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 #ifndef GIT_WINDOWS_NATIVE
 223         /*
 224          * execvp() doesn't return, so we all we can do is tell trace2
 225          * what we are about to do and let it leave a hint in the log
 226          * (unless of course the execvp() fails).
 227          *
 228          * we skip this for Windows because the compat layer already
 229          * has to emulate the execvp() call anyway.
 230          */
 231         int exec_id = trace2_exec(file, (const char **)argv);
 232 #endif
 233
 234         if (!execvp(file, argv))
 235                 return 0; /* cannot happen ;-) */
 236
 237 #ifndef GIT_WINDOWS_NATIVE
 238         {
 239                 int ec = errno;
 240                 trace2_exec_result(exec_id, ec);
 241                 errno = ec;
 242         }
 243 #endif
 244
 245         /*
 246          * When a command can't be found because one of the directories
 247          * listed in $PATH is unsearchable, execvp reports EACCES, but
 248          * careful usability testing (read: analysis of occasional bug
 249          * reports) reveals that "No such file or directory" is more
 250          * intuitive.
 251          *
 252          * We avoid commands with "/", because execvp will not do $PATH
 253          * lookups in that case.
 254          *
 255          * The reassignment of EACCES to errno looks like a no-op below,
 256          * but we need to protect against exists_in_PATH overwriting errno.
 257          */
 258         if (errno == EACCES && !strchr(file, '/'))
 259                 errno = exists_in_PATH(file) ? EACCES : ENOENT;
 260         else if (errno == ENOTDIR && !strchr(file, '/'))
 261                 errno = ENOENT;
 262         return -1;
 263 }
 264
 265 static const char **prepare_shell_cmd(struct argv_array *out, const char **argv)
 266 {
 267         if (!argv[0])
 268                 BUG("shell command is empty");
 269
 270         if (strcspn(argv[0], "|&;<>()$`\\\"' \t\n*?[#~=%") != strlen(argv[0])) {
 271 #ifndef GIT_WINDOWS_NATIVE
 272                 argv_array_push(out, SHELL_PATH);
 273 #else
 274                 argv_array_push(out, "sh");
 275 #endif
 276                 argv_array_push(out, "-c");
 277
 278                 /*
 279                  * If we have no extra arguments, we do not even need to
 280                  * bother with the "$@" magic.
 281                  */
 282                 if (!argv[1])
 283                         argv_array_push(out, argv[0]);
 284                 else
 285                         argv_array_pushf(out, "%s \"$@\"", argv[0]);
 286         }
 287
 288         argv_array_pushv(out, argv);
 289         return out->argv;
 290 }
 291
 292 #ifndef GIT_WINDOWS_NATIVE
 293 static int child_notifier = -1;
 294
 295 enum child_errcode {
 296         CHILD_ERR_CHDIR,
 297         CHILD_ERR_DUP2,
 298         CHILD_ERR_CLOSE,
 299         CHILD_ERR_SIGPROCMASK,
 300         CHILD_ERR_ENOENT,
 301         CHILD_ERR_SILENT,
 302         CHILD_ERR_ERRNO
 303 };
 304
 305 struct child_err {
 306         enum child_errcode err;
 307         int syserr; /* errno */
 308 };
 309
 310 static void child_die(enum child_errcode err)
 311 {
 312         struct child_err buf;
 313
 314         buf.err = err;
 315         buf.syserr = errno;
 316
 317         /* write(2) on buf smaller than PIPE_BUF (min 512) is atomic: */
 318         xwrite(child_notifier, &buf, sizeof(buf));
 319         _exit(1);
 320 }
 321
 322 static void child_dup2(int fd, int to)
 323 {
 324         if (dup2(fd, to) < 0)
 325                 child_die(CHILD_ERR_DUP2);
 326 }
 327
 328 static void child_close(int fd)
 329 {
 330         if (close(fd))
 331                 child_die(CHILD_ERR_CLOSE);
 332 }
 333
 334 static void child_close_pair(int fd[2])
 335 {
 336         child_close(fd[0]);
 337         child_close(fd[1]);
 338 }
 339
 340 /*
 341  * parent will make it look like the child spewed a fatal error and died
 342  * this is needed to prevent changes to t0061.
 343  */
 344 static void fake_fatal(const char *err, va_list params)
 345 {
 346         vreportf("fatal: ", err, params);
 347 }
 348
 349 static void child_error_fn(const char *err, va_list params)
 350 {
 351         const char msg[] = "error() should not be called in child\n";
 352         xwrite(2, msg, sizeof(msg) - 1);
 353 }
 354
 355 static void child_warn_fn(const char *err, va_list params)
 356 {
 357         const char msg[] = "warn() should not be called in child\n";
 358         xwrite(2, msg, sizeof(msg) - 1);
 359 }
 360
 361 static void NORETURN child_die_fn(const char *err, va_list params)
 362 {
 363         const char msg[] = "die() should not be called in child\n";
 364         xwrite(2, msg, sizeof(msg) - 1);
 365         _exit(2);
 366 }
 367
 368 /* this runs in the parent process */
 369 static void child_err_spew(struct child_process *cmd, struct child_err *cerr)
 370 {
 371         static void (*old_errfn)(const char *err, va_list params);
 372
 373         old_errfn = get_error_routine();
 374         set_error_routine(fake_fatal);
 375         errno = cerr->syserr;
 376
 377         switch (cerr->err) {
 378         case CHILD_ERR_CHDIR:
 379                 error_errno("exec '%s': cd to '%s' failed",
 380                             cmd->argv[0], cmd->dir);
 381                 break;
 382         case CHILD_ERR_DUP2:
 383                 error_errno("dup2() in child failed");
 384                 break;
 385         case CHILD_ERR_CLOSE:
 386                 error_errno("close() in child failed");
 387                 break;
 388         case CHILD_ERR_SIGPROCMASK:
 389                 error_errno("sigprocmask failed restoring signals");
 390                 break;
 391         case CHILD_ERR_ENOENT:
 392                 error_errno("cannot run %s", cmd->argv[0]);
 393                 break;
 394         case CHILD_ERR_SILENT:
 395                 break;
 396         case CHILD_ERR_ERRNO:
 397                 error_errno("cannot exec '%s'", cmd->argv[0]);
 398                 break;
 399         }
 400         set_error_routine(old_errfn);
 401 }
 402
 403 static int prepare_cmd(struct argv_array *out, const struct child_process *cmd)
 404 {
 405         if (!cmd->argv[0])
 406                 BUG("command is empty");
 407
 408         /*
 409          * Add SHELL_PATH so in the event exec fails with ENOEXEC we can
 410          * attempt to interpret the command with 'sh'.
 411          */
 412         argv_array_push(out, SHELL_PATH);
 413
 414         if (cmd->git_cmd) {
 415                 prepare_git_cmd(out, cmd->argv);
 416         } else if (cmd->use_shell) {
 417                 prepare_shell_cmd(out, cmd->argv);
 418         } else {
 419                 argv_array_pushv(out, cmd->argv);
 420         }
 421
 422         /*
 423          * If there are no '/' characters in the command then perform a path
 424          * lookup and use the resolved path as the command to exec.  If there
 425          * are '/' characters, we have exec attempt to invoke the command
 426          * directly.
