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 "strvec.h"
   6 #include "thread-utils.h"
   7 #include "strbuf.h"
   8 #include "string-list.h"
   9 #include "quote.h"
  10 #include "config.h"
  11
  12 void child_process_init(struct child_process *child)
  13 {
  14         memset(child, 0, sizeof(*child));
  15         strvec_init(&child->args);
  16         strvec_init(&child->env_array);
  17 }
  18
  19 void child_process_clear(struct child_process *child)
  20 {
  21         strvec_clear(&child->args);
  22         strvec_clear(&child->env_array);
  23 }
  24
  25 struct child_to_clean {
  26         pid_t pid;
  27         struct child_process *process;
  28         struct child_to_clean *next;
  29 };
  30 static struct child_to_clean *children_to_clean;
  31 static int installed_child_cleanup_handler;
  32
  33 static void cleanup_children(int sig, int in_signal)
  34 {
  35         struct child_to_clean *children_to_wait_for = NULL;
  36
  37         while (children_to_clean) {
  38                 struct child_to_clean *p = children_to_clean;
  39                 children_to_clean = p->next;
  40
  41                 if (p->process && !in_signal) {
  42                         struct child_process *process = p->process;
  43                         if (process->clean_on_exit_handler) {
  44                                 trace_printf(
  45                                         "trace: run_command: running exit handler for pid %"
  46                                         PRIuMAX, (uintmax_t)p->pid
  47                                 );
  48                                 process->clean_on_exit_handler(process);
  49                         }
  50                 }
  51
  52                 kill(p->pid, sig);
  53
  54                 if (p->process && p->process->wait_after_clean) {
  55                         p->next = children_to_wait_for;
  56                         children_to_wait_for = p;
  57                 } else {
  58                         if (!in_signal)
  59                                 free(p);
  60                 }
  61         }
  62
  63         while (children_to_wait_for) {
  64                 struct child_to_clean *p = children_to_wait_for;
  65                 children_to_wait_for = p->next;
  66
  67                 while (waitpid(p->pid, NULL, 0) < 0 && errno == EINTR)
  68                         ; /* spin waiting for process exit or error */
  69
  70                 if (!in_signal)
  71                         free(p);
  72         }
  73 }
  74
  75 static void cleanup_children_on_signal(int sig)
  76 {
  77         cleanup_children(sig, 1);
  78         sigchain_pop(sig);
  79         raise(sig);
  80 }
  81
  82 static void cleanup_children_on_exit(void)
  83 {
  84         cleanup_children(SIGTERM, 0);
  85 }
  86
  87 static void mark_child_for_cleanup(pid_t pid, struct child_process *process)
  88 {
  89         struct child_to_clean *p = xmalloc(sizeof(*p));
  90         p->pid = pid;
  91         p->process = process;
  92         p->next = children_to_clean;
  93         children_to_clean = p;
  94
  95         if (!installed_child_cleanup_handler) {
  96                 atexit(cleanup_children_on_exit);
  97                 sigchain_push_common(cleanup_children_on_signal);
  98                 installed_child_cleanup_handler = 1;
  99         }
 100 }
 101
 102 static void clear_child_for_cleanup(pid_t pid)
 103 {
 104         struct child_to_clean **pp;
 105
 106         for (pp = &children_to_clean; *pp; pp = &(*pp)->next) {
 107                 struct child_to_clean *clean_me = *pp;
 108
 109                 if (clean_me->pid == pid) {
 110                         *pp = clean_me->next;
 111                         free(clean_me);
 112                         return;
 113                 }
 114         }
 115 }
 116
 117 static inline void close_pair(int fd[2])
 118 {
 119         close(fd[0]);
 120         close(fd[1]);
 121 }
 122
 123 int is_executable(const char *name)
 124 {
 125         struct stat st;
 126
 127         if (stat(name, &st) || /* stat, not lstat */
 128             !S_ISREG(st.st_mode))
 129                 return 0;
 130
 131 #if defined(GIT_WINDOWS_NATIVE)
 132         /*
 133          * On Windows there is no executable bit. The file extension
 134          * indicates whether it can be run as an executable, and Git
 135          * has special-handling to detect scripts and launch them
 136          * through the indicated script interpreter. We test for the
 137          * file extension first because virus scanners may make
 138          * it quite expensive to open many files.
 139          */
 140         if (ends_with(name, ".exe"))
 141                 return S_IXUSR;
 142
 143 {
 144         /*
 145          * Now that we know it does not have an executable extension,
 146          * peek into the file instead.
 147          */
 148         char buf[3] = { 0 };
 149         int n;
 150         int fd = open(name, O_RDONLY);
 151         st.st_mode &= ~S_IXUSR;
 152         if (fd >= 0) {
 153                 n = read(fd, buf, 2);
 154                 if (n == 2)
 155                         /* look for a she-bang */
 156                         if (!strcmp(buf, "#!"))
 157                                 st.st_mode |= S_IXUSR;
 158                 close(fd);
 159         }
 160 }
 161 #endif
 162         return st.st_mode & S_IXUSR;
 163 }
 164
 165 /*
 166  * Search $PATH for a command.  This emulates the path search that
 167  * execvp would perform, without actually executing the command so it
 168  * can be used before fork() to prepare to run a command using
 169  * execve() or after execvp() to diagnose why it failed.
 170  *
 171  * The caller should ensure that file contains no directory
 172  * separators.
 173  *
 174  * Returns the path to the command, as found in $PATH or NULL if the
 175  * command could not be found.  The caller inherits ownership of the memory
 176  * used to store the resultant path.
 177  *
 178  * This should not be used on Windows, where the $PATH search rules
 179  * are more complicated (e.g., a search for "foo" should find
 180  * "foo.exe").
 181  */
 182 static char *locate_in_PATH(const char *file)
 183 {
 184         const char *p = getenv("PATH");
 185         struct strbuf buf = STRBUF_INIT;
 186
 187         if (!p || !*p)
 188                 return NULL;
 189
 190         while (1) {
 191                 const char *end = strchrnul(p, ':');
 192
 193                 strbuf_reset(&buf);
 194
 195                 /* POSIX specifies an empty entry as the current directory. */
 196                 if (end != p) {
 197                         strbuf_add(&buf, p, end - p);
 198                         strbuf_addch(&buf, '/');
 199                 }
 200                 strbuf_addstr(&buf, file);
 201
 202                 if (is_executable(buf.buf))
 203                         return strbuf_detach(&buf, NULL);
 204
 205                 if (!*end)
 206                         break;
 207                 p = end + 1;
 208         }
 209
 210         strbuf_release(&buf);
 211         return NULL;
 212 }
 213
 214 static int exists_in_PATH(const char *file)
 215 {
 216         char *r = locate_in_PATH(file);
 217         int found = r != NULL;
 218         free(r);
 219         return found;
 220 }
 221
 222 int sane_execvp(const char *file, char * const argv[])
 223 {
 224 #ifndef GIT_WINDOWS_NATIVE
 225         /*
 226          * execvp() doesn't return, so we all we can do is tell trace2
 227          * what we are about to do and let it leave a hint in the log
 228          * (unless of course the execvp() fails).
 229          *
 230          * we skip this for Windows because the compat layer already
 231          * has to emulate the execvp() call anyway.
 232          */
 233         int exec_id = trace2_exec(file, (const char **)argv);
 234 #endif
 235
 236         if (!execvp(file, argv))
 237                 return 0; /* cannot happen ;-) */
 238
 239 #ifndef GIT_WINDOWS_NATIVE
 240         {
 241                 int ec = errno;
 242                 trace2_exec_result(exec_id, ec);
 243                 errno = ec;
 244         }
 245 #endif
 246
 247         /*
 248          * When a command can't be found because one of the directories
 249          * listed in $PATH is unsearchable, execvp reports EACCES, but
 250          * careful usability testing (read: analysis of occasional bug
 251          * reports) reveals that "No such file or directory" is more
 252          * intuitive.
