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 #include "string-list.h"
   9 #include "quote.h"
  10
  11 void child_process_init(struct child_process *child)
  12 {
  13         memset(child, 0, sizeof(*child));
  14         argv_array_init(&child->args);
  15         argv_array_init(&child->env_array);
  16 }
  17
  18 void child_process_clear(struct child_process *child)
  19 {
  20         argv_array_clear(&child->args);
  21         argv_array_clear(&child->env_array);
  22 }
  23
  24 struct child_to_clean {
  25         pid_t pid;
  26         struct child_process *process;
  27         struct child_to_clean *next;
  28 };
  29 static struct child_to_clean *children_to_clean;
  30 static int installed_child_cleanup_handler;
  31
  32 static void cleanup_children(int sig, int in_signal)
  33 {
  34         struct child_to_clean *children_to_wait_for = NULL;
  35
  36         while (children_to_clean) {
  37                 struct child_to_clean *p = children_to_clean;
  38                 children_to_clean = p->next;
  39
  40                 if (p->process && !in_signal) {
  41                         struct child_process *process = p->process;
  42                         if (process->clean_on_exit_handler) {
  43                                 trace_printf(
  44                                         "trace: run_command: running exit handler for pid %"
  45                                         PRIuMAX, (uintmax_t)p->pid
  46                                 );
  47                                 process->clean_on_exit_handler(process);
  48                         }
  49                 }
  50
  51                 kill(p->pid, sig);
  52
  53                 if (p->process && p->process->wait_after_clean) {
  54                         p->next = children_to_wait_for;
  55                         children_to_wait_for = p;
  56                 } else {
  57                         if (!in_signal)
  58                                 free(p);
  59                 }
  60         }
  61
  62         while (children_to_wait_for) {
  63                 struct child_to_clean *p = children_to_wait_for;
  64                 children_to_wait_for = p->next;
  65
  66                 while (waitpid(p->pid, NULL, 0) < 0 && errno == EINTR)
  67                         ; /* spin waiting for process exit or error */
  68
  69                 if (!in_signal)
  70                         free(p);
  71         }
  72 }
  73
  74 static void cleanup_children_on_signal(int sig)
  75 {
  76         cleanup_children(sig, 1);
  77         sigchain_pop(sig);
  78         raise(sig);
  79 }
  80
  81 static void cleanup_children_on_exit(void)
  82 {
  83         cleanup_children(SIGTERM, 0);
  84 }
  85
  86 static void mark_child_for_cleanup(pid_t pid, struct child_process *process)
  87 {
  88         struct child_to_clean *p = xmalloc(sizeof(*p));
  89         p->pid = pid;
  90         p->process = process;
  91         p->next = children_to_clean;
  92         children_to_clean = p;
  93
  94         if (!installed_child_cleanup_handler) {
  95                 atexit(cleanup_children_on_exit);
  96                 sigchain_push_common(cleanup_children_on_signal);
  97                 installed_child_cleanup_handler = 1;
  98         }
  99 }
 100
 101 static void clear_child_for_cleanup(pid_t pid)
 102 {
 103         struct child_to_clean **pp;
 104
 105         for (pp = &children_to_clean; *pp; pp = &(*pp)->next) {
 106                 struct child_to_clean *clean_me = *pp;
 107
 108                 if (clean_me->pid == pid) {
 109                         *pp = clean_me->next;
 110                         free(clean_me);
 111                         return;
 112                 }
 113         }
 114 }
 115
 116 static inline void close_pair(int fd[2])
 117 {
 118         close(fd[0]);
 119         close(fd[1]);
 120 }
 121
 122 int is_executable(const char *name)
 123 {
 124         struct stat st;
 125
 126         if (stat(name, &st) || /* stat, not lstat */
 127             !S_ISREG(st.st_mode))
 128                 return 0;
 129
 130 #if defined(GIT_WINDOWS_NATIVE)
 131         /*
 132          * On Windows there is no executable bit. The file extension
 133          * indicates whether it can be run as an executable, and Git
 134          * has special-handling to detect scripts and launch them
 135          * through the indicated script interpreter. We test for the
 136          * file extension first because virus scanners may make
 137          * it quite expensive to open many files.
 138          */
 139         if (ends_with(name, ".exe"))
 140                 return S_IXUSR;
 141
 142 {
 143         /*
 144          * Now that we know it does not have an executable extension,
 145          * peek into the file instead.
 146          */
 147         char buf[3] = { 0 };
 148         int n;
 149         int fd = open(name, O_RDONLY);
 150         st.st_mode &= ~S_IXUSR;
 151         if (fd >= 0) {
 152                 n = read(fd, buf, 2);
 153                 if (n == 2)
 154                         /* look for a she-bang */
 155                         if (!strcmp(buf, "#!"))
 156                                 st.st_mode |= S_IXUSR;
 157                 close(fd);
 158         }
 159 }
 160 #endif
 161         return st.st_mode & S_IXUSR;
 162 }
 163
 164 /*
 165  * Search $PATH for a command.  This emulates the path search that
 166  * execvp would perform, without actually executing the command so it
 167  * can be used before fork() to prepare to run a command using
 168  * execve() or after execvp() to diagnose why it failed.
 169  *
 170  * The caller should ensure that file contains no directory
 171  * separators.
 172  *
 173  * Returns the path to the command, as found in $PATH or NULL if the
 174  * command could not be found.  The caller inherits ownership of the memory
 175  * used to store the resultant path.
 176  *
 177  * This should not be used on Windows, where the $PATH search rules
 178  * are more complicated (e.g., a search for "foo" should find
 179  * "foo.exe").
 180  */
 181 static char *locate_in_PATH(const char *file)
 182 {
 183         const char *p = getenv("PATH");
 184         struct strbuf buf = STRBUF_INIT;
 185
 186         if (!p || !*p)
 187                 return NULL;
 188
 189         while (1) {
 190                 const char *end = strchrnul(p, ':');
 191
 192                 strbuf_reset(&buf);
 193
 194                 /* POSIX specifies an empty entry as the current directory. */
 195                 if (end != p) {
 196                         strbuf_add(&buf, p, end - p);
 197                         strbuf_addch(&buf, '/');
 198                 }
 199                 strbuf_addstr(&buf, file);
 200
 201                 if (is_executable(buf.buf))
 202                         return strbuf_detach(&buf, NULL);
 203
 204                 if (!*end)
 205                         break;
 206                 p = end + 1;
 207         }
 208
 209         strbuf_release(&buf);
 210         return NULL;
 211 }
 212
 213 static int exists_in_PATH(const char *file)
 214 {
 215         char *r = locate_in_PATH(file);
 216         free(r);
 217         return r != NULL;
 218 }
 219
 220 int sane_execvp(const char *file, char * const argv[])
 221 {
 222         if (!execvp(file, argv))
 223                 return 0; /* cannot happen ;-) */
 224
 225         /*
 226          * When a command can't be found because one of the directories
 227          * listed in $PATH is unsearchable, execvp reports EACCES, but
 228          * careful usability testing (read: analysis of occasional bug
 229          * reports) reveals that "No such file or directory" is more
 230          * intuitive.
 231          *
 232          * We avoid commands with "/", because execvp will not do $PATH
 233          * lookups in that case.
 234          *
 235          * The reassignment of EACCES to errno looks like a no-op below,
 236          * but we need to protect against exists_in_PATH overwriting errno.