 427          */
 428         if (!strchr(out->argv[1], '/')) {
 429                 char *program = locate_in_PATH(out->argv[1]);
 430                 if (program) {
 431                         free((char *)out->argv[1]);
 432                         out->argv[1] = program;
 433                 } else {
 434                         argv_array_clear(out);
 435                         errno = ENOENT;
 436                         return -1;
 437                 }
 438         }
 439
 440         return 0;
 441 }
 442
 443 static char **prep_childenv(const char *const *deltaenv)
 444 {
 445         extern char **environ;
 446         char **childenv;
 447         struct string_list env = STRING_LIST_INIT_DUP;
 448         struct strbuf key = STRBUF_INIT;
 449         const char *const *p;
 450         int i;
 451
 452         /* Construct a sorted string list consisting of the current environ */
 453         for (p = (const char *const *) environ; p && *p; p++) {
 454                 const char *equals = strchr(*p, '=');
 455
 456                 if (equals) {
 457                         strbuf_reset(&key);
 458                         strbuf_add(&key, *p, equals - *p);
 459                         string_list_append(&env, key.buf)->util = (void *) *p;
 460                 } else {
 461                         string_list_append(&env, *p)->util = (void *) *p;
 462                 }
 463         }
 464         string_list_sort(&env);
 465
 466         /* Merge in 'deltaenv' with the current environ */
 467         for (p = deltaenv; p && *p; p++) {
 468                 const char *equals = strchr(*p, '=');
 469
 470                 if (equals) {
 471                         /* ('key=value'), insert or replace entry */
 472                         strbuf_reset(&key);
 473                         strbuf_add(&key, *p, equals - *p);
 474                         string_list_insert(&env, key.buf)->util = (void *) *p;
 475                 } else {
 476                         /* otherwise ('key') remove existing entry */
 477                         string_list_remove(&env, *p, 0);
 478                 }
 479         }
 480
 481         /* Create an array of 'char *' to be used as the childenv */
 482         ALLOC_ARRAY(childenv, env.nr + 1);
 483         for (i = 0; i < env.nr; i++)
 484                 childenv[i] = env.items[i].util;
 485         childenv[env.nr] = NULL;
 486
 487         string_list_clear(&env, 0);
 488         strbuf_release(&key);
 489         return childenv;
 490 }
 491
 492 struct atfork_state {
 493 #ifndef NO_PTHREADS
 494         int cs;
 495 #endif
 496         sigset_t old;
 497 };
 498
 499 #define CHECK_BUG(err, msg) \
 500         do { \
 501                 int e = (err); \
 502                 if (e) \
 503                         BUG("%s: %s", msg, strerror(e)); \
 504         } while(0)
 505
 506 static void atfork_prepare(struct atfork_state *as)
 507 {
 508         sigset_t all;
 509
 510         if (sigfillset(&all))
 511                 die_errno("sigfillset");
 512 #ifdef NO_PTHREADS
 513         if (sigprocmask(SIG_SETMASK, &all, &as->old))
 514                 die_errno("sigprocmask");
 515 #else
 516         CHECK_BUG(pthread_sigmask(SIG_SETMASK, &all, &as->old),
 517                 "blocking all signals");
 518         CHECK_BUG(pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &as->cs),
 519                 "disabling cancellation");
 520 #endif
 521 }
 522
 523 static void atfork_parent(struct atfork_state *as)
 524 {
 525 #ifdef NO_PTHREADS
 526         if (sigprocmask(SIG_SETMASK, &as->old, NULL))
 527                 die_errno("sigprocmask");
 528 #else
 529         CHECK_BUG(pthread_setcancelstate(as->cs, NULL),
 530                 "re-enabling cancellation");
 531         CHECK_BUG(pthread_sigmask(SIG_SETMASK, &as->old, NULL),
 532                 "restoring signal mask");
 533 #endif
 534 }
 535 #endif /* GIT_WINDOWS_NATIVE */
 536
 537 static inline void set_cloexec(int fd)
 538 {
 539         int flags = fcntl(fd, F_GETFD);
 540         if (flags >= 0)
 541                 fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
 542 }
 543
 544 static int wait_or_whine(pid_t pid, const char *argv0, int in_signal)
 545 {
 546         int status, code = -1;
 547         pid_t waiting;
 548         int failed_errno = 0;
 549
 550         while ((waiting = waitpid(pid, &status, 0)) < 0 && errno == EINTR)
 551                 ;       /* nothing */
 552         if (in_signal)
 553                 return 0;
 554
 555         if (waiting < 0) {
 556                 failed_errno = errno;
 557                 error_errno("waitpid for %s failed", argv0);
 558         } else if (waiting != pid) {
 559                 error("waitpid is confused (%s)", argv0);
 560         } else if (WIFSIGNALED(status)) {
 561                 code = WTERMSIG(status);
 562                 if (code != SIGINT && code != SIGQUIT && code != SIGPIPE)
 563                         error("%s died of signal %d", argv0, code);
 564                 /*
 565                  * This return value is chosen so that code & 0xff
 566                  * mimics the exit code that a POSIX shell would report for
 567                  * a program that died from this signal.
 568                  */
 569                 code += 128;
 570         } else if (WIFEXITED(status)) {
 571                 code = WEXITSTATUS(status);
 572         } else {
 573                 error("waitpid is confused (%s)", argv0);
 574         }
 575
 576         clear_child_for_cleanup(pid);
 577
 578         errno = failed_errno;
 579         return code;
 580 }
 581
 582 static void trace_add_env(struct strbuf *dst, const char *const *deltaenv)
 583 {
 584         struct string_list envs = STRING_LIST_INIT_DUP;
 585         const char *const *e;
 586         int i;
 587         int printed_unset = 0;
 588
 589         /* Last one wins, see run-command.c:prep_childenv() for context */
 590         for (e = deltaenv; e && *e; e++) {
 591                 struct strbuf key = STRBUF_INIT;
 592                 char *equals = strchr(*e, '=');
 593
 594                 if (equals) {
 595                         strbuf_add(&key, *e, equals - *e);
 596                         string_list_insert(&envs, key.buf)->util = equals + 1;
 597                 } else {
 598                         string_list_insert(&envs, *e)->util = NULL;
 599                 }
 600                 strbuf_release(&key);
 601         }
 602
 603         /* "unset X Y...;" */
 604         for (i = 0; i < envs.nr; i++) {
 605                 const char *var = envs.items[i].string;
 606                 const char *val = envs.items[i].util;
 607
 608                 if (val || !getenv(var))
 609                         continue;
 610
 611                 if (!printed_unset) {
 612                         strbuf_addstr(dst, " unset");
 613                         printed_unset = 1;
 614                 }
 615                 strbuf_addf(dst, " %s", var);
 616         }
 617         if (printed_unset)
 618                 strbuf_addch(dst, ';');
 619
 620         /* ... followed by "A=B C=D ..." */
 621         for (i = 0; i < envs.nr; i++) {
 622                 const char *var = envs.items[i].string;
 623                 const char *val = envs.items[i].util;
 624                 const char *oldval;
 625
 626                 if (!val)
 627                         continue;
 628
 629                 oldval = getenv(var);
 630                 if (oldval && !strcmp(val, oldval))
 631                         continue;
 632
 633                 strbuf_addf(dst, " %s=", var);
 634                 sq_quote_buf_pretty(dst, val);
 635         }
 636         string_list_clear(&envs, 0);
 637 }
 638
 639 static void trace_run_command(const struct child_process *cp)
 640 {
 641         struct strbuf buf = STRBUF_INIT;
 642
 643         if (!trace_want(&trace_default_key))
 644                 return;
 645
 646         strbuf_addstr(&buf, "trace: run_command:");
 647         if (cp->dir) {
 648                 strbuf_addstr(&buf, " cd ");
 649                 sq_quote_buf_pretty(&buf, cp->dir);
 650                 strbuf_addch(&buf, ';');
 651         }
 652         /*
 653          * The caller is responsible for initializing cp->env from
 654          * cp->env_array if needed. We only check one place.
