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 "symlinks.h"
   9 #include "thread-utils.h"
  10 #include "strbuf.h"
  11 #include "string-list.h"
  12 #include "trace.h"
  13 #include "trace2.h"
  14 #include "quote.h"
  15 #include "config.h"
  16 #include "packfile.h"
  17 #include "hook.h"
  18 #include "compat/nonblock.h"
  19 #include "alloc.h"
  20
  21 void child_process_init(struct child_process *child)
  22 {
  23         struct child_process blank = CHILD_PROCESS_INIT;
  24         memcpy(child, &blank, sizeof(*child));
  25 }
  26
  27 void child_process_clear(struct child_process *child)
  28 {
  29         strvec_clear(&child->args);
  30         strvec_clear(&child->env);
  31 }
  32
  33 struct child_to_clean {
  34         pid_t pid;
  35         struct child_process *process;
  36         struct child_to_clean *next;
  37 };
  38 static struct child_to_clean *children_to_clean;
  39 static int installed_child_cleanup_handler;
  40
  41 static void cleanup_children(int sig, int in_signal)
  42 {
  43         struct child_to_clean *children_to_wait_for = NULL;
  44
  45         while (children_to_clean) {
  46                 struct child_to_clean *p = children_to_clean;
  47                 children_to_clean = p->next;
  48
  49                 if (p->process && !in_signal) {
  50                         struct child_process *process = p->process;
  51                         if (process->clean_on_exit_handler) {
  52                                 trace_printf(
  53                                         "trace: run_command: running exit handler for pid %"
  54                                         PRIuMAX, (uintmax_t)p->pid
  55                                 );
  56                                 process->clean_on_exit_handler(process);
  57                         }
  58                 }
  59
  60                 kill(p->pid, sig);
  61
  62                 if (p->process && p->process->wait_after_clean) {
  63                         p->next = children_to_wait_for;
  64                         children_to_wait_for = p;
  65                 } else {
  66                         if (!in_signal)
  67                                 free(p);
  68                 }
  69         }
  70
  71         while (children_to_wait_for) {
  72                 struct child_to_clean *p = children_to_wait_for;
  73                 children_to_wait_for = p->next;
  74
  75                 while (waitpid(p->pid, NULL, 0) < 0 && errno == EINTR)
  76                         ; /* spin waiting for process exit or error */
  77
  78                 if (!in_signal)
  79                         free(p);
  80         }
  81 }
  82
  83 static void cleanup_children_on_signal(int sig)
  84 {
  85         cleanup_children(sig, 1);
  86         sigchain_pop(sig);
  87         raise(sig);
  88 }
  89
  90 static void cleanup_children_on_exit(void)
  91 {
  92         cleanup_children(SIGTERM, 0);
  93 }
  94
  95 static void mark_child_for_cleanup(pid_t pid, struct child_process *process)
  96 {
  97         struct child_to_clean *p = xmalloc(sizeof(*p));
  98         p->pid = pid;
  99         p->process = process;
 100         p->next = children_to_clean;
 101         children_to_clean = p;
 102
 103         if (!installed_child_cleanup_handler) {
 104                 atexit(cleanup_children_on_exit);
 105                 sigchain_push_common(cleanup_children_on_signal);
 106                 installed_child_cleanup_handler = 1;
 107         }
 108 }
 109
 110 static void clear_child_for_cleanup(pid_t pid)
 111 {
 112         struct child_to_clean **pp;
 113
 114         for (pp = &children_to_clean; *pp; pp = &(*pp)->next) {
 115                 struct child_to_clean *clean_me = *pp;
 116
 117                 if (clean_me->pid == pid) {
 118                         *pp = clean_me->next;
 119                         free(clean_me);
 120                         return;
 121                 }
 122         }
 123 }
 124
 125 static inline void close_pair(int fd[2])
 126 {
 127         close(fd[0]);
 128         close(fd[1]);
 129 }
 130
 131 int is_executable(const char *name)
 132 {
 133         struct stat st;
 134
 135         if (stat(name, &st) || /* stat, not lstat */
 136             !S_ISREG(st.st_mode))
 137                 return 0;
 138
 139 #if defined(GIT_WINDOWS_NATIVE)
 140         /*
 141          * On Windows there is no executable bit. The file extension
 142          * indicates whether it can be run as an executable, and Git
 143          * has special-handling to detect scripts and launch them
 144          * through the indicated script interpreter. We test for the
 145          * file extension first because virus scanners may make
 146          * it quite expensive to open many files.