 237          */
 238         if (errno == EACCES && !strchr(file, '/'))
 239                 errno = exists_in_PATH(file) ? EACCES : ENOENT;
 240         else if (errno == ENOTDIR && !strchr(file, '/'))
 241                 errno = ENOENT;
 242         return -1;
 243 }
 244
 245 static const char **prepare_shell_cmd(struct argv_array *out, const char **argv)
 246 {
 247         if (!argv[0])
 248                 BUG("shell command is empty");
 249
 250         if (strcspn(argv[0], "|&;<>()$`\\\"' \t\n*?[#~=%") != strlen(argv[0])) {
 251 #ifndef GIT_WINDOWS_NATIVE
 252                 argv_array_push(out, SHELL_PATH);
 253 #else
 254                 argv_array_push(out, "sh");
 255 #endif
 256                 argv_array_push(out, "-c");
 257
 258                 /*
 259                  * If we have no extra arguments, we do not even need to
 260                  * bother with the "$@" magic.
 261                  */
 262                 if (!argv[1])
 263                         argv_array_push(out, argv[0]);
 264                 else
 265                         argv_array_pushf(out, "%s \"$@\"", argv[0]);
 266         }
 267
 268         argv_array_pushv(out, argv);
 269         return out->argv;
 270 }
 271
 272 #ifndef GIT_WINDOWS_NATIVE
 273 static int child_notifier = -1;
 274
 275 enum child_errcode {
 276         CHILD_ERR_CHDIR,
 277         CHILD_ERR_DUP2,
 278         CHILD_ERR_CLOSE,
 279         CHILD_ERR_SIGPROCMASK,
 280         CHILD_ERR_ENOENT,
 281         CHILD_ERR_SILENT,
 282         CHILD_ERR_ERRNO
 283 };
 284
 285 struct child_err {
 286         enum child_errcode err;
 287         int syserr; /* errno */
 288 };
 289
 290 static void child_die(enum child_errcode err)
 291 {
 292         struct child_err buf;
 293
 294         buf.err = err;
 295         buf.syserr = errno;
 296
 297         /* write(2) on buf smaller than PIPE_BUF (min 512) is atomic: */
 298         xwrite(child_notifier, &buf, sizeof(buf));
 299         _exit(1);
 300 }
 301
 302 static void child_dup2(int fd, int to)
 303 {
 304         if (dup2(fd, to) < 0)
 305                 child_die(CHILD_ERR_DUP2);
 306 }
 307
 308 static void child_close(int fd)
 309 {
 310         if (close(fd))
 311                 child_die(CHILD_ERR_CLOSE);
 312 }
 313
 314 static void child_close_pair(int fd[2])
 315 {
 316         child_close(fd[0]);
 317         child_close(fd[1]);
 318 }
 319
 320 /*
 321  * parent will make it look like the child spewed a fatal error and died
 322  * this is needed to prevent changes to t0061.
 323  */
 324 static void fake_fatal(const char *err, va_list params)
 325 {
 326         vreportf("fatal: ", err, params);
 327 }
 328
 329 static void child_error_fn(const char *err, va_list params)
 330 {
 331         const char msg[] = "error() should not be called in child\n";
 332         xwrite(2, msg, sizeof(msg) - 1);
 333 }
 334
 335 static void child_warn_fn(const char *err, va_list params)
 336 {
 337         const char msg[] = "warn() should not be called in child\n";
 338         xwrite(2, msg, sizeof(msg) - 1);
 339 }
 340
 341 static void NORETURN child_die_fn(const char *err, va_list params)
 342 {
 343         const char msg[] = "die() should not be called in child\n";
 344         xwrite(2, msg, sizeof(msg) - 1);
 345         _exit(2);
 346 }
 347
 348 /* this runs in the parent process */
 349 static void child_err_spew(struct child_process *cmd, struct child_err *cerr)
 350 {
 351         static void (*old_errfn)(const char *err, va_list params);
 352
 353         old_errfn = get_error_routine();
 354         set_error_routine(fake_fatal);
 355         errno = cerr->syserr;
 356
 357         switch (cerr->err) {
 358         case CHILD_ERR_CHDIR:
 359                 error_errno("exec '%s': cd to '%s' failed",
 360                             cmd->argv[0], cmd->dir);
 361                 break;
 362         case CHILD_ERR_DUP2:
 363                 error_errno("dup2() in child failed");
 364                 break;
 365         case CHILD_ERR_CLOSE:
 366                 error_errno("close() in child failed");
 367                 break;
 368         case CHILD_ERR_SIGPROCMASK:
 369                 error_errno("sigprocmask failed restoring signals");
 370                 break;
 371         case CHILD_ERR_ENOENT:
 372                 error_errno("cannot run %s", cmd->argv[0]);
 373                 break;
 374         case CHILD_ERR_SILENT:
 375                 break;
 376         case CHILD_ERR_ERRNO:
 377                 error_errno("cannot exec '%s'", cmd->argv[0]);
 378                 break;
 379         }
 380         set_error_routine(old_errfn);
 381 }
 382
 383 static int prepare_cmd(struct argv_array *out, const struct child_process *cmd)
 384 {
 385         if (!cmd->argv[0])
 386                 BUG("command is empty");
 387
 388         /*
 389          * Add SHELL_PATH so in the event exec fails with ENOEXEC we can
 390          * attempt to interpret the command with 'sh'.
 391          */
 392         argv_array_push(out, SHELL_PATH);
 393
 394         if (cmd->git_cmd) {
 395                 argv_array_push(out, "git");
 396                 argv_array_pushv(out, cmd->argv);
 397         } else if (cmd->use_shell) {
 398                 prepare_shell_cmd(out, cmd->argv);
 399         } else {
 400                 argv_array_pushv(out, cmd->argv);
 401         }
 402
 403         /*
 404          * If there are no '/' characters in the command then perform a path
 405          * lookup and use the resolved path as the command to exec.  If there
 406          * are '/' characters, we have exec attempt to invoke the command
 407          * directly.
