git.oblomov.eu Git - git/blob - run-command.c

   1 #include "cache.h"
   2 #include "run-command.h"
   3 #include "exec_cmd.h"
   4 #include "sigchain.h"
   5 #include "argv-array.h"
   6 #include "thread-utils.h"
   7 #include "strbuf.h"
   8
   9 void child_process_init(struct child_process *child)
  10 {
  11         memset(child, 0, sizeof(*child));
  12         argv_array_init(&child->args);
  13         argv_array_init(&child->env_array);
  14 }
  15
  16 void child_process_clear(struct child_process *child)
  17 {
  18         argv_array_clear(&child->args);
  19         argv_array_clear(&child->env_array);
  20 }
  21
  22 struct child_to_clean {
  23         pid_t pid;
  24         struct child_process *process;
  25         struct child_to_clean *next;
  26 };
  27 static struct child_to_clean *children_to_clean;
  28 static int installed_child_cleanup_handler;
  29
  30 static void cleanup_children(int sig, int in_signal)
  31 {
  32         while (children_to_clean) {
  33                 struct child_to_clean *p = children_to_clean;
  34                 children_to_clean = p->next;
  35
  36                 if (p->process && !in_signal) {
  37                         struct child_process *process = p->process;
  38                         if (process->clean_on_exit_handler) {
  39                                 trace_printf(
  40                                         "trace: run_command: running exit handler for pid %"
  41                                         PRIuMAX, (uintmax_t)p->pid
  42                                 );
  43                                 process->clean_on_exit_handler(process);
  44                         }
  45                 }
  46
  47                 kill(p->pid, sig);
  48                 if (!in_signal)
  49                         free(p);
  50         }
  51 }
  52
  53 static void cleanup_children_on_signal(int sig)
  54 {
  55         cleanup_children(sig, 1);
  56         sigchain_pop(sig);
  57         raise(sig);
  58 }
  59
  60 static void cleanup_children_on_exit(void)
  61 {
  62         cleanup_children(SIGTERM, 0);
  63 }
  64
  65 static void mark_child_for_cleanup(pid_t pid, struct child_process *process)
  66 {
  67         struct child_to_clean *p = xmalloc(sizeof(*p));
  68         p->pid = pid;
  69         p->process = process;
  70         p->next = children_to_clean;
  71         children_to_clean = p;
  72
  73         if (!installed_child_cleanup_handler) {
  74                 atexit(cleanup_children_on_exit);
  75                 sigchain_push_common(cleanup_children_on_signal);
  76                 installed_child_cleanup_handler = 1;
  77         }
  78 }
  79
  80 static void clear_child_for_cleanup(pid_t pid)
  81 {
  82         struct child_to_clean **pp;
  83
  84         for (pp = &children_to_clean; *pp; pp = &(*pp)->next) {
  85                 struct child_to_clean *clean_me = *pp;
  86
  87                 if (clean_me->pid == pid) {
  88                         *pp = clean_me->next;
  89                         free(clean_me);
  90                         return;
  91                 }
  92         }
  93 }
  94
  95 static inline void close_pair(int fd[2])
  96 {
  97         close(fd[0]);
  98         close(fd[1]);
  99 }
 100
 101 #ifndef GIT_WINDOWS_NATIVE
 102 static inline void dup_devnull(int to)
 103 {
 104         int fd = open("/dev/null", O_RDWR);
 105         if (fd < 0)
 106                 die_errno(_("open /dev/null failed"));
 107         if (dup2(fd, to) < 0)
 108                 die_errno(_("dup2(%d,%d) failed"), fd, to);
 109         close(fd);
 110 }
 111 #endif
 112
 113 static char *locate_in_PATH(const char *file)
 114 {
 115         const char *p = getenv("PATH");
 116         struct strbuf buf = STRBUF_INIT;
 117
 118         if (!p || !*p)
 119                 return NULL;
 120
 121         while (1) {
 122                 const char *end = strchrnul(p, ':');
 123
 124                 strbuf_reset(&buf);
 125
 126                 /* POSIX specifies an empty entry as the current directory. */
 127                 if (end != p) {
 128                         strbuf_add(&buf, p, end - p);
 129                         strbuf_addch(&buf, '/');
 130                 }
 131                 strbuf_addstr(&buf, file);
 132
 133                 if (!access(buf.buf, F_OK))
 134                         return strbuf_detach(&buf, NULL);
 135
 136                 if (!*end)
 137                         break;
 138                 p = end + 1;
 139         }
 140
 141         strbuf_release(&buf);
 142         return NULL;
 143 }
 144
 145 static int exists_in_PATH(const char *file)
 146 {
 147         char *r = locate_in_PATH(file);
 148         free(r);
 149         return r != NULL;
 150 }
 151
 152 int sane_execvp(const char *file, char * const argv[])
 153 {
 154         if (!execvp(file, argv))
 155                 return 0; /* cannot happen ;-) */
 156
 157         /*
 158          * When a command can't be found because one of the directories
 159          * listed in $PATH is unsearchable, execvp reports EACCES, but
 160          * careful usability testing (read: analysis of occasional bug
 161          * reports) reveals that "No such file or directory" is more
 162          * intuitive.
 163          *
 164          * We avoid commands with "/", because execvp will not do $PATH
 165          * lookups in that case.
 166          *
 167          * The reassignment of EACCES to errno looks like a no-op below,
 168          * but we need to protect against exists_in_PATH overwriting errno.
