run-command.c

   1 #include "cache.h"
   2 #include "run-command.h"
   3 #include "environment.h"
   4 #include "exec-cmd.h"
   5 #include "gettext.h"
   6 #include "sigchain.h"
   7 #include "strvec.h"
   8 #include "thread-utils.h"
   9 #include "strbuf.h"
  10 #include "string-list.h"
  11 #include "trace.h"
  12 #include "trace2.h"
  13 #include "quote.h"
  14 #include "config.h"
  15 #include "packfile.h"
  16 #include "hook.h"
  17 #include "compat/nonblock.h"
  18
  19 void child_process_init(struct child_process *child)
  20 {
  21         struct child_process blank = CHILD_PROCESS_INIT;
  22         memcpy(child, &blank, sizeof(*child));
  23 }
  24
  25 void child_process_clear(struct child_process *child)
  26 {
  27         strvec_clear(&child->args);
  28         strvec_clear(&child->env);
  29 }
  30
  31 struct child_to_clean {
  32         pid_t pid;
  33         struct child_process *process;
  34         struct child_to_clean *next;
  35 };
  36 static struct child_to_clean *children_to_clean;
  37 static int installed_child_cleanup_handler;
  38
  39 static void cleanup_children(int sig, int in_signal)
  40 {
  41         struct child_to_clean *children_to_wait_for = NULL;
  42
  43         while (children_to_clean) {
  44                 struct child_to_clean *p = children_to_clean;
  45                 children_to_clean = p->next;
  46
  47                 if (p->process && !in_signal) {
  48                         struct child_process *process = p->process;
  49                         if (process->clean_on_exit_handler) {
  50                                 trace_printf(
  51                                         "trace: run_command: running exit handler for pid %"
  52                                         PRIuMAX, (uintmax_t)p->pid
  53                                 );
  54                                 process->clean_on_exit_handler(process);
  55                         }
  56                 }
  57
  58                 kill(p->pid, sig);
  59
  60                 if (p->process && p->process->wait_after_clean) {
  61                         p->next = children_to_wait_for;
  62                         children_to_wait_for = p;
  63                 } else {
  64                         if (!in_signal)
  65                                 free(p);
  66                 }
  67         }
  68
  69         while (children_to_wait_for) {
  70                 struct child_to_clean *p = children_to_wait_for;
  71                 children_to_wait_for = p->next;
  72
  73                 while (waitpid(p->pid, NULL, 0) < 0 && errno == EINTR)
  74                         ; /* spin waiting for process exit or error */
  75
  76                 if (!in_signal)
  77                         free(p);
  78         }
  79 }
  80
  81 static void cleanup_children_on_signal(int sig)
  82 {
  83         cleanup_children(sig, 1);
  84         sigchain_pop(sig);
  85         raise(sig);
  86 }
  87
  88 static void cleanup_children_on_exit(void)
  89 {
  90         cleanup_children(SIGTERM, 0);
  91 }
  92
  93 static void mark_child_for_cleanup(pid_t pid, struct child_process *process)
  94 {
  95         struct child_to_clean *p = xmalloc(sizeof(*p));
  96         p->pid = pid;
  97         p->process = process;
  98         p->next = children_to_clean;
  99         children_to_clean = p;
 100
 101         if (!installed_child_cleanup_handler) {
 102                 atexit(cleanup_children_on_exit);
 103                 sigchain_push_common(cleanup_children_on_signal);
 104                 installed_child_cleanup_handler = 1;
 105         }
 106 }
 107
 108 static void clear_child_for_cleanup(pid_t pid)
 109 {
 110         struct child_to_clean **pp;
 111
 112         for (pp = &children_to_clean; *pp; pp = &(*pp)->next) {
 113                 struct child_to_clean *clean_me = *pp;
 114
 115                 if (clean_me->pid == pid) {
 116                         *pp = clean_me->next;
 117                         free(clean_me);
 118                         return;
 119                 }
 120         }
 121 }
 122
 123 static inline void close_pair(int fd[2])
 124 {
 125         close(fd[0]);
 126         close(fd[1]);
 127 }
 128
 129 int is_executable(const char *name)
 130 {
 131         struct stat st;
 132
 133         if (stat(name, &st) || /* stat, not lstat */
 134             !S_ISREG(st.st_mode))
 135                 return 0;
 136
 137 #if defined(GIT_WINDOWS_NATIVE)
 138         /*
 139          * On Windows there is no executable bit. The file extension
 140          * indicates whether it can be run as an executable, and Git
 141          * has special-handling to detect scripts and launch them
 142          * through the indicated script interpreter. We test for the
 143          * file extension first because virus scanners may make
 144          * it quite expensive to open many files.
 145          */
 146         if (ends_with(name, ".exe"))
 147                 return S_IXUSR;
 148
 149 {
 150         /*
 151          * Now that we know it does not have an executable extension,
 152          * peek into the file instead.
 153          */
 154         char buf[3] = { 0 };
 155         int n;
 156         int fd = open(name, O_RDONLY);
 157         st.st_mode &= ~S_IXUSR;
 158         if (fd >= 0) {
 159                 n = read(fd, buf, 2);
 160                 if (n == 2)
 161                         /* look for a she-bang */
 162                         if (!strcmp(buf, "#!"))
 163                                 st.st_mode |= S_IXUSR;
 164                 close(fd);
 165         }
 166 }
 167 #endif
 168         return st.st_mode & S_IXUSR;
 169 }
 170
 171 /*
 172  * Search $PATH for a command.  This emulates the path search that
 173  * execvp would perform, without actually executing the command so it
 174  * can be used before fork() to prepare to run a command using
 175  * execve() or after execvp() to diagnose why it failed.
 176  *
 177  * The caller should ensure that file contains no directory
 178  * separators.
 179  *
 180  * Returns the path to the command, as found in $PATH or NULL if the
 181  * command could not be found.  The caller inherits ownership of the memory
 182  * used to store the resultant path.
 183  *
 184  * This should not be used on Windows, where the $PATH search rules
 185  * are more complicated (e.g., a search for "foo" should find
 186  * "foo.exe").
 187  */
 188 static char *locate_in_PATH(const char *file)
 189 {
 190         const char *p = getenv("PATH");
 191         struct strbuf buf = STRBUF_INIT;
 192
 193         if (!p || !*p)
 194                 return NULL;
 195
 196         while (1) {
 197                 const char *end = strchrnul(p, ':');
 198
 199                 strbuf_reset(&buf);
 200
 201                 /* POSIX specifies an empty entry as the current directory. */
 202                 if (end != p) {
 203                         strbuf_add(&buf, p, end - p);
 204                         strbuf_addch(&buf, '/');
 205                 }
 206                 strbuf_addstr(&buf, file);
 207
 208                 if (is_executable(buf.buf))
 209                         return strbuf_detach(&buf, NULL);
 210
 211                 if (!*end)
 212                         break;
 213                 p = end + 1;
 214         }
 215
 216         strbuf_release(&buf);
 217         return NULL;
 218 }
 219
 220 int exists_in_PATH(const char *command)
 221 {
 222         char *r = locate_in_PATH(command);
 223         int found = r != NULL;
 224         free(r);
 225         return found;
 226 }
 227
 228 int sane_execvp(const char *file, char * const argv[])
 229 {
 230 #ifndef GIT_WINDOWS_NATIVE
 231         /*
 232          * execvp() doesn't return, so we all we can do is tell trace2
 233          * what we are about to do and let it leave a hint in the log
 234          * (unless of course the execvp() fails).
