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("waitpid for %s failed: %s", argv0, strerror(errno));
 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("cannot fork() for %s: %s", cmd->argv[0],
 424                         strerror(errno));
 425         else if (cmd->clean_on_exit)
 426                 mark_child_for_cleanup(cmd->pid);
 427
 428         /*
 429          * Wait for child's execvp. If the execvp succeeds (or if fork()
 430          * failed), EOF is seen immediately by the parent. Otherwise, the
 431          * child process sends a single byte.
 432          * Note that use of this infrastructure is completely advisory,
 433          * therefore, we keep error checks minimal.
 434          */
 435         close(notify_pipe[1]);
 436         if (read(notify_pipe[0], &notify_pipe[1], 1) == 1) {
 437                 /*
 438                  * At this point we know that fork() succeeded, but execvp()
 439                  * failed. Errors have been reported to our stderr.
 440                  */
 441                 wait_or_whine(cmd->pid, cmd->argv[0], 0);
 442                 failed_errno = errno;
 443                 cmd->pid = -1;
 444         }
 445         close(notify_pipe[0]);
 446 }
 447 #else
 448 {
 449         int fhin = 0, fhout = 1, fherr = 2;
 450         const char **sargv = cmd->argv;
 451         struct argv_array nargv = ARGV_ARRAY_INIT;
 452
 453         if (cmd->no_stdin)
 454                 fhin = open("/dev/null", O_RDWR);
 455         else if (need_in)
 456                 fhin = dup(fdin[0]);
 457         else if (cmd->in)
 458                 fhin = dup(cmd->in);
 459
 460         if (cmd->no_stderr)
 461                 fherr = open("/dev/null", O_RDWR);
 462         else if (need_err)
 463                 fherr = dup(fderr[1]);
 464         else if (cmd->err > 2)
 465                 fherr = dup(cmd->err);
 466
 467         if (cmd->no_stdout)
 468                 fhout = open("/dev/null", O_RDWR);
 469         else if (cmd->stdout_to_stderr)
 470                 fhout = dup(fherr);
 471         else if (need_out)
 472                 fhout = dup(fdout[1]);
 473         else if (cmd->out > 1)
 474                 fhout = dup(cmd->out);
 475
 476         if (cmd->git_cmd)
 477                 cmd->argv = prepare_git_cmd(&nargv, cmd->argv);
 478         else if (cmd->use_shell)
 479                 cmd->argv = prepare_shell_cmd(&nargv, cmd->argv);
 480
 481         cmd->pid = mingw_spawnvpe(cmd->argv[0], cmd->argv, (char**) cmd->env,
 482                         cmd->dir, fhin, fhout, fherr);
 483         failed_errno = errno;
 484         if (cmd->pid < 0 && (!cmd->silent_exec_failure || errno != ENOENT))
 485                 error("cannot spawn %s: %s", cmd->argv[0], strerror(errno));
 486         if (cmd->clean_on_exit && cmd->pid >= 0)
 487                 mark_child_for_cleanup(cmd->pid);
 488
 489         argv_array_clear(&nargv);
 490         cmd->argv = sargv;
 491         if (fhin != 0)
 492                 close(fhin);
 493         if (fhout != 1)
 494                 close(fhout);
 495         if (fherr != 2)
 496                 close(fherr);
 497 }
 498 #endif
 499
 500         if (cmd->pid < 0) {
 501                 if (need_in)
 502                         close_pair(fdin);
 503                 else if (cmd->in)
 504                         close(cmd->in);
 505                 if (need_out)
 506                         close_pair(fdout);
 507                 else if (cmd->out)
 508                         close(cmd->out);
 509                 if (need_err)
 510                         close_pair(fderr);
 511                 else if (cmd->err)
 512                         close(cmd->err);
 513                 child_process_clear(cmd);
 514                 errno = failed_errno;