 169          */
 170         if (errno == EACCES && !strchr(file, '/'))
 171                 errno = exists_in_PATH(file) ? EACCES : ENOENT;
 172         else if (errno == ENOTDIR && !strchr(file, '/'))
 173                 errno = ENOENT;
 174         return -1;
 175 }
 176
 177 static const char **prepare_shell_cmd(struct argv_array *out, const char **argv)
 178 {
 179         if (!argv[0])
 180                 die("BUG: shell command is empty");
 181
 182         if (strcspn(argv[0], "|&;<>()$`\\\"' \t\n*?[#~=%") != strlen(argv[0])) {
 183 #ifndef GIT_WINDOWS_NATIVE
 184                 argv_array_push(out, SHELL_PATH);
 185 #else
 186                 argv_array_push(out, "sh");
 187 #endif
 188                 argv_array_push(out, "-c");
 189
 190                 /*
 191                  * If we have no extra arguments, we do not even need to
 192                  * bother with the "$@" magic.
 193                  */
 194                 if (!argv[1])
 195                         argv_array_push(out, argv[0]);
 196                 else
 197                         argv_array_pushf(out, "%s \"$@\"", argv[0]);
 198         }
 199
 200         argv_array_pushv(out, argv);
 201         return out->argv;
 202 }
 203
 204 #ifndef GIT_WINDOWS_NATIVE
 205 static int execv_shell_cmd(const char **argv)
 206 {
 207         struct argv_array nargv = ARGV_ARRAY_INIT;
 208         prepare_shell_cmd(&nargv, argv);
 209         trace_argv_printf(nargv.argv, "trace: exec:");
 210         sane_execvp(nargv.argv[0], (char **)nargv.argv);
 211         argv_array_clear(&nargv);
 212         return -1;
 213 }
 214 #endif
 215
 216 #ifndef GIT_WINDOWS_NATIVE
 217 static int child_notifier = -1;
 218
 219 static void notify_parent(void)
 220 {
 221         /*
 222          * execvp failed.  If possible, we'd like to let start_command
 223          * know, so failures like ENOENT can be handled right away; but
 224          * otherwise, finish_command will still report the error.
 225          */
 226         xwrite(child_notifier, "", 1);
 227 }
 228 #endif
 229
 230 static inline void set_cloexec(int fd)
 231 {
 232         int flags = fcntl(fd, F_GETFD);
 233         if (flags >= 0)
 234                 fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
 235 }
 236
 237 static int wait_or_whine(pid_t pid, const char *argv0, int in_signal)
 238 {
 239         int status, code = -1;
 240         pid_t waiting;
 241         int failed_errno = 0;
 242
 243         while ((waiting = waitpid(pid, &status, 0)) < 0 && errno == EINTR)
 244                 ;       /* nothing */
 245         if (in_signal)
 246                 return 0;
 247
 248         if (waiting < 0) {
 249                 failed_errno = errno;
 250                 error_errno("waitpid for %s failed", argv0);
 251         } else if (waiting != pid) {
 252                 error("waitpid is confused (%s)", argv0);
 253         } else if (WIFSIGNALED(status)) {
 254                 code = WTERMSIG(status);
 255                 if (code != SIGINT && code != SIGQUIT && code != SIGPIPE)
 256                         error("%s died of signal %d", argv0, code);
 257                 /*
 258                  * This return value is chosen so that code & 0xff
 259                  * mimics the exit code that a POSIX shell would report for
 260                  * a program that died from this signal.
 261                  */
 262                 code += 128;
 263         } else if (WIFEXITED(status)) {
 264                 code = WEXITSTATUS(status);
 265                 /*
 266                  * Convert special exit code when execvp failed.
 267                  */
 268                 if (code == 127) {
 269                         code = -1;
 270                         failed_errno = ENOENT;
 271                 }
 272         } else {
 273                 error("waitpid is confused (%s)", argv0);
 274         }
 275
 276         clear_child_for_cleanup(pid);
 277
 278         errno = failed_errno;
 279         return code;
 280 }
 281
 282 int start_command(struct child_process *cmd)
 283 {
 284         int need_in, need_out, need_err;
 285         int fdin[2], fdout[2], fderr[2];
 286         int failed_errno;
 287         char *str;
 288
 289         if (!cmd->argv)
 290                 cmd->argv = cmd->args.argv;
 291         if (!cmd->env)
 292                 cmd->env = cmd->env_array.argv;
 293
 294         /*
 295          * In case of errors we must keep the promise to close FDs
 296          * that have been passed in via ->in and ->out.
 297          */
 298
 299         need_in = !cmd->no_stdin && cmd->in < 0;
 300         if (need_in) {
 301                 if (pipe(fdin) < 0) {
 302                         failed_errno = errno;
 303                         if (cmd->out > 0)
 304                                 close(cmd->out);
 305                         str = "standard input";
 306                         goto fail_pipe;
 307                 }
 308                 cmd->in = fdin[1];
 309         }
 310
 311         need_out = !cmd->no_stdout
 312                 && !cmd->stdout_to_stderr
 313                 && cmd->out < 0;
 314         if (need_out) {
 315                 if (pipe(fdout) < 0) {
 316                         failed_errno = errno;
 317                         if (need_in)
 318                                 close_pair(fdin);
 319                         else if (cmd->in)
 320                                 close(cmd->in);
 321                         str = "standard output";
 322                         goto fail_pipe;
 323                 }
 324                 cmd->out = fdout[0];
 325         }
 326
 327         need_err = !cmd->no_stderr && cmd->err < 0;
 328         if (need_err) {
 329                 if (pipe(fderr) < 0) {
 330                         failed_errno = errno;
 331                         if (need_in)
 332                                 close_pair(fdin);
 333                         else if (cmd->in)
 334                                 close(cmd->in);
 335                         if (need_out)
 336                                 close_pair(fdout);
 337                         else if (cmd->out)
 338                                 close(cmd->out);
 339                         str = "standard error";
 340 fail_pipe:
 341                         error("cannot create %s pipe for %s: %s",
 342                                 str, cmd->argv[0], strerror(failed_errno));
 343                         child_process_clear(cmd);
 344                         errno = failed_errno;
 345                         return -1;
 346                 }
 347                 cmd->err = fderr[0];
 348         }
 349
 350         trace_argv_printf(cmd->argv, "trace: run_command:");
 351         fflush(NULL);
 352
 353 #ifndef GIT_WINDOWS_NATIVE
 354 {
 355         int notify_pipe[2];
 356         if (pipe(notify_pipe))
 357                 notify_pipe[0] = notify_pipe[1] = -1;
 358
 359         cmd->pid = fork();
 360         failed_errno = errno;
 361         if (!cmd->pid) {
 362                 /*
 363                  * Redirect the channel to write syscall error messages to
 364                  * before redirecting the process's stderr so that all die()
 365                  * in subsequent call paths use the parent's stderr.