 235          *
 236          * we skip this for Windows because the compat layer already
 237          * has to emulate the execvp() call anyway.
 238          */
 239         int exec_id = trace2_exec(file, (const char **)argv);
 240 #endif
 241
 242         if (!execvp(file, argv))
 243                 return 0; /* cannot happen ;-) */
 244
 245 #ifndef GIT_WINDOWS_NATIVE
 246         {
 247                 int ec = errno;
 248                 trace2_exec_result(exec_id, ec);
 249                 errno = ec;
 250         }
 251 #endif
 252
 253         /*
 254          * When a command can't be found because one of the directories
 255          * listed in $PATH is unsearchable, execvp reports EACCES, but
 256          * careful usability testing (read: analysis of occasional bug
 257          * reports) reveals that "No such file or directory" is more
 258          * intuitive.
 259          *
 260          * We avoid commands with "/", because execvp will not do $PATH
 261          * lookups in that case.
 262          *
 263          * The reassignment of EACCES to errno looks like a no-op below,
 264          * but we need to protect against exists_in_PATH overwriting errno.
 265          */
 266         if (errno == EACCES && !strchr(file, '/'))
 267                 errno = exists_in_PATH(file) ? EACCES : ENOENT;
 268         else if (errno == ENOTDIR && !strchr(file, '/'))
 269                 errno = ENOENT;
 270         return -1;
 271 }
 272
 273 static const char **prepare_shell_cmd(struct strvec *out, const char **argv)
 274 {
 275         if (!argv[0])
 276                 BUG("shell command is empty");
 277
 278         if (strcspn(argv[0], "|&;<>()$`\\\"' \t\n*?[#~=%") != strlen(argv[0])) {
 279 #ifndef GIT_WINDOWS_NATIVE
 280                 strvec_push(out, SHELL_PATH);
 281 #else
 282                 strvec_push(out, "sh");
 283 #endif
 284                 strvec_push(out, "-c");
 285
 286                 /*
 287                  * If we have no extra arguments, we do not even need to
 288                  * bother with the "$@" magic.
 289                  */
 290                 if (!argv[1])
 291                         strvec_push(out, argv[0]);
 292                 else
 293                         strvec_pushf(out, "%s \"$@\"", argv[0]);
 294         }
 295
 296         strvec_pushv(out, argv);
 297         return out->v;
 298 }
 299
 300 #ifndef GIT_WINDOWS_NATIVE
 301 static int child_notifier = -1;
 302
 303 enum child_errcode {
 304         CHILD_ERR_CHDIR,
 305         CHILD_ERR_DUP2,
 306         CHILD_ERR_CLOSE,
 307         CHILD_ERR_SIGPROCMASK,
 308         CHILD_ERR_ENOENT,
 309         CHILD_ERR_SILENT,
 310         CHILD_ERR_ERRNO
 311 };
 312
 313 struct child_err {
 314         enum child_errcode err;
 315         int syserr; /* errno */
 316 };
 317
 318 static void child_die(enum child_errcode err)
 319 {
 320         struct child_err buf;
 321
 322         buf.err = err;
 323         buf.syserr = errno;
 324
 325         /* write(2) on buf smaller than PIPE_BUF (min 512) is atomic: */
 326         xwrite(child_notifier, &buf, sizeof(buf));
 327         _exit(1);
 328 }
 329
 330 static void child_dup2(int fd, int to)
 331 {
 332         if (dup2(fd, to) < 0)
 333                 child_die(CHILD_ERR_DUP2);
 334 }
 335
 336 static void child_close(int fd)
 337 {
 338         if (close(fd))
 339                 child_die(CHILD_ERR_CLOSE);
 340 }
 341
 342 static void child_close_pair(int fd[2])
 343 {
 344         child_close(fd[0]);
 345         child_close(fd[1]);
 346 }
 347
 348 static void child_error_fn(const char *err UNUSED, va_list params UNUSED)
 349 {
 350         const char msg[] = "error() should not be called in child\n";
 351         xwrite(2, msg, sizeof(msg) - 1);
 352 }
 353
 354 static void child_warn_fn(const char *err UNUSED, va_list params UNUSED)
 355 {
 356         const char msg[] = "warn() should not be called in child\n";
 357         xwrite(2, msg, sizeof(msg) - 1);
 358 }
 359
 360 static void NORETURN child_die_fn(const char *err UNUSED, va_list params UNUSED)
 361 {
 362         const char msg[] = "die() should not be called in child\n";
 363         xwrite(2, msg, sizeof(msg) - 1);
 364         _exit(2);
 365 }
 366
 367 /* this runs in the parent process */
 368 static void child_err_spew(struct child_process *cmd, struct child_err *cerr)
 369 {
 370         static void (*old_errfn)(const char *err, va_list params);
 371         report_fn die_message_routine = get_die_message_routine();
 372
 373         old_errfn = get_error_routine();
 374         set_error_routine(die_message_routine);
 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->args.v[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->args.v[0]);
 393                 break;
 394         case CHILD_ERR_SILENT:
 395                 break;
 396         case CHILD_ERR_ERRNO:
 397                 error_errno("cannot exec '%s'", cmd->args.v[0]);
 398                 break;
 399         }
 400         set_error_routine(old_errfn);
 401 }
 402
 403 static int prepare_cmd(struct strvec *out, const struct child_process *cmd)
 404 {
 405         if (!cmd->args.v[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         strvec_push(out, SHELL_PATH);
 413
 414         if (cmd->git_cmd) {
 415                 prepare_git_cmd(out, cmd->args.v);
 416         } else if (cmd->use_shell) {
 417                 prepare_shell_cmd(out, cmd->args.v);
 418         } else {
 419                 strvec_pushv(out, cmd->args.v);
 420         }
 421
 422         /*
 423          * If there are no dir separator characters in the command then perform
 424          * a path lookup and use the resolved path as the command to exec. If
 425          * there are dir separator characters, we have exec attempt to invoke
 426          * the command directly.
 427          */
 428         if (!has_dir_sep(out->v[1])) {
 429                 char *program = locate_in_PATH(out->v[1]);
 430                 if (program) {
 431                         free((char *)out->v[1]);
 432                         out->v[1] = program;
 433                 } else {
 434                         strvec_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
 553         if (waiting < 0) {
 554                 failed_errno = errno;
 555                 if (!in_signal)
 556                         error_errno("waitpid for %s failed", argv0);
 557         } else if (waiting != pid) {
 558                 if (!in_signal)
 559                         error("waitpid is confused (%s)", argv0);
 560         } else if (WIFSIGNALED(status)) {
 561                 code = WTERMSIG(status);
 562                 if (!in_signal && 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                 if (!in_signal)
 574                         error("waitpid is confused (%s)", argv0);
 575         }
 576
 577         if (!in_signal)
 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         trace_add_env(&buf, cp->env.v);
 655         if (cp->git_cmd)
 656                 strbuf_addstr(&buf, " git");
 657         sq_quote_argv_pretty(&buf, cp->args.v);
 658
 659         trace_printf("%s", buf.buf);
 660         strbuf_release(&buf);
 661 }
 662
 663 int start_command(struct child_process *cmd)
 664 {
 665         int need_in, need_out, need_err;
 666         int fdin[2], fdout[2], fderr[2];
 667         int failed_errno;
 668         char *str;
 669
 670         /*
 671          * In case of errors we must keep the promise to close FDs
 672          * that have been passed in via ->in and ->out.