 147          */
 148         if (ends_with(name, ".exe"))
 149                 return S_IXUSR;
 150
 151 {
 152         /*
 153          * Now that we know it does not have an executable extension,
 154          * peek into the file instead.
 155          */
 156         char buf[3] = { 0 };
 157         int n;
 158         int fd = open(name, O_RDONLY);
 159         st.st_mode &= ~S_IXUSR;
 160         if (fd >= 0) {
 161                 n = read(fd, buf, 2);
 162                 if (n == 2)
 163                         /* look for a she-bang */
 164                         if (!strcmp(buf, "#!"))
 165                                 st.st_mode |= S_IXUSR;
 166                 close(fd);
 167         }
 168 }
 169 #endif
 170         return st.st_mode & S_IXUSR;
 171 }
 172
 173 /*
 174  * Search $PATH for a command.  This emulates the path search that
 175  * execvp would perform, without actually executing the command so it
 176  * can be used before fork() to prepare to run a command using
 177  * execve() or after execvp() to diagnose why it failed.
 178  *
 179  * The caller should ensure that file contains no directory
 180  * separators.
 181  *
 182  * Returns the path to the command, as found in $PATH or NULL if the
 183  * command could not be found.  The caller inherits ownership of the memory
 184  * used to store the resultant path.
 185  *
 186  * This should not be used on Windows, where the $PATH search rules
 187  * are more complicated (e.g., a search for "foo" should find
 188  * "foo.exe").
 189  */
 190 static char *locate_in_PATH(const char *file)
 191 {
 192         const char *p = getenv("PATH");
 193         struct strbuf buf = STRBUF_INIT;
 194
 195         if (!p || !*p)
 196                 return NULL;
 197
 198         while (1) {
 199                 const char *end = strchrnul(p, ':');
 200
 201                 strbuf_reset(&buf);
 202
 203                 /* POSIX specifies an empty entry as the current directory. */
 204                 if (end != p) {
 205                         strbuf_add(&buf, p, end - p);
 206                         strbuf_addch(&buf, '/');
 207                 }
 208                 strbuf_addstr(&buf, file);
 209
 210                 if (is_executable(buf.buf))
 211                         return strbuf_detach(&buf, NULL);
 212
 213                 if (!*end)
 214                         break;
 215                 p = end + 1;
 216         }
 217
 218         strbuf_release(&buf);
 219         return NULL;
 220 }
 221
 222 int exists_in_PATH(const char *command)
 223 {
 224         char *r = locate_in_PATH(command);
 225         int found = r != NULL;
 226         free(r);
 227         return found;
 228 }
 229
 230 int sane_execvp(const char *file, char * const argv[])
 231 {
 232 #ifndef GIT_WINDOWS_NATIVE
 233         /*
 234          * execvp() doesn't return, so we all we can do is tell trace2
 235          * what we are about to do and let it leave a hint in the log
 236          * (unless of course the execvp() fails).
 237          *
 238          * we skip this for Windows because the compat layer already
 239          * has to emulate the execvp() call anyway.
 240          */
 241         int exec_id = trace2_exec(file, (const char **)argv);
 242 #endif
 243
 244         if (!execvp(file, argv))
 245                 return 0; /* cannot happen ;-) */
 246
 247 #ifndef GIT_WINDOWS_NATIVE
 248         {
 249                 int ec = errno;
 250                 trace2_exec_result(exec_id, ec);
 251                 errno = ec;
 252         }
 253 #endif
 254
 255         /*
 256          * When a command can't be found because one of the directories
 257          * listed in $PATH is unsearchable, execvp reports EACCES, but
 258          * careful usability testing (read: analysis of occasional bug
 259          * reports) reveals that "No such file or directory" is more
 260          * intuitive.
 261          *
 262          * We avoid commands with "/", because execvp will not do $PATH
 263          * lookups in that case.
 264          *
 265          * The reassignment of EACCES to errno looks like a no-op below,
 266          * but we need to protect against exists_in_PATH overwriting errno.