 515                 return -1;
 516         }
 517
 518         if (need_in)
 519                 close(fdin[0]);
 520         else if (cmd->in)
 521                 close(cmd->in);
 522
 523         if (need_out)
 524                 close(fdout[1]);
 525         else if (cmd->out)
 526                 close(cmd->out);
 527
 528         if (need_err)
 529                 close(fderr[1]);
 530         else if (cmd->err)
 531                 close(cmd->err);
 532
 533         return 0;
 534 }
 535
 536 int finish_command(struct child_process *cmd)
 537 {
 538         int ret = wait_or_whine(cmd->pid, cmd->argv[0], 0);
 539         child_process_clear(cmd);
 540         return ret;
 541 }
 542
 543 int finish_command_in_signal(struct child_process *cmd)
 544 {
 545         return wait_or_whine(cmd->pid, cmd->argv[0], 1);
 546 }
 547
 548
 549 int run_command(struct child_process *cmd)
 550 {
 551         int code;
 552
 553         if (cmd->out < 0 || cmd->err < 0)
 554                 die("BUG: run_command with a pipe can cause deadlock");
 555
 556         code = start_command(cmd);
 557         if (code)
 558                 return code;
 559         return finish_command(cmd);
 560 }
 561
 562 int run_command_v_opt(const char **argv, int opt)
 563 {
 564         return run_command_v_opt_cd_env(argv, opt, NULL, NULL);
 565 }
 566
 567 int run_command_v_opt_cd_env(const char **argv, int opt, const char *dir, const char *const *env)
 568 {
 569         struct child_process cmd = CHILD_PROCESS_INIT;
 570         cmd.argv = argv;
 571         cmd.no_stdin = opt & RUN_COMMAND_NO_STDIN ? 1 : 0;
 572         cmd.git_cmd = opt & RUN_GIT_CMD ? 1 : 0;
 573         cmd.stdout_to_stderr = opt & RUN_COMMAND_STDOUT_TO_STDERR ? 1 : 0;
 574         cmd.silent_exec_failure = opt & RUN_SILENT_EXEC_FAILURE ? 1 : 0;
 575         cmd.use_shell = opt & RUN_USING_SHELL ? 1 : 0;
 576         cmd.clean_on_exit = opt & RUN_CLEAN_ON_EXIT ? 1 : 0;
 577         cmd.dir = dir;
 578         cmd.env = env;
 579         return run_command(&cmd);
 580 }
 581
 582 #ifndef NO_PTHREADS
 583 static pthread_t main_thread;
 584 static int main_thread_set;
 585 static pthread_key_t async_key;
 586 static pthread_key_t async_die_counter;
 587
 588 static void *run_thread(void *data)
 589 {
 590         struct async *async = data;
 591         intptr_t ret;
 592
 593         pthread_setspecific(async_key, async);
 594         ret = async->proc(async->proc_in, async->proc_out, async->data);
 595         return (void *)ret;
 596 }
 597
 598 static NORETURN void die_async(const char *err, va_list params)
 599 {
 600         vreportf("fatal: ", err, params);
 601
 602         if (in_async()) {
 603                 struct async *async = pthread_getspecific(async_key);
 604                 if (async->proc_in >= 0)
 605                         close(async->proc_in);
 606                 if (async->proc_out >= 0)
 607                         close(async->proc_out);
 608                 pthread_exit((void *)128);
 609         }
 610
 611         exit(128);
 612 }
 613
 614 static int async_die_is_recursing(void)
 615 {
 616         void *ret = pthread_getspecific(async_die_counter);
 617         pthread_setspecific(async_die_counter, (void *)1);
 618         return ret != NULL;
 619 }
 620
 621 int in_async(void)
 622 {
 623         if (!main_thread_set)
 624                 return 0; /* no asyncs started yet */
 625         return !pthread_equal(main_thread, pthread_self());
 626 }
 627
 628 void NORETURN async_exit(int code)
 629 {
 630         pthread_exit((void *)(intptr_t)code);
 631 }
 632
 633 #else
 634
 635 static struct {
 636         void (**handlers)(void);
 637         size_t nr;
 638         size_t alloc;
 639 } git_atexit_hdlrs;
 640
 641 static int git_atexit_installed;
