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                 if (!cmd->silent_exec_failure)
 732                         error_errno("cannot run %s", cmd->argv[0]);
 733                 goto end_of_spawn;
 734         }
 735
 736         if (pipe(notify_pipe))
 737                 notify_pipe[0] = notify_pipe[1] = -1;
 738
 739         if (cmd->no_stdin || cmd->no_stdout || cmd->no_stderr) {
 740                 null_fd = open("/dev/null", O_RDWR | O_CLOEXEC);
 741                 if (null_fd < 0)
 742                         die_errno(_("open /dev/null failed"));
 743                 set_cloexec(null_fd);
 744         }
 745
 746         childenv = prep_childenv(cmd->env);
 747         atfork_prepare(&as);
 748
 749         /*
 750          * NOTE: In order to prevent deadlocking when using threads special
 751          * care should be taken with the function calls made in between the
 752          * fork() and exec() calls.  No calls should be made to functions which
 753          * require acquiring a lock (e.g. malloc) as the lock could have been
 754          * held by another thread at the time of forking, causing the lock to
 755          * never be released in the child process.  This means only
 756          * Async-Signal-Safe functions are permitted in the child.
 757          */
 758         cmd->pid = fork();
 759         failed_errno = errno;
 760         if (!cmd->pid) {
 761                 int sig;
 762                 /*
 763                  * Ensure the default die/error/warn routines do not get
 764                  * called, they can take stdio locks and malloc.
 765                  */
 766                 set_die_routine(child_die_fn);
 767                 set_error_routine(child_error_fn);
 768                 set_warn_routine(child_warn_fn);
 769
 770                 close(notify_pipe[0]);
 771                 set_cloexec(notify_pipe[1]);
 772                 child_notifier = notify_pipe[1];
 773
 774                 if (cmd->no_stdin)
 775                         child_dup2(null_fd, 0);
 776                 else if (need_in) {
 777                         child_dup2(fdin[0], 0);
 778                         child_close_pair(fdin);
 779                 } else if (cmd->in) {
 780                         child_dup2(cmd->in, 0);
 781                         child_close(cmd->in);
 782                 }
 783
 784                 if (cmd->no_stderr)
 785                         child_dup2(null_fd, 2);
 786                 else if (need_err) {
 787                         child_dup2(fderr[1], 2);
 788                         child_close_pair(fderr);
 789                 } else if (cmd->err > 1) {
 790                         child_dup2(cmd->err, 2);
 791                         child_close(cmd->err);
 792                 }
 793
 794                 if (cmd->no_stdout)
 795                         child_dup2(null_fd, 1);
 796                 else if (cmd->stdout_to_stderr)
 797                         child_dup2(2, 1);
 798                 else if (need_out) {
 799                         child_dup2(fdout[1], 1);
 800                         child_close_pair(fdout);
 801                 } else if (cmd->out > 1) {
 802                         child_dup2(cmd->out, 1);
 803                         child_close(cmd->out);
 804                 }
 805
 806                 if (cmd->dir && chdir(cmd->dir))
 807                         child_die(CHILD_ERR_CHDIR);
 808
 809                 /*
 810                  * restore default signal handlers here, in case
 811                  * we catch a signal right before execve below
 812                  */
 813                 for (sig = 1; sig < NSIG; sig++) {
 814                         /* ignored signals get reset to SIG_DFL on execve */
 815                         if (signal(sig, SIG_DFL) == SIG_IGN)
 816                                 signal(sig, SIG_IGN);
 817                 }
 818
 819                 if (sigprocmask(SIG_SETMASK, &as.old, NULL) != 0)
 820                         child_die(CHILD_ERR_SIGPROCMASK);
 821
 822                 /*
 823                  * Attempt to exec using the command and arguments starting at
 824                  * argv.argv[1].  argv.argv[0] contains SHELL_PATH which will
 825                  * be used in the event exec failed with ENOEXEC at which point
 826                  * we will try to interpret the command using 'sh'.
 827                  */
 828                 execve(argv.argv[1], (char *const *) argv.argv + 1,
 829                        (char *const *) childenv);
 830                 if (errno == ENOEXEC)
 831                         execve(argv.argv[0], (char *const *) argv.argv,
 832                                (char *const *) childenv);
 833
 834                 if (errno == ENOENT) {
 835                         if (cmd->silent_exec_failure)
 836                                 child_die(CHILD_ERR_SILENT);
 837                         child_die(CHILD_ERR_ENOENT);
 838                 } else {
 839                         child_die(CHILD_ERR_ERRNO);
 840                 }
 841         }
 842         atfork_parent(&as);
 843         if (cmd->pid < 0)
 844                 error_errno("cannot fork() for %s", cmd->argv[0]);
 845         else if (cmd->clean_on_exit)
 846                 mark_child_for_cleanup(cmd->pid, cmd);
 847
 848         /*
 849          * Wait for child's exec. If the exec succeeds (or if fork()
 850          * failed), EOF is seen immediately by the parent. Otherwise, the
 851          * child process sends a child_err struct.