 366                  */
 367                 if (cmd->no_stderr || need_err) {
 368                         int child_err = dup(2);
 369                         set_cloexec(child_err);
 370                         set_error_handle(fdopen(child_err, "w"));
 371                 }
 372
 373                 close(notify_pipe[0]);
 374                 set_cloexec(notify_pipe[1]);
 375                 child_notifier = notify_pipe[1];
 376                 atexit(notify_parent);
 377
 378                 if (cmd->no_stdin)
 379                         dup_devnull(0);
 380                 else if (need_in) {
 381                         dup2(fdin[0], 0);
 382                         close_pair(fdin);
 383                 } else if (cmd->in) {
 384                         dup2(cmd->in, 0);
 385                         close(cmd->in);
 386                 }
 387
 388                 if (cmd->no_stderr)
 389                         dup_devnull(2);
 390                 else if (need_err) {
 391                         dup2(fderr[1], 2);
 392                         close_pair(fderr);
 393                 } else if (cmd->err > 1) {
 394                         dup2(cmd->err, 2);
 395                         close(cmd->err);
 396                 }
 397
 398                 if (cmd->no_stdout)
 399                         dup_devnull(1);
 400                 else if (cmd->stdout_to_stderr)
 401                         dup2(2, 1);
 402                 else if (need_out) {
 403                         dup2(fdout[1], 1);
 404                         close_pair(fdout);
 405                 } else if (cmd->out > 1) {
 406                         dup2(cmd->out, 1);
 407                         close(cmd->out);
 408                 }
 409
 410                 if (cmd->dir && chdir(cmd->dir))
 411                         die_errno("exec '%s': cd to '%s' failed", cmd->argv[0],
 412                             cmd->dir);
 413                 if (cmd->env) {
 414                         for (; *cmd->env; cmd->env++) {
 415                                 if (strchr(*cmd->env, '='))
 416                                         putenv((char *)*cmd->env);
 417                                 else
 418                                         unsetenv(*cmd->env);
 419                         }
 420                 }
 421                 if (cmd->git_cmd)
 422                         execv_git_cmd(cmd->argv);
 423                 else if (cmd->use_shell)
 424                         execv_shell_cmd(cmd->argv);
 425                 else
 426                         sane_execvp(cmd->argv[0], (char *const*) cmd->argv);
 427                 if (errno == ENOENT) {
 428                         if (!cmd->silent_exec_failure)
 429                                 error("cannot run %s: %s", cmd->argv[0],
 430                                         strerror(ENOENT));
 431                         exit(127);
 432                 } else {
 433                         die_errno("cannot exec '%s'", cmd->argv[0]);
 434                 }
 435         }
 436         if (cmd->pid < 0)
 437                 error_errno("cannot fork() for %s", cmd->argv[0]);
 438         else if (cmd->clean_on_exit)
 439                 mark_child_for_cleanup(cmd->pid, cmd);
 440
 441         /*
 442          * Wait for child's execvp. If the execvp succeeds (or if fork()
 443          * failed), EOF is seen immediately by the parent. Otherwise, the
 444          * child process sends a single byte.
 445          * Note that use of this infrastructure is completely advisory,
 446          * therefore, we keep error checks minimal.
 447          */
 448         close(notify_pipe[1]);
 449         if (read(notify_pipe[0], &notify_pipe[1], 1) == 1) {
 450                 /*
 451                  * At this point we know that fork() succeeded, but execvp()
 452                  * failed. Errors have been reported to our stderr.