 267          */
 268         if (errno == EACCES && !strchr(file, '/'))
 269                 errno = exists_in_PATH(file) ? EACCES : ENOENT;
 270         else if (errno == ENOTDIR && !strchr(file, '/'))
 271                 errno = ENOENT;
 272         return -1;
 273 }
 274
 275 static const char **prepare_shell_cmd(struct strvec *out, const char **argv)
 276 {
 277         if (!argv[0])
 278                 BUG("shell command is empty");
 279
 280         if (strcspn(argv[0], "|&;<>()$`\\\"' \t\n*?[#~=%") != strlen(argv[0])) {
 281 #ifndef GIT_WINDOWS_NATIVE
 282                 strvec_push(out, SHELL_PATH);
 283 #else
 284                 strvec_push(out, "sh");
 285 #endif
 286                 strvec_push(out, "-c");
 287
 288                 /*
 289                  * If we have no extra arguments, we do not even need to
 290                  * bother with the "$@" magic.
 291                  */
 292                 if (!argv[1])
 293                         strvec_push(out, argv[0]);
 294                 else
 295                         strvec_pushf(out, "%s \"$@\"", argv[0]);
 296         }
 297
 298         strvec_pushv(out, argv);
 299         return out->v;
 300 }
 301
 302 #ifndef GIT_WINDOWS_NATIVE
 303 static int child_notifier = -1;
 304
 305 enum child_errcode {
 306         CHILD_ERR_CHDIR,
 307         CHILD_ERR_DUP2,
 308         CHILD_ERR_CLOSE,
 309         CHILD_ERR_SIGPROCMASK,
 310         CHILD_ERR_SILENT,
 311         CHILD_ERR_ERRNO
 312 };
 313
 314 struct child_err {
 315         enum child_errcode err;
 316         int syserr; /* errno */
 317 };
 318
 319 static void child_die(enum child_errcode err)
 320 {
 321         struct child_err buf;
 322
 323         buf.err = err;
 324         buf.syserr = errno;
 325
 326         /* write(2) on buf smaller than PIPE_BUF (min 512) is atomic: */
 327         xwrite(child_notifier, &buf, sizeof(buf));
 328         _exit(1);
 329 }
 330
 331 static void child_dup2(int fd, int to)
 332 {
 333         if (dup2(fd, to) < 0)
 334                 child_die(CHILD_ERR_DUP2);
 335 }
 336
 337 static void child_close(int fd)
 338 {
 339         if (close(fd))
 340                 child_die(CHILD_ERR_CLOSE);
 341 }
 342
 343 static void child_close_pair(int fd[2])
 344 {
 345         child_close(fd[0]);
 346         child_close(fd[1]);
 347 }
 348
 349 static void child_error_fn(const char *err UNUSED, va_list params UNUSED)
 350 {
 351         const char msg[] = "error() should not be called in child\n";
 352         xwrite(2, msg, sizeof(msg) - 1);
 353 }
 354
 355 static void child_warn_fn(const char *err UNUSED, va_list params UNUSED)
 356 {
 357         const char msg[] = "warn() should not be called in child\n";
 358         xwrite(2, msg, sizeof(msg) - 1);
 359 }
 360
 361 static void NORETURN child_die_fn(const char *err UNUSED, va_list params UNUSED)
 362 {
 363         const char msg[] = "die() should not be called in child\n";
 364         xwrite(2, msg, sizeof(msg) - 1);
 365         _exit(2);
 366 }
 367
 368 /* this runs in the parent process */
 369 static void child_err_spew(struct child_process *cmd, struct child_err *cerr)
 370 {
 371         static void (*old_errfn)(const char *err, va_list params);
 372         report_fn die_message_routine = get_die_message_routine();
 373
 374         old_errfn = get_error_routine();
 375         set_error_routine(die_message_routine);
 376         errno = cerr->syserr;
 377
 378         switch (cerr->err) {
 379         case CHILD_ERR_CHDIR:
 380                 error_errno("exec '%s': cd to '%s' failed",
 381                             cmd->args.v[0], cmd->dir);
 382                 break;
 383         case CHILD_ERR_DUP2:
 384                 error_errno("dup2() in child failed");
 385                 break;
 386         case CHILD_ERR_CLOSE:
 387                 error_errno("close() in child failed");
 388                 break;
 389         case CHILD_ERR_SIGPROCMASK:
 390                 error_errno("sigprocmask failed restoring signals");
 391                 break;
 392         case CHILD_ERR_SILENT:
 393                 break;
 394         case CHILD_ERR_ERRNO:
 395                 error_errno("cannot exec '%s'", cmd->args.v[0]);
 396                 break;
 397         }
 398         set_error_routine(old_errfn);
 399 }
 400
 401 static int prepare_cmd(struct strvec *out, const struct child_process *cmd)
 402 {
 403         if (!cmd->args.v[0])
 404                 BUG("command is empty");
 405
 406         /*
 407          * Add SHELL_PATH so in the event exec fails with ENOEXEC we can
 408          * attempt to interpret the command with 'sh'.
