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 int is_executable(const char *name)
 121 {
 122         struct stat st;
 123
 124         if (stat(name, &st) || /* stat, not lstat */
 125             !S_ISREG(st.st_mode))
 126                 return 0;
 127
 128 #if defined(GIT_WINDOWS_NATIVE)
 129         /*
 130          * On Windows there is no executable bit. The file extension
 131          * indicates whether it can be run as an executable, and Git
 132          * has special-handling to detect scripts and launch them
 133          * through the indicated script interpreter. We test for the
 134          * file extension first because virus scanners may make
 135          * it quite expensive to open many files.
 136          */
 137         if (ends_with(name, ".exe"))
 138                 return S_IXUSR;
 139
 140 {
 141         /*
 142          * Now that we know it does not have an executable extension,
 143          * peek into the file instead.
 144          */
 145         char buf[3] = { 0 };
 146         int n;
 147         int fd = open(name, O_RDONLY);
 148         st.st_mode &= ~S_IXUSR;
 149         if (fd >= 0) {
 150                 n = read(fd, buf, 2);
 151                 if (n == 2)
 152                         /* look for a she-bang */
 153                         if (!strcmp(buf, "#!"))
 154                                 st.st_mode |= S_IXUSR;
 155                 close(fd);
 156         }
 157 }
 158 #endif
 159         return st.st_mode & S_IXUSR;
 160 }
 161
 162 static char *locate_in_PATH(const char *file)
 163 {
 164         const char *p = getenv("PATH");
 165         struct strbuf buf = STRBUF_INIT;
 166
 167         if (!p || !*p)
 168                 return NULL;
 169
 170         while (1) {
 171                 const char *end = strchrnul(p, ':');
 172
 173                 strbuf_reset(&buf);
 174
 175                 /* POSIX specifies an empty entry as the current directory. */
 176                 if (end != p) {
 177                         strbuf_add(&buf, p, end - p);
 178                         strbuf_addch(&buf, '/');
 179                 }
 180                 strbuf_addstr(&buf, file);
 181
 182                 if (!access(buf.buf, F_OK))
 183                         return strbuf_detach(&buf, NULL);
 184
 185                 if (!*end)
 186                         break;
 187                 p = end + 1;
 188         }
 189
 190         strbuf_release(&buf);
 191         return NULL;
 192 }
 193
 194 static int exists_in_PATH(const char *file)
 195 {
 196         char *r = locate_in_PATH(file);
 197         free(r);
 198         return r != NULL;
 199 }
 200
 201 int sane_execvp(const char *file, char * const argv[])
 202 {
 203         if (!execvp(file, argv))
 204                 return 0; /* cannot happen ;-) */
 205
 206         /*
 207          * When a command can't be found because one of the directories
 208          * listed in $PATH is unsearchable, execvp reports EACCES, but
 209          * careful usability testing (read: analysis of occasional bug
 210          * reports) reveals that "No such file or directory" is more
 211          * intuitive.
 212          *
 213          * We avoid commands with "/", because execvp will not do $PATH
 214          * lookups in that case.
 215          *
 216          * The reassignment of EACCES to errno looks like a no-op below,
 217          * but we need to protect against exists_in_PATH overwriting errno.
 218          */
 219         if (errno == EACCES && !strchr(file, '/'))
 220                 errno = exists_in_PATH(file) ? EACCES : ENOENT;
 221         else if (errno == ENOTDIR && !strchr(file, '/'))
 222                 errno = ENOENT;
 223         return -1;
 224 }
 225
 226 static const char **prepare_shell_cmd(struct argv_array *out, const char **argv)
 227 {
 228         if (!argv[0])
 229                 die("BUG: shell command is empty");
 230
 231         if (strcspn(argv[0], "|&;<>()$`\\\"' \t\n*?[#~=%") != strlen(argv[0])) {
 232 #ifndef GIT_WINDOWS_NATIVE
 233                 argv_array_push(out, SHELL_PATH);
 234 #else
 235                 argv_array_push(out, "sh");
 236 #endif
 237                 argv_array_push(out, "-c");
 238
 239                 /*
 240                  * If we have no extra arguments, we do not even need to
 241                  * bother with the "$@" magic.
 242                  */
 243                 if (!argv[1])
 244                         argv_array_push(out, argv[0]);
 245                 else
 246                         argv_array_pushf(out, "%s \"$@\"", argv[0]);
 247         }
 248
 249         argv_array_pushv(out, argv);
 250         return out->argv;
 251 }
 252
 253 #ifndef GIT_WINDOWS_NATIVE
 254 static int child_notifier = -1;
 255
 256 enum child_errcode {
 257         CHILD_ERR_CHDIR,
 258         CHILD_ERR_DUP2,
 259         CHILD_ERR_CLOSE,
 260         CHILD_ERR_SIGPROCMASK,
 261         CHILD_ERR_ENOENT,
 262         CHILD_ERR_SILENT,
 263         CHILD_ERR_ERRNO
 264 };
 265
 266 struct child_err {
 267         enum child_errcode err;
 268         int syserr; /* errno */
 269 };
 270
 271 static void child_die(enum child_errcode err)
 272 {
 273         struct child_err buf;
 274
 275         buf.err = err;
 276         buf.syserr = errno;
 277
 278         /* write(2) on buf smaller than PIPE_BUF (min 512) is atomic: */
 279         xwrite(child_notifier, &buf, sizeof(buf));
 280         _exit(1);
 281 }
 282
 283 static void child_dup2(int fd, int to)
 284 {
 285         if (dup2(fd, to) < 0)
 286                 child_die(CHILD_ERR_DUP2);
 287 }
 288
 289 static void child_close(int fd)
 290 {
 291         if (close(fd))
 292                 child_die(CHILD_ERR_CLOSE);
 293 }
 294
 295 static void child_close_pair(int fd[2])
 296 {
 297         child_close(fd[0]);
 298         child_close(fd[1]);
 299 }
 300
 301 /*
 302  * parent will make it look like the child spewed a fatal error and died
 303  * this is needed to prevent changes to t0061.