 453                  */
 454                 wait_or_whine(cmd->pid, cmd->argv[0], 0);
 455                 failed_errno = errno;
 456                 cmd->pid = -1;
 457         }
 458         close(notify_pipe[0]);
 459 }
 460 #else
 461 {
 462         int fhin = 0, fhout = 1, fherr = 2;
 463         const char **sargv = cmd->argv;
 464         struct argv_array nargv = ARGV_ARRAY_INIT;
 465
 466         if (cmd->no_stdin)
 467                 fhin = open("/dev/null", O_RDWR);
 468         else if (need_in)
 469                 fhin = dup(fdin[0]);
 470         else if (cmd->in)
 471                 fhin = dup(cmd->in);
 472
 473         if (cmd->no_stderr)
 474                 fherr = open("/dev/null", O_RDWR);
 475         else if (need_err)
 476                 fherr = dup(fderr[1]);
 477         else if (cmd->err > 2)
 478                 fherr = dup(cmd->err);
 479
 480         if (cmd->no_stdout)
 481                 fhout = open("/dev/null", O_RDWR);
 482         else if (cmd->stdout_to_stderr)
 483                 fhout = dup(fherr);
 484         else if (need_out)
 485                 fhout = dup(fdout[1]);
 486         else if (cmd->out > 1)
 487                 fhout = dup(cmd->out);
 488
 489         if (cmd->git_cmd)
 490                 cmd->argv = prepare_git_cmd(&nargv, cmd->argv);
 491         else if (cmd->use_shell)
 492                 cmd->argv = prepare_shell_cmd(&nargv, cmd->argv);
 493
 494         cmd->pid = mingw_spawnvpe(cmd->argv[0], cmd->argv, (char**) cmd->env,
 495                         cmd->dir, fhin, fhout, fherr);
 496         failed_errno = errno;
 497         if (cmd->pid < 0 && (!cmd->silent_exec_failure || errno != ENOENT))
 498                 error_errno("cannot spawn %s", cmd->argv[0]);
 499         if (cmd->clean_on_exit && cmd->pid >= 0)
 500                 mark_child_for_cleanup(cmd->pid, cmd);
 501
 502         argv_array_clear(&nargv);
 503         cmd->argv = sargv;
 504         if (fhin != 0)
 505                 close(fhin);
 506         if (fhout != 1)
 507                 close(fhout);
 508         if (fherr != 2)
 509                 close(fherr);
 510 }
 511 #endif
 512
 513         if (cmd->pid < 0) {
 514                 if (need_in)
 515                         close_pair(fdin);
 516                 else if (cmd->in)
 517                         close(cmd->in);
 518                 if (need_out)
 519                         close_pair(fdout);
 520                 else if (cmd->out)
 521                         close(cmd->out);
 522                 if (need_err)
 523                         close_pair(fderr);
 524                 else if (cmd->err)
 525                         close(cmd->err);
 526                 child_process_clear(cmd);
 527                 errno = failed_errno;
 528                 return -1;
 529         }
 530
 531         if (need_in)
 532                 close(fdin[0]);
 533         else if (cmd->in)
 534                 close(cmd->in);
 535
 536         if (need_out)
 537                 close(fdout[1]);
 538         else if (cmd->out)
 539                 close(cmd->out);
 540
 541         if (need_err)
 542                 close(fderr[1]);
 543         else if (cmd->err)
 544                 close(cmd->err);
 545
 546         return 0;
 547 }
 548
 549 int finish_command(struct child_process *cmd)
 550 {
 551         int ret = wait_or_whine(cmd->pid, cmd->argv[0], 0);
 552         child_process_clear(cmd);
 553         return ret;
 554 }
 555
 556 int finish_command_in_signal(struct child_process *cmd)
 557 {
 558         return wait_or_whine(cmd->pid, cmd->argv[0], 1);
 559 }
 560
 561
 562 int run_command(struct child_process *cmd)
 563 {
 564         int code;
 565
 566         if (cmd->out < 0 || cmd->err < 0)
 567                 die("BUG: run_command with a pipe can cause deadlock");
 568
 569         code = start_command(cmd);
 570         if (code)
 571                 return code;
 572         return finish_command(cmd);
 573 }
 574
 575 int run_command_v_opt(const char **argv, int opt)
 576 {
 577         return run_command_v_opt_cd_env(argv, opt, NULL, NULL);
 578 }
 579
 580 int run_command_v_opt_cd_env(const char **argv, int opt, const char *dir, const char *const *env)
 581 {
 582         struct child_process cmd = CHILD_PROCESS_INIT;
 583         cmd.argv = argv;
 584         cmd.no_stdin = opt & RUN_COMMAND_NO_STDIN ? 1 : 0;
 585         cmd.git_cmd = opt & RUN_GIT_CMD ? 1 : 0;
 586         cmd.stdout_to_stderr = opt & RUN_COMMAND_STDOUT_TO_STDERR ? 1 : 0;
 587         cmd.silent_exec_failure = opt & RUN_SILENT_EXEC_FAILURE ? 1 : 0;
 588         cmd.use_shell = opt & RUN_USING_SHELL ? 1 : 0;
 589         cmd.clean_on_exit = opt & RUN_CLEAN_ON_EXIT ? 1 : 0;
 590         cmd.dir = dir;
 591         cmd.env = env;
 592         return run_command(&cmd);
 593 }
 594
 595 #ifndef NO_PTHREADS
 596 static pthread_t main_thread;
 597 static int main_thread_set;
 598 static pthread_key_t async_key;
 599 static pthread_key_t async_die_counter;
 600
 601 static void *run_thread(void *data)
 602 {
 603         struct async *async = data;
 604         intptr_t ret;
 605
 606         if (async->isolate_sigpipe) {
 607                 sigset_t mask;
 608                 sigemptyset(&mask);
 609                 sigaddset(&mask, SIGPIPE);
 610                 if (pthread_sigmask(SIG_BLOCK, &mask, NULL) < 0) {
 611                         ret = error("unable to block SIGPIPE in async thread");
 612                         return (void *)ret;
 613                 }
 614         }
 615