 642
 643 static void git_atexit_dispatch(void)
 644 {
 645         size_t i;
 646
 647         for (i=git_atexit_hdlrs.nr ; i ; i--)
 648                 git_atexit_hdlrs.handlers[i-1]();
 649 }
 650
 651 static void git_atexit_clear(void)
 652 {
 653         free(git_atexit_hdlrs.handlers);
 654         memset(&git_atexit_hdlrs, 0, sizeof(git_atexit_hdlrs));
 655         git_atexit_installed = 0;
 656 }
 657
 658 #undef atexit
 659 int git_atexit(void (*handler)(void))
 660 {
 661         ALLOC_GROW(git_atexit_hdlrs.handlers, git_atexit_hdlrs.nr + 1, git_atexit_hdlrs.alloc);
 662         git_atexit_hdlrs.handlers[git_atexit_hdlrs.nr++] = handler;
 663         if (!git_atexit_installed) {
 664                 if (atexit(&git_atexit_dispatch))
 665                         return -1;
 666                 git_atexit_installed = 1;
 667         }
 668         return 0;
 669 }
 670 #define atexit git_atexit
 671
 672 static int process_is_async;
 673 int in_async(void)
 674 {
 675         return process_is_async;
 676 }
 677
 678 void NORETURN async_exit(int code)
 679 {
 680         exit(code);
 681 }
 682
 683 #endif
 684
 685 int start_async(struct async *async)
 686 {
 687         int need_in, need_out;
 688         int fdin[2], fdout[2];
 689         int proc_in, proc_out;
 690
 691         need_in = async->in < 0;
 692         if (need_in) {
 693                 if (pipe(fdin) < 0) {
 694                         if (async->out > 0)
 695                                 close(async->out);
 696                         return error("cannot create pipe: %s", strerror(errno));
 697                 }
 698                 async->in = fdin[1];
 699         }
 700
 701         need_out = async->out < 0;
 702         if (need_out) {
 703                 if (pipe(fdout) < 0) {
 704                         if (need_in)
 705                                 close_pair(fdin);
 706                         else if (async->in)
 707                                 close(async->in);
 708                         return error("cannot create pipe: %s", strerror(errno));
 709                 }
 710                 async->out = fdout[0];
 711         }
 712
 713         if (need_in)
 714                 proc_in = fdin[0];
 715         else if (async->in)
 716                 proc_in = async->in;
 717         else
 718                 proc_in = -1;
 719
 720         if (need_out)
 721                 proc_out = fdout[1];
 722         else if (async->out)
 723                 proc_out = async->out;
 724         else
 725                 proc_out = -1;
 726
 727 #ifdef NO_PTHREADS
 728         /* Flush stdio before fork() to avoid cloning buffers */
 729         fflush(NULL);
 730
 731         async->pid = fork();
 732         if (async->pid < 0) {
 733                 error("fork (async) failed: %s", strerror(errno));
 734                 goto error;
 735         }
 736         if (!async->pid) {
 737                 if (need_in)
 738                         close(fdin[1]);
 739                 if (need_out)
 740                         close(fdout[0]);
 741                 git_atexit_clear();
 742                 process_is_async = 1;
 743                 exit(!!async->proc(proc_in, proc_out, async->data));
 744         }
 745
 746         mark_child_for_cleanup(async->pid);
 747
 748         if (need_in)
 749                 close(fdin[0]);
 750         else if (async->in)
 751                 close(async->in);
 752
 753         if (need_out)
 754                 close(fdout[1]);
 755         else if (async->out)
 756                 close(async->out);
 757 #else
 758         if (!main_thread_set) {
 759                 /*
 760                  * We assume that the first time that start_async is called
 761                  * it is from the main thread.