 409          */
 410         strvec_push(out, SHELL_PATH);
 411
 412         if (cmd->git_cmd) {
 413                 prepare_git_cmd(out, cmd->args.v);
 414         } else if (cmd->use_shell) {
 415                 prepare_shell_cmd(out, cmd->args.v);
 416         } else {
 417                 strvec_pushv(out, cmd->args.v);
 418         }
 419
 420         /*
 421          * If there are no dir separator characters in the command then perform
 422          * a path lookup and use the resolved path as the command to exec. If
 423          * there are dir separator characters, we have exec attempt to invoke
 424          * the command directly.
 425          */
 426         if (!has_dir_sep(out->v[1])) {
 427                 char *program = locate_in_PATH(out->v[1]);
 428                 if (program) {
 429                         free((char *)out->v[1]);
 430                         out->v[1] = program;
 431                 } else {
 432                         strvec_clear(out);
 433                         errno = ENOENT;
 434                         return -1;
 435                 }
 436         }
 437
 438         return 0;
 439 }
 440
 441 static char **prep_childenv(const char *const *deltaenv)
 442 {
 443         extern char **environ;
 444         char **childenv;
 445         struct string_list env = STRING_LIST_INIT_DUP;
 446         struct strbuf key = STRBUF_INIT;
 447         const char *const *p;
 448         int i;
 449
 450         /* Construct a sorted string list consisting of the current environ */
 451         for (p = (const char *const *) environ; p && *p; p++) {
 452                 const char *equals = strchr(*p, '=');
 453
 454                 if (equals) {
 455                         strbuf_reset(&key);
 456                         strbuf_add(&key, *p, equals - *p);
 457                         string_list_append(&env, key.buf)->util = (void *) *p;
 458                 } else {
 459                         string_list_append(&env, *p)->util = (void *) *p;
 460                 }
 461         }
 462         string_list_sort(&env);
 463
 464         /* Merge in 'deltaenv' with the current environ */
 465         for (p = deltaenv; p && *p; p++) {
 466                 const char *equals = strchr(*p, '=');
 467
 468                 if (equals) {
 469                         /* ('key=value'), insert or replace entry */
 470                         strbuf_reset(&key);
 471                         strbuf_add(&key, *p, equals - *p);
 472                         string_list_insert(&env, key.buf)->util = (void *) *p;
 473                 } else {
 474                         /* otherwise ('key') remove existing entry */
 475                         string_list_remove(&env, *p, 0);
 476                 }
 477         }
 478
 479         /* Create an array of 'char *' to be used as the childenv */
 480         ALLOC_ARRAY(childenv, env.nr + 1);
 481         for (i = 0; i < env.nr; i++)
 482                 childenv[i] = env.items[i].util;
 483         childenv[env.nr] = NULL;
 484
 485         string_list_clear(&env, 0);
 486         strbuf_release(&key);
 487         return childenv;
 488 }
 489
 490 struct atfork_state {
 491 #ifndef NO_PTHREADS
 492         int cs;
 493 #endif
 494         sigset_t old;
 495 };
 496
 497 #define CHECK_BUG(err, msg) \
 498         do { \
 499                 int e = (err); \
 500                 if (e) \
 501                         BUG("%s: %s", msg, strerror(e)); \
 502         } while(0)
 503
 504 static void atfork_prepare(struct atfork_state *as)
 505 {
 506         sigset_t all;
 507
 508         if (sigfillset(&all))
 509                 die_errno("sigfillset");
 510 #ifdef NO_PTHREADS
 511         if (sigprocmask(SIG_SETMASK, &all, &as->old))
 512                 die_errno("sigprocmask");
 513 #else
 514         CHECK_BUG(pthread_sigmask(SIG_SETMASK, &all, &as->old),
 515                 "blocking all signals");
 516         CHECK_BUG(pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &as->cs),
 517                 "disabling cancellation");
 518 #endif
 519 }
 520
 521 static void atfork_parent(struct atfork_state *as)
 522 {
 523 #ifdef NO_PTHREADS
 524         if (sigprocmask(SIG_SETMASK, &as->old, NULL))
 525                 die_errno("sigprocmask");
 526 #else
 527         CHECK_BUG(pthread_setcancelstate(as->cs, NULL),
 528                 "re-enabling cancellation");
 529         CHECK_BUG(pthread_sigmask(SIG_SETMASK, &as->old, NULL),
 530                 "restoring signal mask");