 408          */
 409         if (!strchr(out->argv[1], '/')) {
 410                 char *program = locate_in_PATH(out->argv[1]);
 411                 if (program) {
 412                         free((char *)out->argv[1]);
 413                         out->argv[1] = program;
 414                 } else {
 415                         argv_array_clear(out);
 416                         errno = ENOENT;
 417                         return -1;
 418                 }
 419         }
 420
 421         return 0;
 422 }
 423
 424 static char **prep_childenv(const char *const *deltaenv)
 425 {
 426         extern char **environ;
 427         char **childenv;
 428         struct string_list env = STRING_LIST_INIT_DUP;
 429         struct strbuf key = STRBUF_INIT;
 430         const char *const *p;
 431         int i;
 432
 433         /* Construct a sorted string list consisting of the current environ */
 434         for (p = (const char *const *) environ; p && *p; p++) {
 435                 const char *equals = strchr(*p, '=');
 436
 437                 if (equals) {
 438                         strbuf_reset(&key);
 439                         strbuf_add(&key, *p, equals - *p);
 440                         string_list_append(&env, key.buf)->util = (void *) *p;
 441                 } else {
 442                         string_list_append(&env, *p)->util = (void *) *p;
 443                 }
 444         }
 445         string_list_sort(&env);
 446
 447         /* Merge in 'deltaenv' with the current environ */
 448         for (p = deltaenv; p && *p; p++) {
 449                 const char *equals = strchr(*p, '=');
 450
 451                 if (equals) {
 452                         /* ('key=value'), insert or replace entry */
 453                         strbuf_reset(&key);
 454                         strbuf_add(&key, *p, equals - *p);
 455                         string_list_insert(&env, key.buf)->util = (void *) *p;
 456                 } else {
 457                         /* otherwise ('key') remove existing entry */
 458                         string_list_remove(&env, *p, 0);
 459                 }
 460         }
 461
 462         /* Create an array of 'char *' to be used as the childenv */
 463         ALLOC_ARRAY(childenv, env.nr + 1);
 464         for (i = 0; i < env.nr; i++)
 465                 childenv[i] = env.items[i].util;
 466         childenv[env.nr] = NULL;
 467
 468         string_list_clear(&env, 0);
 469         strbuf_release(&key);
 470         return childenv;
 471 }
 472
 473 struct atfork_state {
 474 #ifndef NO_PTHREADS
 475         int cs;
 476 #endif
 477         sigset_t old;
 478 };
 479
 480 #define CHECK_BUG(err, msg) \
 481         do { \
 482                 int e = (err); \
 483                 if (e) \
 484                         BUG("%s: %s", msg, strerror(e)); \
 485         } while(0)
 486
 487 static void atfork_prepare(struct atfork_state *as)
 488 {
 489         sigset_t all;
 490
 491         if (sigfillset(&all))
 492                 die_errno("sigfillset");
 493 #ifdef NO_PTHREADS
 494         if (sigprocmask(SIG_SETMASK, &all, &as->old))
 495                 die_errno("sigprocmask");
 496 #else
 497         CHECK_BUG(pthread_sigmask(SIG_SETMASK, &all, &as->old),
 498                 "blocking all signals");
 499         CHECK_BUG(pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &as->cs),
 500                 "disabling cancellation");
 501 #endif
 502 }
 503
 504 static void atfork_parent(struct atfork_state *as)
 505 {
 506 #ifdef NO_PTHREADS
 507         if (sigprocmask(SIG_SETMASK, &as->old, NULL))
 508                 die_errno("sigprocmask");
 509 #else
 510         CHECK_BUG(pthread_setcancelstate(as->cs, NULL),
 511                 "re-enabling cancellation");
 512         CHECK_BUG(pthread_sigmask(SIG_SETMASK, &as->old, NULL),
 513                 "restoring signal mask");
 514 #endif
 515 }
 516 #endif /* GIT_WINDOWS_NATIVE */
 517
 518 static inline void set_cloexec(int fd)
 519 {
 520         int flags = fcntl(fd, F_GETFD);
 521         if (flags >= 0)
 522                 fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
 523 }
 524
 525 static int wait_or_whine(pid_t pid, const char *argv0, int in_signal)
 526 {
 527         int status, code = -1;
 528         pid_t waiting;
 529         int failed_errno = 0;
 530
 531         while ((waiting = waitpid(pid, &status, 0)) < 0 && errno == EINTR)
 532                 ;       /* nothing */
 533         if (in_signal)
 534                 return 0;
 535
 536         if (waiting < 0) {
 537                 failed_errno = errno;
 538                 error_errno("waitpid for %s failed", argv0);
 539         } else if (waiting != pid) {
 540                 error("waitpid is confused (%s)", argv0);
 541         } else if (WIFSIGNALED(status)) {
 542                 code = WTERMSIG(status);
 543                 if (code != SIGINT && code != SIGQUIT && code != SIGPIPE)
 544                         error("%s died of signal %d", argv0, code);
 545                 /*
 546                  * This return value is chosen so that code & 0xff
 547                  * mimics the exit code that a POSIX shell would report for
 548                  * a program that died from this signal.
 549                  */
 550                 code += 128;
 551         } else if (WIFEXITED(status)) {
 552                 code = WEXITSTATUS(status);
 553         } else {
 554                 error("waitpid is confused (%s)", argv0);
 555         }
 556
 557         clear_child_for_cleanup(pid);
 558
 559         errno = failed_errno;
 560         return code;
 561 }
 562
 563 static void trace_add_env(struct strbuf *dst, const char *const *deltaenv)
 564 {
 565         struct string_list envs = STRING_LIST_INIT_DUP;
 566         const char *const *e;
 567         int i;
 568         int printed_unset = 0;
 569
 570         /* Last one wins, see run-command.c:prep_childenv() for context */
 571         for (e = deltaenv; e && *e; e++) {
 572                 struct strbuf key = STRBUF_INIT;
 573                 char *equals = strchr(*e, '=');
 574
 575                 if (equals) {
 576                         strbuf_add(&key, *e, equals - *e);
 577                         string_list_insert(&envs, key.buf)->util = equals + 1;
 578                 } else {
 579                         string_list_insert(&envs, *e)->util = NULL;
 580                 }
 581                 strbuf_release(&key);
 582         }
 583
 584         /* "unset X Y...;" */
 585         for (i = 0; i < envs.nr; i++) {
 586                 const char *var = envs.items[i].string;
 587                 const char *val = envs.items[i].util;
 588
 589                 if (val || !getenv(var))
 590                         continue;
 591
 592                 if (!printed_unset) {
 593                         strbuf_addstr(dst, " unset");
 594                         printed_unset = 1;
 595                 }
 596                 strbuf_addf(dst, " %s", var);
 597         }
 598         if (printed_unset)
 599                 strbuf_addch(dst, ';');
 600
 601         /* ... followed by "A=B C=D ..." */
 602         for (i = 0; i < envs.nr; i++) {
 603                 const char *var = envs.items[i].string;
 604                 const char *val = envs.items[i].util;
 605                 const char *oldval;
 606
 607                 if (!val)
 608                         continue;
 609
 610                 oldval = getenv(var);
 611                 if (oldval && !strcmp(val, oldval))
 612                         continue;
 613
 614                 strbuf_addf(dst, " %s=", var);
 615                 sq_quote_buf_pretty(dst, val);
 616         }
 617         string_list_clear(&envs, 0);
 618 }
 619
 620 static void trace_run_command(const struct child_process *cp)
 621 {
 622         struct strbuf buf = STRBUF_INIT;
 623
 624         if (!trace_want(&trace_default_key))
 625                 return;
 626
 627         strbuf_addstr(&buf, "trace: run_command:");
 628         if (cp->dir) {
 629                 strbuf_addstr(&buf, " cd ");
 630                 sq_quote_buf_pretty(&buf, cp->dir);
 631                 strbuf_addch(&buf, ';');
 632         }
 633         /*
 634          * The caller is responsible for initializing cp->env from
 635          * cp->env_array if needed. We only check one place.
 636          */
 637         if (cp->env)
 638                 trace_add_env(&buf, cp->env);
 639         if (cp->git_cmd)
 640                 strbuf_addstr(&buf, " git");
 641         sq_quote_argv_pretty(&buf, cp->argv);
 642
 643         trace_printf("%s", buf.buf);
 644         strbuf_release(&buf);
 645 }
 646
 647 int start_command(struct child_process *cmd)
 648 {
 649         int need_in, need_out, need_err;
 650         int fdin[2], fdout[2], fderr[2];
 651         int failed_errno;
 652         char *str;
 653
 654         if (!cmd->argv)
 655                 cmd->argv = cmd->args.argv;
 656         if (!cmd->env)
 657                 cmd->env = cmd->env_array.argv;
 658
 659         /*
 660          * In case of errors we must keep the promise to close FDs
 661          * that have been passed in via ->in and ->out.