 762                  */
 763                 main_thread_set = 1;
 764                 main_thread = pthread_self();
 765                 pthread_key_create(&async_key, NULL);
 766                 pthread_key_create(&async_die_counter, NULL);
 767                 set_die_routine(die_async);
 768                 set_die_is_recursing_routine(async_die_is_recursing);
 769         }
 770
 771         if (proc_in >= 0)
 772                 set_cloexec(proc_in);
 773         if (proc_out >= 0)
 774                 set_cloexec(proc_out);
 775         async->proc_in = proc_in;
 776         async->proc_out = proc_out;
 777         {
 778                 int err = pthread_create(&async->tid, NULL, run_thread, async);
 779                 if (err) {
 780                         error("cannot create thread: %s", strerror(err));
 781                         goto error;
 782                 }
 783         }
 784 #endif
 785         return 0;
 786
 787 error:
 788         if (need_in)
 789                 close_pair(fdin);
 790         else if (async->in)
 791                 close(async->in);
 792
 793         if (need_out)
 794                 close_pair(fdout);
 795         else if (async->out)
 796                 close(async->out);
 797         return -1;
 798 }
 799
 800 int finish_async(struct async *async)
 801 {
 802 #ifdef NO_PTHREADS
 803         return wait_or_whine(async->pid, "child process", 0);
 804 #else
 805         void *ret = (void *)(intptr_t)(-1);
 806
 807         if (pthread_join(async->tid, &ret))
 808                 error("pthread_join failed");
 809         return (int)(intptr_t)ret;
 810 #endif
 811 }
 812
 813 const char *find_hook(const char *name)
 814 {
 815         static struct strbuf path = STRBUF_INIT;
 816
 817         strbuf_reset(&path);
 818         strbuf_git_path(&path, "hooks/%s", name);
 819         if (access(path.buf, X_OK) < 0)
 820                 return NULL;
 821         return path.buf;
 822 }
 823
 824 int run_hook_ve(const char *const *env, const char *name, va_list args)
 825 {
 826         struct child_process hook = CHILD_PROCESS_INIT;
 827         const char *p;
 828
 829         p = find_hook(name);
 830         if (!p)
 831                 return 0;
 832
 833         argv_array_push(&hook.args, p);
 834         while ((p = va_arg(args, const char *)))
 835                 argv_array_push(&hook.args, p);
 836         hook.env = env;
 837         hook.no_stdin = 1;
 838         hook.stdout_to_stderr = 1;
 839
 840         return run_command(&hook);
 841 }
 842
 843 int run_hook_le(const char *const *env, const char *name, ...)
 844 {
 845         va_list args;
 846         int ret;
 847
 848         va_start(args, name);
 849         ret = run_hook_ve(env, name, args);
 850         va_end(args);
 851
 852         return ret;
 853 }
 854
 855 int capture_command(struct child_process *cmd, struct strbuf *buf, size_t hint)
 856 {
 857         cmd->out = -1;
 858         if (start_command(cmd) < 0)
 859                 return -1;
 860
 861         if (strbuf_read(buf, cmd->out, hint) < 0) {
 862                 close(cmd->out);
 863                 finish_command(cmd); /* throw away exit code */
 864                 return -1;
 865         }
 866
 867         close(cmd->out);
 868         return finish_command(cmd);
 869 }
 870
 871 enum child_state {
 872         GIT_CP_FREE,
 873         GIT_CP_WORKING,
 874         GIT_CP_WAIT_CLEANUP,
 875 };
 876
 877 struct parallel_processes {
 878         void *data;
 879
 880         int max_processes;
 881         int nr_processes;
 882
 883         get_next_task_fn get_next_task;
 884         start_failure_fn start_failure;
 885         task_finished_fn task_finished;
 886
 887         struct {
 888                 enum child_state state;
 889                 struct child_process process;
 890                 struct strbuf err;
 891                 void *data;
 892         } *children;
 893         /*
 894          * The struct pollfd is logically part of *children,
 895          * but the system call expects it as its own array.
 896          */
 897         struct pollfd *pfd;
 898
 899         unsigned shutdown : 1;
 900
 901         int output_owner;
 902         struct strbuf buffered_output; /* of finished children */
 903 };
 904
 905 static int default_start_failure(struct strbuf *out,
 906                                  void *pp_cb,
 907                                  void *pp_task_cb)
 908 {
 909         return 0;
 910 }
 911
 912 static int default_task_finished(int result,
 913                                  struct strbuf *out,
 914                                  void *pp_cb,
 915                                  void *pp_task_cb)
 916 {
 917         return 0;
 918 }
 919
 920 static void kill_children(struct parallel_processes *pp, int signo)
 921 {
 922         int i, n = pp->max_processes;
 923
 924         for (i = 0; i < n; i++)
 925                 if (pp->children[i].state == GIT_CP_WORKING)
 926                         kill(pp->children[i].process.pid, signo);
 927 }
 928
 929 static struct parallel_processes *pp_for_signal;