 253          *
 254          * We avoid commands with "/", because execvp will not do $PATH
 255          * lookups in that case.
 256          *
 257          * The reassignment of EACCES to errno looks like a no-op below,
 258          * but we need to protect against exists_in_PATH overwriting errno.
 259          */
 260         if (errno == EACCES && !strchr(file, '/'))
 261                 errno = exists_in_PATH(file) ? EACCES : ENOENT;
 262         else if (errno == ENOTDIR && !strchr(file, '/'))
 263                 errno = ENOENT;
 264         return -1;
 265 }
 266
 267 static const char **prepare_shell_cmd(struct strvec *out, const char **argv)
 268 {
 269         if (!argv[0])
 270                 BUG("shell command is empty");
 271
 272         if (strcspn(argv[0], "|&;<>()$`\\\"' \t\n*?[#~=%") != strlen(argv[0])) {
 273 #ifndef GIT_WINDOWS_NATIVE
 274                 strvec_push(out, SHELL_PATH);
 275 #else
 276                 strvec_push(out, "sh");
 277 #endif
 278                 strvec_push(out, "-c");
 279
 280                 /*
 281                  * If we have no extra arguments, we do not even need to
 282                  * bother with the "$@" magic.
 283                  */
 284                 if (!argv[1])
 285                         strvec_push(out, argv[0]);
 286                 else
 287                         strvec_pushf(out, "%s \"$@\"", argv[0]);
 288         }
 289
 290         strvec_pushv(out, argv);
 291         return out->v;
 292 }
 293
 294 #ifndef GIT_WINDOWS_NATIVE
 295 static int child_notifier = -1;
 296
 297 enum child_errcode {
 298         CHILD_ERR_CHDIR,
 299         CHILD_ERR_DUP2,
 300         CHILD_ERR_CLOSE,
 301         CHILD_ERR_SIGPROCMASK,
 302         CHILD_ERR_ENOENT,
 303         CHILD_ERR_SILENT,
 304         CHILD_ERR_ERRNO
 305 };
 306
 307 struct child_err {
 308         enum child_errcode err;
 309         int syserr; /* errno */
 310 };
 311
 312 static void child_die(enum child_errcode err)
 313 {
 314         struct child_err buf;
 315
 316         buf.err = err;
 317         buf.syserr = errno;
 318
 319         /* write(2) on buf smaller than PIPE_BUF (min 512) is atomic: */
 320         xwrite(child_notifier, &buf, sizeof(buf));
 321         _exit(1);
 322 }
 323
 324 static void child_dup2(int fd, int to)
 325 {
 326         if (dup2(fd, to) < 0)
 327                 child_die(CHILD_ERR_DUP2);
 328 }
 329
 330 static void child_close(int fd)
 331 {
 332         if (close(fd))
 333                 child_die(CHILD_ERR_CLOSE);
 334 }
 335
 336 static void child_close_pair(int fd[2])
 337 {
 338         child_close(fd[0]);
 339         child_close(fd[1]);
 340 }
 341
 342 /*
 343  * parent will make it look like the child spewed a fatal error and died
 344  * this is needed to prevent changes to t0061.
 345  */
 346 static void fake_fatal(const char *err, va_list params)
 347 {
 348         vreportf("fatal: ", err, params);
 349 }
 350
 351 static void child_error_fn(const char *err, va_list params)
 352 {
 353         const char msg[] = "error() should not be called in child\n";
 354         xwrite(2, msg, sizeof(msg) - 1);
 355 }
 356
 357 static void child_warn_fn(const char *err, va_list params)
 358 {
 359         const char msg[] = "warn() should not be called in child\n";
 360         xwrite(2, msg, sizeof(msg) - 1);
 361 }
 362
 363 static void NORETURN child_die_fn(const char *err, va_list params)
 364 {
 365         const char msg[] = "die() should not be called in child\n";
 366         xwrite(2, msg, sizeof(msg) - 1);
 367         _exit(2);
 368 }
 369
 370 /* this runs in the parent process */
 371 static void child_err_spew(struct child_process *cmd, struct child_err *cerr)
 372 {
 373         static void (*old_errfn)(const char *err, va_list params);
 374
 375         old_errfn = get_error_routine();
 376         set_error_routine(fake_fatal);
 377         errno = cerr->syserr;
 378
 379         switch (cerr->err) {
 380         case CHILD_ERR_CHDIR:
 381                 error_errno("exec '%s': cd to '%s' failed",
 382                             cmd->argv[0], cmd->dir);
 383                 break;
 384         case CHILD_ERR_DUP2:
 385                 error_errno("dup2() in child failed");
 386                 break;
 387         case CHILD_ERR_CLOSE:
 388                 error_errno("close() in child failed");
 389                 break;
 390         case CHILD_ERR_SIGPROCMASK:
 391                 error_errno("sigprocmask failed restoring signals");
 392                 break;
 393         case CHILD_ERR_ENOENT:
 394                 error_errno("cannot run %s", cmd->argv[0]);
 395                 break;
 396         case CHILD_ERR_SILENT:
 397                 break;
 398         case CHILD_ERR_ERRNO:
 399                 error_errno("cannot exec '%s'", cmd->argv[0]);
 400                 break;
 401         }
 402         set_error_routine(old_errfn);
 403 }
 404
 405 static int prepare_cmd(struct strvec *out, const struct child_process *cmd)
 406 {
 407         if (!cmd->argv[0])
 408                 BUG("command is empty");
 409
 410         /*
 411          * Add SHELL_PATH so in the event exec fails with ENOEXEC we can
 412          * attempt to interpret the command with 'sh'.
 413          */
 414         strvec_push(out, SHELL_PATH);
 415
 416         if (cmd->git_cmd) {
 417                 prepare_git_cmd(out, cmd->argv);
 418         } else if (cmd->use_shell) {
 419                 prepare_shell_cmd(out, cmd->argv);
 420         } else {
 421                 strvec_pushv(out, cmd->argv);
 422         }
 423
 424         /*
 425          * If there are no dir separator characters in the command then perform
 426          * a path lookup and use the resolved path as the command to exec. If
 427          * there are dir separator characters, we have exec attempt to invoke
 428          * the command directly.
