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