 930
 931 static void handle_children_on_signal(int signo)
 932 {
 933         kill_children(pp_for_signal, signo);
 934         sigchain_pop(signo);
 935         raise(signo);
 936 }
 937
 938 static void pp_init(struct parallel_processes *pp,
 939                     int n,
 940                     get_next_task_fn get_next_task,
 941                     start_failure_fn start_failure,
 942                     task_finished_fn task_finished,
 943                     void *data)
 944 {
 945         int i;
 946
 947         if (n < 1)
 948                 n = online_cpus();
 949
 950         pp->max_processes = n;
 951
 952         trace_printf("run_processes_parallel: preparing to run up to %d tasks", n);
 953
 954         pp->data = data;
 955         if (!get_next_task)
 956                 die("BUG: you need to specify a get_next_task function");
 957         pp->get_next_task = get_next_task;
 958
 959         pp->start_failure = start_failure ? start_failure : default_start_failure;
 960         pp->task_finished = task_finished ? task_finished : default_task_finished;
 961
 962         pp->nr_processes = 0;
 963         pp->output_owner = 0;
 964         pp->shutdown = 0;
 965         pp->children = xcalloc(n, sizeof(*pp->children));
 966         pp->pfd = xcalloc(n, sizeof(*pp->pfd));
 967         strbuf_init(&pp->buffered_output, 0);
 968
 969         for (i = 0; i < n; i++) {
 970                 strbuf_init(&pp->children[i].err, 0);
 971                 child_process_init(&pp->children[i].process);
 972                 pp->pfd[i].events = POLLIN | POLLHUP;
 973                 pp->pfd[i].fd = -1;
 974         }
 975
 976         pp_for_signal = pp;
 977         sigchain_push_common(handle_children_on_signal);
 978 }
 979
 980 static void pp_cleanup(struct parallel_processes *pp)
 981 {
 982         int i;
 983
 984         trace_printf("run_processes_parallel: done");
 985         for (i = 0; i < pp->max_processes; i++) {
 986                 strbuf_release(&pp->children[i].err);
 987                 child_process_clear(&pp->children[i].process);
 988         }
 989
 990         free(pp->children);
 991         free(pp->pfd);
 992
 993         /*
 994          * When get_next_task added messages to the buffer in its last
 995          * iteration, the buffered output is non empty.
 996          */
 997         strbuf_write(&pp->buffered_output, stderr);
 998         strbuf_release(&pp->buffered_output);
 999
1000         sigchain_pop_common();
1001 }
1002
1003 /* returns
1004  *  0 if a new task was started.
1005  *  1 if no new jobs was started (get_next_task ran out of work, non critical
1006  *    problem with starting a new command)
1007  * <0 no new job was started, user wishes to shutdown early. Use negative code
1008  *    to signal the children.
1009  */
1010 static int pp_start_one(struct parallel_processes *pp)
1011 {
1012         int i, code;
1013
1014         for (i = 0; i < pp->max_processes; i++)
1015                 if (pp->children[i].state == GIT_CP_FREE)
1016                         break;
1017         if (i == pp->max_processes)
1018                 die("BUG: bookkeeping is hard");
1019
1020         code = pp->get_next_task(&pp->children[i].process,
1021                                  &pp->children[i].err,
1022                                  pp->data,
1023                                  &pp->children[i].data);
1024         if (!code) {
1025                 strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1026                 strbuf_reset(&pp->children[i].err);
1027                 return 1;
1028         }
1029         pp->children[i].process.err = -1;
1030         pp->children[i].process.stdout_to_stderr = 1;
1031         pp->children[i].process.no_stdin = 1;
1032
1033         if (start_command(&pp->children[i].process)) {
1034                 code = pp->start_failure(&pp->children[i].err,
1035                                          pp->data,
1036                                          &pp->children[i].data);
1037                 strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1038                 strbuf_reset(&pp->children[i].err);
1039                 if (code)
1040                         pp->shutdown = 1;
1041                 return code;
1042         }
1043
1044         pp->nr_processes++;
1045         pp->children[i].state = GIT_CP_WORKING;
1046         pp->pfd[i].fd = pp->children[i].process.err;
1047         return 0;
1048 }
1049
1050 static void pp_buffer_stderr(struct parallel_processes *pp, int output_timeout)
1051 {
1052         int i;
1053
1054         while ((i = poll(pp->pfd, pp->max_processes, output_timeout)) < 0) {
1055                 if (errno == EINTR)
1056                         continue;
1057                 pp_cleanup(pp);
1058                 die_errno("poll");
1059         }
1060
1061         /* Buffer output from all pipes. */
1062         for (i = 0; i < pp->max_processes; i++) {
1063                 if (pp->children[i].state == GIT_CP_WORKING &&
1064                     pp->pfd[i].revents & (POLLIN | POLLHUP)) {