 673          */
 674
 675         need_in = !cmd->no_stdin && cmd->in < 0;
 676         if (need_in) {
 677                 if (pipe(fdin) < 0) {
 678                         failed_errno = errno;
 679                         if (cmd->out > 0)
 680                                 close(cmd->out);
 681                         str = "standard input";
 682                         goto fail_pipe;
 683                 }
 684                 cmd->in = fdin[1];
 685         }
 686
 687         need_out = !cmd->no_stdout
 688                 && !cmd->stdout_to_stderr
 689                 && cmd->out < 0;
 690         if (need_out) {
 691                 if (pipe(fdout) < 0) {
 692                         failed_errno = errno;
 693                         if (need_in)
 694                                 close_pair(fdin);
 695                         else if (cmd->in)
 696                                 close(cmd->in);
 697                         str = "standard output";
 698                         goto fail_pipe;
 699                 }
 700                 cmd->out = fdout[0];
 701         }
 702
 703         need_err = !cmd->no_stderr && cmd->err < 0;
 704         if (need_err) {
 705                 if (pipe(fderr) < 0) {
 706                         failed_errno = errno;
 707                         if (need_in)
 708                                 close_pair(fdin);
 709                         else if (cmd->in)
 710                                 close(cmd->in);
 711                         if (need_out)
 712                                 close_pair(fdout);
 713                         else if (cmd->out)
 714                                 close(cmd->out);
 715                         str = "standard error";
 716 fail_pipe:
 717                         error("cannot create %s pipe for %s: %s",
 718                                 str, cmd->args.v[0], strerror(failed_errno));
 719                         child_process_clear(cmd);
 720                         errno = failed_errno;
 721                         return -1;
 722                 }
 723                 cmd->err = fderr[0];
 724         }
 725
 726         trace2_child_start(cmd);
 727         trace_run_command(cmd);
 728
 729         fflush(NULL);
 730
 731         if (cmd->close_object_store)
 732                 close_object_store(the_repository->objects);
 733
 734 #ifndef GIT_WINDOWS_NATIVE
 735 {
 736         int notify_pipe[2];
 737         int null_fd = -1;
 738         char **childenv;
 739         struct strvec argv = STRVEC_INIT;
 740         struct child_err cerr;
 741         struct atfork_state as;
 742
 743         if (prepare_cmd(&argv, cmd) < 0) {
 744                 failed_errno = errno;
 745                 cmd->pid = -1;
 746                 if (!cmd->silent_exec_failure)
 747                         error_errno("cannot run %s", cmd->args.v[0]);
 748                 goto end_of_spawn;
 749         }
 750
 751         if (pipe(notify_pipe))
 752                 notify_pipe[0] = notify_pipe[1] = -1;
 753
 754         if (cmd->no_stdin || cmd->no_stdout || cmd->no_stderr) {
 755                 null_fd = xopen("/dev/null", O_RDWR | O_CLOEXEC);
 756                 set_cloexec(null_fd);
 757         }
 758
 759         childenv = prep_childenv(cmd->env.v);
 760         atfork_prepare(&as);
 761
 762         /*
 763          * NOTE: In order to prevent deadlocking when using threads special
 764          * care should be taken with the function calls made in between the
 765          * fork() and exec() calls.  No calls should be made to functions which
 766          * require acquiring a lock (e.g. malloc) as the lock could have been
 767          * held by another thread at the time of forking, causing the lock to
 768          * never be released in the child process.  This means only
 769          * Async-Signal-Safe functions are permitted in the child.
 770          */
 771         cmd->pid = fork();
 772         failed_errno = errno;
 773         if (!cmd->pid) {
 774                 int sig;
 775                 /*
 776                  * Ensure the default die/error/warn routines do not get
 777                  * called, they can take stdio locks and malloc.
 778                  */
 779                 set_die_routine(child_die_fn);
 780                 set_error_routine(child_error_fn);
 781                 set_warn_routine(child_warn_fn);
 782
 783                 close(notify_pipe[0]);
 784                 set_cloexec(notify_pipe[1]);
 785                 child_notifier = notify_pipe[1];
 786
 787                 if (cmd->no_stdin)
 788                         child_dup2(null_fd, 0);
 789                 else if (need_in) {
 790                         child_dup2(fdin[0], 0);
 791                         child_close_pair(fdin);
 792                 } else if (cmd->in) {
 793                         child_dup2(cmd->in, 0);
 794                         child_close(cmd->in);
 795                 }
 796
 797                 if (cmd->no_stderr)
 798                         child_dup2(null_fd, 2);
 799                 else if (need_err) {
 800                         child_dup2(fderr[1], 2);
 801                         child_close_pair(fderr);
 802                 } else if (cmd->err > 1) {
 803                         child_dup2(cmd->err, 2);
 804                         child_close(cmd->err);
 805                 }
 806
 807                 if (cmd->no_stdout)
 808                         child_dup2(null_fd, 1);
 809                 else if (cmd->stdout_to_stderr)
 810                         child_dup2(2, 1);
 811                 else if (need_out) {
 812                         child_dup2(fdout[1], 1);
 813                         child_close_pair(fdout);
 814                 } else if (cmd->out > 1) {
 815                         child_dup2(cmd->out, 1);
 816                         child_close(cmd->out);
 817                 }
 818
 819                 if (cmd->dir && chdir(cmd->dir))
 820                         child_die(CHILD_ERR_CHDIR);
 821
 822                 /*
 823                  * restore default signal handlers here, in case
 824                  * we catch a signal right before execve below
 825                  */
 826                 for (sig = 1; sig < NSIG; sig++) {
 827                         /* ignored signals get reset to SIG_DFL on execve */
 828                         if (signal(sig, SIG_DFL) == SIG_IGN)
 829                                 signal(sig, SIG_IGN);
 830                 }
 831
 832                 if (sigprocmask(SIG_SETMASK, &as.old, NULL) != 0)
 833                         child_die(CHILD_ERR_SIGPROCMASK);
 834
 835                 /*
 836                  * Attempt to exec using the command and arguments starting at
 837                  * argv.argv[1].  argv.argv[0] contains SHELL_PATH which will
 838                  * be used in the event exec failed with ENOEXEC at which point
 839                  * we will try to interpret the command using 'sh'.
 840                  */
 841                 execve(argv.v[1], (char *const *) argv.v + 1,
 842                        (char *const *) childenv);
 843                 if (errno == ENOEXEC)
 844                         execve(argv.v[0], (char *const *) argv.v,
 845                                (char *const *) childenv);
 846
 847                 if (errno == ENOENT) {
 848                         if (cmd->silent_exec_failure)
 849                                 child_die(CHILD_ERR_SILENT);
 850                         child_die(CHILD_ERR_ENOENT);
 851                 } else {
 852                         child_die(CHILD_ERR_ERRNO);
 853                 }
 854         }
 855         atfork_parent(&as);
 856         if (cmd->pid < 0)
 857                 error_errno("cannot fork() for %s", cmd->args.v[0]);
 858         else if (cmd->clean_on_exit)
 859                 mark_child_for_cleanup(cmd->pid, cmd);
 860
 861         /*
 862          * Wait for child's exec. If the exec succeeds (or if fork()
 863          * failed), EOF is seen immediately by the parent. Otherwise, the
 864          * child process sends a child_err struct.
