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