 616         pthread_setspecific(async_key, async);
 617         ret = async->proc(async->proc_in, async->proc_out, async->data);
 618         return (void *)ret;
 619 }
 620
 621 static NORETURN void die_async(const char *err, va_list params)
 622 {
 623         vreportf("fatal: ", err, params);
 624
 625         if (in_async()) {
 626                 struct async *async = pthread_getspecific(async_key);
 627                 if (async->proc_in >= 0)
 628                         close(async->proc_in);
 629                 if (async->proc_out >= 0)
 630                         close(async->proc_out);
 631                 pthread_exit((void *)128);
 632         }
 633
 634         exit(128);
 635 }
 636
 637 static int async_die_is_recursing(void)
 638 {
 639         void *ret = pthread_getspecific(async_die_counter);
 640         pthread_setspecific(async_die_counter, (void *)1);
 641         return ret != NULL;
 642 }
 643
 644 int in_async(void)
 645 {
 646         if (!main_thread_set)
 647                 return 0; /* no asyncs started yet */
 648         return !pthread_equal(main_thread, pthread_self());
 649 }
 650
 651 static void NORETURN async_exit(int code)
 652 {
 653         pthread_exit((void *)(intptr_t)code);
 654 }
 655
 656 #else
 657
 658 static struct {
 659         void (**handlers)(void);
 660         size_t nr;
 661         size_t alloc;
 662 } git_atexit_hdlrs;
 663
 664 static int git_atexit_installed;
 665
 666 static void git_atexit_dispatch(void)
 667 {
 668         size_t i;
 669
 670         for (i=git_atexit_hdlrs.nr ; i ; i--)
 671                 git_atexit_hdlrs.handlers[i-1]();
 672 }
 673
 674 static void git_atexit_clear(void)
 675 {
 676         free(git_atexit_hdlrs.handlers);
 677         memset(&git_atexit_hdlrs, 0, sizeof(git_atexit_hdlrs));
 678         git_atexit_installed = 0;
 679 }
 680
 681 #undef atexit
 682 int git_atexit(void (*handler)(void))
 683 {
 684         ALLOC_GROW(git_atexit_hdlrs.handlers, git_atexit_hdlrs.nr + 1, git_atexit_hdlrs.alloc);
 685         git_atexit_hdlrs.handlers[git_atexit_hdlrs.nr++] = handler;
 686         if (!git_atexit_installed) {
 687                 if (atexit(&git_atexit_dispatch))
 688                         return -1;
 689                 git_atexit_installed = 1;
 690         }
 691         return 0;
 692 }
 693 #define atexit git_atexit
 694
 695 static int process_is_async;
 696 int in_async(void)
 697 {
 698         return process_is_async;
 699 }
 700
 701 static void NORETURN async_exit(int code)
 702 {
 703         exit(code);
 704 }
 705
 706 #endif
 707
 708 void check_pipe(int err)
 709 {
 710         if (err == EPIPE) {
 711                 if (in_async())
 712                         async_exit(141);
 713
 714                 signal(SIGPIPE, SIG_DFL);
 715                 raise(SIGPIPE);
 716                 /* Should never happen, but just in case... */
 717                 exit(141);
 718         }
 719 }
 720
 721 int start_async(struct async *async)
 722 {
 723         int need_in, need_out;
 724         int fdin[2], fdout[2];
 725         int proc_in, proc_out;
 726
 727         need_in = async->in < 0;
 728         if (need_in) {
 729                 if (pipe(fdin) < 0) {
 730                         if (async->out > 0)
 731                                 close(async->out);
 732                         return error_errno("cannot create pipe");
 733                 }
 734                 async->in = fdin[1];
 735         }
 736
 737         need_out = async->out < 0;
 738         if (need_out) {
 739                 if (pipe(fdout) < 0) {
 740                         if (need_in)
 741                                 close_pair(fdin);
 742                         else if (async->in)
 743                                 close(async->in);
 744                         return error_errno("cannot create pipe");
 745                 }
 746                 async->out = fdout[0];
 747         }
 748
 749         if (need_in)
 750                 proc_in = fdin[0];
 751         else if (async->in)
 752                 proc_in = async->in;
 753         else
 754                 proc_in = -1;
 755
 756         if (need_out)
 757                 proc_out = fdout[1];
 758         else if (async->out)
 759                 proc_out = async->out;
 760         else
 761                 proc_out = -1;
 762
 763 #ifdef NO_PTHREADS
 764         /* Flush stdio before fork() to avoid cloning buffers */
 765         fflush(NULL);
 766
 767         async->pid = fork();
 768         if (async->pid < 0) {
 769                 error_errno("fork (async) failed");
 770                 goto error;
 771         }
 772         if (!async->pid) {
 773                 if (need_in)
 774                         close(fdin[1]);
 775                 if (need_out)
 776                         close(fdout[0]);
 777                 git_atexit_clear();
 778                 process_is_async = 1;
 779                 exit(!!async->proc(proc_in, proc_out, async->data));
 780         }
 781
 782         mark_child_for_cleanup(async->pid, NULL);
 783
 784         if (need_in)
 785                 close(fdin[0]);
 786         else if (async->in)
 787                 close(async->in);
 788
 789         if (need_out)
 790                 close(fdout[1]);
 791         else if (async->out)
 792                 close(async->out);
 793 #else
 794         if (!main_thread_set) {
 795                 /*
 796                  * We assume that the first time that start_async is called
 797                  * it is from the main thread.