 865          * Note that use of this infrastructure is completely advisory,
 866          * therefore, we keep error checks minimal.
 867          */
 868         close(notify_pipe[1]);
 869         if (xread(notify_pipe[0], &cerr, sizeof(cerr)) == sizeof(cerr)) {
 870                 /*
 871                  * At this point we know that fork() succeeded, but exec()
 872                  * failed. Errors have been reported to our stderr.
 873                  */
 874                 wait_or_whine(cmd->pid, cmd->args.v[0], 0);
 875                 child_err_spew(cmd, &cerr);
 876                 failed_errno = errno;
 877                 cmd->pid = -1;
 878         }
 879         close(notify_pipe[0]);
 880
 881         if (null_fd >= 0)
 882                 close(null_fd);
 883         strvec_clear(&argv);
 884         free(childenv);
 885 }
 886 end_of_spawn:
 887
 888 #else
 889 {
 890         int fhin = 0, fhout = 1, fherr = 2;
 891         const char **sargv = cmd->args.v;
 892         struct strvec nargv = STRVEC_INIT;
 893
 894         if (cmd->no_stdin)
 895                 fhin = open("/dev/null", O_RDWR);
 896         else if (need_in)
 897                 fhin = dup(fdin[0]);
 898         else if (cmd->in)
 899                 fhin = dup(cmd->in);
 900
 901         if (cmd->no_stderr)
 902                 fherr = open("/dev/null", O_RDWR);
 903         else if (need_err)
 904                 fherr = dup(fderr[1]);
 905         else if (cmd->err > 2)
 906                 fherr = dup(cmd->err);
 907
 908         if (cmd->no_stdout)
 909                 fhout = open("/dev/null", O_RDWR);
 910         else if (cmd->stdout_to_stderr)
 911                 fhout = dup(fherr);
 912         else if (need_out)
 913                 fhout = dup(fdout[1]);
 914         else if (cmd->out > 1)
 915                 fhout = dup(cmd->out);
 916
 917         if (cmd->git_cmd)
 918                 cmd->args.v = prepare_git_cmd(&nargv, sargv);
 919         else if (cmd->use_shell)
 920                 cmd->args.v = prepare_shell_cmd(&nargv, sargv);
 921
 922         cmd->pid = mingw_spawnvpe(cmd->args.v[0], cmd->args.v,
 923                                   (char**) cmd->env.v,
 924                                   cmd->dir, fhin, fhout, fherr);
 925         failed_errno = errno;
 926         if (cmd->pid < 0 && (!cmd->silent_exec_failure || errno != ENOENT))
 927                 error_errno("cannot spawn %s", cmd->args.v[0]);
 928         if (cmd->clean_on_exit && cmd->pid >= 0)
 929                 mark_child_for_cleanup(cmd->pid, cmd);
 930
 931         strvec_clear(&nargv);
 932         cmd->args.v = sargv;
 933         if (fhin != 0)
 934                 close(fhin);
 935         if (fhout != 1)
 936                 close(fhout);
 937         if (fherr != 2)
 938                 close(fherr);
 939 }
 940 #endif
 941
 942         if (cmd->pid < 0) {
 943                 trace2_child_exit(cmd, -1);
 944
 945                 if (need_in)
 946                         close_pair(fdin);
 947                 else if (cmd->in)
 948                         close(cmd->in);
 949                 if (need_out)
 950                         close_pair(fdout);
 951                 else if (cmd->out)
 952                         close(cmd->out);
 953                 if (need_err)
 954                         close_pair(fderr);
 955                 else if (cmd->err)
 956                         close(cmd->err);
 957                 child_process_clear(cmd);
 958                 errno = failed_errno;
 959                 return -1;
 960         }
 961
 962         if (need_in)
 963                 close(fdin[0]);
 964         else if (cmd->in)
 965                 close(cmd->in);
 966
 967         if (need_out)
 968                 close(fdout[1]);
 969         else if (cmd->out)
 970                 close(cmd->out);
 971
 972         if (need_err)
 973                 close(fderr[1]);
 974         else if (cmd->err)
 975                 close(cmd->err);
 976
 977         return 0;
 978 }
 979
 980 int finish_command(struct child_process *cmd)
 981 {
 982         int ret = wait_or_whine(cmd->pid, cmd->args.v[0], 0);
 983         trace2_child_exit(cmd, ret);
 984         child_process_clear(cmd);
 985         invalidate_lstat_cache();
 986         return ret;
 987 }
 988
 989 int finish_command_in_signal(struct child_process *cmd)
 990 {
 991         int ret = wait_or_whine(cmd->pid, cmd->args.v[0], 1);
 992         if (ret != -1)
 993                 trace2_child_exit(cmd, ret);
 994         return ret;
 995 }
 996
 997
 998 int run_command(struct child_process *cmd)
 999 {
1000         int code;
1001
1002         if (cmd->out < 0 || cmd->err < 0)
1003                 BUG("run_command with a pipe can cause deadlock");
1004
1005         code = start_command(cmd);
1006         if (code)
1007                 return code;
1008         return finish_command(cmd);
1009 }
1010
1011 #ifndef NO_PTHREADS
1012 static pthread_t main_thread;
1013 static int main_thread_set;
1014 static pthread_key_t async_key;
1015 static pthread_key_t async_die_counter;
1016
1017 static void *run_thread(void *data)
1018 {
1019         struct async *async = data;
1020         intptr_t ret;
1021
1022         if (async->isolate_sigpipe) {
1023                 sigset_t mask;
1024                 sigemptyset(&mask);
1025                 sigaddset(&mask, SIGPIPE);
1026                 if (pthread_sigmask(SIG_BLOCK, &mask, NULL)) {
1027                         ret = error("unable to block SIGPIPE in async thread");
1028                         return (void *)ret;
1029                 }
1030         }
1031
1032         pthread_setspecific(async_key, async);
1033         ret = async->proc(async->proc_in, async->proc_out, async->data);
1034         return (void *)ret;
1035 }
1036
1037 static NORETURN void die_async(const char *err, va_list params)
1038 {
1039         report_fn die_message_fn = get_die_message_routine();
1040
1041         die_message_fn(err, params);
1042
1043         if (in_async()) {
1044                 struct async *async = pthread_getspecific(async_key);
1045                 if (async->proc_in >= 0)
1046                         close(async->proc_in);
1047                 if (async->proc_out >= 0)
1048                         close(async->proc_out);
1049                 pthread_exit((void *)128);
1050         }
1051
1052         exit(128);
1053 }
1054
1055 static int async_die_is_recursing(void)
1056 {
1057         void *ret = pthread_getspecific(async_die_counter);
1058         pthread_setspecific(async_die_counter, &async_die_counter); /* set to any non-NULL valid pointer */
1059         return ret != NULL;
1060 }
1061
1062 int in_async(void)
1063 {
1064         if (!main_thread_set)
1065                 return 0; /* no asyncs started yet */
1066         return !pthread_equal(main_thread, pthread_self());
1067 }
1068
1069 static void NORETURN async_exit(int code)
1070 {
1071         pthread_exit((void *)(intptr_t)code);
1072 }
1073
1074 #else
1075
1076 static struct {
1077         void (**handlers)(void);
1078         size_t nr;
1079         size_t alloc;
1080 } git_atexit_hdlrs;
1081
1082 static int git_atexit_installed;
1083
1084 static void git_atexit_dispatch(void)
1085 {
1086         size_t i;
1087
1088         for (i=git_atexit_hdlrs.nr ; i ; i--)
1089                 git_atexit_hdlrs.handlers[i-1]();
1090 }
1091
1092 static void git_atexit_clear(void)
1093 {
1094         free(git_atexit_hdlrs.handlers);
1095         memset(&git_atexit_hdlrs, 0, sizeof(git_atexit_hdlrs));
1096         git_atexit_installed = 0;
1097 }
1098