 655          */
 656         if (cp->env)
 657                 trace_add_env(&buf, cp->env);
 658         if (cp->git_cmd)
 659                 strbuf_addstr(&buf, " git");
 660         sq_quote_argv_pretty(&buf, cp->argv);
 661
 662         trace_printf("%s", buf.buf);
 663         strbuf_release(&buf);
 664 }
 665
 666 int start_command(struct child_process *cmd)
 667 {
 668         int need_in, need_out, need_err;
 669         int fdin[2], fdout[2], fderr[2];
 670         int failed_errno;
 671         char *str;
 672
 673         if (!cmd->argv)
 674                 cmd->argv = cmd->args.argv;
 675         if (!cmd->env)
 676                 cmd->env = cmd->env_array.argv;
 677
 678         /*
 679          * In case of errors we must keep the promise to close FDs
 680          * that have been passed in via ->in and ->out.
 681          */
 682
 683         need_in = !cmd->no_stdin && cmd->in < 0;
 684         if (need_in) {
 685                 if (pipe(fdin) < 0) {
 686                         failed_errno = errno;
 687                         if (cmd->out > 0)
 688                                 close(cmd->out);
 689                         str = "standard input";
 690                         goto fail_pipe;
 691                 }
 692                 cmd->in = fdin[1];
 693         }
 694
 695         need_out = !cmd->no_stdout
 696                 && !cmd->stdout_to_stderr
 697                 && cmd->out < 0;
 698         if (need_out) {
 699                 if (pipe(fdout) < 0) {
 700                         failed_errno = errno;
 701                         if (need_in)
 702                                 close_pair(fdin);
 703                         else if (cmd->in)
 704                                 close(cmd->in);
 705                         str = "standard output";
 706                         goto fail_pipe;
 707                 }
 708                 cmd->out = fdout[0];
 709         }
 710
 711         need_err = !cmd->no_stderr && cmd->err < 0;
 712         if (need_err) {
 713                 if (pipe(fderr) < 0) {
 714                         failed_errno = errno;
 715                         if (need_in)
 716                                 close_pair(fdin);
 717                         else if (cmd->in)
 718                                 close(cmd->in);
 719                         if (need_out)
 720                                 close_pair(fdout);
 721                         else if (cmd->out)
 722                                 close(cmd->out);
 723                         str = "standard error";
 724 fail_pipe:
 725                         error("cannot create %s pipe for %s: %s",
 726                                 str, cmd->argv[0], strerror(failed_errno));
 727                         child_process_clear(cmd);
 728                         errno = failed_errno;
 729                         return -1;
 730                 }
 731                 cmd->err = fderr[0];
 732         }
 733
 734         trace2_child_start(cmd);
 735         trace_run_command(cmd);
 736
 737         fflush(NULL);
 738
 739 #ifndef GIT_WINDOWS_NATIVE
 740 {
 741         int notify_pipe[2];
 742         int null_fd = -1;
 743         char **childenv;
 744         struct argv_array argv = ARGV_ARRAY_INIT;
 745         struct child_err cerr;
 746         struct atfork_state as;
 747
 748         if (prepare_cmd(&argv, cmd) < 0) {
 749                 failed_errno = errno;
 750                 cmd->pid = -1;
 751                 if (!cmd->silent_exec_failure)
 752                         error_errno("cannot run %s", cmd->argv[0]);
 753                 goto end_of_spawn;
 754         }
 755
 756         if (pipe(notify_pipe))
 757                 notify_pipe[0] = notify_pipe[1] = -1;
 758
 759         if (cmd->no_stdin || cmd->no_stdout || cmd->no_stderr) {
 760                 null_fd = open("/dev/null", O_RDWR | O_CLOEXEC);
 761                 if (null_fd < 0)
 762                         die_errno(_("open /dev/null failed"));
 763                 set_cloexec(null_fd);
 764         }
 765
 766         childenv = prep_childenv(cmd->env);
 767         atfork_prepare(&as);
 768
 769         /*
 770          * NOTE: In order to prevent deadlocking when using threads special
 771          * care should be taken with the function calls made in between the
 772          * fork() and exec() calls.  No calls should be made to functions which
 773          * require acquiring a lock (e.g. malloc) as the lock could have been
 774          * held by another thread at the time of forking, causing the lock to
 775          * never be released in the child process.  This means only
 776          * Async-Signal-Safe functions are permitted in the child.
 777          */
 778         cmd->pid = fork();
 779         failed_errno = errno;
 780         if (!cmd->pid) {
 781                 int sig;
 782                 /*
 783                  * Ensure the default die/error/warn routines do not get
 784                  * called, they can take stdio locks and malloc.