 852          * Note that use of this infrastructure is completely advisory,
 853          * therefore, we keep error checks minimal.
 854          */
 855         close(notify_pipe[1]);
 856         if (xread(notify_pipe[0], &cerr, sizeof(cerr)) == sizeof(cerr)) {
 857                 /*
 858                  * At this point we know that fork() succeeded, but exec()
 859                  * failed. Errors have been reported to our stderr.
 860                  */
 861                 wait_or_whine(cmd->pid, cmd->argv[0], 0);
 862                 child_err_spew(cmd, &cerr);
 863                 failed_errno = errno;
 864                 cmd->pid = -1;
 865         }
 866         close(notify_pipe[0]);
 867
 868         if (null_fd >= 0)
 869                 close(null_fd);
 870         argv_array_clear(&argv);
 871         free(childenv);
 872 }
 873 end_of_spawn:
 874
 875 #else
 876 {
 877         int fhin = 0, fhout = 1, fherr = 2;
 878         const char **sargv = cmd->argv;
 879         struct argv_array nargv = ARGV_ARRAY_INIT;
 880
 881         if (cmd->no_stdin)
 882                 fhin = open("/dev/null", O_RDWR);
 883         else if (need_in)
 884                 fhin = dup(fdin[0]);
 885         else if (cmd->in)
 886                 fhin = dup(cmd->in);
 887
 888         if (cmd->no_stderr)
 889                 fherr = open("/dev/null", O_RDWR);
 890         else if (need_err)
 891                 fherr = dup(fderr[1]);
 892         else if (cmd->err > 2)
 893                 fherr = dup(cmd->err);
 894
 895         if (cmd->no_stdout)
 896                 fhout = open("/dev/null", O_RDWR);
 897         else if (cmd->stdout_to_stderr)
 898                 fhout = dup(fherr);
 899         else if (need_out)
 900                 fhout = dup(fdout[1]);
 901         else if (cmd->out > 1)
 902                 fhout = dup(cmd->out);
 903
 904         if (cmd->git_cmd)
 905                 cmd->argv = prepare_git_cmd(&nargv, cmd->argv);
 906         else if (cmd->use_shell)
 907                 cmd->argv = prepare_shell_cmd(&nargv, cmd->argv);
 908
 909         cmd->pid = mingw_spawnvpe(cmd->argv[0], cmd->argv, (char**) cmd->env,
 910                         cmd->dir, fhin, fhout, fherr);
 911         failed_errno = errno;
 912         if (cmd->pid < 0 && (!cmd->silent_exec_failure || errno != ENOENT))
 913                 error_errno("cannot spawn %s", cmd->argv[0]);
 914         if (cmd->clean_on_exit && cmd->pid >= 0)
 915                 mark_child_for_cleanup(cmd->pid, cmd);
 916
 917         argv_array_clear(&nargv);
 918         cmd->argv = sargv;
 919         if (fhin != 0)
 920                 close(fhin);
 921         if (fhout != 1)
 922                 close(fhout);
 923         if (fherr != 2)
 924                 close(fherr);
 925 }
 926 #endif
 927
 928         if (cmd->pid < 0) {
 929                 if (need_in)
 930                         close_pair(fdin);
 931                 else if (cmd->in)
 932                         close(cmd->in);
 933                 if (need_out)
 934                         close_pair(fdout);
 935                 else if (cmd->out)
 936                         close(cmd->out);
 937                 if (need_err)
 938                         close_pair(fderr);
 939                 else if (cmd->err)
 940                         close(cmd->err);
 941                 child_process_clear(cmd);
 942                 errno = failed_errno;
 943                 return -1;
 944         }
 945
 946         if (need_in)
 947                 close(fdin[0]);
 948         else if (cmd->in)
 949                 close(cmd->in);
 950
 951         if (need_out)
 952                 close(fdout[1]);
 953         else if (cmd->out)
 954                 close(cmd->out);
 955
 956         if (need_err)
 957                 close(fderr[1]);
 958         else if (cmd->err)
 959                 close(cmd->err);
 960
 961         return 0;
 962 }
 963