 798                  */
 799                 main_thread_set = 1;
 800                 main_thread = pthread_self();
 801                 pthread_key_create(&async_key, NULL);
 802                 pthread_key_create(&async_die_counter, NULL);
 803                 set_die_routine(die_async);
 804                 set_die_is_recursing_routine(async_die_is_recursing);
 805         }
 806
 807         if (proc_in >= 0)
 808                 set_cloexec(proc_in);
 809         if (proc_out >= 0)
 810                 set_cloexec(proc_out);
 811         async->proc_in = proc_in;
 812         async->proc_out = proc_out;
 813         {
 814                 int err = pthread_create(&async->tid, NULL, run_thread, async);
 815                 if (err) {
 816                         error_errno("cannot create thread");
 817                         goto error;
 818                 }
 819         }
 820 #endif
 821         return 0;
 822
 823 error:
 824         if (need_in)
 825                 close_pair(fdin);
 826         else if (async->in)
 827                 close(async->in);
 828
 829         if (need_out)
 830                 close_pair(fdout);
 831         else if (async->out)
 832                 close(async->out);
 833         return -1;
 834 }
 835
 836 int finish_async(struct async *async)
 837 {
 838 #ifdef NO_PTHREADS
 839         return wait_or_whine(async->pid, "child process", 0);
 840 #else
 841         void *ret = (void *)(intptr_t)(-1);
 842
 843         if (pthread_join(async->tid, &ret))
 844                 error("pthread_join failed");
 845         return (int)(intptr_t)ret;
 846 #endif
 847 }
 848
 849 const char *find_hook(const char *name)
 850 {
 851         static struct strbuf path = STRBUF_INIT;
 852
 853         strbuf_reset(&path);
 854         strbuf_git_path(&path, "hooks/%s", name);
 855         if (access(path.buf, X_OK) < 0) {
 856 #ifdef STRIP_EXTENSION
 857                 strbuf_addstr(&path, STRIP_EXTENSION);
 858                 if (access(path.buf, X_OK) >= 0)
 859                         return path.buf;
 860 #endif
 861                 return NULL;
 862         }
 863         return path.buf;
 864 }
 865
 866 int run_hook_ve(const char *const *env, const char *name, va_list args)
 867 {
 868         struct child_process hook = CHILD_PROCESS_INIT;
 869         const char *p;
 870
 871         p = find_hook(name);
 872         if (!p)
 873                 return 0;
 874
 875         argv_array_push(&hook.args, p);
 876         while ((p = va_arg(args, const char *)))
 877                 argv_array_push(&hook.args, p);
 878         hook.env = env;
 879         hook.no_stdin = 1;
 880         hook.stdout_to_stderr = 1;
 881
 882         return run_command(&hook);
 883 }
 884
 885 int run_hook_le(const char *const *env, const char *name, ...)
 886 {
 887         va_list args;
 888         int ret;
 889
 890         va_start(args, name);
 891         ret = run_hook_ve(env, name, args);
 892         va_end(args);
 893
 894         return ret;
 895 }
 896
 897 struct io_pump {
 898         /* initialized by caller */
 899         int fd;
 900         int type; /* POLLOUT or POLLIN */
 901         union {
 902                 struct {
 903                         const char *buf;
 904                         size_t len;
 905                 } out;
 906                 struct {
 907                         struct strbuf *buf;
 908                         size_t hint;
 909                 } in;
 910         } u;
 911
 912         /* returned by pump_io */
 913         int error; /* 0 for success, otherwise errno */
 914
 915         /* internal use */
 916         struct pollfd *pfd;
 917 };
 918
 919 static int pump_io_round(struct io_pump *slots, int nr, struct pollfd *pfd)
 920 {
 921         int pollsize = 0;
 922         int i;
 923
 924         for (i = 0; i < nr; i++) {
 925                 struct io_pump *io = &slots[i];
 926                 if (io->fd < 0)
 927                         continue;
 928                 pfd[pollsize].fd = io->fd;
 929                 pfd[pollsize].events = io->type;
 930                 io->pfd = &pfd[pollsize++];
 931         }
 932
 933         if (!pollsize)
 934                 return 0;
 935
 936         if (poll(pfd, pollsize, -1) < 0) {
 937                 if (errno == EINTR)
 938                         return 1;
 939                 die_errno("poll failed");
 940         }
 941
 942         for (i = 0; i < nr; i++) {
 943                 struct io_pump *io = &slots[i];
 944
 945                 if (io->fd < 0)
 946                         continue;
 947
 948                 if (!(io->pfd->revents & (POLLOUT|POLLIN|POLLHUP|POLLERR|POLLNVAL)))
 949                         continue;
 950
 951                 if (io->type == POLLOUT) {
 952                         ssize_t len = xwrite(io->fd,
 953                                              io->u.out.buf, io->u.out.len);
 954                         if (len < 0) {
 955                                 io->error = errno;
 956                                 close(io->fd);
 957                                 io->fd = -1;
 958                         } else {
 959                                 io->u.out.buf += len;
 960                                 io->u.out.len -= len;
 961                                 if (!io->u.out.len) {
 962                                         close(io->fd);
 963                                         io->fd = -1;
 964                                 }
 965                         }
 966                 }
 967
 968                 if (io->type == POLLIN) {
 969                         ssize_t len = strbuf_read_once(io->u.in.buf,
 970                                                        io->fd, io->u.in.hint);
 971                         if (len < 0)
 972                                 io->error = errno;
 973                         if (len <= 0) {
 974                                 close(io->fd);
 975                                 io->fd = -1;
 976                         }
 977                 }
 978         }
 979
 980         return 1;
 981 }
 982
 983 static int pump_io(struct io_pump *slots, int nr)
 984 {
 985         struct pollfd *pfd;
 986         int i;
 987
 988         for (i = 0; i < nr; i++)
 989                 slots[i].error = 0;
 990
 991         ALLOC_ARRAY(pfd, nr);
 992         while (pump_io_round(slots, nr, pfd))
 993                 ; /* nothing */
 994         free(pfd);
 995
 996         /* There may be multiple errno values, so just pick the first. */
 997         for (i = 0; i < nr; i++) {
 998                 if (slots[i].error) {
 999                         errno = slots[i].error;
1000                         return -1;
1001                 }
1002         }
1003         return 0;
1004 }
1005
1006
1007 int pipe_command(struct child_process *cmd,
1008                  const char *in, size_t in_len,
1009                  struct strbuf *out, size_t out_hint,
1010                  struct strbuf *err, size_t err_hint)
1011 {
1012         struct io_pump io[3];
1013         int nr = 0;
1014
1015         if (in)
1016                 cmd->in = -1;
1017         if (out)
1018                 cmd->out = -1;
1019         if (err)
1020                 cmd->err = -1;
1021
1022         if (start_command(cmd) < 0)
1023                 return -1;
1024
1025         if (in) {
1026                 io[nr].fd = cmd->in;
1027                 io[nr].type = POLLOUT;
1028                 io[nr].u.out.buf = in;
1029                 io[nr].u.out.len = in_len;
1030                 nr++;
1031         }
1032         if (out) {
1033                 io[nr].fd = cmd->out;
1034                 io[nr].type = POLLIN;
1035                 io[nr].u.in.buf = out;
1036                 io[nr].u.in.hint = out_hint;
1037                 nr++;
1038         }
1039         if (err) {
1040                 io[nr].fd = cmd->err;
1041                 io[nr].type = POLLIN;
1042                 io[nr].u.in.buf = err;
1043                 io[nr].u.in.hint = err_hint;
1044                 nr++;
1045         }
1046
1047         if (pump_io(io, nr) < 0) {
1048                 finish_command(cmd); /* throw away exit code */
1049                 return -1;
1050         }
1051
1052         return finish_command(cmd);
1053 }
1054
1055 enum child_state {
1056         GIT_CP_FREE,
1057         GIT_CP_WORKING,
1058         GIT_CP_WAIT_CLEANUP,
1059 };
1060
1061 struct parallel_processes {
1062         void *data;
1063
1064         int max_processes;
1065         int nr_processes;
1066
1067         get_next_task_fn get_next_task;
1068         start_failure_fn start_failure;
1069         task_finished_fn task_finished;
1070
1071         struct {
1072                 enum child_state state;
1073                 struct child_process process;
1074                 struct strbuf err;
1075                 void *data;
1076         } *children;
1077         /*
1078          * The struct pollfd is logically part of *children,
1079          * but the system call expects it as its own array.