 429          */
 430         if (!has_dir_sep(out->v[1])) {
 431                 char *program = locate_in_PATH(out->v[1]);
 432                 if (program) {
 433                         free((char *)out->v[1]);
 434                         out->v[1] = program;
 435                 } else {
 436                         strvec_clear(out);
 437                         errno = ENOENT;
 438                         return -1;
 439                 }
 440         }
 441
 442         return 0;
 443 }
 444
 445 static char **prep_childenv(const char *const *deltaenv)
 446 {
 447         extern char **environ;
 448         char **childenv;
 449         struct string_list env = STRING_LIST_INIT_DUP;
 450         struct strbuf key = STRBUF_INIT;
 451         const char *const *p;
 452         int i;
 453
 454         /* Construct a sorted string list consisting of the current environ */
 455         for (p = (const char *const *) environ; p && *p; p++) {
 456                 const char *equals = strchr(*p, '=');
 457
 458                 if (equals) {
 459                         strbuf_reset(&key);
 460                         strbuf_add(&key, *p, equals - *p);
 461                         string_list_append(&env, key.buf)->util = (void *) *p;
 462                 } else {
 463                         string_list_append(&env, *p)->util = (void *) *p;
 464                 }
 465         }
 466         string_list_sort(&env);
 467
 468         /* Merge in 'deltaenv' with the current environ */
 469         for (p = deltaenv; p && *p; p++) {
 470                 const char *equals = strchr(*p, '=');
 471
 472                 if (equals) {
 473                         /* ('key=value'), insert or replace entry */
 474                         strbuf_reset(&key);
 475                         strbuf_add(&key, *p, equals - *p);
 476                         string_list_insert(&env, key.buf)->util = (void *) *p;
 477                 } else {
 478                         /* otherwise ('key') remove existing entry */
 479                         string_list_remove(&env, *p, 0);
 480                 }
 481         }
 482
 483         /* Create an array of 'char *' to be used as the childenv */
 484         ALLOC_ARRAY(childenv, env.nr + 1);
 485         for (i = 0; i < env.nr; i++)
 486                 childenv[i] = env.items[i].util;
 487         childenv[env.nr] = NULL;
 488
 489         string_list_clear(&env, 0);
 490         strbuf_release(&key);
 491         return childenv;
 492 }
 493
 494 struct atfork_state {
 495 #ifndef NO_PTHREADS
 496         int cs;
 497 #endif
 498         sigset_t old;
 499 };
 500
 501 #define CHECK_BUG(err, msg) \
 502         do { \
 503                 int e = (err); \
 504                 if (e) \
 505                         BUG("%s: %s", msg, strerror(e)); \
 506         } while(0)
 507
 508 static void atfork_prepare(struct atfork_state *as)
 509 {
 510         sigset_t all;
 511
 512         if (sigfillset(&all))
 513                 die_errno("sigfillset");
 514 #ifdef NO_PTHREADS
 515         if (sigprocmask(SIG_SETMASK, &all, &as->old))
 516                 die_errno("sigprocmask");
 517 #else
 518         CHECK_BUG(pthread_sigmask(SIG_SETMASK, &all, &as->old),
 519                 "blocking all signals");
 520         CHECK_BUG(pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &as->cs),
 521                 "disabling cancellation");
 522 #endif
 523 }
 524
 525 static void atfork_parent(struct atfork_state *as)
 526 {
 527 #ifdef NO_PTHREADS
 528         if (sigprocmask(SIG_SETMASK, &as->old, NULL))
 529                 die_errno("sigprocmask");
 530 #else
 531         CHECK_BUG(pthread_setcancelstate(as->cs, NULL),
 532                 "re-enabling cancellation");
 533         CHECK_BUG(pthread_sigmask(SIG_SETMASK, &as->old, NULL),
 534                 "restoring signal mask");
 535 #endif
 536 }
 537 #endif /* GIT_WINDOWS_NATIVE */
 538
 539 static inline void set_cloexec(int fd)
 540 {
 541         int flags = fcntl(fd, F_GETFD);
 542         if (flags >= 0)
 543                 fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
 544 }
 545
 546 static int wait_or_whine(pid_t pid, const char *argv0, int in_signal)
 547 {
 548         int status, code = -1;
 549         pid_t waiting;
 550         int failed_errno = 0;
 551
 552         while ((waiting = waitpid(pid, &status, 0)) < 0 && errno == EINTR)
 553                 ;       /* nothing */
 554         if (in_signal)
 555                 return 0;
 556
 557         if (waiting < 0) {
 558                 failed_errno = errno;
 559                 error_errno("waitpid for %s failed", argv0);
 560         } else if (waiting != pid) {
 561                 error("waitpid is confused (%s)", argv0);
 562         } else if (WIFSIGNALED(status)) {
 563                 code = WTERMSIG(status);
 564                 if (code != SIGINT && code != SIGQUIT && code != SIGPIPE)
 565                         error("%s died of signal %d", argv0, code);
 566                 /*
 567                  * This return value is chosen so that code & 0xff
 568                  * mimics the exit code that a POSIX shell would report for
 569                  * a program that died from this signal.
 570                  */
 571                 code += 128;
 572         } else if (WIFEXITED(status)) {
 573                 code = WEXITSTATUS(status);
 574         } else {
 575                 error("waitpid is confused (%s)", argv0);
 576         }
 577
 578         clear_child_for_cleanup(pid);
 579
 580         errno = failed_errno;
 581         return code;
 582 }
 583
 584 static void trace_add_env(struct strbuf *dst, const char *const *deltaenv)
 585 {
 586         struct string_list envs = STRING_LIST_INIT_DUP;
 587         const char *const *e;
 588         int i;
 589         int printed_unset = 0;
 590
 591         /* Last one wins, see run-command.c:prep_childenv() for context */
 592         for (e = deltaenv; e && *e; e++) {
 593                 struct strbuf key = STRBUF_INIT;
 594                 char *equals = strchr(*e, '=');
 595
 596                 if (equals) {
 597                         strbuf_add(&key, *e, equals - *e);
 598                         string_list_insert(&envs, key.buf)->util = equals + 1;
 599                 } else {
 600                         string_list_insert(&envs, *e)->util = NULL;
 601                 }
 602                 strbuf_release(&key);
 603         }
 604
 605         /* "unset X Y...;" */
 606         for (i = 0; i < envs.nr; i++) {
 607                 const char *var = envs.items[i].string;
 608                 const char *val = envs.items[i].util;
 609
 610                 if (val || !getenv(var))
 611                         continue;
 612
 613                 if (!printed_unset) {
 614                         strbuf_addstr(dst, " unset");
 615                         printed_unset = 1;
 616                 }
 617                 strbuf_addf(dst, " %s", var);
 618         }
 619         if (printed_unset)
 620                 strbuf_addch(dst, ';');
 621
 622         /* ... followed by "A=B C=D ..." */
 623         for (i = 0; i < envs.nr; i++) {
 624                 const char *var = envs.items[i].string;
 625                 const char *val = envs.items[i].util;
 626                 const char *oldval;
 627
 628                 if (!val)
 629                         continue;
 630
 631                 oldval = getenv(var);
 632                 if (oldval && !strcmp(val, oldval))
 633                         continue;
 634
 635                 strbuf_addf(dst, " %s=", var);
 636                 sq_quote_buf_pretty(dst, val);
 637         }
 638         string_list_clear(&envs, 0);
 639 }
 640
 641 static void trace_run_command(const struct child_process *cp)
 642 {
 643         struct strbuf buf = STRBUF_INIT;
 644
 645         if (!trace_want(&trace_default_key))
 646                 return;
 647
 648         strbuf_addstr(&buf, "trace: run_command:");
 649         if (cp->dir) {
 650                 strbuf_addstr(&buf, " cd ");
 651                 sq_quote_buf_pretty(&buf, cp->dir);
 652                 strbuf_addch(&buf, ';');
 653         }
 654         /*
 655          * The caller is responsible for initializing cp->env from
 656          * cp->env_array if needed. We only check one place.
 657          */
 658         if (cp->env)
 659                 trace_add_env(&buf, cp->env);
 660         if (cp->git_cmd)
 661                 strbuf_addstr(&buf, " git");
 662         sq_quote_argv_pretty(&buf, cp->argv);
 663
 664         trace_printf("%s", buf.buf);
 665         strbuf_release(&buf);
 666 }
 667
 668 int start_command(struct child_process *cmd)
 669 {
 670         int need_in, need_out, need_err;
 671         int fdin[2], fdout[2], fderr[2];
 672         int failed_errno;
 673         char *str;
 674
 675         if (!cmd->argv)
 676                 cmd->argv = cmd->args.v;
 677         if (!cmd->env)
 678                 cmd->env = cmd->env_array.v;
 679
 680         /*
 681          * In case of errors we must keep the promise to close FDs
 682          * that have been passed in via ->in and ->out.