 964 int finish_command(struct child_process *cmd)
 965 {
 966         int ret = wait_or_whine(cmd->pid, cmd->argv[0], 0);
 967         child_process_clear(cmd);
 968         invalidate_lstat_cache();
 969         return ret;
 970 }
 971
 972 int finish_command_in_signal(struct child_process *cmd)
 973 {
 974         return wait_or_whine(cmd->pid, cmd->argv[0], 1);
 975 }
 976
 977
 978 int run_command(struct child_process *cmd)
 979 {
 980         int code;
 981
 982         if (cmd->out < 0 || cmd->err < 0)
 983                 BUG("run_command with a pipe can cause deadlock");
 984
 985         code = start_command(cmd);
 986         if (code)
 987                 return code;
 988         return finish_command(cmd);
 989 }
 990
 991 int run_command_v_opt(const char **argv, int opt)
 992 {
 993         return run_command_v_opt_cd_env(argv, opt, NULL, NULL);
 994 }
 995
 996 int run_command_v_opt_cd_env(const char **argv, int opt, const char *dir, const char *const *env)
 997 {
 998         struct child_process cmd = CHILD_PROCESS_INIT;
 999         cmd.argv = argv;
1000         cmd.no_stdin = opt & RUN_COMMAND_NO_STDIN ? 1 : 0;
1001         cmd.git_cmd = opt & RUN_GIT_CMD ? 1 : 0;
1002         cmd.stdout_to_stderr = opt & RUN_COMMAND_STDOUT_TO_STDERR ? 1 : 0;
1003         cmd.silent_exec_failure = opt & RUN_SILENT_EXEC_FAILURE ? 1 : 0;
1004         cmd.use_shell = opt & RUN_USING_SHELL ? 1 : 0;
1005         cmd.clean_on_exit = opt & RUN_CLEAN_ON_EXIT ? 1 : 0;
1006         cmd.dir = dir;
1007         cmd.env = env;
1008         return run_command(&cmd);
1009 }
1010
1011 #ifndef NO_PTHREADS
1012 static pthread_t main_thread;
1013 static int main_thread_set;
1014 static pthread_key_t async_key;
1015 static pthread_key_t async_die_counter;
1016
1017 static void *run_thread(void *data)
1018 {
1019         struct async *async = data;
1020         intptr_t ret;
1021
1022         if (async->isolate_sigpipe) {
1023                 sigset_t mask;
1024                 sigemptyset(&mask);
1025                 sigaddset(&mask, SIGPIPE);
1026                 if (pthread_sigmask(SIG_BLOCK, &mask, NULL) < 0) {
1027                         ret = error("unable to block SIGPIPE in async thread");
1028                         return (void *)ret;
1029                 }
1030         }
1031
1032         pthread_setspecific(async_key, async);
1033         ret = async->proc(async->proc_in, async->proc_out, async->data);
1034         return (void *)ret;
1035 }
1036
1037 static NORETURN void die_async(const char *err, va_list params)
1038 {
1039         vreportf("fatal: ", err, params);
1040
1041         if (in_async()) {
1042                 struct async *async = pthread_getspecific(async_key);
1043                 if (async->proc_in >= 0)
1044                         close(async->proc_in);
1045                 if (async->proc_out >= 0)
1046                         close(async->proc_out);
1047                 pthread_exit((void *)128);
1048         }
1049
1050         exit(128);
1051 }
1052
1053 static int async_die_is_recursing(void)
1054 {
1055         void *ret = pthread_getspecific(async_die_counter);
1056         pthread_setspecific(async_die_counter, (void *)1);
1057         return ret != NULL;
1058 }
1059
1060 int in_async(void)
1061 {
1062         if (!main_thread_set)
1063                 return 0; /* no asyncs started yet */
1064         return !pthread_equal(main_thread, pthread_self());
1065 }
1066
1067 static void NORETURN async_exit(int code)
1068 {
1069         pthread_exit((void *)(intptr_t)code);
1070 }
1071
1072 #else
1073
1074 static struct {
1075         void (**handlers)(void);
1076         size_t nr;
1077         size_t alloc;
1078 } git_atexit_hdlrs;
1079
1080 static int git_atexit_installed;
1081
1082 static void git_atexit_dispatch(void)
1083 {
1084         size_t i;
1085
1086         for (i=git_atexit_hdlrs.nr ; i ; i--)
1087                 git_atexit_hdlrs.handlers[i-1]();