1080          */
1081         struct pollfd *pfd;
1082
1083         unsigned shutdown : 1;
1084
1085         int output_owner;
1086         struct strbuf buffered_output; /* of finished children */
1087 };
1088
1089 static int default_start_failure(struct strbuf *out,
1090                                  void *pp_cb,
1091                                  void *pp_task_cb)
1092 {
1093         return 0;
1094 }
1095
1096 static int default_task_finished(int result,
1097                                  struct strbuf *out,
1098                                  void *pp_cb,
1099                                  void *pp_task_cb)
1100 {
1101         return 0;
1102 }
1103
1104 static void kill_children(struct parallel_processes *pp, int signo)
1105 {
1106         int i, n = pp->max_processes;
1107
1108         for (i = 0; i < n; i++)
1109                 if (pp->children[i].state == GIT_CP_WORKING)
1110                         kill(pp->children[i].process.pid, signo);
1111 }
1112
1113 static struct parallel_processes *pp_for_signal;
1114
1115 static void handle_children_on_signal(int signo)
1116 {
1117         kill_children(pp_for_signal, signo);
1118         sigchain_pop(signo);
1119         raise(signo);
1120 }
1121
1122 static void pp_init(struct parallel_processes *pp,
1123                     int n,
1124                     get_next_task_fn get_next_task,
1125                     start_failure_fn start_failure,
1126                     task_finished_fn task_finished,
1127                     void *data)
1128 {
1129         int i;
1130
1131         if (n < 1)
1132                 n = online_cpus();
1133
1134         pp->max_processes = n;
1135
1136         trace_printf("run_processes_parallel: preparing to run up to %d tasks", n);
1137
1138         pp->data = data;
1139         if (!get_next_task)
1140                 die("BUG: you need to specify a get_next_task function");
1141         pp->get_next_task = get_next_task;
1142
1143         pp->start_failure = start_failure ? start_failure : default_start_failure;
1144         pp->task_finished = task_finished ? task_finished : default_task_finished;
1145
1146         pp->nr_processes = 0;
1147         pp->output_owner = 0;
1148         pp->shutdown = 0;
1149         pp->children = xcalloc(n, sizeof(*pp->children));
1150         pp->pfd = xcalloc(n, sizeof(*pp->pfd));
1151         strbuf_init(&pp->buffered_output, 0);
1152
1153         for (i = 0; i < n; i++) {
1154                 strbuf_init(&pp->children[i].err, 0);
1155                 child_process_init(&pp->children[i].process);
1156                 pp->pfd[i].events = POLLIN | POLLHUP;
1157                 pp->pfd[i].fd = -1;
1158         }
1159
1160         pp_for_signal = pp;
1161         sigchain_push_common(handle_children_on_signal);
1162 }
1163
1164 static void pp_cleanup(struct parallel_processes *pp)
1165 {
1166         int i;
1167
1168         trace_printf("run_processes_parallel: done");
1169         for (i = 0; i < pp->max_processes; i++) {
1170                 strbuf_release(&pp->children[i].err);
1171                 child_process_clear(&pp->children[i].process);
1172         }
1173
1174         free(pp->children);
1175         free(pp->pfd);
1176
1177         /*
1178          * When get_next_task added messages to the buffer in its last
1179          * iteration, the buffered output is non empty.
1180          */
1181         strbuf_write(&pp->buffered_output, stderr);
1182         strbuf_release(&pp->buffered_output);
1183
1184         sigchain_pop_common();
1185 }
1186
1187 /* returns
1188  *  0 if a new task was started.
1189  *  1 if no new jobs was started (get_next_task ran out of work, non critical
1190  *    problem with starting a new command)
1191  * <0 no new job was started, user wishes to shutdown early. Use negative code
1192  *    to signal the children.