 304  */
 305 static void fake_fatal(const char *err, va_list params)
 306 {
 307         vreportf("fatal: ", err, params);
 308 }
 309
 310 static void child_error_fn(const char *err, va_list params)
 311 {
 312         const char msg[] = "error() should not be called in child\n";
 313         xwrite(2, msg, sizeof(msg) - 1);
 314 }
 315
 316 static void child_warn_fn(const char *err, va_list params)
 317 {
 318         const char msg[] = "warn() should not be called in child\n";
 319         xwrite(2, msg, sizeof(msg) - 1);
 320 }
 321
 322 static void NORETURN child_die_fn(const char *err, va_list params)
 323 {
 324         const char msg[] = "die() should not be called in child\n";
 325         xwrite(2, msg, sizeof(msg) - 1);
 326         _exit(2);
 327 }
 328
 329 /* this runs in the parent process */
 330 static void child_err_spew(struct child_process *cmd, struct child_err *cerr)
 331 {
 332         static void (*old_errfn)(const char *err, va_list params);
 333
 334         old_errfn = get_error_routine();
 335         set_error_routine(fake_fatal);
 336         errno = cerr->syserr;
 337
 338         switch (cerr->err) {
 339         case CHILD_ERR_CHDIR:
 340                 error_errno("exec '%s': cd to '%s' failed",
 341                             cmd->argv[0], cmd->dir);
 342                 break;
 343         case CHILD_ERR_DUP2:
 344                 error_errno("dup2() in child failed");
 345                 break;
 346         case CHILD_ERR_CLOSE:
 347                 error_errno("close() in child failed");
 348                 break;
 349         case CHILD_ERR_SIGPROCMASK:
 350                 error_errno("sigprocmask failed restoring signals");
 351                 break;
 352         case CHILD_ERR_ENOENT:
 353                 error_errno("cannot run %s", cmd->argv[0]);
 354                 break;
 355         case CHILD_ERR_SILENT:
 356                 break;
 357         case CHILD_ERR_ERRNO:
 358                 error_errno("cannot exec '%s'", cmd->argv[0]);
 359                 break;
 360         }
 361         set_error_routine(old_errfn);
 362 }
 363
 364 static void prepare_cmd(struct argv_array *out, const struct child_process *cmd)
 365 {
 366         if (!cmd->argv[0])
 367                 die("BUG: command is empty");
 368
 369         /*
 370          * Add SHELL_PATH so in the event exec fails with ENOEXEC we can
 371          * attempt to interpret the command with 'sh'.
 372          */
 373         argv_array_push(out, SHELL_PATH);
 374
 375         if (cmd->git_cmd) {
 376                 argv_array_push(out, "git");
 377                 argv_array_pushv(out, cmd->argv);
 378         } else if (cmd->use_shell) {
 379                 prepare_shell_cmd(out, cmd->argv);
 380         } else {
 381                 argv_array_pushv(out, cmd->argv);
 382         }
 383
 384         /*
 385          * If there are no '/' characters in the command then perform a path
 386          * lookup and use the resolved path as the command to exec.  If there
 387          * are no '/' characters or if the command wasn't found in the path,
 388          * have exec attempt to invoke the command directly.
 389          */
 390         if (!strchr(out->argv[1], '/')) {
 391                 char *program = locate_in_PATH(out->argv[1]);
 392                 if (program) {
 393                         free((char *)out->argv[1]);
 394                         out->argv[1] = program;
 395                 }
 396         }
 397 }
 398
 399 static char **prep_childenv(const char *const *deltaenv)
 400 {
 401         extern char **environ;
 402         char **childenv;
 403         struct string_list env = STRING_LIST_INIT_DUP;
 404         struct strbuf key = STRBUF_INIT;
 405         const char *const *p;
 406         int i;
 407
 408         /* Construct a sorted string list consisting of the current environ */
 409         for (p = (const char *const *) environ; p && *p; p++) {
 410                 const char *equals = strchr(*p, '=');
 411
 412                 if (equals) {
 413                         strbuf_reset(&key);
 414                         strbuf_add(&key, *p, equals - *p);
 415                         string_list_append(&env, key.buf)->util = (void *) *p;
 416                 } else {
 417                         string_list_append(&env, *p)->util = (void *) *p;
 418                 }
 419         }
 420         string_list_sort(&env);
 421
 422         /* Merge in 'deltaenv' with the current environ */
 423         for (p = deltaenv; p && *p; p++) {
 424                 const char *equals = strchr(*p, '=');
 425
 426                 if (equals) {
 427                         /* ('key=value'), insert or replace entry */
 428                         strbuf_reset(&key);
 429                         strbuf_add(&key, *p, equals - *p);
 430                         string_list_insert(&env, key.buf)->util = (void *) *p;
 431                 } else {
 432                         /* otherwise ('key') remove existing entry */
 433                         string_list_remove(&env, *p, 0);
 434                 }
 435         }
 436
 437         /* Create an array of 'char *' to be used as the childenv */
 438         childenv = xmalloc((env.nr + 1) * sizeof(char *));
 439         for (i = 0; i < env.nr; i++)
 440                 childenv[i] = env.items[i].util;
 441         childenv[env.nr] = NULL;
 442
 443         string_list_clear(&env, 0);
 444         strbuf_release(&key);
 445         return childenv;
 446 }
 447
 448 struct atfork_state {
 449 #ifndef NO_PTHREADS
 450         int cs;
 451 #endif
 452         sigset_t old;
 453 };
 454
 455 #ifndef NO_PTHREADS
 456 static void bug_die(int err, const char *msg)
 457 {
 458         if (err) {
 459                 errno = err;
 460                 die_errno("BUG: %s", msg);
 461         }
 462 }
 463 #endif
 464
 465 static void atfork_prepare(struct atfork_state *as)
 466 {
 467         sigset_t all;
 468
 469         if (sigfillset(&all))
 470                 die_errno("sigfillset");
 471 #ifdef NO_PTHREADS
 472         if (sigprocmask(SIG_SETMASK, &all, &as->old))
 473                 die_errno("sigprocmask");
 474 #else
 475         bug_die(pthread_sigmask(SIG_SETMASK, &all, &as->old),
 476                 "blocking all signals");
 477         bug_die(pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &as->cs),
 478                 "disabling cancellation");
 479 #endif
 480 }
 481
 482 static void atfork_parent(struct atfork_state *as)
 483 {
 484 #ifdef NO_PTHREADS
 485         if (sigprocmask(SIG_SETMASK, &as->old, NULL))
 486                 die_errno("sigprocmask");
 487 #else
 488         bug_die(pthread_setcancelstate(as->cs, NULL),
 489                 "re-enabling cancellation");
 490         bug_die(pthread_sigmask(SIG_SETMASK, &as->old, NULL),
 491                 "restoring signal mask");
 492 #endif
 493 }
 494 #endif /* GIT_WINDOWS_NATIVE */
 495
 496 static inline void set_cloexec(int fd)
 497 {
 498         int flags = fcntl(fd, F_GETFD);
 499         if (flags >= 0)
 500                 fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
 501 }
 502
 503 static int wait_or_whine(pid_t pid, const char *argv0, int in_signal)
 504 {
 505         int status, code = -1;
 506         pid_t waiting;
 507         int failed_errno = 0;
 508
 509         while ((waiting = waitpid(pid, &status, 0)) < 0 && errno == EINTR)
 510                 ;       /* nothing */
 511         if (in_signal)
 512                 return 0;
 513
 514         if (waiting < 0) {
 515                 failed_errno = errno;
 516                 error_errno("waitpid for %s failed", argv0);
 517         } else if (waiting != pid) {
 518                 error("waitpid is confused (%s)", argv0);
 519         } else if (WIFSIGNALED(status)) {
 520                 code = WTERMSIG(status);
 521                 if (code != SIGINT && code != SIGQUIT && code != SIGPIPE)
 522                         error("%s died of signal %d", argv0, code);
 523                 /*
 524                  * This return value is chosen so that code & 0xff
 525                  * mimics the exit code that a POSIX shell would report for
 526                  * a program that died from this signal.