 662          */
 663
 664         need_in = !cmd->no_stdin && cmd->in < 0;
 665         if (need_in) {
 666                 if (pipe(fdin) < 0) {
 667                         failed_errno = errno;
 668                         if (cmd->out > 0)
 669                                 close(cmd->out);
 670                         str = "standard input";
 671                         goto fail_pipe;
 672                 }
 673                 cmd->in = fdin[1];
 674         }
 675
 676         need_out = !cmd->no_stdout
 677                 && !cmd->stdout_to_stderr
 678                 && cmd->out < 0;
 679         if (need_out) {
 680                 if (pipe(fdout) < 0) {
 681                         failed_errno = errno;
 682                         if (need_in)
 683                                 close_pair(fdin);
 684                         else if (cmd->in)
 685                                 close(cmd->in);
 686                         str = "standard output";
 687                         goto fail_pipe;
 688                 }
 689                 cmd->out = fdout[0];
 690         }
 691
 692         need_err = !cmd->no_stderr && cmd->err < 0;
 693         if (need_err) {
 694                 if (pipe(fderr) < 0) {
 695                         failed_errno = errno;
 696                         if (need_in)
 697                                 close_pair(fdin);
 698                         else if (cmd->in)
 699                                 close(cmd->in);
 700                         if (need_out)
 701                                 close_pair(fdout);
 702                         else if (cmd->out)
 703                                 close(cmd->out);
 704                         str = "standard error";
 705 fail_pipe:
 706                         error("cannot create %s pipe for %s: %s",
 707                                 str, cmd->argv[0], strerror(failed_errno));
 708                         child_process_clear(cmd);
 709                         errno = failed_errno;
 710                         return -1;
 711                 }
 712                 cmd->err = fderr[0];
 713         }
 714
 715         trace_run_command(cmd);
 716
 717         fflush(NULL);
 718
 719 #ifndef GIT_WINDOWS_NATIVE
 720 {
 721         int notify_pipe[2];
 722         int null_fd = -1;
 723         char **childenv;
 724         struct argv_array argv = ARGV_ARRAY_INIT;
 725         struct child_err cerr;
 726         struct atfork_state as;
 727
 728         if (prepare_cmd(&argv, cmd) < 0) {
 729                 failed_errno = errno;
 730                 cmd->pid = -1;
 731                 goto end_of_spawn;
 732         }
 733
 734         if (pipe(notify_pipe))
 735                 notify_pipe[0] = notify_pipe[1] = -1;
 736
 737         if (cmd->no_stdin || cmd->no_stdout || cmd->no_stderr) {
 738                 null_fd = open("/dev/null", O_RDWR | O_CLOEXEC);
 739                 if (null_fd < 0)
 740                         die_errno(_("open /dev/null failed"));
 741                 set_cloexec(null_fd);
 742         }
 743
 744         childenv = prep_childenv(cmd->env);
 745         atfork_prepare(&as);
 746
 747         /*
 748          * NOTE: In order to prevent deadlocking when using threads special
 749          * care should be taken with the function calls made in between the
 750          * fork() and exec() calls.  No calls should be made to functions which
 751          * require acquiring a lock (e.g. malloc) as the lock could have been
 752          * held by another thread at the time of forking, causing the lock to
 753          * never be released in the child process.  This means only
 754          * Async-Signal-Safe functions are permitted in the child.
 755          */
 756         cmd->pid = fork();
 757         failed_errno = errno;
 758         if (!cmd->pid) {
 759                 int sig;
 760                 /*
 761                  * Ensure the default die/error/warn routines do not get
 762                  * called, they can take stdio locks and malloc.
 763                  */
 764                 set_die_routine(child_die_fn);
 765                 set_error_routine(child_error_fn);
 766                 set_warn_routine(child_warn_fn);
 767
 768                 close(notify_pipe[0]);
 769                 set_cloexec(notify_pipe[1]);
 770                 child_notifier = notify_pipe[1];
 771
 772                 if (cmd->no_stdin)
 773                         child_dup2(null_fd, 0);
 774                 else if (need_in) {
 775                         child_dup2(fdin[0], 0);
 776                         child_close_pair(fdin);
 777                 } else if (cmd->in) {
 778                         child_dup2(cmd->in, 0);
 779                         child_close(cmd->in);
 780                 }
 781
 782                 if (cmd->no_stderr)
 783                         child_dup2(null_fd, 2);
 784                 else if (need_err) {
 785                         child_dup2(fderr[1], 2);
 786                         child_close_pair(fderr);
 787                 } else if (cmd->err > 1) {
 788                         child_dup2(cmd->err, 2);
 789                         child_close(cmd->err);
 790                 }
 791
 792                 if (cmd->no_stdout)
 793                         child_dup2(null_fd, 1);
 794                 else if (cmd->stdout_to_stderr)
 795                         child_dup2(2, 1);
 796                 else if (need_out) {
 797                         child_dup2(fdout[1], 1);
 798                         child_close_pair(fdout);
 799                 } else if (cmd->out > 1) {
 800                         child_dup2(cmd->out, 1);
 801                         child_close(cmd->out);
 802                 }
 803
 804                 if (cmd->dir && chdir(cmd->dir))
 805                         child_die(CHILD_ERR_CHDIR);
 806
 807                 /*
 808                  * restore default signal handlers here, in case
 809                  * we catch a signal right before execve below
 810                  */
 811                 for (sig = 1; sig < NSIG; sig++) {
 812                         /* ignored signals get reset to SIG_DFL on execve */
 813                         if (signal(sig, SIG_DFL) == SIG_IGN)
 814                                 signal(sig, SIG_IGN);
 815                 }
 816
 817                 if (sigprocmask(SIG_SETMASK, &as.old, NULL) != 0)
 818                         child_die(CHILD_ERR_SIGPROCMASK);
 819
 820                 /*
 821                  * Attempt to exec using the command and arguments starting at
 822                  * argv.argv[1].  argv.argv[0] contains SHELL_PATH which will
 823                  * be used in the event exec failed with ENOEXEC at which point
 824                  * we will try to interpret the command using 'sh'.
 825                  */
 826                 execve(argv.argv[1], (char *const *) argv.argv + 1,
 827                        (char *const *) childenv);
 828                 if (errno == ENOEXEC)
 829                         execve(argv.argv[0], (char *const *) argv.argv,
 830                                (char *const *) childenv);
 831
 832                 if (errno == ENOENT) {
 833                         if (cmd->silent_exec_failure)
 834                                 child_die(CHILD_ERR_SILENT);
 835                         child_die(CHILD_ERR_ENOENT);
 836                 } else {
 837                         child_die(CHILD_ERR_ERRNO);
 838                 }
 839         }
 840         atfork_parent(&as);
 841         if (cmd->pid < 0)
 842                 error_errno("cannot fork() for %s", cmd->argv[0]);
 843         else if (cmd->clean_on_exit)
 844                 mark_child_for_cleanup(cmd->pid, cmd);
 845
 846         /*
 847          * Wait for child's exec. If the exec succeeds (or if fork()
 848          * failed), EOF is seen immediately by the parent. Otherwise, the
 849          * child process sends a child_err struct.
 850          * Note that use of this infrastructure is completely advisory,
 851          * therefore, we keep error checks minimal.
 852          */
 853         close(notify_pipe[1]);
 854         if (xread(notify_pipe[0], &cerr, sizeof(cerr)) == sizeof(cerr)) {
 855                 /*
 856                  * At this point we know that fork() succeeded, but exec()
 857                  * failed. Errors have been reported to our stderr.