 785                  */
 786                 set_die_routine(child_die_fn);
 787                 set_error_routine(child_error_fn);
 788                 set_warn_routine(child_warn_fn);
 789
 790                 close(notify_pipe[0]);
 791                 set_cloexec(notify_pipe[1]);
 792                 child_notifier = notify_pipe[1];
 793
 794                 if (cmd->no_stdin)
 795                         child_dup2(null_fd, 0);
 796                 else if (need_in) {
 797                         child_dup2(fdin[0], 0);
 798                         child_close_pair(fdin);
 799                 } else if (cmd->in) {
 800                         child_dup2(cmd->in, 0);
 801                         child_close(cmd->in);
 802                 }
 803
 804                 if (cmd->no_stderr)
 805                         child_dup2(null_fd, 2);
 806                 else if (need_err) {
 807                         child_dup2(fderr[1], 2);
 808                         child_close_pair(fderr);
 809                 } else if (cmd->err > 1) {
 810                         child_dup2(cmd->err, 2);
 811                         child_close(cmd->err);
 812                 }
 813
 814                 if (cmd->no_stdout)
 815                         child_dup2(null_fd, 1);
 816                 else if (cmd->stdout_to_stderr)
 817                         child_dup2(2, 1);
 818                 else if (need_out) {
 819                         child_dup2(fdout[1], 1);
 820                         child_close_pair(fdout);
 821                 } else if (cmd->out > 1) {
 822                         child_dup2(cmd->out, 1);
 823                         child_close(cmd->out);
 824                 }
 825
 826                 if (cmd->dir && chdir(cmd->dir))
 827                         child_die(CHILD_ERR_CHDIR);
 828
 829                 /*
 830                  * restore default signal handlers here, in case
 831                  * we catch a signal right before execve below
 832                  */
 833                 for (sig = 1; sig < NSIG; sig++) {
 834                         /* ignored signals get reset to SIG_DFL on execve */
 835                         if (signal(sig, SIG_DFL) == SIG_IGN)
 836                                 signal(sig, SIG_IGN);
 837                 }
 838
 839                 if (sigprocmask(SIG_SETMASK, &as.old, NULL) != 0)
 840                         child_die(CHILD_ERR_SIGPROCMASK);
 841
 842                 /*
 843                  * Attempt to exec using the command and arguments starting at
 844                  * argv.argv[1].  argv.argv[0] contains SHELL_PATH which will
 845                  * be used in the event exec failed with ENOEXEC at which point
 846                  * we will try to interpret the command using 'sh'.
 847                  */
 848                 execve(argv.argv[1], (char *const *) argv.argv + 1,
 849                        (char *const *) childenv);
 850                 if (errno == ENOEXEC)
 851                         execve(argv.argv[0], (char *const *) argv.argv,
 852                                (char *const *) childenv);
 853
 854                 if (errno == ENOENT) {
 855                         if (cmd->silent_exec_failure)
 856                                 child_die(CHILD_ERR_SILENT);
 857                         child_die(CHILD_ERR_ENOENT);
 858                 } else {
 859                         child_die(CHILD_ERR_ERRNO);
 860                 }
 861         }
 862         atfork_parent(&as);
 863         if (cmd->pid < 0)
 864                 error_errno("cannot fork() for %s", cmd->argv[0]);
 865         else if (cmd->clean_on_exit)
 866                 mark_child_for_cleanup(cmd->pid, cmd);
 867
 868         /*
 869          * Wait for child's exec. If the exec succeeds (or if fork()
 870          * failed), EOF is seen immediately by the parent. Otherwise, the
 871          * child process sends a child_err struct.
 872          * Note that use of this infrastructure is completely advisory,
 873          * therefore, we keep error checks minimal.
 874          */
 875         close(notify_pipe[1]);
 876         if (xread(notify_pipe[0], &cerr, sizeof(cerr)) == sizeof(cerr)) {
 877                 /*
 878                  * At this point we know that fork() succeeded, but exec()
 879                  * failed. Errors have been reported to our stderr.
 880                  */
 881                 wait_or_whine(cmd->pid, cmd->argv[0], 0);
 882                 child_err_spew(cmd, &cerr);
 883                 failed_errno = errno;
 884                 cmd->pid = -1;
 885         }
 886         close(notify_pipe[0]);
 887
 888         if (null_fd >= 0)
 889                 close(null_fd);
 890         argv_array_clear(&argv);
 891         free(childenv);
 892 }
 893 end_of_spawn:
 894
 895 #else
 896 {
 897         int fhin = 0, fhout = 1, fherr = 2;
 898         const char **sargv = cmd->argv;
 899         struct argv_array nargv = ARGV_ARRAY_INIT;
 900
 901         if (cmd->no_stdin)
 902                 fhin = open("/dev/null", O_RDWR);
 903         else if (need_in)
 904                 fhin = dup(fdin[0]);
 905         else if (cmd->in)
 906                 fhin = dup(cmd->in);
 907
 908         if (cmd->no_stderr)
 909                 fherr = open("/dev/null", O_RDWR);
 910         else if (need_err)
 911                 fherr = dup(fderr[1]);
 912         else if (cmd->err > 2)
 913                 fherr = dup(cmd->err);
 914
 915         if (cmd->no_stdout)
 916                 fhout = open("/dev/null", O_RDWR);
 917         else if (cmd->stdout_to_stderr)
 918                 fhout = dup(fherr);
 919         else if (need_out)
 920                 fhout = dup(fdout[1]);
 921         else if (cmd->out > 1)
 922                 fhout = dup(cmd->out);
 923
 924         if (cmd->git_cmd)
 925                 cmd->argv = prepare_git_cmd(&nargv, cmd->argv);
 926         else if (cmd->use_shell)
 927                 cmd->argv = prepare_shell_cmd(&nargv, cmd->argv);
 928
 929         cmd->pid = mingw_spawnvpe(cmd->argv[0], cmd->argv, (char**) cmd->env,
 930                         cmd->dir, fhin, fhout, fherr);
 931         failed_errno = errno;
 932         if (cmd->pid < 0 && (!cmd->silent_exec_failure || errno != ENOENT))
 933                 error_errno("cannot spawn %s", cmd->argv[0]);
 934         if (cmd->clean_on_exit && cmd->pid >= 0)
 935                 mark_child_for_cleanup(cmd->pid, cmd);
 936
 937         argv_array_clear(&nargv);
 938         cmd->argv = sargv;
 939         if (fhin != 0)
 940                 close(fhin);
 941         if (fhout != 1)
 942                 close(fhout);
 943         if (fherr != 2)
 944                 close(fherr);
 945 }
 946 #endif
 947
 948         if (cmd->pid < 0) {
 949                 trace2_child_exit(cmd, -1);
 950
 951                 if (need_in)
 952                         close_pair(fdin);
 953                 else if (cmd->in)
 954                         close(cmd->in);
 955                 if (need_out)
 956                         close_pair(fdout);
 957                 else if (cmd->out)
 958                         close(cmd->out);
 959                 if (need_err)
 960                         close_pair(fderr);
 961                 else if (cmd->err)
 962                         close(cmd->err);
 963                 child_process_clear(cmd);
 964                 errno = failed_errno;
 965                 return -1;
 966         }
 967
 968         if (need_in)
 969                 close(fdin[0]);
 970         else if (cmd->in)
 971                 close(cmd->in);
 972
 973         if (need_out)
 974                 close(fdout[1]);
 975         else if (cmd->out)
 976                 close(cmd->out);
 977
 978         if (need_err)
 979                 close(fderr[1]);
 980         else if (cmd->err)
 981                 close(cmd->err);
 982
 983         return 0;
 984 }
 985
 986 int finish_command(struct child_process *cmd)
 987 {
 988         int ret = wait_or_whine(cmd->pid, cmd->argv[0], 0);
 989         trace2_child_exit(cmd, ret);
 990         child_process_clear(cmd);
 991         return ret;
 992 }
 993
