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_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 static 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 static void NORETURN async_exit(int code)
 688 {
 689         exit(code);
 690 }
 691
 692 #endif
 693
 694 void check_pipe(int err)
 695 {
 696         if (err == EPIPE) {
 697                 if (in_async())
 698                         async_exit(141);
 699
 700                 signal(SIGPIPE, SIG_DFL);
 701                 raise(SIGPIPE);
 702                 /* Should never happen, but just in case... */
 703                 exit(141);
 704         }
 705 }
 706
 707 int start_async(struct async *async)
 708 {
 709         int need_in, need_out;
 710         int fdin[2], fdout[2];
 711         int proc_in, proc_out;
 712
 713         need_in = async->in < 0;
 714         if (need_in) {
 715                 if (pipe(fdin) < 0) {
 716                         if (async->out > 0)
 717                                 close(async->out);
 718                         return error_errno("cannot create pipe");
 719                 }
 720                 async->in = fdin[1];
 721         }
 722
 723         need_out = async->out < 0;
 724         if (need_out) {
 725                 if (pipe(fdout) < 0) {
 726                         if (need_in)
 727                                 close_pair(fdin);
 728                         else if (async->in)
 729                                 close(async->in);
 730                         return error_errno("cannot create pipe");
 731                 }
 732                 async->out = fdout[0];
 733         }
 734
 735         if (need_in)
 736                 proc_in = fdin[0];
 737         else if (async->in)
 738                 proc_in = async->in;
 739         else
 740                 proc_in = -1;
 741
 742         if (need_out)
 743                 proc_out = fdout[1];
 744         else if (async->out)
 745                 proc_out = async->out;
 746         else
 747                 proc_out = -1;
 748
 749 #ifdef NO_PTHREADS
 750         /* Flush stdio before fork() to avoid cloning buffers */
 751         fflush(NULL);
 752
 753         async->pid = fork();
 754         if (async->pid < 0) {
 755                 error_errno("fork (async) failed");
 756                 goto error;
 757         }
 758         if (!async->pid) {
 759                 if (need_in)
 760                         close(fdin[1]);
 761                 if (need_out)
 762                         close(fdout[0]);
 763                 git_atexit_clear();
 764                 process_is_async = 1;
 765                 exit(!!async->proc(proc_in, proc_out, async->data));
 766         }
 767
 768         mark_child_for_cleanup(async->pid);
 769
 770         if (need_in)
 771                 close(fdin[0]);
 772         else if (async->in)
 773                 close(async->in);
 774
 775         if (need_out)
 776                 close(fdout[1]);
 777         else if (async->out)
 778                 close(async->out);
 779 #else
 780         if (!main_thread_set) {
 781                 /*
 782                  * We assume that the first time that start_async is called
 783                  * it is from the main thread.
 784                  */
 785                 main_thread_set = 1;
 786                 main_thread = pthread_self();
 787                 pthread_key_create(&async_key, NULL);
 788                 pthread_key_create(&async_die_counter, NULL);
 789                 set_die_routine(die_async);
 790                 set_die_is_recursing_routine(async_die_is_recursing);
 791         }
 792
 793         if (proc_in >= 0)
 794                 set_cloexec(proc_in);
 795         if (proc_out >= 0)
 796                 set_cloexec(proc_out);
 797         async->proc_in = proc_in;
 798         async->proc_out = proc_out;
 799         {
 800                 int err = pthread_create(&async->tid, NULL, run_thread, async);
 801                 if (err) {
 802                         error_errno("cannot create thread");
 803                         goto error;
 804                 }
 805         }
 806 #endif
 807         return 0;
 808
 809 error:
 810         if (need_in)
 811                 close_pair(fdin);
 812         else if (async->in)
 813                 close(async->in);
 814
 815         if (need_out)
 816                 close_pair(fdout);
 817         else if (async->out)
 818                 close(async->out);
 819         return -1;
 820 }
 821
 822 int finish_async(struct async *async)
 823 {
 824 #ifdef NO_PTHREADS
 825         return wait_or_whine(async->pid, "child process", 0);
 826 #else
 827         void *ret = (void *)(intptr_t)(-1);
 828
 829         if (pthread_join(async->tid, &ret))
 830                 error("pthread_join failed");
 831         return (int)(intptr_t)ret;
 832 #endif
 833 }
 834
 835 const char *find_hook(const char *name)
 836 {
 837         static struct strbuf path = STRBUF_INIT;
 838
 839         strbuf_reset(&path);
 840         strbuf_git_path(&path, "hooks/%s", name);
 841         if (access(path.buf, X_OK) < 0)
 842                 return NULL;
 843         return path.buf;
 844 }
 845
 846 int run_hook_ve(const char *const *env, const char *name, va_list args)
 847 {
 848         struct child_process hook = CHILD_PROCESS_INIT;
 849         const char *p;
 850
 851         p = find_hook(name);
 852         if (!p)
 853                 return 0;
 854
 855         argv_array_push(&hook.args, p);
 856         while ((p = va_arg(args, const char *)))
 857                 argv_array_push(&hook.args, p);
 858         hook.env = env;
 859         hook.no_stdin = 1;
 860         hook.stdout_to_stderr = 1;
 861
 862         return run_command(&hook);
 863 }
 864
 865 int run_hook_le(const char *const *env, const char *name, ...)