 858                  */
 859                 wait_or_whine(cmd->pid, cmd->argv[0], 0);
 860                 child_err_spew(cmd, &cerr);
 861                 failed_errno = errno;
 862                 cmd->pid = -1;
 863         }
 864         close(notify_pipe[0]);
 865
 866         if (null_fd >= 0)
 867                 close(null_fd);
 868         argv_array_clear(&argv);
 869         free(childenv);
 870 }
 871 end_of_spawn:
 872
 873 #else
 874 {
 875         int fhin = 0, fhout = 1, fherr = 2;
 876         const char **sargv = cmd->argv;
 877         struct argv_array nargv = ARGV_ARRAY_INIT;
 878
 879         if (cmd->no_stdin)
 880                 fhin = open("/dev/null", O_RDWR);
 881         else if (need_in)
 882                 fhin = dup(fdin[0]);
 883         else if (cmd->in)
 884                 fhin = dup(cmd->in);
 885
 886         if (cmd->no_stderr)
 887                 fherr = open("/dev/null", O_RDWR);
 888         else if (need_err)
 889                 fherr = dup(fderr[1]);
 890         else if (cmd->err > 2)
 891                 fherr = dup(cmd->err);
 892
 893         if (cmd->no_stdout)
 894                 fhout = open("/dev/null", O_RDWR);
 895         else if (cmd->stdout_to_stderr)
 896                 fhout = dup(fherr);
 897         else if (need_out)
 898                 fhout = dup(fdout[1]);
 899         else if (cmd->out > 1)
 900                 fhout = dup(cmd->out);
 901
 902         if (cmd->git_cmd)
 903                 cmd->argv = prepare_git_cmd(&nargv, cmd->argv);
 904         else if (cmd->use_shell)
 905                 cmd->argv = prepare_shell_cmd(&nargv, cmd->argv);
 906
 907         cmd->pid = mingw_spawnvpe(cmd->argv[0], cmd->argv, (char**) cmd->env,
 908                         cmd->dir, fhin, fhout, fherr);
 909         failed_errno = errno;
 910         if (cmd->pid < 0 && (!cmd->silent_exec_failure || errno != ENOENT))
 911                 error_errno("cannot spawn %s", cmd->argv[0]);
 912         if (cmd->clean_on_exit && cmd->pid >= 0)
 913                 mark_child_for_cleanup(cmd->pid, cmd);
 914
 915         argv_array_clear(&nargv);
 916         cmd->argv = sargv;
 917         if (fhin != 0)
 918                 close(fhin);
 919         if (fhout != 1)
 920                 close(fhout);
 921         if (fherr != 2)
 922                 close(fherr);
 923 }
 924 #endif
 925
 926         if (cmd->pid < 0) {
 927                 if (need_in)
 928                         close_pair(fdin);
 929                 else if (cmd->in)
 930                         close(cmd->in);
 931                 if (need_out)
 932                         close_pair(fdout);
 933                 else if (cmd->out)
 934                         close(cmd->out);
 935                 if (need_err)
 936                         close_pair(fderr);
 937                 else if (cmd->err)
 938                         close(cmd->err);
 939                 child_process_clear(cmd);
 940                 errno = failed_errno;
 941                 return -1;
 942         }
 943
 944         if (need_in)
 945                 close(fdin[0]);
 946         else if (cmd->in)
 947                 close(cmd->in);
 948
 949         if (need_out)
 950                 close(fdout[1]);
 951         else if (cmd->out)
 952                 close(cmd->out);
 953
 954         if (need_err)
 955                 close(fderr[1]);
 956         else if (cmd->err)
 957                 close(cmd->err);
 958
 959         return 0;
 960 }
 961
 962 int finish_command(struct child_process *cmd)
 963 {
 964         int ret = wait_or_whine(cmd->pid, cmd->argv[0], 0);
 965         child_process_clear(cmd);
 966         return ret;
 967 }
 968
 969 int finish_command_in_signal(struct child_process *cmd)
 970 {
 971         return wait_or_whine(cmd->pid, cmd->argv[0], 1);
 972 }
 973
 974
 975 int run_command(struct child_process *cmd)
 976 {
 977         int code;
 978
 979         if (cmd->out < 0 || cmd->err < 0)
 980                 BUG("run_command with a pipe can cause deadlock");
 981
 982         code = start_command(cmd);
 983         if (code)
 984                 return code;
 985         return finish_command(cmd);
 986 }
 987
 988 int run_command_v_opt(const char **argv, int opt)
 989 {
 990         return run_command_v_opt_cd_env(argv, opt, NULL, NULL);
 991 }
 992
 993 int run_command_v_opt_cd_env(const char **argv, int opt, const char *dir, const char *const *env)
 994 {
 995         struct child_process cmd = CHILD_PROCESS_INIT;
 996         cmd.argv = argv;
 997         cmd.no_stdin = opt & RUN_COMMAND_NO_STDIN ? 1 : 0;
 998         cmd.git_cmd = opt & RUN_GIT_CMD ? 1 : 0;
 999         cmd.stdout_to_stderr = opt & RUN_COMMAND_STDOUT_TO_STDERR ? 1 : 0;
1000         cmd.silent_exec_failure = opt & RUN_SILENT_EXEC_FAILURE ? 1 : 0;
1001         cmd.use_shell = opt & RUN_USING_SHELL ? 1 : 0;
1002         cmd.clean_on_exit = opt & RUN_CLEAN_ON_EXIT ? 1 : 0;
1003         cmd.dir = dir;
1004         cmd.env = env;
1005         return run_command(&cmd);
1006 }
1007
1008 #ifndef NO_PTHREADS
1009 static pthread_t main_thread;
1010 static int main_thread_set;
1011 static pthread_key_t async_key;
1012 static pthread_key_t async_die_counter;
1013
1014 static void *run_thread(void *data)
1015 {
1016         struct async *async = data;
1017         intptr_t ret;
1018
1019         if (async->isolate_sigpipe) {
1020                 sigset_t mask;
1021                 sigemptyset(&mask);
1022                 sigaddset(&mask, SIGPIPE);
1023                 if (pthread_sigmask(SIG_BLOCK, &mask, NULL) < 0) {
1024                         ret = error("unable to block SIGPIPE in async thread");
1025                         return (void *)ret;
1026                 }
1027         }
1028
1029         pthread_setspecific(async_key, async);
1030         ret = async->proc(async->proc_in, async->proc_out, async->data);
1031         return (void *)ret;
1032 }
1033
1034 static NORETURN void die_async(const char *err, va_list params)
1035 {
1036         vreportf("fatal: ", err, params);
1037
1038         if (in_async()) {
1039                 struct async *async = pthread_getspecific(async_key);
1040                 if (async->proc_in >= 0)
1041                         close(async->proc_in);
1042                 if (async->proc_out >= 0)
1043                         close(async->proc_out);
1044                 pthread_exit((void *)128);
1045         }
1046
1047         exit(128);
1048 }
1049
1050 static int async_die_is_recursing(void)
1051 {
1052         void *ret = pthread_getspecific(async_die_counter);
1053         pthread_setspecific(async_die_counter, (void *)1);
1054         return ret != NULL;
1055 }
1056
1057 int in_async(void)
1058 {
1059         if (!main_thread_set)
1060                 return 0; /* no asyncs started yet */
1061         return !pthread_equal(main_thread, pthread_self());
1062 }
1063
1064 static void NORETURN async_exit(int code)
1065 {
1066         pthread_exit((void *)(intptr_t)code);
1067 }
1068
1069 #else
1070
1071 static struct {
1072         void (**handlers)(void);
1073         size_t nr;
1074         size_t alloc;
1075 } git_atexit_hdlrs;
1076
1077 static int git_atexit_installed;
1078
1079 static void git_atexit_dispatch(void)
1080 {
1081         size_t i;
1082
1083         for (i=git_atexit_hdlrs.nr ; i ; i--)
1084                 git_atexit_hdlrs.handlers[i-1]();
1085 }
1086
1087 static void git_atexit_clear(void)
1088 {
1089         free(git_atexit_hdlrs.handlers);
1090         memset(&git_atexit_hdlrs, 0, sizeof(git_atexit_hdlrs));
1091         git_atexit_installed = 0;