1099 #undef atexit
1100 int git_atexit(void (*handler)(void))
1101 {
1102         ALLOC_GROW(git_atexit_hdlrs.handlers, git_atexit_hdlrs.nr + 1, git_atexit_hdlrs.alloc);
1103         git_atexit_hdlrs.handlers[git_atexit_hdlrs.nr++] = handler;
1104         if (!git_atexit_installed) {
1105                 if (atexit(&git_atexit_dispatch))
1106                         return -1;
1107                 git_atexit_installed = 1;
1108         }
1109         return 0;
1110 }
1111 #define atexit git_atexit
1112
1113 static int process_is_async;
1114 int in_async(void)
1115 {
1116         return process_is_async;
1117 }
1118
1119 static void NORETURN async_exit(int code)
1120 {
1121         exit(code);
1122 }
1123
1124 #endif
1125
1126 void check_pipe(int err)
1127 {
1128         if (err == EPIPE) {
1129                 if (in_async())
1130                         async_exit(141);
1131
1132                 signal(SIGPIPE, SIG_DFL);
1133                 raise(SIGPIPE);
1134                 /* Should never happen, but just in case... */
1135                 exit(141);
1136         }
1137 }
1138
1139 int start_async(struct async *async)
1140 {
1141         int need_in, need_out;
1142         int fdin[2], fdout[2];
1143         int proc_in, proc_out;
1144
1145         need_in = async->in < 0;
1146         if (need_in) {
1147                 if (pipe(fdin) < 0) {
1148                         if (async->out > 0)
1149                                 close(async->out);
1150                         return error_errno("cannot create pipe");
1151                 }
1152                 async->in = fdin[1];
1153         }
1154
1155         need_out = async->out < 0;
1156         if (need_out) {
1157                 if (pipe(fdout) < 0) {
1158                         if (need_in)
1159                                 close_pair(fdin);
1160                         else if (async->in)
1161                                 close(async->in);
1162                         return error_errno("cannot create pipe");
1163                 }
1164                 async->out = fdout[0];
1165         }
1166
1167         if (need_in)
1168                 proc_in = fdin[0];
1169         else if (async->in)
1170                 proc_in = async->in;
1171         else
1172                 proc_in = -1;
1173
1174         if (need_out)
1175                 proc_out = fdout[1];
1176         else if (async->out)
1177                 proc_out = async->out;
1178         else
1179                 proc_out = -1;
1180
1181 #ifdef NO_PTHREADS
1182         /* Flush stdio before fork() to avoid cloning buffers */
1183         fflush(NULL);
1184
1185         async->pid = fork();
1186         if (async->pid < 0) {
1187                 error_errno("fork (async) failed");
1188                 goto error;
1189         }
1190         if (!async->pid) {
1191                 if (need_in)
1192                         close(fdin[1]);
1193                 if (need_out)
1194                         close(fdout[0]);
1195                 git_atexit_clear();
1196                 process_is_async = 1;
1197                 exit(!!async->proc(proc_in, proc_out, async->data));
1198         }
1199
1200         mark_child_for_cleanup(async->pid, NULL);
1201
1202         if (need_in)
1203                 close(fdin[0]);
1204         else if (async->in)
1205                 close(async->in);
1206
1207         if (need_out)
1208                 close(fdout[1]);
1209         else if (async->out)
1210                 close(async->out);
1211 #else
1212         if (!main_thread_set) {
1213                 /*
1214                  * We assume that the first time that start_async is called
1215                  * it is from the main thread.
1216                  */
1217                 main_thread_set = 1;
1218                 main_thread = pthread_self();
1219                 pthread_key_create(&async_key, NULL);
1220                 pthread_key_create(&async_die_counter, NULL);
1221                 set_die_routine(die_async);
1222                 set_die_is_recursing_routine(async_die_is_recursing);
1223         }
1224
1225         if (proc_in >= 0)
1226                 set_cloexec(proc_in);
1227         if (proc_out >= 0)
1228                 set_cloexec(proc_out);
1229         async->proc_in = proc_in;
1230         async->proc_out = proc_out;
1231         {
1232                 int err = pthread_create(&async->tid, NULL, run_thread, async);
1233                 if (err) {
1234                         error(_("cannot create async thread: %s"), strerror(err));
1235                         goto error;
1236                 }
1237         }
1238 #endif
1239         return 0;
1240
1241 error:
1242         if (need_in)
1243                 close_pair(fdin);
1244         else if (async->in)
1245                 close(async->in);
1246
1247         if (need_out)
1248                 close_pair(fdout);
1249         else if (async->out)
1250                 close(async->out);
1251         return -1;
1252 }
1253
1254 int finish_async(struct async *async)
1255 {
1256 #ifdef NO_PTHREADS
1257         int ret = wait_or_whine(async->pid, "child process", 0);
1258
1259         invalidate_lstat_cache();
1260
1261         return ret;
1262 #else
1263         void *ret = (void *)(intptr_t)(-1);
1264
1265         if (pthread_join(async->tid, &ret))
1266                 error("pthread_join failed");
1267         invalidate_lstat_cache();
1268         return (int)(intptr_t)ret;
1269
1270 #endif
1271 }
1272
1273 int async_with_fork(void)
1274 {
1275 #ifdef NO_PTHREADS
1276         return 1;
1277 #else
1278         return 0;
1279 #endif
1280 }
1281
1282 struct io_pump {
1283         /* initialized by caller */
1284         int fd;
1285         int type; /* POLLOUT or POLLIN */
1286         union {
1287                 struct {
1288                         const char *buf;
1289                         size_t len;
1290                 } out;
1291                 struct {
1292                         struct strbuf *buf;
1293                         size_t hint;
1294                 } in;
1295         } u;
1296
1297         /* returned by pump_io */
1298         int error; /* 0 for success, otherwise errno */
1299
1300         /* internal use */
1301         struct pollfd *pfd;
1302 };
1303
1304 static int pump_io_round(struct io_pump *slots, int nr, struct pollfd *pfd)
1305 {
1306         int pollsize = 0;
1307         int i;
1308
1309         for (i = 0; i < nr; i++) {
1310                 struct io_pump *io = &slots[i];
1311                 if (io->fd < 0)
1312                         continue;
1313                 pfd[pollsize].fd = io->fd;
1314                 pfd[pollsize].events = io->type;
1315                 io->pfd = &pfd[pollsize++];
1316         }
1317
1318         if (!pollsize)
1319                 return 0;
1320
1321         if (poll(pfd, pollsize, -1) < 0) {
1322                 if (errno == EINTR)
1323                         return 1;
1324                 die_errno("poll failed");
1325         }
1326
1327         for (i = 0; i < nr; i++) {
1328                 struct io_pump *io = &slots[i];
1329
1330                 if (io->fd < 0)
1331                         continue;
1332
1333                 if (!(io->pfd->revents & (POLLOUT|POLLIN|POLLHUP|POLLERR|POLLNVAL)))
1334                         continue;
1335
1336                 if (io->type == POLLOUT) {
1337                         ssize_t len;
1338
1339                         /*
1340                          * Don't use xwrite() here. It loops forever on EAGAIN,
1341                          * and we're in our own poll() loop here.