1193  */
1194 static int pp_start_one(struct parallel_processes *pp)
1195 {
1196         int i, code;
1197
1198         for (i = 0; i < pp->max_processes; i++)
1199                 if (pp->children[i].state == GIT_CP_FREE)
1200                         break;
1201         if (i == pp->max_processes)
1202                 die("BUG: bookkeeping is hard");
1203
1204         code = pp->get_next_task(&pp->children[i].process,
1205                                  &pp->children[i].err,
1206                                  pp->data,
1207                                  &pp->children[i].data);
1208         if (!code) {
1209                 strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1210                 strbuf_reset(&pp->children[i].err);
1211                 return 1;
1212         }
1213         pp->children[i].process.err = -1;
1214         pp->children[i].process.stdout_to_stderr = 1;
1215         pp->children[i].process.no_stdin = 1;
1216
1217         if (start_command(&pp->children[i].process)) {
1218                 code = pp->start_failure(&pp->children[i].err,
1219                                          pp->data,
1220                                          &pp->children[i].data);
1221                 strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1222                 strbuf_reset(&pp->children[i].err);
1223                 if (code)
1224                         pp->shutdown = 1;
1225                 return code;
1226         }
1227
1228         pp->nr_processes++;
1229         pp->children[i].state = GIT_CP_WORKING;
1230         pp->pfd[i].fd = pp->children[i].process.err;
1231         return 0;
1232 }
1233
1234 static void pp_buffer_stderr(struct parallel_processes *pp, int output_timeout)
1235 {
1236         int i;
1237
1238         while ((i = poll(pp->pfd, pp->max_processes, output_timeout)) < 0) {
1239                 if (errno == EINTR)
1240                         continue;
1241                 pp_cleanup(pp);
1242                 die_errno("poll");
1243         }
1244
1245         /* Buffer output from all pipes. */
1246         for (i = 0; i < pp->max_processes; i++) {
1247                 if (pp->children[i].state == GIT_CP_WORKING &&
1248                     pp->pfd[i].revents & (POLLIN | POLLHUP)) {
1249                         int n = strbuf_read_once(&pp->children[i].err,
1250                                                  pp->children[i].process.err, 0);
1251                         if (n == 0) {
1252                                 close(pp->children[i].process.err);
1253                                 pp->children[i].state = GIT_CP_WAIT_CLEANUP;
1254                         } else if (n < 0)
1255                                 if (errno != EAGAIN)
1256                                         die_errno("read");
1257                 }
1258         }
1259 }
1260
1261 static void pp_output(struct parallel_processes *pp)
1262 {
1263         int i = pp->output_owner;
1264         if (pp->children[i].state == GIT_CP_WORKING &&
1265             pp->children[i].err.len) {
1266                 strbuf_write(&pp->children[i].err, stderr);
1267                 strbuf_reset(&pp->children[i].err);
1268         }
1269 }
1270
1271 static int pp_collect_finished(struct parallel_processes *pp)
1272 {
1273         int i, code;
1274         int n = pp->max_processes;
1275         int result = 0;
1276
1277         while (pp->nr_processes > 0) {
1278                 for (i = 0; i < pp->max_processes; i++)
1279                         if (pp->children[i].state == GIT_CP_WAIT_CLEANUP)
1280                                 break;
1281                 if (i == pp->max_processes)
1282                         break;
1283
1284                 code = finish_command(&pp->children[i].process);
1285
1286                 code = pp->task_finished(code,
1287                                          &pp->children[i].err, pp->data,
1288                                          &pp->children[i].data);
1289
1290                 if (code)
1291                         result = code;
1292                 if (code < 0)
1293                         break;
1294
1295                 pp->nr_processes--;
1296                 pp->children[i].state = GIT_CP_FREE;
1297                 pp->pfd[i].fd = -1;
1298                 child_process_init(&pp->children[i].process);
1299
1300                 if (i != pp->output_owner) {
1301                         strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1302                         strbuf_reset(&pp->children[i].err);
1303                 } else {
1304                         strbuf_write(&pp->children[i].err, stderr);
1305                         strbuf_reset(&pp->children[i].err);
1306
1307                         /* Output all other finished child processes */
1308                         strbuf_write(&pp->buffered_output, stderr);
1309                         strbuf_reset(&pp->buffered_output);
1310
1311                         /*
1312                          * Pick next process to output live.
1313                          * NEEDSWORK:
1314                          * For now we pick it randomly by doing a round
1315                          * robin. Later we may want to pick the one with
1316                          * the most output or the longest or shortest
1317                          * running process time.
1318                          */
1319                         for (i = 0; i < n; i++)
1320                                 if (pp->children[(pp->output_owner + i) % n].state == GIT_CP_WORKING)
1321                                         break;
1322                         pp->output_owner = (pp->output_owner + i) % n;
1323                 }
1324         }
1325         return result;
1326 }
1327
1328 int run_processes_parallel(int n,
1329                            get_next_task_fn get_next_task,
1330                            start_failure_fn start_failure,
1331                            task_finished_fn task_finished,
1332                            void *pp_cb)
1333 {
1334         int i, code;
1335         int output_timeout = 100;
1336         int spawn_cap = 4;
1337         struct parallel_processes pp;
1338
1339         pp_init(&pp, n, get_next_task, start_failure, task_finished, pp_cb);
1340         while (1) {
1341                 for (i = 0;
1342                     i < spawn_cap && !pp.shutdown &&
1343                     pp.nr_processes < pp.max_processes;
1344                     i++) {
1345                         code = pp_start_one(&pp);
1346                         if (!code)
1347                                 continue;
1348                         if (code < 0) {
1349                                 pp.shutdown = 1;
1350                                 kill_children(&pp, -code);
1351                         }
1352                         break;
1353                 }
1354                 if (!pp.nr_processes)
1355                         break;
1356                 pp_buffer_stderr(&pp, output_timeout);
1357                 pp_output(&pp);
1358                 code = pp_collect_finished(&pp);
1359                 if (code) {
1360                         pp.shutdown = 1;
1361                         if (code < 0)
1362                                 kill_children(&pp, -code);
1363                 }
1364         }
1365
1366         pp_cleanup(&pp);
1367         return 0;
1368 }