1092 }
1093
1094 #undef atexit
1095 int git_atexit(void (*handler)(void))
1096 {
1097         ALLOC_GROW(git_atexit_hdlrs.handlers, git_atexit_hdlrs.nr + 1, git_atexit_hdlrs.alloc);
1098         git_atexit_hdlrs.handlers[git_atexit_hdlrs.nr++] = handler;
1099         if (!git_atexit_installed) {
1100                 if (atexit(&git_atexit_dispatch))
1101                         return -1;
1102                 git_atexit_installed = 1;
1103         }
1104         return 0;
1105 }
1106 #define atexit git_atexit
1107
1108 static int process_is_async;
1109 int in_async(void)
1110 {
1111         return process_is_async;
1112 }
1113
1114 static void NORETURN async_exit(int code)
1115 {
1116         exit(code);
1117 }
1118
1119 #endif
1120
1121 void check_pipe(int err)
1122 {
1123         if (err == EPIPE) {
1124                 if (in_async())
1125                         async_exit(141);
1126
1127                 signal(SIGPIPE, SIG_DFL);
1128                 raise(SIGPIPE);
1129                 /* Should never happen, but just in case... */
1130                 exit(141);
1131         }
1132 }
1133
1134 int start_async(struct async *async)
1135 {
1136         int need_in, need_out;
1137         int fdin[2], fdout[2];
1138         int proc_in, proc_out;
1139
1140         need_in = async->in < 0;
1141         if (need_in) {
1142                 if (pipe(fdin) < 0) {
1143                         if (async->out > 0)
1144                                 close(async->out);
1145                         return error_errno("cannot create pipe");
1146                 }
1147                 async->in = fdin[1];
1148         }
1149
1150         need_out = async->out < 0;
1151         if (need_out) {
1152                 if (pipe(fdout) < 0) {
1153                         if (need_in)
1154                                 close_pair(fdin);
1155                         else if (async->in)
1156                                 close(async->in);
1157                         return error_errno("cannot create pipe");
1158                 }
1159                 async->out = fdout[0];
1160         }
1161
1162         if (need_in)
1163                 proc_in = fdin[0];
1164         else if (async->in)
1165                 proc_in = async->in;
1166         else
1167                 proc_in = -1;
1168
1169         if (need_out)
1170                 proc_out = fdout[1];
1171         else if (async->out)
1172                 proc_out = async->out;
1173         else
1174                 proc_out = -1;
1175
1176 #ifdef NO_PTHREADS
1177         /* Flush stdio before fork() to avoid cloning buffers */
1178         fflush(NULL);
1179
1180         async->pid = fork();
1181         if (async->pid < 0) {
1182                 error_errno("fork (async) failed");
1183                 goto error;
1184         }
1185         if (!async->pid) {
1186                 if (need_in)
1187                         close(fdin[1]);
1188                 if (need_out)
1189                         close(fdout[0]);
1190                 git_atexit_clear();
1191                 process_is_async = 1;
1192                 exit(!!async->proc(proc_in, proc_out, async->data));
1193         }
1194
1195         mark_child_for_cleanup(async->pid, NULL);
1196
1197         if (need_in)
1198                 close(fdin[0]);
1199         else if (async->in)
1200                 close(async->in);
1201
1202         if (need_out)
1203                 close(fdout[1]);
1204         else if (async->out)
1205                 close(async->out);
1206 #else
1207         if (!main_thread_set) {
1208                 /*
1209                  * We assume that the first time that start_async is called
1210                  * it is from the main thread.
1211                  */
1212                 main_thread_set = 1;
1213                 main_thread = pthread_self();
1214                 pthread_key_create(&async_key, NULL);
1215                 pthread_key_create(&async_die_counter, NULL);
1216                 set_die_routine(die_async);
1217                 set_die_is_recursing_routine(async_die_is_recursing);
1218         }
1219
1220         if (proc_in >= 0)
1221                 set_cloexec(proc_in);
1222         if (proc_out >= 0)
1223                 set_cloexec(proc_out);
1224         async->proc_in = proc_in;
1225         async->proc_out = proc_out;
1226         {
1227                 int err = pthread_create(&async->tid, NULL, run_thread, async);
1228                 if (err) {
1229                         error(_("cannot create async thread: %s"), strerror(err));
1230                         goto error;
1231                 }
1232         }
1233 #endif
1234         return 0;
1235
1236 error:
1237         if (need_in)
1238                 close_pair(fdin);
1239         else if (async->in)
1240                 close(async->in);
1241
1242         if (need_out)
1243                 close_pair(fdout);
1244         else if (async->out)
1245                 close(async->out);
1246         return -1;
1247 }
1248
1249 int finish_async(struct async *async)
1250 {
1251 #ifdef NO_PTHREADS
1252         return wait_or_whine(async->pid, "child process", 0);
1253 #else
1254         void *ret = (void *)(intptr_t)(-1);
1255
1256         if (pthread_join(async->tid, &ret))
1257                 error("pthread_join failed");
1258         return (int)(intptr_t)ret;
1259 #endif
1260 }
1261
1262 int async_with_fork(void)
1263 {
1264 #ifdef NO_PTHREADS
1265         return 1;
1266 #else
1267         return 0;
1268 #endif
1269 }
1270
1271 const char *find_hook(const char *name)
1272 {
1273         static struct strbuf path = STRBUF_INIT;
1274
1275         strbuf_reset(&path);
1276         strbuf_git_path(&path, "hooks/%s", name);
1277         if (access(path.buf, X_OK) < 0) {
1278                 int err = errno;
1279
1280 #ifdef STRIP_EXTENSION
1281                 strbuf_addstr(&path, STRIP_EXTENSION);
1282                 if (access(path.buf, X_OK) >= 0)
1283                         return path.buf;
1284                 if (errno == EACCES)
1285                         err = errno;
1286 #endif
1287
1288                 if (err == EACCES && advice_ignored_hook) {
1289                         static struct string_list advise_given = STRING_LIST_INIT_DUP;
1290
1291                         if (!string_list_lookup(&advise_given, name)) {
1292                                 string_list_insert(&advise_given, name);
1293                                 advise(_("The '%s' hook was ignored because "
1294                                          "it's not set as executable.\n"
1295                                          "You can disable this warning with "
1296                                          "`git config advice.ignoredHook false`."),
1297                                        path.buf);
1298                         }
1299                 }
1300                 return NULL;
1301         }
1302         return path.buf;
1303 }
1304
1305 int run_hook_ve(const char *const *env, const char *name, va_list args)
1306 {
1307         struct child_process hook = CHILD_PROCESS_INIT;
1308         const char *p;
1309
1310         p = find_hook(name);
1311         if (!p)
1312                 return 0;
1313
1314         argv_array_push(&hook.args, p);
1315         while ((p = va_arg(args, const char *)))
1316                 argv_array_push(&hook.args, p);
1317         hook.env = env;
1318         hook.no_stdin = 1;
1319         hook.stdout_to_stderr = 1;
1320
1321         return run_command(&hook);
1322 }
1323
1324 int run_hook_le(const char *const *env, const char *name, ...)