1342                          *
1343                          * Note that we lose xwrite()'s handling of MAX_IO_SIZE
1344                          * and EINTR, so we have to implement those ourselves.
1345                          */
1346                         len = write(io->fd, io->u.out.buf,
1347                                     io->u.out.len <= MAX_IO_SIZE ?
1348                                     io->u.out.len : MAX_IO_SIZE);
1349                         if (len < 0) {
1350                                 if (errno != EINTR && errno != EAGAIN &&
1351                                     errno != ENOSPC) {
1352                                         io->error = errno;
1353                                         close(io->fd);
1354                                         io->fd = -1;
1355                                 }
1356                         } else {
1357                                 io->u.out.buf += len;
1358                                 io->u.out.len -= len;
1359                                 if (!io->u.out.len) {
1360                                         close(io->fd);
1361                                         io->fd = -1;
1362                                 }
1363                         }
1364                 }
1365
1366                 if (io->type == POLLIN) {
1367                         ssize_t len = strbuf_read_once(io->u.in.buf,
1368                                                        io->fd, io->u.in.hint);
1369                         if (len < 0)
1370                                 io->error = errno;
1371                         if (len <= 0) {
1372                                 close(io->fd);
1373                                 io->fd = -1;
1374                         }
1375                 }
1376         }
1377
1378         return 1;
1379 }
1380
1381 static int pump_io(struct io_pump *slots, int nr)
1382 {
1383         struct pollfd *pfd;
1384         int i;
1385
1386         for (i = 0; i < nr; i++)
1387                 slots[i].error = 0;
1388
1389         ALLOC_ARRAY(pfd, nr);
1390         while (pump_io_round(slots, nr, pfd))
1391                 ; /* nothing */
1392         free(pfd);
1393
1394         /* There may be multiple errno values, so just pick the first. */
1395         for (i = 0; i < nr; i++) {
1396                 if (slots[i].error) {
1397                         errno = slots[i].error;
1398                         return -1;
1399                 }
1400         }
1401         return 0;
1402 }
1403
1404
1405 int pipe_command(struct child_process *cmd,
1406                  const char *in, size_t in_len,
1407                  struct strbuf *out, size_t out_hint,
1408                  struct strbuf *err, size_t err_hint)
1409 {
1410         struct io_pump io[3];
1411         int nr = 0;
1412
1413         if (in)
1414                 cmd->in = -1;
1415         if (out)
1416                 cmd->out = -1;
1417         if (err)
1418                 cmd->err = -1;
1419
1420         if (start_command(cmd) < 0)
1421                 return -1;
1422
1423         if (in) {
1424                 if (enable_pipe_nonblock(cmd->in) < 0) {
1425                         error_errno("unable to make pipe non-blocking");
1426                         close(cmd->in);
1427                         if (out)
1428                                 close(cmd->out);
1429                         if (err)
1430                                 close(cmd->err);
1431                         return -1;
1432                 }
1433                 io[nr].fd = cmd->in;
1434                 io[nr].type = POLLOUT;
1435                 io[nr].u.out.buf = in;
1436                 io[nr].u.out.len = in_len;
1437                 nr++;
1438         }
1439         if (out) {
1440                 io[nr].fd = cmd->out;
1441                 io[nr].type = POLLIN;
1442                 io[nr].u.in.buf = out;
1443                 io[nr].u.in.hint = out_hint;
1444                 nr++;
1445         }
1446         if (err) {
1447                 io[nr].fd = cmd->err;
1448                 io[nr].type = POLLIN;
1449                 io[nr].u.in.buf = err;
1450                 io[nr].u.in.hint = err_hint;
1451                 nr++;
1452         }
1453
1454         if (pump_io(io, nr) < 0) {
1455                 finish_command(cmd); /* throw away exit code */
1456                 return -1;
1457         }
1458
1459         return finish_command(cmd);
1460 }
1461
1462 enum child_state {
1463         GIT_CP_FREE,
1464         GIT_CP_WORKING,
1465         GIT_CP_WAIT_CLEANUP,
1466 };
1467
1468 struct parallel_processes {
1469         size_t nr_processes;
1470
1471         struct {
1472                 enum child_state state;
1473                 struct child_process process;
1474                 struct strbuf err;
1475                 void *data;
1476         } *children;
1477         /*
1478          * The struct pollfd is logically part of *children,
1479          * but the system call expects it as its own array.
1480          */
1481         struct pollfd *pfd;
1482
1483         unsigned shutdown : 1;
1484
1485         size_t output_owner;
1486         struct strbuf buffered_output; /* of finished children */
1487 };
1488
1489 struct parallel_processes_for_signal {
1490         const struct run_process_parallel_opts *opts;
1491         const struct parallel_processes *pp;
1492 };
1493
1494 static void kill_children(const struct parallel_processes *pp,
1495                           const struct run_process_parallel_opts *opts,
1496                           int signo)
1497 {
1498         for (size_t i = 0; i < opts->processes; i++)
1499                 if (pp->children[i].state == GIT_CP_WORKING)
1500                         kill(pp->children[i].process.pid, signo);
1501 }
1502
1503 static void kill_children_signal(const struct parallel_processes_for_signal *pp_sig,
1504                                  int signo)
1505 {
1506         kill_children(pp_sig->pp, pp_sig->opts, signo);
1507 }
1508
1509 static struct parallel_processes_for_signal *pp_for_signal;
1510
1511 static void handle_children_on_signal(int signo)
1512 {
1513         kill_children_signal(pp_for_signal, signo);
1514         sigchain_pop(signo);
1515         raise(signo);
1516 }
1517
1518 static void pp_init(struct parallel_processes *pp,
1519                     const struct run_process_parallel_opts *opts,
1520                     struct parallel_processes_for_signal *pp_sig)
1521 {
1522         const size_t n = opts->processes;
1523
1524         if (!n)
1525                 BUG("you must provide a non-zero number of processes!");
1526
1527         trace_printf("run_processes_parallel: preparing to run up to %"PRIuMAX" tasks",
1528                      (uintmax_t)n);
1529
1530         if (!opts->get_next_task)
1531                 BUG("you need to specify a get_next_task function");
1532
1533         CALLOC_ARRAY(pp->children, n);
1534         if (!opts->ungroup)
1535                 CALLOC_ARRAY(pp->pfd, n);
1536
1537         for (size_t i = 0; i < n; i++) {
1538                 strbuf_init(&pp->children[i].err, 0);
1539                 child_process_init(&pp->children[i].process);
1540                 if (pp->pfd) {
1541                         pp->pfd[i].events = POLLIN | POLLHUP;
1542                         pp->pfd[i].fd = -1;
1543                 }
1544         }
1545
1546         pp_sig->pp = pp;
1547         pp_sig->opts = opts;
1548         pp_for_signal = pp_sig;
1549         sigchain_push_common(handle_children_on_signal);
1550 }
1551
1552 static void pp_cleanup(struct parallel_processes *pp,
1553                        const struct run_process_parallel_opts *opts)
1554 {
1555         trace_printf("run_processes_parallel: done");
1556         for (size_t i = 0; i < opts->processes; i++) {
1557                 strbuf_release(&pp->children[i].err);
1558                 child_process_clear(&pp->children[i].process);
1559         }
1560
1561         free(pp->children);
1562         free(pp->pfd);
1563
1564         /*
1565          * When get_next_task added messages to the buffer in its last
1566          * iteration, the buffered output is non empty.