 994 int finish_command_in_signal(struct child_process *cmd)
 995 {
 996         int ret = wait_or_whine(cmd->pid, cmd->argv[0], 1);
 997         trace2_child_exit(cmd, ret);
 998         return ret;
 999 }
1000
1001
1002 int run_command(struct child_process *cmd)
1003 {
1004         int code;
1005
1006         if (cmd->out < 0 || cmd->err < 0)
1007                 BUG("run_command with a pipe can cause deadlock");
1008
1009         code = start_command(cmd);
1010         if (code)
1011                 return code;
1012         return finish_command(cmd);
1013 }
1014
1015 int run_command_v_opt(const char **argv, int opt)
1016 {
1017         return run_command_v_opt_cd_env(argv, opt, NULL, NULL);
1018 }
1019
1020 int run_command_v_opt_tr2(const char **argv, int opt, const char *tr2_class)
1021 {
1022         return run_command_v_opt_cd_env_tr2(argv, opt, NULL, NULL, tr2_class);
1023 }
1024
1025 int run_command_v_opt_cd_env(const char **argv, int opt, const char *dir, const char *const *env)
1026 {
1027         return run_command_v_opt_cd_env_tr2(argv, opt, dir, env, NULL);
1028 }
1029
1030 int run_command_v_opt_cd_env_tr2(const char **argv, int opt, const char *dir,
1031                                  const char *const *env, const char *tr2_class)
1032 {
1033         struct child_process cmd = CHILD_PROCESS_INIT;
1034         cmd.argv = argv;
1035         cmd.no_stdin = opt & RUN_COMMAND_NO_STDIN ? 1 : 0;
1036         cmd.git_cmd = opt & RUN_GIT_CMD ? 1 : 0;
1037         cmd.stdout_to_stderr = opt & RUN_COMMAND_STDOUT_TO_STDERR ? 1 : 0;
1038         cmd.silent_exec_failure = opt & RUN_SILENT_EXEC_FAILURE ? 1 : 0;
1039         cmd.use_shell = opt & RUN_USING_SHELL ? 1 : 0;
1040         cmd.clean_on_exit = opt & RUN_CLEAN_ON_EXIT ? 1 : 0;
1041         cmd.dir = dir;
1042         cmd.env = env;
1043         cmd.trace2_child_class = tr2_class;
1044         return run_command(&cmd);
1045 }
1046
1047 #ifndef NO_PTHREADS
1048 static pthread_t main_thread;
1049 static int main_thread_set;
1050 static pthread_key_t async_key;
1051 static pthread_key_t async_die_counter;
1052
1053 static void *run_thread(void *data)
1054 {
1055         struct async *async = data;
1056         intptr_t ret;
1057
1058         if (async->isolate_sigpipe) {
1059                 sigset_t mask;
1060                 sigemptyset(&mask);
1061                 sigaddset(&mask, SIGPIPE);
1062                 if (pthread_sigmask(SIG_BLOCK, &mask, NULL) < 0) {
1063                         ret = error("unable to block SIGPIPE in async thread");
1064                         return (void *)ret;
1065                 }
1066         }
1067
1068         pthread_setspecific(async_key, async);
1069         ret = async->proc(async->proc_in, async->proc_out, async->data);
1070         return (void *)ret;
1071 }
1072
1073 static NORETURN void die_async(const char *err, va_list params)
1074 {
1075         vreportf("fatal: ", err, params);
1076
1077         if (in_async()) {
1078                 struct async *async = pthread_getspecific(async_key);
1079                 if (async->proc_in >= 0)
1080                         close(async->proc_in);
1081                 if (async->proc_out >= 0)
1082                         close(async->proc_out);
1083                 pthread_exit((void *)128);
1084         }
1085
1086         exit(128);
1087 }
1088
1089 static int async_die_is_recursing(void)
1090 {
1091         void *ret = pthread_getspecific(async_die_counter);
1092         pthread_setspecific(async_die_counter, (void *)1);
1093         return ret != NULL;
1094 }
1095
1096 int in_async(void)
1097 {
1098         if (!main_thread_set)
1099                 return 0; /* no asyncs started yet */
1100         return !pthread_equal(main_thread, pthread_self());
1101 }
1102
1103 static void NORETURN async_exit(int code)
1104 {
1105         pthread_exit((void *)(intptr_t)code);
1106 }
1107
1108 #else
1109
1110 static struct {
1111         void (**handlers)(void);
1112         size_t nr;
1113         size_t alloc;
1114 } git_atexit_hdlrs;
1115
1116 static int git_atexit_installed;
1117
1118 static void git_atexit_dispatch(void)
1119 {
1120         size_t i;
1121
1122         for (i=git_atexit_hdlrs.nr ; i ; i--)
1123                 git_atexit_hdlrs.handlers[i-1]();
1124 }
1125
1126 static void git_atexit_clear(void)
1127 {
1128         free(git_atexit_hdlrs.handlers);
1129         memset(&git_atexit_hdlrs, 0, sizeof(git_atexit_hdlrs));
1130         git_atexit_installed = 0;
1131 }
1132
1133 #undef atexit
1134 int git_atexit(void (*handler)(void))
1135 {
1136         ALLOC_GROW(git_atexit_hdlrs.handlers, git_atexit_hdlrs.nr + 1, git_atexit_hdlrs.alloc);
1137         git_atexit_hdlrs.handlers[git_atexit_hdlrs.nr++] = handler;
1138         if (!git_atexit_installed) {
1139                 if (atexit(&git_atexit_dispatch))
1140                         return -1;
1141                 git_atexit_installed = 1;
1142         }
1143         return 0;
1144 }
1145 #define atexit git_atexit
1146
1147 static int process_is_async;
1148 int in_async(void)
1149 {
1150         return process_is_async;
1151 }
1152
1153 static void NORETURN async_exit(int code)
1154 {
1155         exit(code);
1156 }
1157
1158 #endif
1159
1160 void check_pipe(int err)
1161 {
1162         if (err == EPIPE) {
1163                 if (in_async())
1164                         async_exit(141);
1165
1166                 signal(SIGPIPE, SIG_DFL);
1167                 raise(SIGPIPE);
1168                 /* Should never happen, but just in case... */
1169                 exit(141);
1170         }
1171 }
1172
1173 int start_async(struct async *async)
1174 {
1175         int need_in, need_out;
1176         int fdin[2], fdout[2];
1177         int proc_in, proc_out;
1178
1179         need_in = async->in < 0;
1180         if (need_in) {
1181                 if (pipe(fdin) < 0) {
1182                         if (async->out > 0)
1183                                 close(async->out);
1184                         return error_errno("cannot create pipe");
1185                 }
1186                 async->in = fdin[1];
1187         }
1188
1189         need_out = async->out < 0;
1190         if (need_out) {
1191                 if (pipe(fdout) < 0) {
1192                         if (need_in)
1193                                 close_pair(fdin);
1194                         else if (async->in)
1195                                 close(async->in);
1196                         return error_errno("cannot create pipe");
1197                 }
1198                 async->out = fdout[0];
1199         }
1200
1201         if (need_in)
1202                 proc_in = fdin[0];
1203         else if (async->in)
1204                 proc_in = async->in;
1205         else
1206                 proc_in = -1;
1207
1208         if (need_out)
1209                 proc_out = fdout[1];
1210         else if (async->out)
1211                 proc_out = async->out;
1212         else
1213                 proc_out = -1;
1214
1215 #ifdef NO_PTHREADS
1216         /* Flush stdio before fork() to avoid cloning buffers */
1217         fflush(NULL);
1218
1219         async->pid = fork();
1220         if (async->pid < 0) {
1221                 error_errno("fork (async) failed");
1222                 goto error;
1223         }
1224         if (!async->pid) {
1225                 if (need_in)
1226                         close(fdin[1]);
1227                 if (need_out)
1228                         close(fdout[0]);
1229                 git_atexit_clear();
1230                 process_is_async = 1;
1231                 exit(!!async->proc(proc_in, proc_out, async->data));
1232         }
1233
1234         mark_child_for_cleanup(async->pid, NULL);
1235
1236         if (need_in)
1237                 close(fdin[0]);
1238         else if (async->in)
1239                 close(async->in);
1240
1241         if (need_out)
1242                 close(fdout[1]);
1243         else if (async->out)
1244                 close(async->out);
1245 #else
1246         if (!main_thread_set) {
1247                 /*
1248                  * We assume that the first time that start_async is called
1249                  * it is from the main thread.