 866 {
 867         va_list args;
 868         int ret;
 869
 870         va_start(args, name);
 871         ret = run_hook_ve(env, name, args);
 872         va_end(args);
 873
 874         return ret;
 875 }
 876
 877 struct io_pump {
 878         /* initialized by caller */
 879         int fd;
 880         int type; /* POLLOUT or POLLIN */
 881         union {
 882                 struct {
 883                         const char *buf;
 884                         size_t len;
 885                 } out;
 886                 struct {
 887                         struct strbuf *buf;
 888                         size_t hint;
 889                 } in;
 890         } u;
 891
 892         /* returned by pump_io */
 893         int error; /* 0 for success, otherwise errno */
 894
 895         /* internal use */
 896         struct pollfd *pfd;
 897 };
 898
 899 static int pump_io_round(struct io_pump *slots, int nr, struct pollfd *pfd)
 900 {
 901         int pollsize = 0;
 902         int i;
 903
 904         for (i = 0; i < nr; i++) {
 905                 struct io_pump *io = &slots[i];
 906                 if (io->fd < 0)
 907                         continue;
 908                 pfd[pollsize].fd = io->fd;
 909                 pfd[pollsize].events = io->type;
 910                 io->pfd = &pfd[pollsize++];
 911         }
 912
 913         if (!pollsize)
 914                 return 0;
 915
 916         if (poll(pfd, pollsize, -1) < 0) {
 917                 if (errno == EINTR)
 918                         return 1;
 919                 die_errno("poll failed");
 920         }
 921
 922         for (i = 0; i < nr; i++) {
 923                 struct io_pump *io = &slots[i];
 924
 925                 if (io->fd < 0)
 926                         continue;
 927
 928                 if (!(io->pfd->revents & (POLLOUT|POLLIN|POLLHUP|POLLERR|POLLNVAL)))
 929                         continue;
 930
 931                 if (io->type == POLLOUT) {
 932                         ssize_t len = xwrite(io->fd,
 933                                              io->u.out.buf, io->u.out.len);
 934                         if (len < 0) {
 935                                 io->error = errno;
 936                                 close(io->fd);
 937                                 io->fd = -1;
 938                         } else {
 939                                 io->u.out.buf += len;
 940                                 io->u.out.len -= len;
 941                                 if (!io->u.out.len) {
 942                                         close(io->fd);
 943                                         io->fd = -1;
 944                                 }
 945                         }
 946                 }
 947
 948                 if (io->type == POLLIN) {
 949                         ssize_t len = strbuf_read_once(io->u.in.buf,
 950                                                        io->fd, io->u.in.hint);
 951                         if (len < 0)
 952                                 io->error = errno;
 953                         if (len <= 0) {
 954                                 close(io->fd);
 955                                 io->fd = -1;
 956                         }
 957                 }
 958         }
 959
 960         return 1;
 961 }
 962
 963 static int pump_io(struct io_pump *slots, int nr)
 964 {
 965         struct pollfd *pfd;
 966         int i;
 967
 968         for (i = 0; i < nr; i++)
 969                 slots[i].error = 0;
 970
 971         ALLOC_ARRAY(pfd, nr);
 972         while (pump_io_round(slots, nr, pfd))
 973                 ; /* nothing */
 974         free(pfd);
 975
 976         /* There may be multiple errno values, so just pick the first. */
 977         for (i = 0; i < nr; i++) {
 978                 if (slots[i].error) {
 979                         errno = slots[i].error;
 980                         return -1;
 981                 }
 982         }
 983         return 0;
 984 }
 985
 986
 987 int pipe_command(struct child_process *cmd,
 988                  const char *in, size_t in_len,
 989                  struct strbuf *out, size_t out_hint,
 990                  struct strbuf *err, size_t err_hint)
 991 {
 992         struct io_pump io[3];
 993         int nr = 0;
 994
 995         if (in)
 996                 cmd->in = -1;
 997         if (out)