1567          */
1568         strbuf_write(&pp->buffered_output, stderr);
1569         strbuf_release(&pp->buffered_output);
1570
1571         sigchain_pop_common();
1572 }
1573
1574 /* returns
1575  *  0 if a new task was started.
1576  *  1 if no new jobs was started (get_next_task ran out of work, non critical
1577  *    problem with starting a new command)
1578  * <0 no new job was started, user wishes to shutdown early. Use negative code
1579  *    to signal the children.
1580  */
1581 static int pp_start_one(struct parallel_processes *pp,
1582                         const struct run_process_parallel_opts *opts)
1583 {
1584         size_t i;
1585         int code;
1586
1587         for (i = 0; i < opts->processes; i++)
1588                 if (pp->children[i].state == GIT_CP_FREE)
1589                         break;
1590         if (i == opts->processes)
1591                 BUG("bookkeeping is hard");
1592
1593         /*
1594          * By default, do not inherit stdin from the parent process - otherwise,
1595          * all children would share stdin! Users may overwrite this to provide
1596          * something to the child's stdin by having their 'get_next_task'
1597          * callback assign 0 to .no_stdin and an appropriate integer to .in.
1598          */
1599         pp->children[i].process.no_stdin = 1;
1600
1601         code = opts->get_next_task(&pp->children[i].process,
1602                                    opts->ungroup ? NULL : &pp->children[i].err,
1603                                    opts->data,
1604                                    &pp->children[i].data);
1605         if (!code) {
1606                 if (!opts->ungroup) {
1607                         strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1608                         strbuf_reset(&pp->children[i].err);
1609                 }
1610                 return 1;
1611         }
1612         if (!opts->ungroup) {
1613                 pp->children[i].process.err = -1;
1614                 pp->children[i].process.stdout_to_stderr = 1;
1615         }
1616
1617         if (start_command(&pp->children[i].process)) {
1618                 if (opts->start_failure)
1619                         code = opts->start_failure(opts->ungroup ? NULL :
1620                                                    &pp->children[i].err,
1621                                                    opts->data,
1622                                                    pp->children[i].data);
1623                 else
1624                         code = 0;
1625
1626                 if (!opts->ungroup) {
1627                         strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1628                         strbuf_reset(&pp->children[i].err);
1629                 }
1630                 if (code)
1631                         pp->shutdown = 1;
1632                 return code;
1633         }
1634
1635         pp->nr_processes++;
1636         pp->children[i].state = GIT_CP_WORKING;
1637         if (pp->pfd)
1638                 pp->pfd[i].fd = pp->children[i].process.err;
1639         return 0;
1640 }
1641
1642 static void pp_buffer_stderr(struct parallel_processes *pp,
1643                              const struct run_process_parallel_opts *opts,
1644                              int output_timeout)
1645 {
1646         while (poll(pp->pfd, opts->processes, output_timeout) < 0) {
1647                 if (errno == EINTR)
1648                         continue;
1649                 pp_cleanup(pp, opts);
1650                 die_errno("poll");
1651         }
1652
1653         /* Buffer output from all pipes. */
1654         for (size_t i = 0; i < opts->processes; i++) {
1655                 if (pp->children[i].state == GIT_CP_WORKING &&
1656                     pp->pfd[i].revents & (POLLIN | POLLHUP)) {
1657                         int n = strbuf_read_once(&pp->children[i].err,
1658                                                  pp->children[i].process.err, 0);
1659                         if (n == 0) {
1660                                 close(pp->children[i].process.err);
1661                                 pp->children[i].state = GIT_CP_WAIT_CLEANUP;
1662                         } else if (n < 0)
1663                                 if (errno != EAGAIN)
1664                                         die_errno("read");
1665                 }
1666         }
1667 }
1668
1669 static void pp_output(const struct parallel_processes *pp)
1670 {
1671         size_t i = pp->output_owner;
1672
1673         if (pp->children[i].state == GIT_CP_WORKING &&
1674             pp->children[i].err.len) {
1675                 strbuf_write(&pp->children[i].err, stderr);
1676                 strbuf_reset(&pp->children[i].err);
1677         }
1678 }
1679
1680 static int pp_collect_finished(struct parallel_processes *pp,
1681                                const struct run_process_parallel_opts *opts)
1682 {
1683         int code;
1684         size_t i;
1685         int result = 0;
1686
1687         while (pp->nr_processes > 0) {
1688                 for (i = 0; i < opts->processes; i++)
1689                         if (pp->children[i].state == GIT_CP_WAIT_CLEANUP)
1690                                 break;
1691                 if (i == opts->processes)
1692                         break;
1693
1694                 code = finish_command(&pp->children[i].process);
1695
1696                 if (opts->task_finished)
1697                         code = opts->task_finished(code, opts->ungroup ? NULL :
1698                                                    &pp->children[i].err, opts->data,
1699                                                    pp->children[i].data);
1700                 else
1701                         code = 0;
1702
1703                 if (code)
1704                         result = code;
1705                 if (code < 0)
1706                         break;
1707
1708                 pp->nr_processes--;
1709                 pp->children[i].state = GIT_CP_FREE;
1710                 if (pp->pfd)
1711                         pp->pfd[i].fd = -1;
1712                 child_process_init(&pp->children[i].process);
1713
1714                 if (opts->ungroup) {
1715                         ; /* no strbuf_*() work to do here */
1716                 } else if (i != pp->output_owner) {
1717                         strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1718                         strbuf_reset(&pp->children[i].err);
1719                 } else {
1720                         const size_t n = opts->processes;
1721
1722                         strbuf_write(&pp->children[i].err, stderr);
1723                         strbuf_reset(&pp->children[i].err);
1724
1725                         /* Output all other finished child processes */
1726                         strbuf_write(&pp->buffered_output, stderr);
1727                         strbuf_reset(&pp->buffered_output);
1728
1729                         /*
1730                          * Pick next process to output live.
1731                          * NEEDSWORK:
1732                          * For now we pick it randomly by doing a round
1733                          * robin. Later we may want to pick the one with
1734                          * the most output or the longest or shortest
1735                          * running process time.