1250                  */
1251                 main_thread_set = 1;
1252                 main_thread = pthread_self();
1253                 pthread_key_create(&async_key, NULL);
1254                 pthread_key_create(&async_die_counter, NULL);
1255                 set_die_routine(die_async);
1256                 set_die_is_recursing_routine(async_die_is_recursing);
1257         }
1258
1259         if (proc_in >= 0)
1260                 set_cloexec(proc_in);
1261         if (proc_out >= 0)
1262                 set_cloexec(proc_out);
1263         async->proc_in = proc_in;
1264         async->proc_out = proc_out;
1265         {
1266                 int err = pthread_create(&async->tid, NULL, run_thread, async);
1267                 if (err) {
1268                         error(_("cannot create async thread: %s"), strerror(err));
1269                         goto error;
1270                 }
1271         }
1272 #endif
1273         return 0;
1274
1275 error:
1276         if (need_in)
1277                 close_pair(fdin);
1278         else if (async->in)
1279                 close(async->in);
1280
1281         if (need_out)
1282                 close_pair(fdout);
1283         else if (async->out)
1284                 close(async->out);
1285         return -1;
1286 }
1287
1288 int finish_async(struct async *async)
1289 {
1290 #ifdef NO_PTHREADS
1291         return wait_or_whine(async->pid, "child process", 0);
1292 #else
1293         void *ret = (void *)(intptr_t)(-1);
1294
1295         if (pthread_join(async->tid, &ret))
1296                 error("pthread_join failed");
1297         return (int)(intptr_t)ret;
1298 #endif
1299 }
1300
1301 int async_with_fork(void)
1302 {
1303 #ifdef NO_PTHREADS
1304         return 1;
1305 #else
1306         return 0;
1307 #endif
1308 }
1309
1310 const char *find_hook(const char *name)
1311 {
1312         static struct strbuf path = STRBUF_INIT;
1313
1314         strbuf_reset(&path);
1315         strbuf_git_path(&path, "hooks/%s", name);
1316         if (access(path.buf, X_OK) < 0) {
1317                 int err = errno;
1318
1319 #ifdef STRIP_EXTENSION
1320                 strbuf_addstr(&path, STRIP_EXTENSION);
1321                 if (access(path.buf, X_OK) >= 0)
1322                         return path.buf;
1323                 if (errno == EACCES)
1324                         err = errno;
1325 #endif
1326
1327                 if (err == EACCES && advice_ignored_hook) {
1328                         static struct string_list advise_given = STRING_LIST_INIT_DUP;
1329
1330                         if (!string_list_lookup(&advise_given, name)) {
1331                                 string_list_insert(&advise_given, name);
1332                                 advise(_("The '%s' hook was ignored because "
1333                                          "it's not set as executable.\n"
1334                                          "You can disable this warning with "
1335                                          "`git config advice.ignoredHook false`."),
1336                                        path.buf);
1337                         }
1338                 }
1339                 return NULL;
1340         }
1341         return path.buf;
1342 }
1343
1344 int run_hook_ve(const char *const *env, const char *name, va_list args)
1345 {
1346         struct child_process hook = CHILD_PROCESS_INIT;
1347         const char *p;
1348
1349         p = find_hook(name);
1350         if (!p)
1351                 return 0;
1352
1353         argv_array_push(&hook.args, p);
1354         while ((p = va_arg(args, const char *)))
1355                 argv_array_push(&hook.args, p);
1356         hook.env = env;
1357         hook.no_stdin = 1;
1358         hook.stdout_to_stderr = 1;
1359         hook.trace2_hook_name = name;
1360
1361         return run_command(&hook);
1362 }
1363
1364 int run_hook_le(const char *const *env, const char *name, ...)
1365 {
1366         va_list args;
1367         int ret;
1368
1369         va_start(args, name);
1370         ret = run_hook_ve(env, name, args);
1371         va_end(args);
1372
1373         return ret;
1374 }
1375
1376 struct io_pump {
1377         /* initialized by caller */
1378         int fd;
1379         int type; /* POLLOUT or POLLIN */
1380         union {
1381                 struct {
1382                         const char *buf;
1383                         size_t len;
1384                 } out;
1385                 struct {
1386                         struct strbuf *buf;
1387                         size_t hint;
1388                 } in;
1389         } u;
1390
1391         /* returned by pump_io */
1392         int error; /* 0 for success, otherwise errno */
1393
1394         /* internal use */
1395         struct pollfd *pfd;
1396 };
1397
1398 static int pump_io_round(struct io_pump *slots, int nr, struct pollfd *pfd)
1399 {
1400         int pollsize = 0;
1401         int i;
1402
1403         for (i = 0; i < nr; i++) {
1404                 struct io_pump *io = &slots[i];
1405                 if (io->fd < 0)
1406                         continue;
1407                 pfd[pollsize].fd = io->fd;
1408                 pfd[pollsize].events = io->type;
1409                 io->pfd = &pfd[pollsize++];
1410         }
1411
1412         if (!pollsize)
1413                 return 0;
1414
1415         if (poll(pfd, pollsize, -1) < 0) {
1416                 if (errno == EINTR)
1417                         return 1;
1418                 die_errno("poll failed");
1419         }
1420
1421         for (i = 0; i < nr; i++) {
1422                 struct io_pump *io = &slots[i];
1423
1424                 if (io->fd < 0)
1425                         continue;
1426
1427                 if (!(io->pfd->revents & (POLLOUT|POLLIN|POLLHUP|POLLERR|POLLNVAL)))
1428                         continue;
1429
1430                 if (io->type == POLLOUT) {
1431                         ssize_t len = xwrite(io->fd,
1432                                              io->u.out.buf, io->u.out.len);
1433                         if (len < 0) {
1434                                 io->error = errno;
1435                                 close(io->fd);
1436                                 io->fd = -1;
1437                         } else {
1438                                 io->u.out.buf += len;
1439                                 io->u.out.len -= len;
1440                                 if (!io->u.out.len) {
1441                                         close(io->fd);
1442                                         io->fd = -1;
1443                                 }
1444                         }
1445                 }
1446
1447                 if (io->type == POLLIN) {
1448                         ssize_t len = strbuf_read_once(io->u.in.buf,
1449                                                        io->fd, io->u.in.hint);