1065                         int n = strbuf_read_once(&pp->children[i].err,
1066                                                  pp->children[i].process.err, 0);
1067                         if (n == 0) {
1068                                 close(pp->children[i].process.err);
1069                                 pp->children[i].state = GIT_CP_WAIT_CLEANUP;
1070                         } else if (n < 0)
1071                                 if (errno != EAGAIN)
1072                                         die_errno("read");
1073                 }
1074         }
1075 }
1076
1077 static void pp_output(struct parallel_processes *pp)
1078 {
1079         int i = pp->output_owner;
1080         if (pp->children[i].state == GIT_CP_WORKING &&
1081             pp->children[i].err.len) {
1082                 strbuf_write(&pp->children[i].err, stderr);
1083                 strbuf_reset(&pp->children[i].err);
1084         }
1085 }
1086
1087 static int pp_collect_finished(struct parallel_processes *pp)
1088 {
1089         int i, code;
1090         int n = pp->max_processes;
1091         int result = 0;
1092
1093         while (pp->nr_processes > 0) {
1094                 for (i = 0; i < pp->max_processes; i++)
1095                         if (pp->children[i].state == GIT_CP_WAIT_CLEANUP)
1096                                 break;
1097                 if (i == pp->max_processes)
1098                         break;
1099
1100                 code = finish_command(&pp->children[i].process);
1101
1102                 code = pp->task_finished(code,
1103                                          &pp->children[i].err, pp->data,
1104                                          &pp->children[i].data);
1105
1106                 if (code)
1107                         result = code;
1108                 if (code < 0)
1109                         break;
1110
1111                 pp->nr_processes--;
1112                 pp->children[i].state = GIT_CP_FREE;
1113                 pp->pfd[i].fd = -1;
1114                 child_process_init(&pp->children[i].process);
1115
1116                 if (i != pp->output_owner) {
1117                         strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1118                         strbuf_reset(&pp->children[i].err);
1119                 } else {
1120                         strbuf_write(&pp->children[i].err, stderr);
1121                         strbuf_reset(&pp->children[i].err);
1122
1123                         /* Output all other finished child processes */
1124                         strbuf_write(&pp->buffered_output, stderr);
1125                         strbuf_reset(&pp->buffered_output);
1126
1127                         /*
1128                          * Pick next process to output live.
1129                          * NEEDSWORK:
1130                          * For now we pick it randomly by doing a round
1131                          * robin. Later we may want to pick the one with
1132                          * the most output or the longest or shortest
1133                          * running process time.
1134                          */
1135                         for (i = 0; i < n; i++)
1136                                 if (pp->children[(pp->output_owner + i) % n].state == GIT_CP_WORKING)
1137                                         break;
1138                         pp->output_owner = (pp->output_owner + i) % n;
1139                 }
1140         }
1141         return result;
1142 }
1143
1144 int run_processes_parallel(int n,
1145                            get_next_task_fn get_next_task,
1146                            start_failure_fn start_failure,
1147                            task_finished_fn task_finished,
1148                            void *pp_cb)
1149 {
1150         int i, code;
1151         int output_timeout = 100;
1152         int spawn_cap = 4;
1153         struct parallel_processes pp;
1154
1155         pp_init(&pp, n, get_next_task, start_failure, task_finished, pp_cb);
1156         while (1) {
1157                 for (i = 0;
1158                     i < spawn_cap && !pp.shutdown &&
1159                     pp.nr_processes < pp.max_processes;
1160                     i++) {
1161                         code = pp_start_one(&pp);
1162                         if (!code)
1163                                 continue;
1164                         if (code < 0) {
1165                                 pp.shutdown = 1;
1166                                 kill_children(&pp, -code);
1167                         }
1168                         break;
1169                 }
1170                 if (!pp.nr_processes)
1171                         break;
1172                 pp_buffer_stderr(&pp, output_timeout);
1173                 pp_output(&pp);
1174                 code = pp_collect_finished(&pp);
1175                 if (code) {
1176                         pp.shutdown = 1;
1177                         if (code < 0)
1178                                 kill_children(&pp, -code);
1179                 }
1180         }
1181
1182         pp_cleanup(&pp);
1183         return 0;
1184 }