1736                          */
1737                         for (i = 0; i < n; i++)
1738                                 if (pp->children[(pp->output_owner + i) % n].state == GIT_CP_WORKING)
1739                                         break;
1740                         pp->output_owner = (pp->output_owner + i) % n;
1741                 }
1742         }
1743         return result;
1744 }
1745
1746 void run_processes_parallel(const struct run_process_parallel_opts *opts)
1747 {
1748         int i, code;
1749         int output_timeout = 100;
1750         int spawn_cap = 4;
1751         struct parallel_processes_for_signal pp_sig;
1752         struct parallel_processes pp = {
1753                 .buffered_output = STRBUF_INIT,
1754         };
1755         /* options */
1756         const char *tr2_category = opts->tr2_category;
1757         const char *tr2_label = opts->tr2_label;
1758         const int do_trace2 = tr2_category && tr2_label;
1759
1760         if (do_trace2)
1761                 trace2_region_enter_printf(tr2_category, tr2_label, NULL,
1762                                            "max:%d", opts->processes);
1763
1764         pp_init(&pp, opts, &pp_sig);
1765         while (1) {
1766                 for (i = 0;
1767                     i < spawn_cap && !pp.shutdown &&
1768                     pp.nr_processes < opts->processes;
1769                     i++) {
1770                         code = pp_start_one(&pp, opts);
1771                         if (!code)
1772                                 continue;
1773                         if (code < 0) {
1774                                 pp.shutdown = 1;
1775                                 kill_children(&pp, opts, -code);
1776                         }
1777                         break;
1778                 }
1779                 if (!pp.nr_processes)
1780                         break;
1781                 if (opts->ungroup) {
1782                         for (size_t i = 0; i < opts->processes; i++)
1783                                 pp.children[i].state = GIT_CP_WAIT_CLEANUP;
1784                 } else {
1785                         pp_buffer_stderr(&pp, opts, output_timeout);
1786                         pp_output(&pp);
1787                 }
1788                 code = pp_collect_finished(&pp, opts);
1789                 if (code) {
1790                         pp.shutdown = 1;
1791                         if (code < 0)
1792                                 kill_children(&pp, opts,-code);
1793                 }
1794         }
1795
1796         pp_cleanup(&pp, opts);
1797
1798         if (do_trace2)
1799                 trace2_region_leave(tr2_category, tr2_label, NULL);
1800 }
1801
1802 int run_auto_maintenance(int quiet)
1803 {
1804         int enabled;
1805         struct child_process maint = CHILD_PROCESS_INIT;
1806
1807         if (!git_config_get_bool("maintenance.auto", &enabled) &&
1808             !enabled)
1809                 return 0;
1810
1811         maint.git_cmd = 1;
1812         maint.close_object_store = 1;
1813         strvec_pushl(&maint.args, "maintenance", "run", "--auto", NULL);
1814         strvec_push(&maint.args, quiet ? "--quiet" : "--no-quiet");
1815
1816         return run_command(&maint);
1817 }
1818
1819 void prepare_other_repo_env(struct strvec *env, const char *new_git_dir)
1820 {
1821         const char * const *var;
1822
1823         for (var = local_repo_env; *var; var++) {
1824                 if (strcmp(*var, CONFIG_DATA_ENVIRONMENT) &&
1825                     strcmp(*var, CONFIG_COUNT_ENVIRONMENT))
1826                         strvec_push(env, *var);
1827         }
1828         strvec_pushf(env, "%s=%s", GIT_DIR_ENVIRONMENT, new_git_dir);
1829 }
1830
1831 enum start_bg_result start_bg_command(struct child_process *cmd,
1832                                       start_bg_wait_cb *wait_cb,
1833                                       void *cb_data,
1834                                       unsigned int timeout_sec)
1835 {
1836         enum start_bg_result sbgr = SBGR_ERROR;
1837         int ret;
1838         int wait_status;
1839         pid_t pid_seen;
1840         time_t time_limit;
1841
1842         /*
1843          * We do not allow clean-on-exit because the child process
1844          * should persist in the background and possibly/probably
1845          * after this process exits.  So we don't want to kill the
1846          * child during our atexit routine.
1847          */
1848         if (cmd->clean_on_exit)
1849                 BUG("start_bg_command() does not allow non-zero clean_on_exit");
1850
1851         if (!cmd->trace2_child_class)
1852                 cmd->trace2_child_class = "background";
1853
1854         ret = start_command(cmd);
1855         if (ret) {
1856                 /*
1857                  * We assume that if `start_command()` fails, we
1858                  * either get a complete `trace2_child_start() /
1859                  * trace2_child_exit()` pair or it fails before the
1860                  * `trace2_child_start()` is emitted, so we do not
1861                  * need to worry about it here.
1862                  *
1863                  * We also assume that `start_command()` does not add
1864                  * us to the cleanup list.  And that it calls
1865                  * `child_process_clear()`.
1866                  */
1867                 sbgr = SBGR_ERROR;
1868                 goto done;
1869         }
1870
1871         time(&time_limit);
1872         time_limit += timeout_sec;
1873
1874 wait:
1875         pid_seen = waitpid(cmd->pid, &wait_status, WNOHANG);
1876
1877         if (!pid_seen) {
1878                 /*
1879                  * The child is currently running.  Ask the callback
1880                  * if the child is ready to do work or whether we
1881                  * should keep waiting for it to boot up.
1882                  */
1883                 ret = (*wait_cb)(cmd, cb_data);
1884                 if (!ret) {
1885                         /*
1886                          * The child is running and "ready".
1887                          */
1888                         trace2_child_ready(cmd, "ready");
1889                         sbgr = SBGR_READY;
1890                         goto done;
1891                 } else if (ret > 0) {
1892                         /*
1893                          * The callback said to give it more time to boot up
1894                          * (subject to our timeout limit).
1895                          */
1896                         time_t now;
1897
1898                         time(&now);
1899                         if (now < time_limit)
1900                                 goto wait;
1901
1902                         /*
1903                          * Our timeout has expired.  We don't try to
1904                          * kill the child, but rather let it continue
1905                          * (hopefully) trying to startup.
1906                          */
1907                         trace2_child_ready(cmd, "timeout");
1908                         sbgr = SBGR_TIMEOUT;
1909                         goto done;
1910                 } else {
1911                         /*
1912                          * The cb gave up on this child.  It is still running,
1913                          * but our cb got an error trying to probe it.
1914                          */
1915                         trace2_child_ready(cmd, "error");
1916                         sbgr = SBGR_CB_ERROR;
1917                         goto done;
1918                 }
1919         }
1920
1921         else if (pid_seen == cmd->pid) {
1922                 int child_code = -1;
1923
1924                 /*
1925                  * The child started, but exited or was terminated
1926                  * before becoming "ready".
1927                  *
1928                  * We try to match the behavior of `wait_or_whine()`
1929                  * WRT the handling of WIFSIGNALED() and WIFEXITED()
1930                  * and convert the child's status to a return code for
1931                  * tracing purposes and emit the `trace2_child_exit()`
1932                  * event.
1933                  *
1934                  * We do not want the wait_or_whine() error message
1935                  * because we will be called by client-side library
1936                  * routines.
1937                  */
1938                 if (WIFEXITED(wait_status))
1939                         child_code = WEXITSTATUS(wait_status);
1940                 else if (WIFSIGNALED(wait_status))
1941                         child_code = WTERMSIG(wait_status) + 128;
1942                 trace2_child_exit(cmd, child_code);
1943
1944                 sbgr = SBGR_DIED;
1945                 goto done;
1946         }
1947
1948         else if (pid_seen < 0 && errno == EINTR)
1949                 goto wait;
1950
1951         trace2_child_exit(cmd, -1);
1952         sbgr = SBGR_ERROR;
1953
1954 done:
1955         child_process_clear(cmd);
1956         invalidate_lstat_cache();
1957         return sbgr;
1958 }