1450                         if (len < 0)
1451                                 io->error = errno;
1452                         if (len <= 0) {
1453                                 close(io->fd);
1454                                 io->fd = -1;
1455                         }
1456                 }
1457         }
1458
1459         return 1;
1460 }
1461
1462 static int pump_io(struct io_pump *slots, int nr)
1463 {
1464         struct pollfd *pfd;
1465         int i;
1466
1467         for (i = 0; i < nr; i++)
1468                 slots[i].error = 0;
1469
1470         ALLOC_ARRAY(pfd, nr);
1471         while (pump_io_round(slots, nr, pfd))
1472                 ; /* nothing */
1473         free(pfd);
1474
1475         /* There may be multiple errno values, so just pick the first. */
1476         for (i = 0; i < nr; i++) {
1477                 if (slots[i].error) {
1478                         errno = slots[i].error;
1479                         return -1;
1480                 }
1481         }
1482         return 0;
1483 }
1484
1485
1486 int pipe_command(struct child_process *cmd,
1487                  const char *in, size_t in_len,
1488                  struct strbuf *out, size_t out_hint,
1489                  struct strbuf *err, size_t err_hint)
1490 {
1491         struct io_pump io[3];
1492         int nr = 0;
1493
1494         if (in)
1495                 cmd->in = -1;
1496         if (out)
1497                 cmd->out = -1;
1498         if (err)
1499                 cmd->err = -1;
1500
1501         if (start_command(cmd) < 0)
1502                 return -1;
1503
1504         if (in) {
1505                 io[nr].fd = cmd->in;
1506                 io[nr].type = POLLOUT;
1507                 io[nr].u.out.buf = in;
1508                 io[nr].u.out.len = in_len;
1509                 nr++;
1510         }
1511         if (out) {
1512                 io[nr].fd = cmd->out;
1513                 io[nr].type = POLLIN;
1514                 io[nr].u.in.buf = out;
1515                 io[nr].u.in.hint = out_hint;
1516                 nr++;
1517         }
1518         if (err) {
1519                 io[nr].fd = cmd->err;
1520                 io[nr].type = POLLIN;
1521                 io[nr].u.in.buf = err;
1522                 io[nr].u.in.hint = err_hint;
1523                 nr++;
1524         }
1525
1526         if (pump_io(io, nr) < 0) {
1527                 finish_command(cmd); /* throw away exit code */
1528                 return -1;
1529         }
1530
1531         return finish_command(cmd);
1532 }
1533
1534 enum child_state {
1535         GIT_CP_FREE,
1536         GIT_CP_WORKING,
1537         GIT_CP_WAIT_CLEANUP,
1538 };
1539
1540 struct parallel_processes {
1541         void *data;
1542
1543         int max_processes;
1544         int nr_processes;
1545
1546         get_next_task_fn get_next_task;
1547         start_failure_fn start_failure;
1548         task_finished_fn task_finished;
1549
1550         struct {
1551                 enum child_state state;
1552                 struct child_process process;
1553                 struct strbuf err;
1554                 void *data;
1555         } *children;
1556         /*
1557          * The struct pollfd is logically part of *children,
1558          * but the system call expects it as its own array.
1559          */
1560         struct pollfd *pfd;
1561
1562         unsigned shutdown : 1;
1563
1564         int output_owner;
1565         struct strbuf buffered_output; /* of finished children */
1566 };
1567
1568 static int default_start_failure(struct strbuf *out,
1569                                  void *pp_cb,
1570                                  void *pp_task_cb)
1571 {
1572         return 0;
1573 }
1574
1575 static int default_task_finished(int result,
1576                                  struct strbuf *out,
1577                                  void *pp_cb,
1578                                  void *pp_task_cb)
1579 {
1580         return 0;
1581 }
1582
1583 static void kill_children(struct parallel_processes *pp, int signo)
1584 {
1585         int i, n = pp->max_processes;
1586
1587         for (i = 0; i < n; i++)
1588                 if (pp->children[i].state == GIT_CP_WORKING)
1589                         kill(pp->children[i].process.pid, signo);
1590 }
1591
1592 static struct parallel_processes *pp_for_signal;
1593
1594 static void handle_children_on_signal(int signo)
1595 {
1596         kill_children(pp_for_signal, signo);
1597         sigchain_pop(signo);
1598         raise(signo);
1599 }
1600
1601 static void pp_init(struct parallel_processes *pp,
1602                     int n,
1603                     get_next_task_fn get_next_task,
1604                     start_failure_fn start_failure,
1605                     task_finished_fn task_finished,
1606                     void *data)
1607 {
1608         int i;
1609
1610         if (n < 1)
1611                 n = online_cpus();
1612
1613         pp->max_processes = n;
1614
1615         trace_printf("run_processes_parallel: preparing to run up to %d tasks", n);
1616
1617         pp->data = data;
1618         if (!get_next_task)
1619                 BUG("you need to specify a get_next_task function");
1620         pp->get_next_task = get_next_task;
1621
1622         pp->start_failure = start_failure ? start_failure : default_start_failure;
1623         pp->task_finished = task_finished ? task_finished : default_task_finished;
1624
1625         pp->nr_processes = 0;
1626         pp->output_owner = 0;
1627         pp->shutdown = 0;
1628         pp->children = xcalloc(n, sizeof(*pp->children));
1629         pp->pfd = xcalloc(n, sizeof(*pp->pfd));
1630         strbuf_init(&pp->buffered_output, 0);
1631
1632         for (i = 0; i < n; i++) {
1633                 strbuf_init(&pp->children[i].err, 0);
1634                 child_process_init(&pp->children[i].process);
1635                 pp->pfd[i].events = POLLIN | POLLHUP;
1636                 pp->pfd[i].fd = -1;
1637         }
1638
1639         pp_for_signal = pp;
1640         sigchain_push_common(handle_children_on_signal);
1641 }
1642
1643 static void pp_cleanup(struct parallel_processes *pp)
1644 {
1645         int i;
1646
1647         trace_printf("run_processes_parallel: done");
1648         for (i = 0; i < pp->max_processes; i++) {
1649                 strbuf_release(&pp->children[i].err);
1650                 child_process_clear(&pp->children[i].process);
1651         }
1652
1653         free(pp->children);
1654         free(pp->pfd);
1655
1656         /*
1657          * When get_next_task added messages to the buffer in its last
1658          * iteration, the buffered output is non empty.
1659          */
1660         strbuf_write(&pp->buffered_output, stderr);
1661         strbuf_release(&pp->buffered_output);
1662
1663         sigchain_pop_common();
1664 }
1665
1666 /* returns
1667  *  0 if a new task was started.