 998                 cmd->out = -1;
 999         if (err)
1000                 cmd->err = -1;
1001
1002         if (start_command(cmd) < 0)
1003                 return -1;
1004
1005         if (in) {
1006                 io[nr].fd = cmd->in;
1007                 io[nr].type = POLLOUT;
1008                 io[nr].u.out.buf = in;
1009                 io[nr].u.out.len = in_len;
1010                 nr++;
1011         }
1012         if (out) {
1013                 io[nr].fd = cmd->out;
1014                 io[nr].type = POLLIN;
1015                 io[nr].u.in.buf = out;
1016                 io[nr].u.in.hint = out_hint;
1017                 nr++;
1018         }
1019         if (err) {
1020                 io[nr].fd = cmd->err;
1021                 io[nr].type = POLLIN;
1022                 io[nr].u.in.buf = err;
1023                 io[nr].u.in.hint = err_hint;
1024                 nr++;
1025         }
1026
1027         if (pump_io(io, nr) < 0) {
1028                 finish_command(cmd); /* throw away exit code */
1029                 return -1;
1030         }
1031
1032         return finish_command(cmd);
1033 }
1034
1035 enum child_state {
1036         GIT_CP_FREE,
1037         GIT_CP_WORKING,
1038         GIT_CP_WAIT_CLEANUP,
1039 };
1040
1041 struct parallel_processes {
1042         void *data;
1043
1044         int max_processes;
1045         int nr_processes;
1046
1047         get_next_task_fn get_next_task;
1048         start_failure_fn start_failure;
1049         task_finished_fn task_finished;
1050
1051         struct {
1052                 enum child_state state;
1053                 struct child_process process;
1054                 struct strbuf err;
1055                 void *data;
1056         } *children;
1057         /*
1058          * The struct pollfd is logically part of *children,
1059          * but the system call expects it as its own array.
1060          */
1061         struct pollfd *pfd;
1062
1063         unsigned shutdown : 1;
1064
1065         int output_owner;
1066         struct strbuf buffered_output; /* of finished children */
1067 };
1068
1069 static int default_start_failure(struct strbuf *out,
1070                                  void *pp_cb,
1071                                  void *pp_task_cb)
1072 {
1073         return 0;
1074 }
1075
1076 static int default_task_finished(int result,
1077                                  struct strbuf *out,
1078                                  void *pp_cb,
1079                                  void *pp_task_cb)
1080 {
1081         return 0;
1082 }
1083
1084 static void kill_children(struct parallel_processes *pp, int signo)
1085 {
1086         int i, n = pp->max_processes;
1087
1088         for (i = 0; i < n; i++)
1089                 if (pp->children[i].state == GIT_CP_WORKING)
1090                         kill(pp->children[i].process.pid, signo);
1091 }
1092
1093 static struct parallel_processes *pp_for_signal;
1094
1095 static void handle_children_on_signal(int signo)
1096 {
1097         kill_children(pp_for_signal, signo);
1098         sigchain_pop(signo);
1099         raise(signo);
1100 }
1101
1102 static void pp_init(struct parallel_processes *pp,
1103                     int n,
1104                     get_next_task_fn get_next_task,
1105                     start_failure_fn start_failure,
1106                     task_finished_fn task_finished,
1107                     void *data)
1108 {
1109         int i;
1110
1111         if (n < 1)
1112                 n = online_cpus();
1113
1114         pp->max_processes = n;
1115
1116         trace_printf("run_processes_parallel: preparing to run up to %d tasks", n);
1117
1118         pp->data = data;
1119         if (!get_next_task)
1120                 die("BUG: you need to specify a get_next_task function");
1121         pp->get_next_task = get_next_task;
1122
1123         pp->start_failure = start_failure ? start_failure : default_start_failure;
1124         pp->task_finished = task_finished ? task_finished : default_task_finished;
1125
1126         pp->nr_processes = 0;
1127         pp->output_owner = 0;
1128         pp->shutdown = 0;
1129         pp->children = xcalloc(n, sizeof(*pp->children));
1130         pp->pfd = xcalloc(n, sizeof(*pp->pfd));
1131         strbuf_init(&pp->buffered_output, 0);
1132
1133         for (i = 0; i < n; i++) {
1134                 strbuf_init(&pp->children[i].err, 0);