 527                  */
 528                 code += 128;
 529         } else if (WIFEXITED(status)) {
 530                 code = WEXITSTATUS(status);
 531         } else {
 532                 error("waitpid is confused (%s)", argv0);
 533         }
 534
 535         clear_child_for_cleanup(pid);
 536
 537         errno = failed_errno;
 538         return code;
 539 }
 540
 541 int start_command(struct child_process *cmd)
 542 {
 543         int need_in, need_out, need_err;
 544         int fdin[2], fdout[2], fderr[2];
 545         int failed_errno;
 546         char *str;
 547
 548         if (!cmd->argv)
 549                 cmd->argv = cmd->args.argv;
 550         if (!cmd->env)
 551                 cmd->env = cmd->env_array.argv;
 552
 553         /*
 554          * In case of errors we must keep the promise to close FDs
 555          * that have been passed in via ->in and ->out.
 556          */
 557
 558         need_in = !cmd->no_stdin && cmd->in < 0;
 559         if (need_in) {
 560                 if (pipe(fdin) < 0) {
 561                         failed_errno = errno;
 562                         if (cmd->out > 0)
 563                                 close(cmd->out);
 564                         str = "standard input";
 565                         goto fail_pipe;
 566                 }
 567                 cmd->in = fdin[1];
 568         }
 569
 570         need_out = !cmd->no_stdout
 571                 && !cmd->stdout_to_stderr
 572                 && cmd->out < 0;
 573         if (need_out) {
 574                 if (pipe(fdout) < 0) {
 575                         failed_errno = errno;
 576                         if (need_in)
 577                                 close_pair(fdin);
 578                         else if (cmd->in)
 579                                 close(cmd->in);
 580                         str = "standard output";
 581                         goto fail_pipe;
 582                 }
 583                 cmd->out = fdout[0];
 584         }
 585
 586         need_err = !cmd->no_stderr && cmd->err < 0;
 587         if (need_err) {
 588                 if (pipe(fderr) < 0) {
 589                         failed_errno = errno;
 590                         if (need_in)
 591                                 close_pair(fdin);
 592                         else if (cmd->in)
 593                                 close(cmd->in);
 594                         if (need_out)
 595                                 close_pair(fdout);
 596                         else if (cmd->out)
 597                                 close(cmd->out);
 598                         str = "standard error";
 599 fail_pipe:
 600                         error("cannot create %s pipe for %s: %s",
 601                                 str, cmd->argv[0], strerror(failed_errno));
 602                         child_process_clear(cmd);
 603                         errno = failed_errno;
 604                         return -1;
 605                 }
 606                 cmd->err = fderr[0];
 607         }
 608
 609         trace_argv_printf(cmd->argv, "trace: run_command:");
 610         fflush(NULL);
 611
 612 #ifndef GIT_WINDOWS_NATIVE
 613 {
 614         int notify_pipe[2];
 615         int null_fd = -1;
 616         char **childenv;
 617         struct argv_array argv = ARGV_ARRAY_INIT;
 618         struct child_err cerr;
 619         struct atfork_state as;
 620
 621         if (pipe(notify_pipe))
 622                 notify_pipe[0] = notify_pipe[1] = -1;
 623
 624         if (cmd->no_stdin || cmd->no_stdout || cmd->no_stderr) {
 625                 null_fd = open("/dev/null", O_RDWR | O_CLOEXEC);
 626                 if (null_fd < 0)
 627                         die_errno(_("open /dev/null failed"));
 628                 set_cloexec(null_fd);
 629         }
 630
 631         prepare_cmd(&argv, cmd);
 632         childenv = prep_childenv(cmd->env);
 633         atfork_prepare(&as);
 634
 635         /*
 636          * NOTE: In order to prevent deadlocking when using threads special
 637          * care should be taken with the function calls made in between the
 638          * fork() and exec() calls.  No calls should be made to functions which
 639          * require acquiring a lock (e.g. malloc) as the lock could have been
 640          * held by another thread at the time of forking, causing the lock to
 641          * never be released in the child process.  This means only
 642          * Async-Signal-Safe functions are permitted in the child.
 643          */
 644         cmd->pid = fork();
 645         failed_errno = errno;
 646         if (!cmd->pid) {
 647                 int sig;
 648                 /*
 649                  * Ensure the default die/error/warn routines do not get
 650                  * called, they can take stdio locks and malloc.