 683          */
 684
 685         need_in = !cmd->no_stdin && cmd->in < 0;
 686         if (need_in) {
 687                 if (pipe(fdin) < 0) {
 688                         failed_errno = errno;
 689                         if (cmd->out > 0)
 690                                 close(cmd->out);
 691                         str = "standard input";
 692                         goto fail_pipe;
 693                 }
 694                 cmd->in = fdin[1];
 695         }
 696
 697         need_out = !cmd->no_stdout
 698                 && !cmd->stdout_to_stderr
 699                 && cmd->out < 0;
 700         if (need_out) {
 701                 if (pipe(fdout) < 0) {
 702                         failed_errno = errno;
 703                         if (need_in)
 704                                 close_pair(fdin);
 705                         else if (cmd->in)
 706                                 close(cmd->in);
 707                         str = "standard output";
 708                         goto fail_pipe;
 709                 }
 710                 cmd->out = fdout[0];
 711         }
 712
 713         need_err = !cmd->no_stderr && cmd->err < 0;
 714         if (need_err) {
 715                 if (pipe(fderr) < 0) {
 716                         failed_errno = errno;
 717                         if (need_in)
 718                                 close_pair(fdin);
 719                         else if (cmd->in)
 720                                 close(cmd->in);
 721                         if (need_out)
 722                                 close_pair(fdout);
 723                         else if (cmd->out)
 724                                 close(cmd->out);
 725                         str = "standard error";
 726 fail_pipe:
 727                         error("cannot create %s pipe for %s: %s",
 728                                 str, cmd->argv[0], strerror(failed_errno));
 729                         child_process_clear(cmd);
 730                         errno = failed_errno;
 731                         return -1;
 732                 }
 733                 cmd->err = fderr[0];
 734         }
 735
 736         trace2_child_start(cmd);
 737         trace_run_command(cmd);
 738
 739         fflush(NULL);
 740
 741 #ifndef GIT_WINDOWS_NATIVE
 742 {
 743         int notify_pipe[2];
 744         int null_fd = -1;
 745         char **childenv;
 746         struct strvec argv = STRVEC_INIT;
 747         struct child_err cerr;
 748         struct atfork_state as;
 749
 750         if (prepare_cmd(&argv, cmd) < 0) {
 751                 failed_errno = errno;
 752                 cmd->pid = -1;
 753                 if (!cmd->silent_exec_failure)
 754                         error_errno("cannot run %s", cmd->argv[0]);
 755                 goto end_of_spawn;
 756         }
 757
 758         if (pipe(notify_pipe))
 759                 notify_pipe[0] = notify_pipe[1] = -1;
 760
 761         if (cmd->no_stdin || cmd->no_stdout || cmd->no_stderr) {
 762                 null_fd = open("/dev/null", O_RDWR | O_CLOEXEC);
 763                 if (null_fd < 0)
 764                         die_errno(_("open /dev/null failed"));
 765                 set_cloexec(null_fd);
 766         }
 767
 768         childenv = prep_childenv(cmd->env);
 769         atfork_prepare(&as);
 770
 771         /*
 772          * NOTE: In order to prevent deadlocking when using threads special
 773          * care should be taken with the function calls made in between the
 774          * fork() and exec() calls.  No calls should be made to functions which
 775          * require acquiring a lock (e.g. malloc) as the lock could have been
 776          * held by another thread at the time of forking, causing the lock to
 777          * never be released in the child process.  This means only
 778          * Async-Signal-Safe functions are permitted in the child.
 779          */
 780         cmd->pid = fork();
 781         failed_errno = errno;
 782         if (!cmd->pid) {
 783                 int sig;
 784                 /*
 785                  * Ensure the default die/error/warn routines do not get
 786                  * called, they can take stdio locks and malloc.
 787                  */
 788                 set_die_routine(child_die_fn);
 789                 set_error_routine(child_error_fn);
 790                 set_warn_routine(child_warn_fn);
 791
 792                 close(notify_pipe[0]);
 793                 set_cloexec(notify_pipe[1]);
 794                 child_notifier = notify_pipe[1];
 795
 796                 if (cmd->no_stdin)
 797                         child_dup2(null_fd, 0);
 798                 else if (need_in) {
 799                         child_dup2(fdin[0], 0);
 800                         child_close_pair(fdin);
 801                 } else if (cmd->in) {
 802                         child_dup2(cmd->in, 0);
 803                         child_close(cmd->in);
 804                 }
 805
 806                 if (cmd->no_stderr)
 807                         child_dup2(null_fd, 2);
 808                 else if (need_err) {
 809                         child_dup2(fderr[1], 2);
 810                         child_close_pair(fderr);
 811                 } else if (cmd->err > 1) {
 812                         child_dup2(cmd->err, 2);
 813                         child_close(cmd->err);
 814                 }
 815
 816                 if (cmd->no_stdout)
 817                         child_dup2(null_fd, 1);
 818                 else if (cmd->stdout_to_stderr)
 819                         child_dup2(2, 1);
 820                 else if (need_out) {
 821                         child_dup2(fdout[1], 1);
 822                         child_close_pair(fdout);
 823                 } else if (cmd->out > 1) {
 824                         child_dup2(cmd->out, 1);
 825                         child_close(cmd->out);
 826                 }
 827
 828                 if (cmd->dir && chdir(cmd->dir))
 829                         child_die(CHILD_ERR_CHDIR);
 830
 831                 /*
 832                  * restore default signal handlers here, in case
 833                  * we catch a signal right before execve below
 834                  */
 835                 for (sig = 1; sig < NSIG; sig++) {
 836                         /* ignored signals get reset to SIG_DFL on execve */
 837                         if (signal(sig, SIG_DFL) == SIG_IGN)
 838                                 signal(sig, SIG_IGN);
 839                 }
 840
 841                 if (sigprocmask(SIG_SETMASK, &as.old, NULL) != 0)
 842                         child_die(CHILD_ERR_SIGPROCMASK);
 843
 844                 /*
 845                  * Attempt to exec using the command and arguments starting at
 846                  * argv.argv[1].  argv.argv[0] contains SHELL_PATH which will
 847                  * be used in the event exec failed with ENOEXEC at which point
 848                  * we will try to interpret the command using 'sh'.
 849                  */
 850                 execve(argv.v[1], (char *const *) argv.v + 1,
 851                        (char *const *) childenv);
 852                 if (errno == ENOEXEC)
 853                         execve(argv.v[0], (char *const *) argv.v,
 854                                (char *const *) childenv);
 855
 856                 if (errno == ENOENT) {
 857                         if (cmd->silent_exec_failure)
 858                                 child_die(CHILD_ERR_SILENT);
 859                         child_die(CHILD_ERR_ENOENT);
 860                 } else {
 861                         child_die(CHILD_ERR_ERRNO);
 862                 }
 863         }
 864         atfork_parent(&as);
 865         if (cmd->pid < 0)
 866                 error_errno("cannot fork() for %s", cmd->argv[0]);
 867         else if (cmd->clean_on_exit)
 868                 mark_child_for_cleanup(cmd->pid, cmd);
 869
 870         /*
 871          * Wait for child's exec. If the exec succeeds (or if fork()
 872          * failed), EOF is seen immediately by the parent. Otherwise, the
 873          * child process sends a child_err struct.
 874          * Note that use of this infrastructure is completely advisory,
 875          * therefore, we keep error checks minimal.
 876          */
 877         close(notify_pipe[1]);
 878         if (xread(notify_pipe[0], &cerr, sizeof(cerr)) == sizeof(cerr)) {
 879                 /*
 880                  * At this point we know that fork() succeeded, but exec()
 881                  * failed. Errors have been reported to our stderr.