1135                 child_process_init(&pp->children[i].process);
1136                 pp->pfd[i].events = POLLIN | POLLHUP;
1137                 pp->pfd[i].fd = -1;
1138         }
1139
1140         pp_for_signal = pp;
1141         sigchain_push_common(handle_children_on_signal);
1142 }
1143
1144 static void pp_cleanup(struct parallel_processes *pp)
1145 {
1146         int i;
1147
1148         trace_printf("run_processes_parallel: done");
1149         for (i = 0; i < pp->max_processes; i++) {
1150                 strbuf_release(&pp->children[i].err);
1151                 child_process_clear(&pp->children[i].process);
1152         }
1153
1154         free(pp->children);
1155         free(pp->pfd);
1156
1157         /*
1158          * When get_next_task added messages to the buffer in its last
1159          * iteration, the buffered output is non empty.
1160          */
1161         strbuf_write(&pp->buffered_output, stderr);
1162         strbuf_release(&pp->buffered_output);
1163
1164         sigchain_pop_common();
1165 }
1166
1167 /* returns
1168  *  0 if a new task was started.
1169  *  1 if no new jobs was started (get_next_task ran out of work, non critical
1170  *    problem with starting a new command)
1171  * <0 no new job was started, user wishes to shutdown early. Use negative code
1172  *    to signal the children.
1173  */
1174 static int pp_start_one(struct parallel_processes *pp)
1175 {
1176         int i, code;
1177
1178         for (i = 0; i < pp->max_processes; i++)
1179                 if (pp->children[i].state == GIT_CP_FREE)
1180                         break;
1181         if (i == pp->max_processes)
1182                 die("BUG: bookkeeping is hard");
1183
1184         code = pp->get_next_task(&pp->children[i].process,
1185                                  &pp->children[i].err,
1186                                  pp->data,
1187                                  &pp->children[i].data);
1188         if (!code) {
1189                 strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1190                 strbuf_reset(&pp->children[i].err);
1191                 return 1;
1192         }
1193         pp->children[i].process.err = -1;
1194         pp->children[i].process.stdout_to_stderr = 1;
1195         pp->children[i].process.no_stdin = 1;
1196
1197         if (start_command(&pp->children[i].process)) {
1198                 code = pp->start_failure(&pp->children[i].err,
1199                                          pp->data,
1200                                          &pp->children[i].data);
1201                 strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1202                 strbuf_reset(&pp->children[i].err);
1203                 if (code)
1204                         pp->shutdown = 1;
1205                 return code;
1206         }
1207
1208         pp->nr_processes++;
1209         pp->children[i].state = GIT_CP_WORKING;
1210         pp->pfd[i].fd = pp->children[i].process.err;
1211         return 0;
1212 }
1213
1214 static void pp_buffer_stderr(struct parallel_processes *pp, int output_timeout)
1215 {
1216         int i;
1217
1218         while ((i = poll(pp->pfd, pp->max_processes, output_timeout)) < 0) {
1219                 if (errno == EINTR)
1220                         continue;
1221                 pp_cleanup(pp);
1222                 die_errno("poll");
1223         }
1224
1225         /* Buffer output from all pipes. */
1226         for (i = 0; i < pp->max_processes; i++) {
1227                 if (pp->children[i].state == GIT_CP_WORKING &&
1228                     pp->pfd[i].revents & (POLLIN | POLLHUP)) {
1229                         int n = strbuf_read_once(&pp->children[i].err,
1230                                                  pp->children[i].process.err, 0);
1231                         if (n == 0) {
1232                                 close(pp->children[i].process.err);
1233                                 pp->children[i].state = GIT_CP_WAIT_CLEANUP;
1234                         } else if (n < 0)
1235                                 if (errno != EAGAIN)
1236                                         die_errno("read");
1237                 }
1238         }
1239 }
1240
1241 static void pp_output(struct parallel_processes *pp)
1242 {
1243         int i = pp->output_owner;
1244         if (pp->children[i].state == GIT_CP_WORKING &&