 531 #endif
 532 }
 533 #endif /* GIT_WINDOWS_NATIVE */
 534
 535 static inline void set_cloexec(int fd)
 536 {
 537         int flags = fcntl(fd, F_GETFD);
 538         if (flags >= 0)
 539                 fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
 540 }
 541
 542 static int wait_or_whine(pid_t pid, const char *argv0, int in_signal)
 543 {
 544         int status, code = -1;
 545         pid_t waiting;
 546         int failed_errno = 0;
 547
 548         while ((waiting = waitpid(pid, &status, 0)) < 0 && errno == EINTR)
 549                 ;       /* nothing */
 550
 551         if (waiting < 0) {
 552                 failed_errno = errno;
 553                 if (!in_signal)
 554                         error_errno("waitpid for %s failed", argv0);
 555         } else if (waiting != pid) {
 556                 if (!in_signal)
 557                         error("waitpid is confused (%s)", argv0);
 558         } else if (WIFSIGNALED(status)) {
 559                 code = WTERMSIG(status);
 560                 if (!in_signal && code != SIGINT && code != SIGQUIT && code != SIGPIPE)
 561                         error("%s died of signal %d", argv0, code);
 562                 /*
 563                  * This return value is chosen so that code & 0xff
 564                  * mimics the exit code that a POSIX shell would report for
 565                  * a program that died from this signal.
 566                  */
 567                 code += 128;
 568         } else if (WIFEXITED(status)) {
 569                 code = WEXITSTATUS(status);
 570         } else {
 571                 if (!in_signal)
 572                         error("waitpid is confused (%s)", argv0);
 573         }
 574
 575         if (!in_signal)
 576                 clear_child_for_cleanup(pid);
 577
 578         errno = failed_errno;
 579         return code;
 580 }
 581
 582 static void trace_add_env(struct strbuf *dst, const char *const *deltaenv)
 583 {
 584         struct string_list envs = STRING_LIST_INIT_DUP;
 585         const char *const *e;
 586         int i;
 587         int printed_unset = 0;
 588
 589         /* Last one wins, see run-command.c:prep_childenv() for context */
 590         for (e = deltaenv; e && *e; e++) {
 591                 struct strbuf key = STRBUF_INIT;
 592                 char *equals = strchr(*e, '=');
 593
 594                 if (equals) {
 595                         strbuf_add(&key, *e, equals - *e);
 596                         string_list_insert(&envs, key.buf)->util = equals + 1;
 597                 } else {
 598                         string_list_insert(&envs, *e)->util = NULL;
 599                 }
 600                 strbuf_release(&key);
 601         }
 602
 603         /* "unset X Y...;" */
 604         for (i = 0; i < envs.nr; i++) {
 605                 const char *var = envs.items[i].string;
 606                 const char *val = envs.items[i].util;
 607
 608                 if (val || !getenv(var))
 609                         continue;
 610
 611                 if (!printed_unset) {
 612                         strbuf_addstr(dst, " unset");
 613                         printed_unset = 1;
 614                 }
 615                 strbuf_addf(dst, " %s", var);
 616         }
 617         if (printed_unset)
 618                 strbuf_addch(dst, ';');
 619
 620         /* ... followed by "A=B C=D ..." */
 621         for (i = 0; i < envs.nr; i++) {
 622                 const char *var = envs.items[i].string;
 623                 const char *val = envs.items[i].util;
 624                 const char *oldval;
 625
 626                 if (!val)
 627                         continue;
 628
 629                 oldval = getenv(var);
 630                 if (oldval && !strcmp(val, oldval))
 631                         continue;
 632
 633                 strbuf_addf(dst, " %s=", var);
 634                 sq_quote_buf_pretty(dst, val);
 635         }
 636         string_list_clear(&envs, 0);
 637 }
 638
 639 static void trace_run_command(const struct child_process *cp)
 640 {
 641         struct strbuf buf = STRBUF_INIT;
 642
 643         if (!trace_want(&trace_default_key))
 644                 return;
 645
 646         strbuf_addstr(&buf, "trace: run_command:");
 647         if (cp->dir) {
 648                 strbuf_addstr(&buf, " cd ");
 649                 sq_quote_buf_pretty(&buf, cp->dir);
 650                 strbuf_addch(&buf, ';');
 651         }
 652         trace_add_env(&buf, cp->env.v);