 882                  */
 883                 wait_or_whine(cmd->pid, cmd->argv[0], 0);
 884                 child_err_spew(cmd, &cerr);
 885                 failed_errno = errno;
 886                 cmd->pid = -1;
 887         }
 888         close(notify_pipe[0]);
 889
 890         if (null_fd >= 0)
 891                 close(null_fd);
 892         strvec_clear(&argv);
 893         free(childenv);
 894 }
 895 end_of_spawn:
 896
 897 #else
 898 {
 899         int fhin = 0, fhout = 1, fherr = 2;
 900         const char **sargv = cmd->argv;
 901         struct strvec nargv = STRVEC_INIT;
 902
 903         if (cmd->no_stdin)
 904                 fhin = open("/dev/null", O_RDWR);
 905         else if (need_in)
 906                 fhin = dup(fdin[0]);
 907         else if (cmd->in)
 908                 fhin = dup(cmd->in);
 909
 910         if (cmd->no_stderr)
 911                 fherr = open("/dev/null", O_RDWR);
 912         else if (need_err)
 913                 fherr = dup(fderr[1]);
 914         else if (cmd->err > 2)
 915                 fherr = dup(cmd->err);
 916
 917         if (cmd->no_stdout)
 918                 fhout = open("/dev/null", O_RDWR);
 919         else if (cmd->stdout_to_stderr)
 920                 fhout = dup(fherr);
 921         else if (need_out)
 922                 fhout = dup(fdout[1]);
 923         else if (cmd->out > 1)
 924                 fhout = dup(cmd->out);
 925
 926         if (cmd->git_cmd)
 927                 cmd->argv = prepare_git_cmd(&nargv, cmd->argv);
 928         else if (cmd->use_shell)
 929                 cmd->argv = prepare_shell_cmd(&nargv, cmd->argv);
 930
 931         cmd->pid = mingw_spawnvpe(cmd->argv[0], cmd->argv, (char**) cmd->env,
 932                         cmd->dir, fhin, fhout, fherr);
 933         failed_errno = errno;
 934         if (cmd->pid < 0 && (!cmd->silent_exec_failure || errno != ENOENT))
 935                 error_errno("cannot spawn %s", cmd->argv[0]);
 936         if (cmd->clean_on_exit && cmd->pid >= 0)
 937                 mark_child_for_cleanup(cmd->pid, cmd);
 938
 939         strvec_clear(&nargv);
 940         cmd->argv = sargv;
 941         if (fhin != 0)
 942                 close(fhin);
 943         if (fhout != 1)
 944                 close(fhout);
 945         if (fherr != 2)
 946                 close(fherr);
 947 }
 948 #endif
 949
 950         if (cmd->pid < 0) {
 951                 trace2_child_exit(cmd, -1);
 952
 953                 if (need_in)
 954                         close_pair(fdin);
 955                 else if (cmd->in)
 956                         close(cmd->in);
 957                 if (need_out)
 958                         close_pair(fdout);
 959                 else if (cmd->out)
 960                         close(cmd->out);
 961                 if (need_err)
 962                         close_pair(fderr);
 963                 else if (cmd->err)
 964                         close(cmd->err);
 965                 child_process_clear(cmd);
 966                 errno = failed_errno;
 967                 return -1;
 968         }
 969
 970         if (need_in)
 971                 close(fdin[0]);
 972         else if (cmd->in)
 973                 close(cmd->in);
 974
 975         if (need_out)
 976                 close(fdout[1]);
 977         else if (cmd->out)
 978                 close(cmd->out);
 979
 980         if (need_err)
 981                 close(fderr[1]);
 982         else if (cmd->err)
 983                 close(cmd->err);
 984
 985         return 0;
 986 }
 987
 988 int finish_command(struct child_process *cmd)
 989 {
 990         int ret = wait_or_whine(cmd->pid, cmd->argv[0], 0);
 991         trace2_child_exit(cmd, ret);
 992         child_process_clear(cmd);
 993         invalidate_lstat_cache();
 994         return ret;
 995 }
 996
 997 int finish_command_in_signal(struct child_process *cmd)
 998 {
 999         int ret = wait_or_whine(cmd->pid, cmd->argv[0], 1);
1000         trace2_child_exit(cmd, ret);
1001         return ret;
1002 }
1003
1004
1005 int run_command(struct child_process *cmd)
1006 {
1007         int code;
1008
1009         if (cmd->out < 0 || cmd->err < 0)
1010                 BUG("run_command with a pipe can cause deadlock");
1011
1012         code = start_command(cmd);
1013         if (code)
1014                 return code;
1015         return finish_command(cmd);
1016 }
1017
1018 int run_command_v_opt(const char **argv, int opt)
1019 {
1020         return run_command_v_opt_cd_env(argv, opt, NULL, NULL);
1021 }
1022
1023 int run_command_v_opt_tr2(const char **argv, int opt, const char *tr2_class)
1024 {
1025         return run_command_v_opt_cd_env_tr2(argv, opt, NULL, NULL, tr2_class);
1026 }
1027
1028 int run_command_v_opt_cd_env(const char **argv, int opt, const char *dir, const char *const *env)
1029 {
1030         return run_command_v_opt_cd_env_tr2(argv, opt, dir, env, NULL);
1031 }
1032
1033 int run_command_v_opt_cd_env_tr2(const char **argv, int opt, const char *dir,
1034                                  const char *const *env, const char *tr2_class)
1035 {
1036         struct child_process cmd = CHILD_PROCESS_INIT;
1037         cmd.argv = argv;
1038         cmd.no_stdin = opt & RUN_COMMAND_NO_STDIN ? 1 : 0;
1039         cmd.git_cmd = opt & RUN_GIT_CMD ? 1 : 0;
1040         cmd.stdout_to_stderr = opt & RUN_COMMAND_STDOUT_TO_STDERR ? 1 : 0;
1041         cmd.silent_exec_failure = opt & RUN_SILENT_EXEC_FAILURE ? 1 : 0;
1042         cmd.use_shell = opt & RUN_USING_SHELL ? 1 : 0;
1043         cmd.clean_on_exit = opt & RUN_CLEAN_ON_EXIT ? 1 : 0;
1044         cmd.wait_after_clean = opt & RUN_WAIT_AFTER_CLEAN ? 1 : 0;
1045         cmd.dir = dir;
1046         cmd.env = env;
1047         cmd.trace2_child_class = tr2_class;
1048         return run_command(&cmd);
1049 }
1050
1051 #ifndef NO_PTHREADS
1052 static pthread_t main_thread;
1053 static int main_thread_set;
1054 static pthread_key_t async_key;
1055 static pthread_key_t async_die_counter;
1056
1057 static void *run_thread(void *data)
1058 {
1059         struct async *async = data;
1060         intptr_t ret;
1061
1062         if (async->isolate_sigpipe) {
1063                 sigset_t mask;
1064                 sigemptyset(&mask);
1065                 sigaddset(&mask, SIGPIPE);
1066                 if (pthread_sigmask(SIG_BLOCK, &mask, NULL) < 0) {
1067                         ret = error("unable to block SIGPIPE in async thread");
1068                         return (void *)ret;
1069                 }
1070         }
1071
1072         pthread_setspecific(async_key, async);
1073         ret = async->proc(async->proc_in, async->proc_out, async->data);
1074         return (void *)ret;
1075 }
1076
1077 static NORETURN void die_async(const char *err, va_list params)
1078 {
1079         vreportf("fatal: ", err, params);
1080
1081         if (in_async()) {
1082                 struct async *async = pthread_getspecific(async_key);
1083                 if (async->proc_in >= 0)
1084                         close(async->proc_in);
1085                 if (async->proc_out >= 0)
1086                         close(async->proc_out);
1087                 pthread_exit((void *)128);
1088         }
1089
1090         exit(128);
1091 }
1092
1093 static int async_die_is_recursing(void)
1094 {
1095         void *ret = pthread_getspecific(async_die_counter);
1096         pthread_setspecific(async_die_counter, (void *)1);
1097         return ret != NULL;
1098 }
1099
1100 int in_async(void)
1101 {
1102         if (!main_thread_set)
1103                 return 0; /* no asyncs started yet */
1104         return !pthread_equal(main_thread, pthread_self());
1105 }
1106
1107 static void NORETURN async_exit(int code)
1108 {
1109         pthread_exit((void *)(intptr_t)code);
1110 }
1111
1112 #else
1113
1114 static struct {
1115         void (**handlers)(void);
1116         size_t nr;
1117         size_t alloc;
1118 } git_atexit_hdlrs;
1119
1120 static int git_atexit_installed;
1121
1122 static void git_atexit_dispatch(void)
1123 {
1124         size_t i;
1125