1668  *  1 if no new jobs was started (get_next_task ran out of work, non critical
1669  *    problem with starting a new command)
1670  * <0 no new job was started, user wishes to shutdown early. Use negative code
1671  *    to signal the children.
1672  */
1673 static int pp_start_one(struct parallel_processes *pp)
1674 {
1675         int i, code;
1676
1677         for (i = 0; i < pp->max_processes; i++)
1678                 if (pp->children[i].state == GIT_CP_FREE)
1679                         break;
1680         if (i == pp->max_processes)
1681                 BUG("bookkeeping is hard");
1682
1683         code = pp->get_next_task(&pp->children[i].process,
1684                                  &pp->children[i].err,
1685                                  pp->data,
1686                                  &pp->children[i].data);
1687         if (!code) {
1688                 strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1689                 strbuf_reset(&pp->children[i].err);
1690                 return 1;
1691         }
1692         pp->children[i].process.err = -1;
1693         pp->children[i].process.stdout_to_stderr = 1;
1694         pp->children[i].process.no_stdin = 1;
1695
1696         if (start_command(&pp->children[i].process)) {
1697                 code = pp->start_failure(&pp->children[i].err,
1698                                          pp->data,
1699                                          pp->children[i].data);
1700                 strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1701                 strbuf_reset(&pp->children[i].err);
1702                 if (code)
1703                         pp->shutdown = 1;
1704                 return code;
1705         }
1706
1707         pp->nr_processes++;
1708         pp->children[i].state = GIT_CP_WORKING;
1709         pp->pfd[i].fd = pp->children[i].process.err;
1710         return 0;
1711 }
1712
1713 static void pp_buffer_stderr(struct parallel_processes *pp, int output_timeout)
1714 {
1715         int i;
1716
1717         while ((i = poll(pp->pfd, pp->max_processes, output_timeout)) < 0) {
1718                 if (errno == EINTR)
1719                         continue;
1720                 pp_cleanup(pp);
1721                 die_errno("poll");
1722         }
1723
1724         /* Buffer output from all pipes. */
1725         for (i = 0; i < pp->max_processes; i++) {
1726                 if (pp->children[i].state == GIT_CP_WORKING &&
1727                     pp->pfd[i].revents & (POLLIN | POLLHUP)) {
1728                         int n = strbuf_read_once(&pp->children[i].err,
1729                                                  pp->children[i].process.err, 0);
1730                         if (n == 0) {
1731                                 close(pp->children[i].process.err);
1732                                 pp->children[i].state = GIT_CP_WAIT_CLEANUP;
1733                         } else if (n < 0)
1734                                 if (errno != EAGAIN)
1735                                         die_errno("read");
1736                 }
1737         }
1738 }
1739
1740 static void pp_output(struct parallel_processes *pp)
1741 {
1742         int i = pp->output_owner;
1743         if (pp->children[i].state == GIT_CP_WORKING &&
1744             pp->children[i].err.len) {
1745                 strbuf_write(&pp->children[i].err, stderr);
1746                 strbuf_reset(&pp->children[i].err);
1747         }
1748 }
1749
1750 static int pp_collect_finished(struct parallel_processes *pp)
1751 {
1752         int i, code;
1753         int n = pp->max_processes;
1754         int result = 0;
1755
1756         while (pp->nr_processes > 0) {
1757                 for (i = 0; i < pp->max_processes; i++)
1758                         if (pp->children[i].state == GIT_CP_WAIT_CLEANUP)
1759                                 break;
1760                 if (i == pp->max_processes)
1761                         break;
1762
1763                 code = finish_command(&pp->children[i].process);
1764
1765                 code = pp->task_finished(code,
1766                                          &pp->children[i].err, pp->data,
1767                                          pp->children[i].data);
1768
1769                 if (code)
1770                         result = code;
1771                 if (code < 0)
1772                         break;
1773
1774                 pp->nr_processes--;
1775                 pp->children[i].state = GIT_CP_FREE;
1776                 pp->pfd[i].fd = -1;
1777                 child_process_init(&pp->children[i].process);
1778
1779                 if (i != pp->output_owner) {
1780                         strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1781                         strbuf_reset(&pp->children[i].err);
1782                 } else {
1783                         strbuf_write(&pp->children[i].err, stderr);
1784                         strbuf_reset(&pp->children[i].err);
1785
1786                         /* Output all other finished child processes */
1787                         strbuf_write(&pp->buffered_output, stderr);
1788                         strbuf_reset(&pp->buffered_output);
1789
1790                         /*
1791                          * Pick next process to output live.
1792                          * NEEDSWORK:
1793                          * For now we pick it randomly by doing a round
1794                          * robin. Later we may want to pick the one with
1795                          * the most output or the longest or shortest
1796                          * running process time.
1797                          */
1798                         for (i = 0; i < n; i++)
1799                                 if (pp->children[(pp->output_owner + i) % n].state == GIT_CP_WORKING)
1800                                         break;
1801                         pp->output_owner = (pp->output_owner + i) % n;
1802                 }
1803         }
1804         return result;
1805 }
1806
1807 int run_processes_parallel(int n,
1808                            get_next_task_fn get_next_task,
1809                            start_failure_fn start_failure,
1810                            task_finished_fn task_finished,
1811                            void *pp_cb)
1812 {
1813         int i, code;
1814         int output_timeout = 100;
1815         int spawn_cap = 4;
1816         struct parallel_processes pp;
1817
1818         pp_init(&pp, n, get_next_task, start_failure, task_finished, pp_cb);
1819         while (1) {
1820                 for (i = 0;
1821                     i < spawn_cap && !pp.shutdown &&
1822                     pp.nr_processes < pp.max_processes;
1823                     i++) {
1824                         code = pp_start_one(&pp);
1825                         if (!code)
1826                                 continue;
1827                         if (code < 0) {
1828                                 pp.shutdown = 1;
1829                                 kill_children(&pp, -code);
1830                         }
1831                         break;
1832                 }
1833                 if (!pp.nr_processes)
1834                         break;
1835                 pp_buffer_stderr(&pp, output_timeout);
1836                 pp_output(&pp);
1837                 code = pp_collect_finished(&pp);
1838                 if (code) {
1839                         pp.shutdown = 1;
1840                         if (code < 0)
1841                                 kill_children(&pp, -code);
1842                 }
1843         }
1844
1845         pp_cleanup(&pp);
1846         return 0;
1847 }
1848
1849 int run_processes_parallel_tr2(int n, get_next_task_fn get_next_task,
1850                                start_failure_fn start_failure,
1851                                task_finished_fn task_finished, void *pp_cb,
1852                                const char *tr2_category, const char *tr2_label)
1853 {
1854         int result;
1855
1856         trace2_region_enter_printf(tr2_category, tr2_label, NULL, "max:%d",
1857                                    ((n < 1) ? online_cpus() : n));
1858
1859         result = run_processes_parallel(n, get_next_task, start_failure,
1860                                         task_finished, pp_cb);
1861
1862         trace2_region_leave(tr2_category, tr2_label, NULL);
1863
1864         return result;
1865 }