 651                  */
 652                 set_die_routine(child_die_fn);
 653                 set_error_routine(child_error_fn);
 654                 set_warn_routine(child_warn_fn);
 655
 656                 close(notify_pipe[0]);
 657                 set_cloexec(notify_pipe[1]);
 658                 child_notifier = notify_pipe[1];
 659
 660                 if (cmd->no_stdin)
 661                         child_dup2(null_fd, 0);
 662                 else if (need_in) {
 663                         child_dup2(fdin[0], 0);
 664                         child_close_pair(fdin);
 665                 } else if (cmd->in) {
 666                         child_dup2(cmd->in, 0);
 667                         child_close(cmd->in);
 668                 }
 669
 670                 if (cmd->no_stderr)
 671                         child_dup2(null_fd, 2);
 672                 else if (need_err) {
 673                         child_dup2(fderr[1], 2);
 674                         child_close_pair(fderr);
 675                 } else if (cmd->err > 1) {
 676                         child_dup2(cmd->err, 2);
 677                         child_close(cmd->err);
 678                 }
 679
 680                 if (cmd->no_stdout)
 681                         child_dup2(null_fd, 1);
 682                 else if (cmd->stdout_to_stderr)
 683                         child_dup2(2, 1);
 684                 else if (need_out) {
 685                         child_dup2(fdout[1], 1);
 686                         child_close_pair(fdout);
 687                 } else if (cmd->out > 1) {
 688                         child_dup2(cmd->out, 1);
 689                         child_close(cmd->out);
 690                 }
 691
 692                 if (cmd->dir && chdir(cmd->dir))
 693                         child_die(CHILD_ERR_CHDIR);
 694
 695                 /*
 696                  * restore default signal handlers here, in case
 697                  * we catch a signal right before execve below
 698                  */
 699                 for (sig = 1; sig < NSIG; sig++) {
 700                         /* ignored signals get reset to SIG_DFL on execve */
 701                         if (signal(sig, SIG_DFL) == SIG_IGN)
 702                                 signal(sig, SIG_IGN);
 703                 }
 704
 705                 if (sigprocmask(SIG_SETMASK, &as.old, NULL) != 0)
 706                         child_die(CHILD_ERR_SIGPROCMASK);
 707
 708                 /*
 709                  * Attempt to exec using the command and arguments starting at
 710                  * argv.argv[1].  argv.argv[0] contains SHELL_PATH which will
 711                  * be used in the event exec failed with ENOEXEC at which point
 712                  * we will try to interpret the command using 'sh'.
 713                  */
 714                 execve(argv.argv[1], (char *const *) argv.argv + 1,
 715                        (char *const *) childenv);
 716                 if (errno == ENOEXEC)
 717                         execve(argv.argv[0], (char *const *) argv.argv,
 718                                (char *const *) childenv);
 719
 720                 if (errno == ENOENT) {
 721                         if (cmd->silent_exec_failure)
 722                                 child_die(CHILD_ERR_SILENT);
 723                         child_die(CHILD_ERR_ENOENT);
 724                 } else {
 725                         child_die(CHILD_ERR_ERRNO);
 726                 }
 727         }
 728         atfork_parent(&as);
 729         if (cmd->pid < 0)
 730                 error_errno("cannot fork() for %s", cmd->argv[0]);
 731         else if (cmd->clean_on_exit)
 732                 mark_child_for_cleanup(cmd->pid, cmd);
 733
 734         /*
 735          * Wait for child's exec. If the exec succeeds (or if fork()
 736          * failed), EOF is seen immediately by the parent. Otherwise, the
 737          * child process sends a child_err struct.
 738          * Note that use of this infrastructure is completely advisory,
 739          * therefore, we keep error checks minimal.
 740          */
 741         close(notify_pipe[1]);
 742         if (xread(notify_pipe[0], &cerr, sizeof(cerr)) == sizeof(cerr)) {
 743                 /*
 744                  * At this point we know that fork() succeeded, but exec()
 745                  * failed. Errors have been reported to our stderr.
 746                  */
 747                 wait_or_whine(cmd->pid, cmd->argv[0], 0);
 748                 child_err_spew(cmd, &cerr);
 749                 failed_errno = errno;
 750                 cmd->pid = -1;
 751         }
 752         close(notify_pipe[0]);
 753
 754         if (null_fd >= 0)
 755                 close(null_fd);
 756         argv_array_clear(&argv);
 757         free(childenv);
 758 }
 759 #else
 760 {
 761         int fhin = 0, fhout = 1, fherr = 2;
 762         const char **sargv = cmd->argv;
 763         struct argv_array nargv = ARGV_ARRAY_INIT;
 764
 765         if (cmd->no_stdin)
 766                 fhin = open("/dev/null", O_RDWR);
 767         else if (need_in)
 768                 fhin = dup(fdin[0]);
 769         else if (cmd->in)
 770                 fhin = dup(cmd->in);
 771
 772         if (cmd->no_stderr)
 773                 fherr = open("/dev/null", O_RDWR);
 774         else if (need_err)
 775                 fherr = dup(fderr[1]);
 776         else if (cmd->err > 2)
 777                 fherr = dup(cmd->err);
 778
 779         if (cmd->no_stdout)
 780                 fhout = open("/dev/null", O_RDWR);
 781         else if (cmd->stdout_to_stderr)
 782                 fhout = dup(fherr);
 783         else if (need_out)
 784                 fhout = dup(fdout[1]);
 785         else if (cmd->out > 1)
 786                 fhout = dup(cmd->out);
 787
 788         if (cmd->git_cmd)
 789                 cmd->argv = prepare_git_cmd(&nargv, cmd->argv);
 790         else if (cmd->use_shell)
 791                 cmd->argv = prepare_shell_cmd(&nargv, cmd->argv);
 792
 793         cmd->pid = mingw_spawnvpe(cmd->argv[0], cmd->argv, (char**) cmd->env,
 794                         cmd->dir, fhin, fhout, fherr);
 795         failed_errno = errno;
 796         if (cmd->pid < 0 && (!cmd->silent_exec_failure || errno != ENOENT))
 797                 error_errno("cannot spawn %s", cmd->argv[0]);
 798         if (cmd->clean_on_exit && cmd->pid >= 0)
 799                 mark_child_for_cleanup(cmd->pid, cmd);
 800
 801         argv_array_clear(&nargv);
 802         cmd->argv = sargv;
 803         if (fhin != 0)
 804                 close(fhin);
 805         if (fhout != 1)
 806                 close(fhout);
 807         if (fherr != 2)
 808                 close(fherr);
 809 }
 810 #endif
 811
 812         if (cmd->pid < 0) {
 813                 if (need_in)
 814                         close_pair(fdin);
 815                 else if (cmd->in)
 816                         close(cmd->in);
 817                 if (need_out)
 818                         close_pair(fdout);
 819                 else if (cmd->out)
 820                         close(cmd->out);
 821                 if (need_err)
 822                         close_pair(fderr);
 823                 else if (cmd->err)
 824                         close(cmd->err);
 825                 child_process_clear(cmd);
 826                 errno = failed_errno;
 827                 return -1;
 828         }
 829
 830         if (need_in)
 831                 close(fdin[0]);
 832         else if (cmd->in)
 833                 close(cmd->in);
 834
 835         if (need_out)
 836                 close(fdout[1]);
 837         else if (cmd->out)
 838                 close(cmd->out);
 839
 840         if (need_err)
 841                 close(fderr[1]);
 842         else if (cmd->err)
 843                 close(cmd->err);
 844
 845         return 0;