1126         for (i=git_atexit_hdlrs.nr ; i ; i--)
1127                 git_atexit_hdlrs.handlers[i-1]();
1128 }
1129
1130 static void git_atexit_clear(void)
1131 {
1132         free(git_atexit_hdlrs.handlers);
1133         memset(&git_atexit_hdlrs, 0, sizeof(git_atexit_hdlrs));
1134         git_atexit_installed = 0;
1135 }
1136
1137 #undef atexit
1138 int git_atexit(void (*handler)(void))
1139 {
1140         ALLOC_GROW(git_atexit_hdlrs.handlers, git_atexit_hdlrs.nr + 1, git_atexit_hdlrs.alloc);
1141         git_atexit_hdlrs.handlers[git_atexit_hdlrs.nr++] = handler;
1142         if (!git_atexit_installed) {
1143                 if (atexit(&git_atexit_dispatch))
1144                         return -1;
1145                 git_atexit_installed = 1;
1146         }
1147         return 0;
1148 }
1149 #define atexit git_atexit
1150
1151 static int process_is_async;
1152 int in_async(void)
1153 {
1154         return process_is_async;
1155 }
1156
1157 static void NORETURN async_exit(int code)
1158 {
1159         exit(code);
1160 }
1161
1162 #endif
1163
1164 void check_pipe(int err)
1165 {
1166         if (err == EPIPE) {
1167                 if (in_async())
1168                         async_exit(141);
1169
1170                 signal(SIGPIPE, SIG_DFL);
1171                 raise(SIGPIPE);
1172                 /* Should never happen, but just in case... */
1173                 exit(141);
1174         }
1175 }
1176
1177 int start_async(struct async *async)
1178 {
1179         int need_in, need_out;
1180         int fdin[2], fdout[2];
1181         int proc_in, proc_out;
1182
1183         need_in = async->in < 0;
1184         if (need_in) {
1185                 if (pipe(fdin) < 0) {
1186                         if (async->out > 0)
1187                                 close(async->out);
1188                         return error_errno("cannot create pipe");
1189                 }
1190                 async->in = fdin[1];
1191         }
1192
1193         need_out = async->out < 0;
1194         if (need_out) {
1195                 if (pipe(fdout) < 0) {
1196                         if (need_in)
1197                                 close_pair(fdin);
1198                         else if (async->in)
1199                                 close(async->in);
1200                         return error_errno("cannot create pipe");
1201                 }
1202                 async->out = fdout[0];
1203         }
1204
1205         if (need_in)
1206                 proc_in = fdin[0];
1207         else if (async->in)
1208                 proc_in = async->in;
1209         else
1210                 proc_in = -1;
1211
1212         if (need_out)
1213                 proc_out = fdout[1];
1214         else if (async->out)
1215                 proc_out = async->out;
1216         else
1217                 proc_out = -1;
1218
1219 #ifdef NO_PTHREADS
1220         /* Flush stdio before fork() to avoid cloning buffers */
1221         fflush(NULL);
1222
1223         async->pid = fork();
1224         if (async->pid < 0) {
1225                 error_errno("fork (async) failed");
1226                 goto error;
1227         }
1228         if (!async->pid) {
1229                 if (need_in)
1230                         close(fdin[1]);
1231                 if (need_out)
1232                         close(fdout[0]);
1233                 git_atexit_clear();
1234                 process_is_async = 1;
1235                 exit(!!async->proc(proc_in, proc_out, async->data));
1236         }
1237
1238         mark_child_for_cleanup(async->pid, NULL);
1239
1240         if (need_in)
1241                 close(fdin[0]);
1242         else if (async->in)
1243                 close(async->in);
1244
1245         if (need_out)
1246                 close(fdout[1]);
1247         else if (async->out)
1248                 close(async->out);
1249 #else
1250         if (!main_thread_set) {
1251                 /*
1252                  * We assume that the first time that start_async is called
1253                  * it is from the main thread.
1254                  */
1255                 main_thread_set = 1;
1256                 main_thread = pthread_self();
1257                 pthread_key_create(&async_key, NULL);
1258                 pthread_key_create(&async_die_counter, NULL);
1259                 set_die_routine(die_async);
1260                 set_die_is_recursing_routine(async_die_is_recursing);
1261         }
1262
1263         if (proc_in >= 0)
1264                 set_cloexec(proc_in);
1265         if (proc_out >= 0)
1266                 set_cloexec(proc_out);
1267         async->proc_in = proc_in;
1268         async->proc_out = proc_out;
1269         {
1270                 int err = pthread_create(&async->tid, NULL, run_thread, async);
1271                 if (err) {
1272                         error(_("cannot create async thread: %s"), strerror(err));
1273                         goto error;
1274                 }
1275         }
1276 #endif
1277         return 0;
1278
1279 error:
1280         if (need_in)
1281                 close_pair(fdin);
1282         else if (async->in)
1283                 close(async->in);
1284
1285         if (need_out)
1286                 close_pair(fdout);
1287         else if (async->out)
1288                 close(async->out);
1289         return -1;
1290 }
1291
1292 int finish_async(struct async *async)
1293 {
1294 #ifdef NO_PTHREADS
1295         int ret = wait_or_whine(async->pid, "child process", 0);
1296
1297         invalidate_lstat_cache();
1298
1299         return ret;
1300 #else
1301         void *ret = (void *)(intptr_t)(-1);
1302
1303         if (pthread_join(async->tid, &ret))
1304                 error("pthread_join failed");
1305         invalidate_lstat_cache();
1306         return (int)(intptr_t)ret;
1307
1308 #endif
1309 }
1310
1311 int async_with_fork(void)
1312 {
1313 #ifdef NO_PTHREADS
1314         return 1;
1315 #else
1316         return 0;
1317 #endif
1318 }
1319
1320 const char *find_hook(const char *name)
1321 {
1322         static struct strbuf path = STRBUF_INIT;
1323
1324         strbuf_reset(&path);
1325         strbuf_git_path(&path, "hooks/%s", name);
1326         if (access(path.buf, X_OK) < 0) {
1327                 int err = errno;
1328
1329 #ifdef STRIP_EXTENSION
1330                 strbuf_addstr(&path, STRIP_EXTENSION);
1331                 if (access(path.buf, X_OK) >= 0)
1332                         return path.buf;
1333                 if (errno == EACCES)
1334                         err = errno;
1335 #endif
1336
1337                 if (err == EACCES && advice_ignored_hook) {
1338                         static struct string_list advise_given = STRING_LIST_INIT_DUP;
1339
1340                         if (!string_list_lookup(&advise_given, name)) {
1341                                 string_list_insert(&advise_given, name);
1342                                 advise(_("The '%s' hook was ignored because "
1343                                          "it's not set as executable.\n"
1344                                          "You can disable this warning with "
1345                                          "`git config advice.ignoredHook false`."),
1346                                        path.buf);
1347                         }
1348                 }
1349                 return NULL;
1350         }
1351         return path.buf;
1352 }
1353
1354 int run_hook_ve(const char *const *env, const char *name, va_list args)
1355 {
1356         struct child_process hook = CHILD_PROCESS_INIT;
1357         const char *p;
1358
1359         p = find_hook(name);
1360         if (!p)
1361                 return 0;
1362
1363         strvec_push(&hook.args, p);
1364         while ((p = va_arg(args, const char *)))
1365                 strvec_push(&hook.args, p);
1366         hook.env = env;
1367         hook.no_stdin = 1;
1368         hook.stdout_to_stderr = 1;
1369         hook.trace2_hook_name = name;
1370
1371         return run_command(&hook);
1372 }
1373
1374 int run_hook_le(const char *const *env, const char *name, ...)
