, -code);
1540                         }
1541                         break;
1542                 }
1543                 if (!pp.nr_processes)
1544                         break;
1545                 pp_buffer_stderr(&pp, output_timeout);
1546                 pp_output(&pp);
1547                 code = pp_collect_finished(&pp);
1548                 if (code) {
1549                         pp.shutdown = 1;
1550                         if (code < 0)
1551                                 kill_children(&pp, -code);
1552                 }
1553         }
1554
1555         pp_cleanup(&pp);
1556         return 0;
1557 }