1325 {
1326         va_list args;
1327         int ret;
1328
1329         va_start(args, name);
1330         ret = run_hook_ve(env, name, args);
1331         va_end(args);
1332
1333         return ret;
1334 }
1335
1336 struct io_pump {
1337         /* initialized by caller */
1338         int fd;
1339         int type; /* POLLOUT or POLLIN */
1340         union {
1341                 struct {
1342                         const char *buf;
1343                         size_t len;
1344                 } out;
1345                 struct {
1346                         struct strbuf *buf;
1347                         size_t hint;
1348                 } in;
1349         } u;
1350
1351         /* returned by pump_io */
1352         int error; /* 0 for success, otherwise errno */
1353
1354         /* internal use */
1355         struct pollfd *pfd;
1356 };
1357
1358 static int pump_io_round(struct io_pump *slots, int nr, struct pollfd *pfd)
1359 {
1360         int pollsize = 0;
1361         int i;
1362
1363         for (i = 0; i < nr; i++) {
1364                 struct io_pump *io = &slots[i];
1365                 if (io->fd < 0)
1366                         continue;
1367                 pfd[pollsize].fd = io->fd;
1368                 pfd[pollsize].events = io->type;
1369                 io->pfd = &pfd[pollsize++];
1370         }
1371
1372         if (!pollsize)
1373                 return 0;
1374
1375         if (poll(pfd, pollsize, -1) < 0) {
1376                 if (errno == EINTR)
1377                         return 1;
1378                 die_errno("poll failed");
1379         }
1380
1381         for (i = 0; i < nr; i++) {
1382                 struct io_pump *io = &slots[i];
1383
1384                 if (io->fd < 0)
1385                         continue;
1386
1387                 if (!(io->pfd->revents & (POLLOUT|POLLIN|POLLHUP|POLLERR|POLLNVAL)))
1388                         continue;
1389
1390                 if (io->type == POLLOUT) {
1391                         ssize_t len = xwrite(io->fd,
1392                                              io->u.out.buf, io->u.out.len);
1393                         if (len < 0) {
1394                                 io->error = errno;
1395                                 close(io->fd);
1396                                 io->fd = -1;
1397                         } else {
1398                                 io->u.out.buf += len;
1399                                 io->u.out.len -= len;
1400                                 if (!io->u.out.len) {
1401                                         close(io->fd);
1402                                         io->fd = -1;
1403                                 }
1404                         }
1405                 }
1406
1407                 if (io->type == POLLIN) {
1408                         ssize_t len = strbuf_read_once(io->u.in.buf,
1409                                                        io->fd, io->u.in.hint);
1410                         if (len < 0)
1411                                 io->error = errno;
1412                         if (len <= 0) {
1413                                 close(io->fd);
1414                                 io->fd = -1;
1415                         }
1416                 }
1417         }
1418
1419         return 1;
1420 }
1421
1422 static int pump_io(struct io_pump *slots, int nr)
1423 {
1424         struct pollfd *pfd;
1425         int i;
1426
1427         for (i = 0; i < nr; i++)
1428                 slots[i].error = 0;
1429
1430         ALLOC_ARRAY(pfd, nr);
1431         while (pump_io_round(slots, nr, pfd))
1432                 ; /* nothing */
1433         free(pfd);
1434
1435         /* There may be multiple errno values, so just pick the first. */
1436         for (i = 0; i < nr; i++) {
1437                 if (slots[i].error) {
1438                         errno = slots[i].error;
1439                         return -1;
1440                 }
1441         }
1442         return 0;
1443 }
1444
1445
1446 int pipe_command(struct child_process *cmd,
1447                  const char *in, size_t in_len,
1448                  struct strbuf *out, size_t out_hint,
1449                  struct strbuf *err, size_t err_hint)
1450 {
1451         struct io_pump io[3];
1452         int nr = 0;
1453
1454         if (in)
1455                 cmd->in = -1;
1456         if (out)
1457                 cmd->out = -1;
1458         if (err)
1459                 cmd->err = -1;
1460
1461         if (start_command(cmd) < 0)
1462                 return -1;
1463
1464         if (in) {
1465                 io[nr].fd = cmd->in;
1466                 io[nr].type = POLLOUT;
1467                 io[nr].u.out.buf = in;
1468                 io[nr].u.out.len = in_len;
1469                 nr++;
1470         }
1471         if (out) {
1472                 io[nr].fd = cmd->out;
1473                 io[nr].type = POLLIN;
1474                 io[nr].u.in.buf = out;
1475                 io[nr].u.in.hint = out_hint;
1476                 nr++;
1477         }
1478         if (err) {
1479                 io[nr].fd = cmd->err;
1480                 io[nr].type = POLLIN;
1481                 io[nr].u.in.buf = err;
1482                 io[nr].u.in.hint = err_hint;
1483                 nr++;
1484         }
1485
1486         if (pump_io(io, nr) < 0) {
1487                 finish_command(cmd); /* throw away exit code */
1488                 return -1;
1489         }
1490
1491         return finish_command(cmd);
1492 }
1493
1494 enum child_state {
1495         GIT_CP_FREE,
1496         GIT_CP_WORKING,
1497         GIT_CP_WAIT_CLEANUP,
1498 };
1499
1500 struct parallel_processes {
1501         void *data;
1502
1503         int max_processes;
1504         int nr_processes;
1505
1506         get_next_task_fn get_next_task;
1507         start_failure_fn start_failure;
1508         task_finished_fn task_finished;
1509
1510         struct {
1511                 enum child_state state;
1512                 struct child_process process;
1513                 struct strbuf err;
1514                 void *data;
1515         } *children;
1516         /*
1517          * The struct pollfd is logically part of *children,
1518          * but the system call expects it as its own array.
1519          */
1520         struct pollfd *pfd;
1521
1522         unsigned shutdown : 1;
1523
1524         int output_owner;
1525         struct strbuf buffered_output; /* of finished children */
1526 };
1527
1528 static int default_start_failure(struct strbuf *out,
1529                                  void *pp_cb,
1530                                  void *pp_task_cb)
1531 {
1532         return 0;
1533 }
1534
1535 static int default_task_finished(int result,
1536                                  struct strbuf *out,
1537                                  void *pp_cb,
1538                                  void *pp_task_cb)
1539 {
1540         return 0;
1541 }
1542
1543 static void kill_children(struct parallel_processes *pp, int signo)
1544 {
1545         int i, n = pp->max_processes;
1546
1547         for (i = 0; i < n; i++)
1548                 if (pp->children[i].state == GIT_CP_WORKING)
1549                         kill(pp->children[i].process.pid, signo);
1550 }
1551
1552 static struct parallel_processes *pp_for_signal;
1553
1554 static void handle_children_on_signal(int signo)
1555 {
1556         kill_children(pp_for_signal, signo);
1557         sigchain_pop(signo);
1558         raise(signo);
1559 }
1560
1561 static void pp_init(struct parallel_processes *pp,
1562                     int n,
1563                     get_next_task_fn get_next_task,
1564                     start_failure_fn start_failure,
1565                     task_finished_fn task_finished,
1566                     void *data)
1567 {
1568         int i;
1569
1570         if (n < 1)
1571                 n = online_cpus();
1572
1573         pp->max_processes = n;
1574
1575         trace_printf("run_processes_parallel: preparing to run up to %d tasks", n);
1576
1577         pp->data = data;
1578         if (!get_next_task)
1579                 BUG("you need to specify a get_next_task function");
1580         pp->get_next_task = get_next_task;
1581
1582         pp->start_failure = start_failure ? start_failure : default_start_failure;
1583         pp->task_finished = task_finished ? task_finished : default_task_finished;
1584
1585         pp->nr_processes = 0;
1586         pp->output_owner = 0;
1587         pp->shutdown = 0;
1588         pp->children = xcalloc(n, sizeof(*pp->children));
1589         pp->pfd = xcalloc(n, sizeof(*pp->pfd));
1590         strbuf_init(&pp->buffered_output, 0);
1591
1592         for (i = 0; i < n; i++) {
1593                 strbuf_init(&pp->children[i].err, 0);
1594                 child_process_init(&pp->children[i].process);
1595                 pp->pfd[i].events = POLLIN | POLLHUP;
1596                 pp->pfd[i].fd = -1;
1597         }
1598
1599         pp_for_signal = pp;
1600         sigchain_push_common(handle_children_on_signal);
1601 }
1602
1603 static void pp_cleanup(struct parallel_processes *pp)
1604 {
1605         int i;
1606
1607         trace_printf("run_processes_parallel: done");
1608         for (i = 0; i < pp->max_processes; i++) {
1609                 strbuf_release(&pp->children[i].err);
1610                 child_process_clear(&pp->children[i].process);
1611         }
1612
1613         free(pp->children);
1614         free(pp->pfd);
1615
1616         /*
1617          * When get_next_task added messages to the buffer in its last
1618          * iteration, the buffered output is non empty.