1375 {
1376         va_list args;
1377         int ret;
1378
1379         va_start(args, name);
1380         ret = run_hook_ve(env, name, args);
1381         va_end(args);
1382
1383         return ret;
1384 }
1385
1386 struct io_pump {
1387         /* initialized by caller */
1388         int fd;
1389         int type; /* POLLOUT or POLLIN */
1390         union {
1391                 struct {
1392                         const char *buf;
1393                         size_t len;
1394                 } out;
1395                 struct {
1396                         struct strbuf *buf;
1397                         size_t hint;
1398                 } in;
1399         } u;
1400
1401         /* returned by pump_io */
1402         int error; /* 0 for success, otherwise errno */
1403
1404         /* internal use */
1405         struct pollfd *pfd;
1406 };
1407
1408 static int pump_io_round(struct io_pump *slots, int nr, struct pollfd *pfd)
1409 {
1410         int pollsize = 0;
1411         int i;
1412
1413         for (i = 0; i < nr; i++) {
1414                 struct io_pump *io = &slots[i];
1415                 if (io->fd < 0)
1416                         continue;
1417                 pfd[pollsize].fd = io->fd;
1418                 pfd[pollsize].events = io->type;
1419                 io->pfd = &pfd[pollsize++];
1420         }
1421
1422         if (!pollsize)
1423                 return 0;
1424
1425         if (poll(pfd, pollsize, -1) < 0) {
1426                 if (errno == EINTR)
1427                         return 1;
1428                 die_errno("poll failed");
1429         }
1430
1431         for (i = 0; i < nr; i++) {
1432                 struct io_pump *io = &slots[i];
1433
1434                 if (io->fd < 0)
1435                         continue;
1436
1437                 if (!(io->pfd->revents & (POLLOUT|POLLIN|POLLHUP|POLLERR|POLLNVAL)))
1438                         continue;
1439
1440                 if (io->type == POLLOUT) {
1441                         ssize_t len = xwrite(io->fd,
1442                                              io->u.out.buf, io->u.out.len);
1443                         if (len < 0) {
1444                                 io->error = errno;
1445                                 close(io->fd);
1446                                 io->fd = -1;
1447                         } else {
1448                                 io->u.out.buf += len;
1449                                 io->u.out.len -= len;
1450                                 if (!io->u.out.len) {
1451                                         close(io->fd);
1452                                         io->fd = -1;
1453                                 }
1454                         }
1455                 }
1456
1457                 if (io->type == POLLIN) {
1458                         ssize_t len = strbuf_read_once(io->u.in.buf,
1459                                                        io->fd, io->u.in.hint);
1460                         if (len < 0)
1461                                 io->error = errno;
1462                         if (len <= 0) {
1463                                 close(io->fd);
1464                                 io->fd = -1;
1465                         }
1466                 }
1467         }
1468
1469         return 1;
1470 }
1471
1472 static int pump_io(struct io_pump *slots, int nr)
1473 {
1474         struct pollfd *pfd;
1475         int i;
1476
1477         for (i = 0; i < nr; i++)
1478                 slots[i].error = 0;
1479
1480         ALLOC_ARRAY(pfd, nr);
1481         while (pump_io_round(slots, nr, pfd))
1482                 ; /* nothing */
1483         free(pfd);
1484
1485         /* There may be multiple errno values, so just pick the first. */
1486         for (i = 0; i < nr; i++) {
1487                 if (slots[i].error) {
1488                         errno = slots[i].error;
1489                         return -1;
1490                 }
1491         }
1492         return 0;
1493 }
1494
1495
1496 int pipe_command(struct child_process *cmd,
1497                  const char *in, size_t in_len,
1498                  struct strbuf *out, size_t out_hint,
1499                  struct strbuf *err, size_t err_hint)
1500 {
1501         struct io_pump io[3];
1502         int nr = 0;
1503
1504         if (in)
1505                 cmd->in = -1;
1506         if (out)
1507                 cmd->out = -1;
1508         if (err)
1509                 cmd->err = -1;
1510
1511         if (start_command(cmd) < 0)
1512                 return -1;
1513
1514         if (in) {
1515                 io[nr].fd = cmd->in;
1516                 io[nr].type = POLLOUT;
1517                 io[nr].u.out.buf = in;
1518                 io[nr].u.out.len = in_len;
1519                 nr++;
1520         }
1521         if (out) {
1522                 io[nr].fd = cmd->out;
1523                 io[nr].type = POLLIN;
1524                 io[nr].u.in.buf = out;
1525                 io[nr].u.in.hint = out_hint;
1526                 nr++;
1527         }
1528         if (err) {
1529                 io[nr].fd = cmd->err;
1530                 io[nr].type = POLLIN;
1531                 io[nr].u.in.buf = err;
1532                 io[nr].u.in.hint = err_hint;
1533                 nr++;
1534         }
1535
1536         if (pump_io(io, nr) < 0) {
1537                 finish_command(cmd); /* throw away exit code */
1538                 return -1;
1539         }
1540
1541         return finish_command(cmd);
1542 }
1543
1544 enum child_state {
1545         GIT_CP_FREE,
1546         GIT_CP_WORKING,
1547         GIT_CP_WAIT_CLEANUP,
1548 };
1549
1550 struct parallel_processes {
1551         void *data;
1552
1553         int max_processes;
1554         int nr_processes;
1555
1556         get_next_task_fn get_next_task;
1557         start_failure_fn start_failure;
1558         task_finished_fn task_finished;
1559
1560         struct {
1561                 enum child_state state;
1562                 struct child_process process;
1563                 struct strbuf err;
1564                 void *data;
1565         } *children;
1566         /*
1567          * The struct pollfd is logically part of *children,
1568          * but the system call expects it as its own array.
1569          */
1570         struct pollfd *pfd;
1571
1572         unsigned shutdown : 1;
1573
1574         int output_owner;
1575         struct strbuf buffered_output; /* of finished children */
1576 };
1577
1578 static int default_start_failure(struct strbuf *out,
1579                                  void *pp_cb,
1580                                  void *pp_task_cb)
1581 {
1582         return 0;
1583 }
1584
1585 static int default_task_finished(int result,
1586                                  struct strbuf *out,
1587                                  void *pp_cb,
1588                                  void *pp_task_cb)
1589 {
1590         return 0;
1591 }
1592
1593 static void kill_children(struct parallel_processes *pp, int signo)
1594 {
1595         int i, n = pp->max_processes;
1596
1597         for (i = 0; i < n; i++)
1598                 if (pp->children[i].state == GIT_CP_WORKING)
1599                         kill(pp->children[i].process.pid, signo);
1600 }
1601
1602 static struct parallel_processes *pp_for_signal;
1603
1604 static void handle_children_on_signal(int signo)
1605 {
1606         kill_children(pp_for_signal, signo);
1607         sigchain_pop(signo);
1608         raise(signo);
1609 }
1610
1611 static void pp_init(struct parallel_processes *pp,
1612                     int n,
1613                     get_next_task_fn get_next_task,
1614                     start_failure_fn start_failure,
1615                     task_finished_fn task_finished,
1616                     void *data)
1617 {
1618         int i;
1619
1620         if (n < 1)
1621                 n = online_cpus();
1622
1623         pp->max_processes = n;
1624
1625         trace_printf("run_processes_parallel: preparing to run up to %d tasks", n);
1626
1627         pp->data = data;
1628         if (!get_next_task)
1629                 BUG("you need to specify a get_next_task function");
1630         pp->get_next_task = get_next_task;
1631
1632         pp->start_failure = start_failure ? start_failure : default_start_failure;
1633         pp->task_finished = task_finished ? task_finished : default_task_finished;
1634
1635         pp->nr_processes = 0;
1636         pp->output_owner = 0;
1637         pp->shutdown = 0;
1638         pp->children = xcalloc(n, sizeof(*pp->children));
1639         pp->pfd = xcalloc(n, sizeof(*pp->pfd));
1640         strbuf_init(&pp->buffered_output, 0);
1641
1642         for (i = 0; i < n; i++) {
1643                 strbuf_init(&pp->children[i].err, 0);
1644                 child_process_init(&pp->children[i].process);
1645                 pp->pfd[i].events = POLLIN | POLLHUP;
1646                 pp->pfd[i].fd = -1;
1647         }
1648
1649         pp_for_signal = pp;
1650         sigchain_push_common(handle_children_on_signal);
1651 }
1652
1653 static void pp_cleanup(struct parallel_processes *pp)
1654 {
1655         int i;
1656
1657         trace_printf("run_processes_parallel: done");
1658         for (i = 0; i < pp->max_processes; i++) {
1659                 strbuf_release(&pp->children[i].err);
1660                 child_process_clear(&pp->children[i].process);
1661         }
1662
1663         free(pp->children);
1664         free(pp->pfd);
1665
1666         /*
1667          * When get_next_task added messages to the buffer in its last
1668          * iteration, the buffered output is non empty.