1088 }
1089
1090 static void git_atexit_clear(void)
1091 {
1092         free(git_atexit_hdlrs.handlers);
1093         memset(&git_atexit_hdlrs, 0, sizeof(git_atexit_hdlrs));
1094         git_atexit_installed = 0;
1095 }
1096
1097 #undef atexit
1098 int git_atexit(void (*handler)(void))
1099 {
1100         ALLOC_GROW(git_atexit_hdlrs.handlers, git_atexit_hdlrs.nr + 1, git_atexit_hdlrs.alloc);
1101         git_atexit_hdlrs.handlers[git_atexit_hdlrs.nr++] = handler;
1102         if (!git_atexit_installed) {
1103                 if (atexit(&git_atexit_dispatch))
1104                         return -1;
1105                 git_atexit_installed = 1;
1106         }
1107         return 0;
1108 }
1109 #define atexit git_atexit
1110
1111 static int process_is_async;
1112 int in_async(void)
1113 {
1114         return process_is_async;
1115 }
1116
1117 static void NORETURN async_exit(int code)
1118 {
1119         exit(code);
1120 }
1121
1122 #endif
1123
1124 void check_pipe(int err)
1125 {
1126         if (err == EPIPE) {
1127                 if (in_async())
1128                         async_exit(141);
1129
1130                 signal(SIGPIPE, SIG_DFL);
1131                 raise(SIGPIPE);
1132                 /* Should never happen, but just in case... */
1133                 exit(141);
1134         }
1135 }
1136
1137 int start_async(struct async *async)
1138 {
1139         int need_in, need_out;
1140         int fdin[2], fdout[2];
1141         int proc_in, proc_out;
1142
1143         need_in = async->in < 0;
1144         if (need_in) {
1145                 if (pipe(fdin) < 0) {
1146                         if (async->out > 0)
1147                                 close(async->out);
1148                         return error_errno("cannot create pipe");
1149                 }
1150                 async->in = fdin[1];
1151         }
1152
1153         need_out = async->out < 0;
1154         if (need_out) {
1155                 if (pipe(fdout) < 0) {
1156                         if (need_in)
1157                                 close_pair(fdin);
1158                         else if (async->in)
1159                                 close(async->in);
1160                         return error_errno("cannot create pipe");
1161                 }
1162                 async->out = fdout[0];
1163         }
1164
1165         if (need_in)
1166                 proc_in = fdin[0];
1167         else if (async->in)
1168                 proc_in = async->in;
1169         else
1170                 proc_in = -1;
1171
1172         if (need_out)
1173                 proc_out = fdout[1];
1174         else if (async->out)
1175                 proc_out = async->out;
1176         else
1177                 proc_out = -1;
1178
1179 #ifdef NO_PTHREADS
1180         /* Flush stdio before fork() to avoid cloning buffers */
1181         fflush(NULL);
1182
1183         async->pid = fork();
1184         if (async->pid < 0) {
1185                 error_errno("fork (async) failed");
1186                 goto error;
1187         }
1188         if (!async->pid) {
1189                 if (need_in)
1190                         close(fdin[1]);
1191                 if (need_out)
1192                         close(fdout[0]);
1193                 git_atexit_clear();
1194                 process_is_async = 1;
1195                 exit(!!async->proc(proc_in, proc_out, async->data));
1196         }
1197
1198         mark_child_for_cleanup(async->pid, NULL);
1199
1200         if (need_in)
1201                 close(fdin[0]);
1202         else if (async->in)
1203                 close(async->in);
1204
1205         if (need_out)
1206                 close(fdout[1]);
1207         else if (async->out)
1208                 close(async->out);
1209 #else
1210         if (!main_thread_set) {
1211                 /*
1212                  * We assume that the first time that start_async is called
1213                  * it is from the main thread.