1245             pp->children[i].err.len) {
1246                 strbuf_write(&pp->children[i].err, stderr);
1247                 strbuf_reset(&pp->children[i].err);
1248         }
1249 }
1250
1251 static int pp_collect_finished(struct parallel_processes *pp)
1252 {
1253         int i, code;
1254         int n = pp->max_processes;
1255         int result = 0;
1256
1257         while (pp->nr_processes > 0) {
1258                 for (i = 0; i < pp->max_processes; i++)
1259                         if (pp->children[i].state == GIT_CP_WAIT_CLEANUP)
1260                                 break;
1261                 if (i == pp->max_processes)
1262                         break;
1263
1264                 code = finish_command(&pp->children[i].process);
1265
1266                 code = pp->task_finished(code,
1267                                          &pp->children[i].err, pp->data,
1268                                          &pp->children[i].data);
1269
1270                 if (code)
1271                         result = code;
1272                 if (code < 0)
1273                         break;
1274
1275                 pp->nr_processes--;
1276                 pp->children[i].state = GIT_CP_FREE;
1277                 pp->pfd[i].fd = -1;
1278                 child_process_init(&pp->children[i].process);
1279
1280                 if (i != pp->output_owner) {
1281                         strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1282                         strbuf_reset(&pp->children[i].err);
1283                 } else {
1284                         strbuf_write(&pp->children[i].err, stderr);
1285                         strbuf_reset(&pp->children[i].err);
1286
1287                         /* Output all other finished child processes */
1288                         strbuf_write(&pp->buffered_output, stderr);
1289                         strbuf_reset(&pp->buffered_output);
1290
1291                         /*
1292                          * Pick next process to output live.
1293                          * NEEDSWORK:
1294                          * For now we pick it randomly by doing a round
1295                          * robin. Later we may want to pick the one with
1296                          * the most output or the longest or shortest
1297                          * running process time.
1298                          */
1299                         for (i = 0; i < n; i++)
1300                                 if (pp->children[(pp->output_owner + i) % n].state == GIT_CP_WORKING)
1301                                         break;
1302                         pp->output_owner = (pp->output_owner + i) % n;
1303                 }
1304         }
1305         return result;
1306 }
1307
1308 int run_processes_parallel(int n,
1309                            get_next_task_fn get_next_task,
1310                            start_failure_fn start_failure,
1311                            task_finished_fn task_finished,
1312                            void *pp_cb)
1313 {
1314         int i, code;
1315         int output_timeout = 100;
1316         int spawn_cap = 4;
1317         struct parallel_processes pp;
1318
1319         pp_init(&pp, n, get_next_task, start_failure, task_finished, pp_cb);
1320         while (1) {
1321                 for (i = 0;
1322                     i < spawn_cap && !pp.shutdown &&
1323                     pp.nr_processes < pp.max_processes;
1324                     i++) {
1325                         code = pp_start_one(&pp);
1326                         if (!code)
1327                                 continue;
1328                         if (code < 0) {
1329                                 pp.shutdown = 1;
1330                                 kill_children(&pp, -code);
1331                         }
1332                         break;
1333                 }
1334                 if (!pp.nr_processes)
1335                         break;
1336                 pp_buffer_stderr(&pp, output_timeout);
1337                 pp_output(&pp);
1338                 code = pp_collect_finished(&pp);
1339                 if (code) {
1340                         pp.shutdown = 1;
1341                         if (code < 0)
1342                                 kill_children(&pp, -code);
1343                 }
1344         }
1345
1346         pp_cleanup(&pp);
1347         return 0;
1348 }