 653         if (cp->git_cmd)
 654                 strbuf_addstr(&buf, " git");
 655         sq_quote_argv_pretty(&buf, cp->args.v);
 656
 657         trace_printf("%s", buf.buf);
 658         strbuf_release(&buf);
 659 }
 660
 661 int start_command(struct child_process *cmd)
 662 {
 663         int need_in, need_out, need_err;
 664         int fdin[2], fdout[2], fderr[2];
 665         int failed_errno;
 666         char *str;
 667
 668         /*
 669          * In case of errors we must keep the promise to close FDs
 670          * that have been passed in via ->in and ->out.
 671          */
 672
 673         need_in = !cmd->no_stdin && cmd->in < 0;
 674         if (need_in) {
 675                 if (pipe(fdin) < 0) {
 676                         failed_errno = errno;
 677                         if (cmd->out > 0)
 678                                 close(cmd->out);
 679                         str = "standard input";
 680                         goto fail_pipe;
 681                 }
 682                 cmd->in = fdin[1];
 683         }
 684
 685         need_out = !cmd->no_stdout
 686                 && !cmd->stdout_to_stderr
 687                 && cmd->out < 0;
 688         if (need_out) {
 689                 if (pipe(fdout) < 0) {
 690                         failed_errno = errno;
 691                         if (need_in)
 692                                 close_pair(fdin);
 693                         else if (cmd->in)
 694                                 close(cmd->in);
 695                         str = "standard output";
 696                         goto fail_pipe;
 697                 }
 698                 cmd->out = fdout[0];
 699         }
 700
 701         need_err = !cmd->no_stderr && cmd->err < 0;
 702         if (need_err) {
 703                 if (pipe(fderr) < 0) {
 704                         failed_errno = errno;
 705                         if (need_in)
 706                                 close_pair(fdin);
 707                         else if (cmd->in)
 708                                 close(cmd->in);
 709                         if (need_out)
 710                                 close_pair(fdout);
 711                         else if (cmd->out)
 712                                 close(cmd->out);
 713                         str = "standard error";
 714 fail_pipe:
 715                         error("cannot create %s pipe for %s: %s",
 716                                 str, cmd->args.v[0], strerror(failed_errno));
 717                         child_process_clear(cmd);
 718                         errno = failed_errno;
 719                         return -1;
 720                 }
 721                 cmd->err = fderr[0];
 722         }
 723
 724         trace2_child_start(cmd);
 725         trace_run_command(cmd);
 726
 727         fflush(NULL);
 728
 729         if (cmd->close_object_store)
 730                 close_object_store(the_repository->objects);
 731
 732 #ifndef GIT_WINDOWS_NATIVE
 733 {
 734         int notify_pipe[2];
 735         int null_fd = -1;
 736         char **childenv;
 737         struct strvec argv = STRVEC_INIT;
 738         struct child_err cerr;
 739         struct atfork_state as;
 740
 741         if (prepare_cmd(&argv, cmd) < 0) {
 742                 failed_errno = errno;
 743                 cmd->pid = -1;
 744                 if (!cmd->silent_exec_failure)
 745                         error_errno("cannot run %s", cmd->args.v[0]);
 746                 goto end_of_spawn;
 747         }
 748
 749         if (pipe(notify_pipe))
 750                 notify_pipe[0] = notify_pipe[1] = -1;
 751
 752         if (cmd->no_stdin || cmd->no_stdout || cmd->no_stderr) {
 753                 null_fd = xopen("/dev/null", O_RDWR | O_CLOEXEC);
 754                 set_cloexec(null_fd);
 755         }
 756
 757         childenv = prep_childenv(cmd->env.v);
 758         atfork_prepare(&as);
 759
 760         /*
 761          * NOTE: In order to prevent deadlocking when using threads special
 762          * care should be taken with the function calls made in between the
 763          * fork() and exec() calls.  No calls should be made to functions which
 764          * require acquiring a lock (e.g. malloc) as the lock could have been
 765          * held by another thread at the time of forking, causing the lock to
 766          * never be released in the child process.  This means only
 767          * Async-Signal-Safe functions are permitted in the child.