 846 }
 847
 848 int finish_command(struct child_process *cmd)
 849 {
 850         int ret = wait_or_whine(cmd->pid, cmd->argv[0], 0);
 851         child_process_clear(cmd);
 852         return ret;
 853 }
 854
 855 int finish_command_in_signal(struct child_process *cmd)
 856 {
 857         return wait_or_whine(cmd->pid, cmd->argv[0], 1);
 858 }
 859
 860
 861 int run_command(struct child_process *cmd)
 862 {
 863         int code;
 864
 865         if (cmd->out < 0 || cmd->err < 0)
 866                 die("BUG: run_command with a pipe can cause deadlock");
 867
 868         code = start_command(cmd);
 869         if (code)
 870                 return code;
 871         return finish_command(cmd);
 872 }
 873
 874 int run_command_v_opt(const char **argv, int opt)
 875 {
 876         return run_command_v_opt_cd_env(argv, opt, NULL, NULL);
 877 }
 878
 879 int run_command_v_opt_cd_env(const char **argv, int opt, const char *dir, const char *const *env)
 880 {
 881         struct child_process cmd = CHILD_PROCESS_INIT;
 882         cmd.argv = argv;
 883         cmd.no_stdin = opt & RUN_COMMAND_NO_STDIN ? 1 : 0;
 884         cmd.git_cmd = opt & RUN_GIT_CMD ? 1 : 0;
 885         cmd.stdout_to_stderr = opt & RUN_COMMAND_STDOUT_TO_STDERR ? 1 : 0;
 886         cmd.silent_exec_failure = opt & RUN_SILENT_EXEC_FAILURE ? 1 : 0;
 887         cmd.use_shell = opt & RUN_USING_SHELL ? 1 : 0;
 888         cmd.clean_on_exit = opt & RUN_CLEAN_ON_EXIT ? 1 : 0;
 889         cmd.dir = dir;
 890         cmd.env = env;
 891         return run_command(&cmd);
 892 }
 893
 894 #ifndef NO_PTHREADS
 895 static pthread_t main_thread;
 896 static int main_thread_set;
 897 static pthread_key_t async_key;
 898 static pthread_key_t async_die_counter;
 899
 900 static void *run_thread(void *data)
 901 {
 902         struct async *async = data;
 903         intptr_t ret;
 904
 905         if (async->isolate_sigpipe) {
 906                 sigset_t mask;
 907                 sigemptyset(&mask);
 908                 sigaddset(&mask, SIGPIPE);
 909                 if (pthread_sigmask(SIG_BLOCK, &mask, NULL) < 0) {
 910                         ret = error("unable to block SIGPIPE in async thread");
 911                         return (void *)ret;
 912                 }
 913         }
 914
 915         pthread_setspecific(async_key, async);
 916         ret = async->proc(async->proc_in, async->proc_out, async->data);
 917         return (void *)ret;
 918 }
 919
 920 static NORETURN void die_async(const char *err, va_list params)
 921 {
 922         vreportf("fatal: ", err, params);
 923
 924         if (in_async()) {
 925                 struct async *async = pthread_getspecific(async_key);
 926                 if (async->proc_in >= 0)
 927                         close(async->proc_in);
 928                 if (async->proc_out >= 0)
 929                         close(async->proc_out);
 930                 pthread_exit((void *)128);
 931         }
 932
 933         exit(128);
 934 }
 935
 936 static int async_die_is_recursing(void)
 937 {
 938         void *ret = pthread_getspecific(async_die_counter);
 939         pthread_setspecific(async_die_counter, (void *)1);
 940         return ret != NULL;
 941 }
 942
 943 int in_async(void)
 944 {
 945         if (!main_thread_set)
 946                 return 0; /* no asyncs started yet */
 947         return !pthread_equal(main_thread, pthread_self());
 948 }
 949
 950 static void NORETURN async_exit(int code)
 951 {
 952         pthread_exit((void *)(intptr_t)code);
 953 }
 954
 955 #else
 956
 957 static struct {
 958         void (**handlers)(void);
 959         size_t nr;
 960         size_t alloc;
 961 } git_atexit_hdlrs;
 962
 963 static int git_atexit_installed;
 964
 965 static void git_atexit_dispatch(void)
 966 {
 967         size_t i;
 968
 969         for (i=git_atexit_hdlrs.nr ; i ; i--)
 970                 git_atexit_hdlrs.handlers[i-1]();
 971 }
 972
 973 static void git_atexit_clear(void)
 974 {
 975         free(git_atexit_hdlrs.handlers);
 976         memset(&git_atexit_hdlrs, 0, sizeof(git_atexit_hdlrs));
 977         git_atexit_installed = 0;
 978 }
 979
 980 #undef atexit
 981 int git_atexit(void (*handler)(void))
 982 {
 983         ALLOC_GROW(git_atexit_hdlrs.handlers, git_atexit_hdlrs.nr + 1, git_atexit_hdlrs.alloc);
 984         git_atexit_hdlrs.handlers[git_atexit_hdlrs.nr++] = handler;
 985         if (!git_atexit_installed) {
 986                 if (atexit(&git_atexit_dispatch))
 987                         return -1;
 988                 git_atexit_installed = 1;
 989         }
 990         return 0;
 991 }
 992 #define atexit git_atexit
 993
 994 static int process_is_async;
 995 int in_async(void)
 996 {
 997         return process_is_async;
 998 }
 999
1000 static void NORETURN async_exit(int code)
1001 {
1002         exit(code);
1003 }
1004
1005 #endif
1006
1007 void check_pipe(int err)
1008 {
1009         if (err == EPIPE) {
1010                 if (in_async())
1011                         async_exit(141);
1012
1013                 signal(SIGPIPE, SIG_DFL);
1014                 raise(SIGPIPE);
1015                 /* Should never happen, but just in case... */
1016                 exit(141);
1017         }
1018 }
1019
1020 int start_async(struct async *async)
1021 {
1022         int need_in, need_out;
1023         int fdin[2], fdout[2];
1024         int proc_in, proc_out;
1025
1026         need_in = async->in < 0;
1027         if (need_in) {
1028                 if (pipe(fdin) < 0) {
1029                         if (async->out > 0)
1030                                 close(async->out);
1031                         return error_errno("cannot create pipe");
1032                 }
1033                 async->in = fdin[1];
1034         }
1035
1036         need_out = async->out < 0;
1037         if (need_out) {
1038                 if (pipe(fdout) < 0) {
1039                         if (need_in)
1040                                 close_pair(fdin);
1041                         else if (async->in)
1042                                 close(async->in);
1043                         return error_errno("cannot create pipe");
1044                 }
1045                 async->out = fdout[0];
1046         }
1047
1048         if (need_in)
1049                 proc_in = fdin[0];
1050         else if (async->in)
1051                 proc_in = async->in;
1052         else
1053                 proc_in = -1;
1054
1055         if (need_out)
1056                 proc_out = fdout[1];
1057         else if (async->out)
1058                 proc_out = async->out;
1059         else
1060                 proc_out = -1;
1061
1062 #ifdef NO_PTHREADS
1063         /* Flush stdio before fork() to avoid cloning buffers */
1064         fflush(NULL);
1065
1066         async->pid = fork();
1067         if (async->pid < 0) {
1068                 error_errno("fork (async) failed");
1069                 goto error;
1070         }
1071         if (!async->pid) {
1072                 if (need_in)
1073                         close(fdin[1]);
1074                 if (need_out)
1075                         close(fdout[0]);
1076                 git_atexit_clear();
1077                 process_is_async = 1;
1078                 exit(!!async->proc(proc_in, proc_out, async->data));
1079         }
1080
1081         mark_child_for_cleanup(async->pid, NULL);
1082
1083         if (need_in)
1084                 close(fdin[0]);
1085         else if (async->in)
1086                 close(async->in);
1087
1088         if (need_out)
1089                 close(fdout[1]);
1090         else if (async->out)
1091                 close(async->out);
1092 #else
1093         if (!main_thread_set) {
1094                 /*
1095                  * We assume that the first time that start_async is called
1096                  * it is from the main thread.