1214                  */
1215                 main_thread_set = 1;
1216                 main_thread = pthread_self();
1217                 pthread_key_create(&async_key, NULL);
1218                 pthread_key_create(&async_die_counter, NULL);
1219                 set_die_routine(die_async);
1220                 set_die_is_recursing_routine(async_die_is_recursing);
1221         }
1222
1223         if (proc_in >= 0)
1224                 set_cloexec(proc_in);
1225         if (proc_out >= 0)
1226                 set_cloexec(proc_out);
1227         async->proc_in = proc_in;
1228         async->proc_out = proc_out;
1229         {
1230                 int err = pthread_create(&async->tid, NULL, run_thread, async);
1231                 if (err) {
1232                         error(_("cannot create async thread: %s"), strerror(err));
1233                         goto error;
1234                 }
1235         }
1236 #endif
1237         return 0;
1238
1239 error:
1240         if (need_in)
1241                 close_pair(fdin);
1242         else if (async->in)
1243                 close(async->in);
1244
1245         if (need_out)
1246                 close_pair(fdout);
1247         else if (async->out)
1248                 close(async->out);
1249         return -1;
1250 }
1251
1252 int finish_async(struct async *async)
1253 {
1254 #ifdef NO_PTHREADS
1255         int ret = wait_or_whine(async->pid, "child process", 0);
1256
1257         invalidate_lstat_cache();
1258
1259         return ret;
1260 #else
1261         void *ret = (void *)(intptr_t)(-1);
1262
1263         if (pthread_join(async->tid, &ret))
1264                 error("pthread_join failed");
1265         invalidate_lstat_cache();
1266         return (int)(intptr_t)ret;
1267
1268 #endif
1269 }
1270
1271 int async_with_fork(void)
1272 {
1273 #ifdef NO_PTHREADS
1274         return 1;
1275 #else
1276         return 0;
1277 #endif
1278 }
1279
1280 const char *find_hook(const char *name)
1281 {
1282         static struct strbuf path = STRBUF_INIT;
1283
1284         strbuf_reset(&path);
1285         strbuf_git_path(&path, "hooks/%s", name);
1286         if (access(path.buf, X_OK) < 0) {
1287                 int err = errno;
1288
1289 #ifdef STRIP_EXTENSION
1290                 strbuf_addstr(&path, STRIP_EXTENSION);
1291                 if (access(path.buf, X_OK) >= 0)
1292                         return path.buf;
1293                 if (errno == EACCES)
1294                         err = errno;
1295 #endif
1296
1297                 if (err == EACCES && advice_ignored_hook) {
1298                         static struct string_list advise_given = STRING_LIST_INIT_DUP;
1299
1300                         if (!string_list_lookup(&advise_given, name)) {
1301                                 string_list_insert(&advise_given, name);
1302                                 advise(_("The '%s' hook was ignored because "
1303                                          "it's not set as executable.\n"
1304                                          "You can disable this warning with "
1305                                          "`git config advice.ignoredHook false`."),
1306                                        path.buf);
1307                         }
1308                 }
1309                 return NULL;
1310         }
1311         return path.buf;
1312 }
1313
1314 int run_hook_ve(const char *const *env, const char *name, va_list args)
1315 {
1316         struct child_process hook = CHILD_PROCESS_INIT;
1317         const char *p;
1318
1319         p = find_hook(name);
1320         if (!p)
1321                 return 0;
1322
1323         argv_array_push(&hook.args, p);
1324         while ((p = va_arg(args, const char *)))
1325                 argv_array_push(&hook.args, p);
1326         hook.env = env;
1327         hook.no_stdin = 1;
1328         hook.stdout_to_stderr = 1;
1329
1330         return run_command(&hook);
1331 }
1332
1333 int run_hook_le(const char *const *env, const char *name, ...)
1334 {
1335         va_list args;
1336         int ret;
1337
1338         va_start(args, name);
1339         ret = run_hook_ve(env, name, args);
1340         va_end(args);
1341
1342         return ret;
1343 }
1344
1345 struct io_pump {
1346         /* initialized by caller */
1347         int fd;
1348         int type; /* POLLOUT or POLLIN */
1349         union {
1350                 struct {
1351                         const char *buf;
1352                         size_t len;
1353                 } out;
1354                 struct {
1355                         struct strbuf *buf;
1356                         size_t hint;
1357                 } in;
1358         } u;
1359
1360         /* returned by pump_io */
1361         int error; /* 0 for success, otherwise errno */
1362
1363         /* internal use */
1364         struct pollfd *pfd;
1365 };
1366
1367 static int pump_io_round(struct io_pump *slots, int nr, struct pollfd *pfd)
1368 {
1369         int pollsize = 0;
1370         int i;
1371
1372         for (i = 0; i < nr; i++) {
1373                 struct io_pump *io = &slots[i];
1374                 if (io->fd < 0)