 768          */
 769         cmd->pid = fork();
 770         failed_errno = errno;
 771         if (!cmd->pid) {
 772                 int sig;
 773                 /*
 774                  * Ensure the default die/error/warn routines do not get
 775                  * called, they can take stdio locks and malloc.
 776                  */
 777                 set_die_routine(child_die_fn);
 778                 set_error_routine(child_error_fn);
 779                 set_warn_routine(child_warn_fn);
 780
 781                 close(notify_pipe[0]);
 782                 set_cloexec(notify_pipe[1]);
 783                 child_notifier = notify_pipe[1];
 784
 785                 if (cmd->no_stdin)
 786                         child_dup2(null_fd, 0);
 787                 else if (need_in) {
 788                         child_dup2(fdin[0], 0);
 789                         child_close_pair(fdin);
 790                 } else if (cmd->in) {
 791                         child_dup2(cmd->in, 0);
 792                         child_close(cmd->in);
 793                 }
 794
 795                 if (cmd->no_stderr)
 796                         child_dup2(null_fd, 2);
 797                 else if (need_err) {
 798                         child_dup2(fderr[1], 2);
 799                         child_close_pair(fderr);
 800                 } else if (cmd->err > 1) {
 801                         child_dup2(cmd->err, 2);
 802                         child_close(cmd->err);
 803                 }
 804
 805                 if (cmd->no_stdout)
 806                         child_dup2(null_fd, 1);
 807                 else if (cmd->stdout_to_stderr)
 808                         child_dup2(2, 1);
 809                 else if (need_out) {
 810                         child_dup2(fdout[1], 1);
 811                         child_close_pair(fdout);
 812                 } else if (cmd->out > 1) {
 813                         child_dup2(cmd->out, 1);
 814                         child_close(cmd->out);
 815                 }
 816
 817                 if (cmd->dir && chdir(cmd->dir))
 818                         child_die(CHILD_ERR_CHDIR);
 819
 820                 /*
 821                  * restore default signal handlers here, in case
 822                  * we catch a signal right before execve below
 823                  */
 824                 for (sig = 1; sig < NSIG; sig++) {
 825                         /* ignored signals get reset to SIG_DFL on execve */
 826                         if (signal(sig, SIG_DFL) == SIG_IGN)
 827                                 signal(sig, SIG_IGN);
 828                 }
 829
 830                 if (sigprocmask(SIG_SETMASK, &as.old, NULL) != 0)
 831                         child_die(CHILD_ERR_SIGPROCMASK);
 832
 833                 /*
 834                  * Attempt to exec using the command and arguments starting at
 835                  * argv.argv[1].  argv.argv[0] contains SHELL_PATH which will
 836                  * be used in the event exec failed with ENOEXEC at which point
 837                  * we will try to interpret the command using 'sh'.
 838                  */
 839                 execve(argv.v[1], (char *const *) argv.v + 1,
 840                        (char *const *) childenv);
 841                 if (errno == ENOEXEC)
 842                         execve(argv.v[0], (char *const *) argv.v,
 843                                (char *const *) childenv);
 844
 845                 if (cmd->silent_exec_failure && errno == ENOENT)
 846                         child_die(CHILD_ERR_SILENT);
 847                 child_die(CHILD_ERR_ERRNO);
 848         }
 849         atfork_parent(&as);
 850         if (cmd->pid < 0)
 851                 error_errno("cannot fork() for %s", cmd->args.v[0]);
 852         else if (cmd->clean_on_exit)
 853                 mark_child_for_cleanup(cmd->pid, cmd);
 854
 855         /*
 856          * Wait for child's exec. If the exec succeeds (or if fork()
 857          * failed), EOF is seen immediately by the parent. Otherwise, the
 858          * child process sends a child_err struct.