1097                  */
1098                 main_thread_set = 1;
1099                 main_thread = pthread_self();
1100                 pthread_key_create(&async_key, NULL);
1101                 pthread_key_create(&async_die_counter, NULL);
1102                 set_die_routine(die_async);
1103                 set_die_is_recursing_routine(async_die_is_recursing);
1104         }
1105
1106         if (proc_in >= 0)
1107                 set_cloexec(proc_in);
1108         if (proc_out >= 0)
1109                 set_cloexec(proc_out);
1110         async->proc_in = proc_in;
1111         async->proc_out = proc_out;
1112         {
1113                 int err = pthread_create(&async->tid, NULL, run_thread, async);
1114                 if (err) {
1115                         error_errno("cannot create thread");
1116                         goto error;
1117                 }
1118         }
1119 #endif
1120         return 0;
1121
1122 error:
1123         if (need_in)
1124                 close_pair(fdin);
1125         else if (async->in)
1126                 close(async->in);
1127
1128         if (need_out)
1129                 close_pair(fdout);
1130         else if (async->out)
1131                 close(async->out);
1132         return -1;
1133 }
1134
1135 int finish_async(struct async *async)
1136 {
1137 #ifdef NO_PTHREADS
1138         return wait_or_whine(async->pid, "child process", 0);
1139 #else
1140         void *ret = (void *)(intptr_t)(-1);
1141
1142         if (pthread_join(async->tid, &ret))
1143                 error("pthread_join failed");
1144         return (int)(intptr_t)ret;
1145 #endif
1146 }
1147
1148 const char *find_hook(const char *name)
1149 {
1150         static struct strbuf path = STRBUF_INIT;
1151
1152         strbuf_reset(&path);
1153         strbuf_git_path(&path, "hooks/%s", name);
1154         if (access(path.buf, X_OK) < 0) {
1155 #ifdef STRIP_EXTENSION
1156                 strbuf_addstr(&path, STRIP_EXTENSION);
1157                 if (access(path.buf, X_OK) >= 0)
1158                         return path.buf;
1159 #endif
1160                 return NULL;
1161         }
1162         return path.buf;
1163 }
1164
1165 int run_hook_ve(const char *const *env, const char *name, va_list args)
1166 {
1167         struct child_process hook = CHILD_PROCESS_INIT;
1168         const char *p;
1169
1170         p = find_hook(name);
1171         if (!p)
1172                 return 0;
1173
1174         argv_array_push(&hook.args, p);
1175         while ((p = va_arg(args, const char *)))
1176                 argv_array_push(&hook.args, p);
1177         hook.env = env;
1178         hook.no_stdin = 1;
1179         hook.stdout_to_stderr = 1;
1180
1181         return run_command(&hook);
1182 }
1183
1184 int run_hook_le(const char *const *env, const char *name, ...)
1185 {
1186         va_list args;
1187         int ret;
1188
1189         va_start(args, name);
1190         ret = run_hook_ve(env, name, args);
1191         va_end(args);
1192
1193         return ret;
1194 }
1195
1196 struct io_pump {
1197         /* initialized by caller */
1198         int fd;
1199         int type; /* POLLOUT or POLLIN */
1200         union {
1201                 struct {
1202                         const char *buf;
1203                         size_t len;
1204                 } out;
1205                 struct {
1206                         struct strbuf *buf;
1207                         size_t hint;
1208                 } in;
1209         } u;
1210
1211         /* returned by pump_io */
1212         int error; /* 0 for success, otherwise errno */
1213
1214         /* internal use */
1215         struct pollfd *pfd;
1216 };
1217
1218 static int pump_io_round(struct io_pump *slots, int nr, struct pollfd *pfd)
1219 {
1220         int pollsize = 0;
1221         int i;
1222
1223         for (i = 0; i < nr; i++) {
1224                 struct io_pump *io = &slots[i];
1225                 if (io->fd < 0)
1226                         continue;
1227                 pfd[pollsize].fd = io->fd;
1228                 pfd[pollsize].events = io->type;
1229                 io->pfd = &pfd[pollsize++];
1230         }
1231
1232         if (!pollsize)
1233                 return 0;
1234
1235         if (poll(pfd, pollsize, -1) < 0) {
1236                 if (errno == EINTR)
1237                         return 1;
1238                 die_errno("poll failed");
1239         }
1240
1241         for (i = 0; i < nr; i++) {
1242                 struct io_pump *io = &slots[i];
1243
1244                 if (io->fd < 0)
1245                         continue;
1246
1247                 if (!(io->pfd->revents & (POLLOUT|POLLIN|POLLHUP|POLLERR|POLLNVAL)))
1248                         continue;
1249
1250                 if (io->type == POLLOUT) {
1251                         ssize_t len = xwrite(io->fd,
1252                                              io->u.out.buf, io->u.out.len);
1253                         if (len < 0) {
1254                                 io->error = errno;
1255                                 close(io->fd);
1256                                 io->fd = -1;
1257                         } else {
1258                                 io->u.out.buf += len;
1259                                 io->u.out.len -= len;
1260                                 if (!io->u.out.len) {
1261                                         close(io->fd);
1262                                         io->fd = -1;
1263                                 }
1264                         }
1265                 }
1266
1267                 if (io->type == POLLIN) {
1268                         ssize_t len = strbuf_read_once(io->u.in.buf,
1269                                                        io->fd, io->u.in.hint);
1270                         if (len < 0)
1271                                 io->error = errno;
1272                         if (len <= 0) {
1273                                 close(io->fd);
1274                                 io->fd = -1;
1275                         }
1276                 }
1277         }
1278
1279         return 1;
1280 }
1281
1282 static int pump_io(struct io_pump *slots, int nr)
1283 {
1284         struct pollfd *pfd;