1669          */
1670         strbuf_write(&pp->buffered_output, stderr);
1671         strbuf_release(&pp->buffered_output);
1672
1673         sigchain_pop_common();
1674 }
1675
1676 /* returns
1677  *  0 if a new task was started.
1678  *  1 if no new jobs was started (get_next_task ran out of work, non critical
1679  *    problem with starting a new command)
1680  * <0 no new job was started, user wishes to shutdown early. Use negative code
1681  *    to signal the children.
1682  */
1683 static int pp_start_one(struct parallel_processes *pp)
1684 {
1685         int i, code;
1686
1687         for (i = 0; i < pp->max_processes; i++)
1688                 if (pp->children[i].state == GIT_CP_FREE)
1689                         break;
1690         if (i == pp->max_processes)
1691                 BUG("bookkeeping is hard");
1692
1693         code = pp->get_next_task(&pp->children[i].process,
1694                                  &pp->children[i].err,
1695                                  pp->data,
1696                                  &pp->children[i].data);
1697         if (!code) {
1698                 strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1699                 strbuf_reset(&pp->children[i].err);
1700                 return 1;
1701         }
1702         pp->children[i].process.err = -1;
1703         pp->children[i].process.stdout_to_stderr = 1;
1704         pp->children[i].process.no_stdin = 1;
1705
1706         if (start_command(&pp->children[i].process)) {
1707                 code = pp->start_failure(&pp->children[i].err,
1708                                          pp->data,
1709                                          pp->children[i].data);
1710                 strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1711                 strbuf_reset(&pp->children[i].err);
1712                 if (code)
1713                         pp->shutdown = 1;
1714                 return code;
1715         }
1716
1717         pp->nr_processes++;
1718         pp->children[i].state = GIT_CP_WORKING;
1719         pp->pfd[i].fd = pp->children[i].process.err;
1720         return 0;
1721 }
1722
1723 static void pp_buffer_stderr(struct parallel_processes *pp, int output_timeout)
1724 {
1725         int i;
1726
1727         while ((i = poll(pp->pfd, pp->max_processes, output_timeout)) < 0) {
1728                 if (errno == EINTR)
1729                         continue;
1730                 pp_cleanup(pp);
1731                 die_errno("poll");
1732         }
1733
1734         /* Buffer output from all pipes. */
1735         for (i = 0; i < pp->max_processes; i++) {
1736                 if (pp->children[i].state == GIT_CP_WORKING &&
1737                     pp->pfd[i].revents & (POLLIN | POLLHUP)) {
1738                         int n = strbuf_read_once(&pp->children[i].err,
1739                                                  pp->children[i].process.err, 0);
1740                         if (n == 0) {
1741                                 close(pp->children[i].process.err);
1742                                 pp->children[i].state = GIT_CP_WAIT_CLEANUP;
1743                         } else if (n < 0)
1744                                 if (errno != EAGAIN)
1745                                         die_errno("read");
1746                 }
1747         }
1748 }
1749
1750 static void pp_output(struct parallel_processes *pp)
1751 {
1752         int i = pp->output_owner;
1753         if (pp->children[i].state == GIT_CP_WORKING &&
1754             pp->children[i].err.len) {
1755                 strbuf_write(&pp->children[i].err, stderr);
1756                 strbuf_reset(&pp->children[i].err);
1757         }
1758 }
1759
1760 static int pp_collect_finished(struct parallel_processes *pp)
1761 {
1762         int i, code;
1763         int n = pp->max_processes;
1764         int result = 0;
1765
1766         while (pp->nr_processes > 0) {
1767                 for (i = 0; i < pp->max_processes; i++)
1768                         if (pp->children[i].state == GIT_CP_WAIT_CLEANUP)
1769                                 break;
1770                 if (i == pp->max_processes)
1771                         break;
1772
1773                 code = finish_command(&pp->children[i].process);
1774
1775                 code = pp->task_finished(code,
1776                                          &pp->children[i].err, pp->data,
1777                                          pp->children[i].data);
1778
1779                 if (code)
1780                         result = code;
1781                 if (code < 0)
1782                         break;
1783
1784                 pp->nr_processes--;
1785                 pp->children[i].state = GIT_CP_FREE;
1786                 pp->pfd[i].fd = -1;
1787                 child_process_init(&pp->children[i].process);
1788
1789                 if (i != pp->output_owner) {
1790                         strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1791                         strbuf_reset(&pp->children[i].err);
1792                 } else {
1793                         strbuf_write(&pp->children[i].err, stderr);
1794                         strbuf_reset(&pp->children[i].err);
1795
1796                         /* Output all other finished child processes */
1797                         strbuf_write(&pp->buffered_output, stderr);
1798                         strbuf_reset(&pp->buffered_output);
1799
1800                         /*
1801                          * Pick next process to output live.
1802                          * NEEDSWORK:
1803                          * For now we pick it randomly by doing a round
1804                          * robin. Later we may want to pick the one with
1805                          * the most output or the longest or shortest
1806                          * running process time.
1807                          */
1808                         for (i = 0; i < n; i++)
1809                                 if (pp->children[(pp->output_owner + i) % n].state == GIT_CP_WORKING)
1810                                         break;
1811                         pp->output_owner = (pp->output_owner + i) % n;
1812                 }
1813         }
1814         return result;
1815 }
1816
1817 int run_processes_parallel(int n,
1818                            get_next_task_fn get_next_task,
1819                            start_failure_fn start_failure,
1820                            task_finished_fn task_finished,
1821                            void *pp_cb)
1822 {
1823         int i, code;
1824         int output_timeout = 100;
1825         int spawn_cap = 4;
1826         struct parallel_processes pp;
1827
1828         pp_init(&pp, n, get_next_task, start_failure, task_finished, pp_cb);
1829         while (1) {
1830                 for (i = 0;
1831                     i < spawn_cap && !pp.shutdown &&
1832                     pp.nr_processes < pp.max_processes;
1833                     i++) {
1834                         code = pp_start_one(&pp);
1835                         if (!code)
1836                                 continue;
1837                         if (code < 0) {
1838                                 pp.shutdown = 1;
1839                                 kill_children(&pp, -code);
1840                         }
1841                         break;
1842                 }
1843                 if (!pp.nr_processes)
1844                         break;
1845                 pp_buffer_stderr(&pp, output_timeout);
1846                 pp_output(&pp);
1847                 code = pp_collect_finished(&pp);
1848                 if (code) {
1849                         pp.shutdown = 1;
1850                         if (code < 0)
1851                                 kill_children(&pp, -code);
1852                 }
1853         }
1854
1855         pp_cleanup(&pp);
1856         return 0;
1857 }
1858
1859 int run_processes_parallel_tr2(int n, get_next_task_fn get_next_task,
1860                                start_failure_fn start_failure,
1861                                task_finished_fn task_finished, void *pp_cb,
1862                                const char *tr2_category, const char *tr2_label)
1863 {
1864         int result;
1865
1866         trace2_region_enter_printf(tr2_category, tr2_label, NULL, "max:%d",
1867                                    ((n < 1) ? online_cpus() : n));
1868
1869         result = run_processes_parallel(n, get_next_task, start_failure,
1870                                         task_finished, pp_cb);
1871
1872         trace2_region_leave(tr2_category, tr2_label, NULL);
1873
1874         return result;
1875 }
1876
1877 int run_auto_maintenance(int quiet)
1878 {
1879         int enabled;
1880         struct child_process maint = CHILD_PROCESS_INIT;
1881
1882         if (!git_config_get_bool("maintenance.auto", &enabled) &&
1883             !enabled)
1884                 return 0;
1885
1886         maint.git_cmd = 1;
1887         strvec_pushl(&maint.args, "maintenance", "run", "--auto", NULL);
1888         strvec_push(&maint.args, quiet ? "--quiet" : "--no-quiet");
1889
1890         return run_command(&maint);
1891 }