1375                         continue;
1376                 pfd[pollsize].fd = io->fd;
1377                 pfd[pollsize].events = io->type;
1378                 io->pfd = &pfd[pollsize++];
1379         }
1380
1381         if (!pollsize)
1382                 return 0;
1383
1384         if (poll(pfd, pollsize, -1) < 0) {
1385                 if (errno == EINTR)
1386                         return 1;
1387                 die_errno("poll failed");
1388         }
1389
1390         for (i = 0; i < nr; i++) {
1391                 struct io_pump *io = &slots[i];
1392
1393                 if (io->fd < 0)
1394                         continue;
1395
1396                 if (!(io->pfd->revents & (POLLOUT|POLLIN|POLLHUP|POLLERR|POLLNVAL)))
1397                         continue;
1398
1399                 if (io->type == POLLOUT) {
1400                         ssize_t len = xwrite(io->fd,
1401                                              io->u.out.buf, io->u.out.len);
1402                         if (len < 0) {
1403                                 io->error = errno;
1404                                 close(io->fd);
1405                                 io->fd = -1;
1406                         } else {
1407                                 io->u.out.buf += len;
1408                                 io->u.out.len -= len;
1409                                 if (!io->u.out.len) {
1410                                         close(io->fd);
1411                                         io->fd = -1;
1412                                 }
1413                         }
1414                 }
1415
1416                 if (io->type == POLLIN) {
1417                         ssize_t len = strbuf_read_once(io->u.in.buf,
1418                                                        io->fd, io->u.in.hint);
1419                         if (len < 0)
1420                                 io->error = errno;
1421                         if (len <= 0) {
1422                                 close(io->fd);
1423                                 io->fd = -1;
1424                         }
1425                 }
1426         }
1427
1428         return 1;
1429 }
1430
1431 static int pump_io(struct io_pump *slots, int nr)
1432 {
1433         struct pollfd *pfd;
1434         int i;
1435
1436         for (i = 0; i < nr; i++)
1437                 slots[i].error = 0;
1438
1439         ALLOC_ARRAY(pfd, nr);
1440         while (pump_io_round(slots, nr, pfd))
1441                 ; /* nothing */
1442         free(pfd);
1443
1444         /* There may be multiple errno values, so just pick the first. */
1445         for (i = 0; i < nr; i++) {
1446                 if (slots[i].error) {
1447                         errno = slots[i].error;
1448                         return -1;
1449                 }
1450         }
1451         return 0;
1452 }
1453
1454
1455 int pipe_command(struct child_process *cmd,
1456                  const char *in, size_t in_len,
1457                  struct strbuf *out, size_t out_hint,
1458                  struct strbuf *err, size_t err_hint)
1459 {
1460         struct io_pump io[3];
1461         int nr = 0;
1462
1463         if (in)
1464                 cmd->in = -1;
1465         if (out)
1466                 cmd->out = -1;
1467         if (err)
1468                 cmd->err = -1;
1469
1470         if (start_command(cmd) < 0)
1471                 return -1;
1472
1473         if (in) {
1474                 io[nr].fd = cmd->in;
1475                 io[nr].type = POLLOUT;
1476                 io[nr].u.out.buf = in;
1477                 io[nr].u.out.len = in_len;
1478                 nr++;
1479         }
1480         if (out) {
1481                 io[nr].fd = cmd->out;
1482                 io[nr].type = POLLIN;
1483                 io[nr].u.in.buf = out;
1484                 io[nr].u.in.hint = out_hint;
1485                 nr++;
1486         }
1487         if (err) {
1488                 io[nr].fd = cmd->err;
1489                 io[nr].type = POLLIN;
1490                 io[nr].u.in.buf = err;
1491                 io[nr].u.in.hint = err_hint;
1492                 nr++;
1493         }
1494
1495         if (pump_io(io, nr) < 0) {
1496                 finish_command(cmd); /* throw away exit code */
1497                 return -1;
1498         }
1499
1500         return finish_command(cmd);
1501 }
1502
1503 enum child_state {
1504         GIT_CP_FREE,
1505         GIT_CP_WORKING,
1506         GIT_CP_WAIT_CLEANUP,
1507 };
1508
1509 struct parallel_processes {
1510         void *data;
1511
1512         int max_processes;
1513         int nr_processes;
1514
1515         get_next_task_fn get_next_task;
1516         start_failure_fn start_failure;
1517         task_finished_fn task_finished;
1518
1519         struct {
1520                 enum child_state state;
1521                 struct child_process process;
1522                 struct strbuf err;
1523                 void *data;
1524         } *children;
1525         /*
1526          * The struct pollfd is logically part of *children,
1527          * but the system call expects it as its own array.