1285         int i;
1286
1287         for (i = 0; i < nr; i++)
1288                 slots[i].error = 0;
1289
1290         ALLOC_ARRAY(pfd, nr);
1291         while (pump_io_round(slots, nr, pfd))
1292                 ; /* nothing */
1293         free(pfd);
1294
1295         /* There may be multiple errno values, so just pick the first. */
1296         for (i = 0; i < nr; i++) {
1297                 if (slots[i].error) {
1298                         errno = slots[i].error;
1299                         return -1;
1300                 }
1301         }
1302         return 0;
1303 }
1304
1305
1306 int pipe_command(struct child_process *cmd,
1307                  const char *in, size_t in_len,
1308                  struct strbuf *out, size_t out_hint,
1309                  struct strbuf *err, size_t err_hint)
1310 {
1311         struct io_pump io[3];
1312         int nr = 0;
1313
1314         if (in)
1315                 cmd->in = -1;
1316         if (out)
1317                 cmd->out = -1;
1318         if (err)
1319                 cmd->err = -1;
1320
1321         if (start_command(cmd) < 0)
1322                 return -1;
1323
1324         if (in) {
1325                 io[nr].fd = cmd->in;
1326                 io[nr].type = POLLOUT;
1327                 io[nr].u.out.buf = in;
1328                 io[nr].u.out.len = in_len;
1329                 nr++;
1330         }
1331         if (out) {
1332                 io[nr].fd = cmd->out;
1333                 io[nr].type = POLLIN;
1334                 io[nr].u.in.buf = out;
1335                 io[nr].u.in.hint = out_hint;
1336                 nr++;
1337         }
1338         if (err) {
1339                 io[nr].fd = cmd->err;
1340                 io[nr].type = POLLIN;
1341                 io[nr].u.in.buf = err;
1342                 io[nr].u.in.hint = err_hint;
1343                 nr++;
1344         }
1345
1346         if (pump_io(io, nr) < 0) {
1347                 finish_command(cmd); /* throw away exit code */
1348                 return -1;
1349         }
1350
1351         return finish_command(cmd);
1352 }
1353
1354 enum child_state {
1355         GIT_CP_FREE,
1356         GIT_CP_WORKING,
1357         GIT_CP_WAIT_CLEANUP,
1358 };
1359
1360 struct parallel_processes {
1361         void *data;
1362
1363         int max_processes;
1364         int nr_processes;
1365
1366         get_next_task_fn get_next_task;
1367         start_failure_fn start_failure;
1368         task_finished_fn task_finished;
1369
1370         struct {
1371                 enum child_state state;
1372                 struct child_process process;
1373                 struct strbuf err;
1374                 void *data;
1375         } *children;
1376         /*
1377          * The struct pollfd is logically part of *children,
1378          * but the system call expects it as its own array.
1379          */
1380         struct pollfd *pfd;
1381
1382         unsigned shutdown : 1;
1383
1384         int output_owner;
1385         struct strbuf buffered_output; /* of finished children */
1386 };
1387
1388 static int default_start_failure(struct strbuf *out,
1389                                  void *pp_cb,
1390                                  void *pp_task_cb)
1391 {
1392         return 0;
1393 }
1394
1395 static int default_task_finished(int result,
1396                                  struct strbuf *out,
1397                                  void *pp_cb,
1398                                  void *pp_task_cb)
1399 {
1400         return 0;
1401 }
1402
1403 static void kill_children(struct parallel_processes *pp, int signo)
1404 {
1405         int i, n = pp->max_processes;
1406
1407         for (i = 0; i < n; i++)
1408                 if (pp->children[i].state == GIT_CP_WORKING)
1409                         kill(pp->children[i].process.pid, signo);
1410 }
1411
1412 static struct parallel_processes *pp_for_signal;
1413
1414 static void handle_children_on_signal(int signo)
1415 {
1416         kill_children(pp_for_signal, signo);
1417         sigchain_pop(signo);
1418         raise(signo);
1419 }
1420
1421 static void pp_init(struct parallel_processes *pp,
1422                     int n,
1423                     get_next_task_fn get_next_task,
1424                     start_failure_fn start_failure,
1425                     task_finished_fn task_finished,
1426                     void *data)
1427 {
1428         int i;
1429
1430         if (n < 1)
1431                 n = online_cpus();
1432
1433         pp->max_processes = n;
1434
1435         trace_printf("run_processes_parallel: preparing to run up to %d tasks", n);
1436
1437         pp->data = data;
1438         if (!get_next_task)
1439                 die("BUG: you need to specify a get_next_task function");
1440         pp->get_next_task = get_next_task;
1441
1442         pp->start_failure = start_failure ? start_failure : default_start_failure;
1443         pp->task_finished = task_finished ? task_finished : default_task_finished;
1444
1445         pp->nr_processes = 0;
1446         pp->output_owner = 0;
1447         pp->shutdown = 0;
1448         pp->children = xcalloc(n, sizeof(*pp->children));
1449         pp->pfd = xcalloc(n, sizeof(*pp->pfd));
1450         strbuf_init(&pp->buffered_output, 0);
1451
1452         for (i = 0; i < n; i++) {
1453                 strbuf_init(&pp->children[i].err, 0);
1454                 child_process_init(&pp->children[i].process);
1455                 pp->pfd[i].events = POLLIN | POLLHUP;
1456                 pp->pfd[i].fd = -1;
1457         }
1458
1459         pp_for_signal = pp;
1460         sigchain_push_common(handle_children_on_signal);
1461 }
1462
1463 static void pp_cleanup(struct parallel_processes *pp)
1464 {
1465         int i;
1466
1467         trace_printf("run_processes_parallel: done");
1468         for (i = 0; i < pp->max_processes; i++) {
1469                 strbuf_release(&pp->children[i].err);
1470                 child_process_clear(&pp->children[i].process);
1471         }
1472
1473         free(pp->children);
1474         free(pp->pfd);
1475
1476         /*
1477          * When get_next_task added messages to the buffer in its last
1478          * iteration, the buffered output is non empty.