1619          */
1620         strbuf_write(&pp->buffered_output, stderr);
1621         strbuf_release(&pp->buffered_output);
1622
1623         sigchain_pop_common();
1624 }
1625
1626 /* returns
1627  *  0 if a new task was started.
1628  *  1 if no new jobs was started (get_next_task ran out of work, non critical
1629  *    problem with starting a new command)
1630  * <0 no new job was started, user wishes to shutdown early. Use negative code
1631  *    to signal the children.
1632  */
1633 static int pp_start_one(struct parallel_processes *pp)
1634 {
1635         int i, code;
1636
1637         for (i = 0; i < pp->max_processes; i++)
1638                 if (pp->children[i].state == GIT_CP_FREE)
1639                         break;
1640         if (i == pp->max_processes)
1641                 BUG("bookkeeping is hard");
1642
1643         code = pp->get_next_task(&pp->children[i].process,
1644                                  &pp->children[i].err,
1645                                  pp->data,
1646                                  &pp->children[i].data);
1647         if (!code) {
1648                 strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1649                 strbuf_reset(&pp->children[i].err);
1650                 return 1;
1651         }
1652         pp->children[i].process.err = -1;
1653         pp->children[i].process.stdout_to_stderr = 1;
1654         pp->children[i].process.no_stdin = 1;
1655
1656         if (start_command(&pp->children[i].process)) {
1657                 code = pp->start_failure(&pp->children[i].err,
1658                                          pp->data,
1659                                          pp->children[i].data);
1660                 strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1661                 strbuf_reset(&pp->children[i].err);
1662                 if (code)
1663                         pp->shutdown = 1;
1664                 return code;
1665         }
1666
1667         pp->nr_processes++;
1668         pp->children[i].state = GIT_CP_WORKING;
1669         pp->pfd[i].fd = pp->children[i].process.err;
1670         return 0;
1671 }
1672
1673 static void pp_buffer_stderr(struct parallel_processes *pp, int output_timeout)
1674 {
1675         int i;
1676
1677         while ((i = poll(pp->pfd, pp->max_processes, output_timeout)) < 0) {
1678                 if (errno == EINTR)
1679                         continue;
1680                 pp_cleanup(pp);
1681                 die_errno("poll");
1682         }
1683
1684         /* Buffer output from all pipes. */
1685         for (i = 0; i < pp->max_processes; i++) {
1686                 if (pp->children[i].state == GIT_CP_WORKING &&
1687                     pp->pfd[i].revents & (POLLIN | POLLHUP)) {
1688                         int n = strbuf_read_once(&pp->children[i].err,
1689                                                  pp->children[i].process.err, 0);
1690                         if (n == 0) {
1691                                 close(pp->children[i].process.err);
1692                                 pp->children[i].state = GIT_CP_WAIT_CLEANUP;
1693                         } else if (n < 0)
1694                                 if (errno != EAGAIN)
1695                                         die_errno("read");
1696                 }
1697         }
1698 }
1699
1700 static void pp_output(struct parallel_processes *pp)
1701 {
1702         int i = pp->output_owner;
1703         if (pp->children[i].state == GIT_CP_WORKING &&
1704             pp->children[i].err.len) {
1705                 strbuf_write(&pp->children[i].err, stderr);
1706                 strbuf_reset(&pp->children[i].err);
1707         }
1708 }
1709
1710 static int pp_collect_finished(struct parallel_processes *pp)
1711 {
1712         int i, code;
1713         int n = pp->max_processes;
1714         int result = 0;
1715
1716         while (pp->nr_processes > 0) {
1717                 for (i = 0; i < pp->max_processes; i++)
1718                         if (pp->children[i].state == GIT_CP_WAIT_CLEANUP)
1719                                 break;
1720                 if (i == pp->max_processes)
1721                         break;
1722
1723                 code = finish_command(&pp->children[i].process);
1724
1725                 code = pp->task_finished(code,
1726                                          &pp->children[i].err, pp->data,
1727                                          pp->children[i].data);
1728
1729                 if (code)
1730                         result = code;
1731                 if (code < 0)
1732                         break;
1733
1734                 pp->nr_processes--;
1735                 pp->children[i].state = GIT_CP_FREE;
1736                 pp->pfd[i].fd = -1;
1737                 child_process_init(&pp->children[i].process);
1738
1739                 if (i != pp->output_owner) {
1740                         strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1741                         strbuf_reset(&pp->children[i].err);
1742                 } else {
1743                         strbuf_write(&pp->children[i].err, stderr);
1744                         strbuf_reset(&pp->children[i].err);
1745
1746                         /* Output all other finished child processes */
1747                         strbuf_write(&pp->buffered_output, stderr);
1748                         strbuf_reset(&pp->buffered_output);
1749
1750                         /*
1751                          * Pick next process to output live.
1752                          * NEEDSWORK:
1753                          * For now we pick it randomly by doing a round
1754                          * robin. Later we may want to pick the one with
1755                          * the most output or the longest or shortest
1756                          * running process time.
1757                          */
1758                         for (i = 0; i < n; i++)
1759                                 if (pp->children[(pp->output_owner + i) % n].state == GIT_CP_WORKING)
1760                                         break;
1761                         pp->output_owner = (pp->output_owner + i) % n;
1762                 }
1763         }
1764         return result;
1765 }
1766
1767 int run_processes_parallel(int n,
1768                            get_next_task_fn get_next_task,
1769                            start_failure_fn start_failure,
1770                            task_finished_fn task_finished,
1771                            void *pp_cb)
1772 {
1773         int i, code;
1774         int output_timeout = 100;
1775         int spawn_cap = 4;
1776         struct parallel_processes pp;
1777
1778         pp_init(&pp, n, get_next_task, start_failure, task_finished, pp_cb);
1779         while (1) {
1780                 for (i = 0;
1781                     i < spawn_cap && !pp.shutdown &&
1782                     pp.nr_processes < pp.max_processes;
1783                     i++) {
1784                         code = pp_start_one(&pp);
1785                         if (!code)
1786                                 continue;
1787                         if (code < 0) {
1788                                 pp.shutdown = 1;
1789                                 kill_children(&pp, -code);
1790                         }
1791                         break;
1792                 }
1793                 if (!pp.nr_processes)
1794                         break;
1795                 pp_buffer_stderr(&pp, output_timeout);
1796                 pp_output(&pp);
1797                 code = pp_collect_finished(&pp);
1798                 if (code) {
1799                         pp.shutdown = 1;
1800                         if (code < 0)
1801                                 kill_children(&pp, -code);
1802                 }
1803         }
1804
1805         pp_cleanup(&pp);
1806         return 0;
1807 }