1528          */
1529         struct pollfd *pfd;
1530
1531         unsigned shutdown : 1;
1532
1533         int output_owner;
1534         struct strbuf buffered_output; /* of finished children */
1535 };
1536
1537 static int default_start_failure(struct strbuf *out,
1538                                  void *pp_cb,
1539                                  void *pp_task_cb)
1540 {
1541         return 0;
1542 }
1543
1544 static int default_task_finished(int result,
1545                                  struct strbuf *out,
1546                                  void *pp_cb,
1547                                  void *pp_task_cb)
1548 {
1549         return 0;
1550 }
1551
1552 static void kill_children(struct parallel_processes *pp, int signo)
1553 {
1554         int i, n = pp->max_processes;
1555
1556         for (i = 0; i < n; i++)
1557                 if (pp->children[i].state == GIT_CP_WORKING)
1558                         kill(pp->children[i].process.pid, signo);
1559 }
1560
1561 static struct parallel_processes *pp_for_signal;
1562
1563 static void handle_children_on_signal(int signo)
1564 {
1565         kill_children(pp_for_signal, signo);
1566         sigchain_pop(signo);
1567         raise(signo);
1568 }
1569
1570 static void pp_init(struct parallel_processes *pp,
1571                     int n,
1572                     get_next_task_fn get_next_task,
1573                     start_failure_fn start_failure,
1574                     task_finished_fn task_finished,
1575                     void *data)
1576 {
1577         int i;
1578
1579         if (n < 1)
1580                 n = online_cpus();
1581
1582         pp->max_processes = n;
1583
1584         trace_printf("run_processes_parallel: preparing to run up to %d tasks", n);
1585
1586         pp->data = data;
1587         if (!get_next_task)
1588                 BUG("you need to specify a get_next_task function");
1589         pp->get_next_task = get_next_task;
1590
1591         pp->start_failure = start_failure ? start_failure : default_start_failure;
1592         pp->task_finished = task_finished ? task_finished : default_task_finished;
1593
1594         pp->nr_processes = 0;
1595         pp->output_owner = 0;
1596         pp->shutdown = 0;
1597         pp->children = xcalloc(n, sizeof(*pp->children));
1598         pp->pfd = xcalloc(n, sizeof(*pp->pfd));
1599         strbuf_init(&pp->buffered_output, 0);
1600
1601         for (i = 0; i < n; i++) {
1602                 strbuf_init(&pp->children[i].err, 0);
1603                 child_process_init(&pp->children[i].process);
1604                 pp->pfd[i].events = POLLIN | POLLHUP;
1605                 pp->pfd[i].fd = -1;
1606         }
1607
1608         pp_for_signal = pp;
1609         sigchain_push_common(handle_children_on_signal);
1610 }
1611
1612 static void pp_cleanup(struct parallel_processes *pp)
1613 {
1614         int i;
1615
1616         trace_printf("run_processes_parallel: done");
1617         for (i = 0; i < pp->max_processes; i++) {
1618                 strbuf_release(&pp->children[i].err);
1619                 child_process_clear(&pp->children[i].process);
1620         }
1621
1622         free(pp->children);
1623         free(pp->pfd);
1624
1625         /*
1626          * When get_next_task added messages to the buffer in its last
1627          * iteration, the buffered output is non empty.
1628          */
1629         strbuf_write(&pp->buffered_output, stderr);
1630         strbuf_release(&pp->buffered_output);
1631
1632         sigchain_pop_common();
1633 }
1634
1635 /* returns
1636  *  0 if a new task was started.
1637  *  1 if no new jobs was started (get_next_task ran out of work, non critical
1638  *    problem with starting a new command)
1639  * <0 no new job was started, user wishes to shutdown early. Use negative code
1640  *    to signal the children.
1641  */
1642 static int pp_start_one(struct parallel_processes *pp)
1643 {
1644         int i, code;
1645
1646         for (i = 0; i < pp->max_processes; i++)
1647                 if (pp->children[i].state == GIT_CP_FREE)
1648                         break;
1649         if (i == pp->max_processes)
1650                 BUG("bookkeeping is hard");
1651
1652         code = pp->get_next_task(&pp->children[i].process,
1653                                  &pp->children[i].err,
1654                                  pp->data,
1655                                  &pp->children[i].data);
1656         if (!code) {
1657                 strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1658                 strbuf_reset(&pp->children[i].err);
1659                 return 1;
1660         }
1661         pp->children[i].process.err = -1;
1662         pp->children[i].process.stdout_to_stderr = 1;
1663         pp->children[i].process.no_stdin = 1;
1664
1665         if (start_command(&pp->children[i].process)) {
1666                 code = pp->start_failure(&pp->children[i].err,
1667                                          pp->data,
1668                                          pp->children[i].data);
1669                 strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1670                 strbuf_reset(&pp->children[i].err);
1671                 if (code)
1672                         pp->shutdown = 1;
1673                 return code;
1674         }
1675
1676         pp->nr_processes++;
1677         pp->children[i].state = GIT_CP_WORKING;
1678         pp->pfd[i].fd = pp->children[i].process.err;
1679         return 0;
1680 }
1681
1682 static void pp_buffer_stderr(struct parallel_processes *pp, int output_timeout)
1683 {
1684         int i;