1479          */
1480         strbuf_write(&pp->buffered_output, stderr);
1481         strbuf_release(&pp->buffered_output);
1482
1483         sigchain_pop_common();
1484 }
1485
1486 /* returns
1487  *  0 if a new task was started.
1488  *  1 if no new jobs was started (get_next_task ran out of work, non critical
1489  *    problem with starting a new command)
1490  * <0 no new job was started, user wishes to shutdown early. Use negative code
1491  *    to signal the children.
1492  */
1493 static int pp_start_one(struct parallel_processes *pp)
1494 {
1495         int i, code;
1496
1497         for (i = 0; i < pp->max_processes; i++)
1498                 if (pp->children[i].state == GIT_CP_FREE)
1499                         break;
1500         if (i == pp->max_processes)
1501                 die("BUG: bookkeeping is hard");
1502
1503         code = pp->get_next_task(&pp->children[i].process,
1504                                  &pp->children[i].err,
1505                                  pp->data,
1506                                  &pp->children[i].data);
1507         if (!code) {
1508                 strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1509                 strbuf_reset(&pp->children[i].err);
1510                 return 1;
1511         }
1512         pp->children[i].process.err = -1;
1513         pp->children[i].process.stdout_to_stderr = 1;
1514         pp->children[i].process.no_stdin = 1;
1515
1516         if (start_command(&pp->children[i].process)) {
1517                 code = pp->start_failure(&pp->children[i].err,
1518                                          pp->data,
1519                                          &pp->children[i].data);
1520                 strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1521                 strbuf_reset(&pp->children[i].err);
1522                 if (code)
1523                         pp->shutdown = 1;
1524                 return code;
1525         }
1526
1527         pp->nr_processes++;
1528         pp->children[i].state = GIT_CP_WORKING;
1529         pp->pfd[i].fd = pp->children[i].process.err;
1530         return 0;
1531 }
1532
1533 static void pp_buffer_stderr(struct parallel_processes *pp, int output_timeout)
1534 {
1535         int i;
1536
1537         while ((i = poll(pp->pfd, pp->max_processes, output_timeout)) < 0) {
1538                 if (errno == EINTR)
1539                         continue;
1540                 pp_cleanup(pp);
1541                 die_errno("poll");
1542         }
1543
1544         /* Buffer output from all pipes. */
1545         for (i = 0; i < pp->max_processes; i++) {
1546                 if (pp->children[i].state == GIT_CP_WORKING &&
1547                     pp->pfd[i].revents & (POLLIN | POLLHUP)) {
1548                         int n = strbuf_read_once(&pp->children[i].err,
1549                                                  pp->children[i].process.err, 0);
1550                         if (n == 0) {
1551                                 close(pp->children[i].process.err);
1552                                 pp->children[i].state = GIT_CP_WAIT_CLEANUP;
1553                         } else if (n < 0)
1554                                 if (errno != EAGAIN)
1555                                         die_errno("read");
1556                 }
1557         }
1558 }
1559
1560 static void pp_output(struct parallel_processes *pp)
1561 {
1562         int i = pp->output_owner;
1563         if (pp->children[i].state == GIT_CP_WORKING &&
1564             pp->children[i].err.len) {
1565                 strbuf_write(&pp->children[i].err, stderr);
1566                 strbuf_reset(&pp->children[i].err);
1567         }
1568 }
1569
1570 static int pp_collect_finished(struct parallel_processes *pp)
1571 {
1572         int i, code;
1573         int n = pp->max_processes;
1574         int result = 0;
1575
1576         while (pp->nr_processes > 0) {
1577                 for (i = 0; i < pp->max_processes; i++)
1578                         if (pp->children[i].state == GIT_CP_WAIT_CLEANUP)
1579                                 break;
1580                 if (i == pp->max_processes)
1581                         break;
1582
1583                 code = finish_command(&pp->children[i].process);
1584
1585                 code = pp->task_finished(code,
1586                                          &pp->children[i].err, pp->data,
1587                                          &pp->children[i].data);
1588
1589                 if (code)
1590                         result = code;
1591                 if (code < 0)
1592                         break;
1593
1594                 pp->nr_processes--;
1595                 pp->children[i].state = GIT_CP_FREE;
1596                 pp->pfd[i].fd = -1;
1597                 child_process_init(&pp->children[i].process);
1598
1599                 if (i != pp->output_owner) {
1600                         strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1601                         strbuf_reset(&pp->children[i].err);
1602                 } else {
1603                         strbuf_write(&pp->children[i].err, stderr);
1604                         strbuf_reset(&pp->children[i].err);
1605
1606                         /* Output all other finished child processes */
1607                         strbuf_write(&pp->buffered_output, stderr);
1608                         strbuf_reset(&pp->buffered_output);
1609
1610                         /*
1611                          * Pick next process to output live.
1612                          * NEEDSWORK:
1613                          * For now we pick it randomly by doing a round
1614                          * robin. Later we may want to pick the one with
1615                          * the most output or the longest or shortest
1616                          * running process time.
1617                          */
1618                         for (i = 0; i < n; i++)
1619                                 if (pp->children[(pp->output_owner + i) % n].state == GIT_CP_WORKING)
1620                                         break;
1621                         pp->output_owner = (pp->output_owner + i) % n;
1622                 }
1623         }
1624         return result;
1625 }
1626
1627 int run_processes_parallel(int n,
1628                            get_next_task_fn get_next_task,
1629                            start_failure_fn start_failure,
1630                            task_finished_fn task_finished,
1631                            void *pp_cb)
1632 {
1633         int i, code;
1634         int output_timeout = 100;
1635         int spawn_cap = 4;
1636         struct parallel_processes pp;
1637
1638         pp_init(&pp, n, get_next_task, start_failure, task_finished, pp_cb);
1639         while (1) {
1640                 for (i = 0;
1641                     i < spawn_cap && !pp.shutdown &&
1642                     pp.nr_processes < pp.max_processes;
1643                     i++) {
1644                         code = pp_start_one(&pp);
1645                         if (!code)
1646                                 continue;
1647                         if (code < 0) {
1648                                 pp.shutdown = 1;
1649                                 kill_children(&pp, -code);
1650                         }
1651                         break;
1652                 }
1653                 if (!pp.nr_processes)
1654                         break;
1655                 pp_buffer_stderr(&pp, output_timeout);
1656                 pp_output(&pp);
1657                 code = pp_collect_finished(&pp);
1658                 if (code) {
1659                         pp.shutdown = 1;
1660                         if (code < 0)
1661                                 kill_children(&pp, -code);
1662                 }
1663         }
1664
1665         pp_cleanup(&pp);
1666         return 0;
1667 }