1685
1686         while ((i = poll(pp->pfd, pp->max_processes, output_timeout)) < 0) {
1687                 if (errno == EINTR)
1688                         continue;
1689                 pp_cleanup(pp);
1690                 die_errno("poll");
1691         }
1692
1693         /* Buffer output from all pipes. */
1694         for (i = 0; i < pp->max_processes; i++) {
1695                 if (pp->children[i].state == GIT_CP_WORKING &&
1696                     pp->pfd[i].revents & (POLLIN | POLLHUP)) {
1697                         int n = strbuf_read_once(&pp->children[i].err,
1698                                                  pp->children[i].process.err, 0);
1699                         if (n == 0) {
1700                                 close(pp->children[i].process.err);
1701                                 pp->children[i].state = GIT_CP_WAIT_CLEANUP;
1702                         } else if (n < 0)
1703                                 if (errno != EAGAIN)
1704                                         die_errno("read");
1705                 }
1706         }
1707 }
1708
1709 static void pp_output(struct parallel_processes *pp)
1710 {
1711         int i = pp->output_owner;
1712         if (pp->children[i].state == GIT_CP_WORKING &&
1713             pp->children[i].err.len) {
1714                 strbuf_write(&pp->children[i].err, stderr);
1715                 strbuf_reset(&pp->children[i].err);
1716         }
1717 }
1718
1719 static int pp_collect_finished(struct parallel_processes *pp)
1720 {
1721         int i, code;
1722         int n = pp->max_processes;
1723         int result = 0;
1724
1725         while (pp->nr_processes > 0) {
1726                 for (i = 0; i < pp->max_processes; i++)
1727                         if (pp->children[i].state == GIT_CP_WAIT_CLEANUP)
1728                                 break;
1729                 if (i == pp->max_processes)
1730                         break;
1731
1732                 code = finish_command(&pp->children[i].process);
1733
1734                 code = pp->task_finished(code,
1735                                          &pp->children[i].err, pp->data,
1736                                          pp->children[i].data);
1737
1738                 if (code)
1739                         result = code;
1740                 if (code < 0)
1741                         break;
1742
1743                 pp->nr_processes--;
1744                 pp->children[i].state = GIT_CP_FREE;
1745                 pp->pfd[i].fd = -1;
1746                 child_process_init(&pp->children[i].process);
1747
1748                 if (i != pp->output_owner) {
1749                         strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1750                         strbuf_reset(&pp->children[i].err);
1751                 } else {
1752                         strbuf_write(&pp->children[i].err, stderr);
1753                         strbuf_reset(&pp->children[i].err);
1754
1755                         /* Output all other finished child processes */
1756                         strbuf_write(&pp->buffered_output, stderr);
1757                         strbuf_reset(&pp->buffered_output);
1758
1759                         /*
1760                          * Pick next process to output live.
1761                          * NEEDSWORK:
1762                          * For now we pick it randomly by doing a round
1763                          * robin. Later we may want to pick the one with
1764                          * the most output or the longest or shortest
1765                          * running process time.
1766                          */
1767                         for (i = 0; i < n; i++)
1768                                 if (pp->children[(pp->output_owner + i) % n].state == GIT_CP_WORKING)
1769                                         break;
1770                         pp->output_owner = (pp->output_owner + i) % n;
1771                 }
1772         }
1773         return result;
1774 }
1775
1776 int run_processes_parallel(int n,
1777                            get_next_task_fn get_next_task,
1778                            start_failure_fn start_failure,
1779                            task_finished_fn task_finished,
1780                            void *pp_cb)
1781 {
1782         int i, code;
1783         int output_timeout = 100;
1784         int spawn_cap = 4;
1785         struct parallel_processes pp;
1786
1787         pp_init(&pp, n, get_next_task, start_failure, task_finished, pp_cb);
1788         while (1) {
1789                 for (i = 0;
1790                     i < spawn_cap && !pp.shutdown &&
1791                     pp.nr_processes < pp.max_processes;
1792                     i++) {
1793                         code = pp_start_one(&pp);
1794                         if (!code)
1795                                 continue;
1796                         if (code < 0) {
1797                                 pp.shutdown = 1;
1798                                 kill_children(&pp, -code);
1799                         }
1800                         break;
1801                 }
1802                 if (!pp.nr_processes)
1803                         break;
1804                 pp_buffer_stderr(&pp, output_timeout);
1805                 pp_output(&pp);
1806                 code = pp_collect_finished(&pp);
1807                 if (code) {
1808                         pp.shutdown = 1;
1809                         if (code < 0)
1810                                 kill_children(&pp, -code);
1811                 }
1812         }
1813
1814         pp_cleanup(&pp);
1815         return 0;
1816 }