 859          * Note that use of this infrastructure is completely advisory,
 860          * therefore, we keep error checks minimal.
 861          */
 862         close(notify_pipe[1]);
 863         if (xread(notify_pipe[0], &cerr, sizeof(cerr)) == sizeof(cerr)) {
 864                 /*
 865                  * At this point we know that fork() succeeded, but exec()
 866                  * failed. Errors have been reported to our stderr.
 867                  */
 868                 wait_or_whine(cmd->pid, cmd->args.v[0], 0);
 869                 child_err_spew(cmd, &cerr);
 870                 failed_errno = errno;
 871                 cmd->pid = -1;
 872         }
 873         close(notify_pipe[0]);
 874
 875         if (null_fd >= 0)
 876                 close(null_fd);
 877         strvec_clear(&argv);
 878         free(childenv);
 879 }
 880 end_of_spawn:
 881
 882 #else
 883 {
 884         int fhin = 0, fhout = 1, fherr = 2;
 885         const char **sargv = cmd->args.v;
 886         struct strvec nargv = STRVEC_INIT;
 887
 888         if (cmd->no_stdin)
 889                 fhin = open("/dev/null", O_RDWR);
 890         else if (need_in)
 891                 fhin = dup(fdin[0]);
 892         else if (cmd->in)
 893                 fhin = dup(cmd->in);
 894
 895         if (cmd->no_stderr)
 896                 fherr = open("/dev/null", O_RDWR);
 897         else if (need_err)
 898                 fherr = dup(fderr[1]);
 899         else if (cmd->err > 2)
 900                 fherr = dup(cmd->err);
 901
 902         if (cmd->no_stdout)
 903                 fhout = open("/dev/null", O_RDWR);
 904         else if (cmd->stdout_to_stderr)
 905                 fhout = dup(fherr);
 906         else if (need_out)
 907                 fhout = dup(fdout[1]);
 908         else if (cmd->out > 1)
 909                 fhout = dup(cmd->out);
 910
 911         if (cmd->git_cmd)
 912                 cmd->args.v = prepare_git_cmd(&nargv, sargv);
 913         else if (cmd->use_shell)
 914                 cmd->args.v = prepare_shell_cmd(&nargv, sargv);
 915
 916         cmd->pid = mingw_spawnvpe(cmd->args.v[0], cmd->args.v,
 917                                   (char**) cmd->env.v,
 918                                   cmd->dir, fhin, fhout, fherr);
 919         failed_errno = errno;
 920         if (cmd->pid < 0 && (!cmd->silent_exec_failure || errno != ENOENT))
 921                 error_errno("cannot spawn %s", cmd->args.v[0]);
 922         if (cmd->clean_on_exit && cmd->pid >= 0)
 923                 mark_child_for_cleanup(cmd->pid, cmd);
 924
 925         strvec_clear(&nargv);
 926         cmd->args.v = sargv;
 927         if (fhin != 0)
 928                 close(fhin);
 929         if (fhout != 1)
 930                 close(fhout);
 931         if (fherr != 2)
 932                 close(fherr);
 933 }
 934 #endif
 935
 936         if (cmd->pid < 0) {
 937                 trace2_child_exit(cmd, -1);
 938
 939                 if (need_in)
 940                         close_pair(fdin);
 941                 else if (cmd->in)
 942                         close(cmd->in);
 943                 if (need_out)
 944                         close_pair(fdout);
 945                 else if (cmd->out)
 946                         close(cmd->out);
 947                 if (need_err)
 948                         close_pair(fderr);
 949                 else if (cmd->err)
 950                         close(cmd->err);
 951                 child_process_clear(cmd);
 952                 errno = failed_errno;
 953                 return -1;
 954         }
 955
 956         if (need_in)
 957                 close(fdin[0]);
 958         else if (cmd->in)
 959                 close(cmd->in);
 960
 961         if (need_out)
 962                 close(fdout[1]);
 963         else if (cmd->out)
 964                 close(cmd->out);
 965
 966         if (need_err)
 967                 close(fderr[1]);
 968         else if (cmd->err)
 969                 close(cmd->err);
 970
 971         return 0;
 972 }
 973
 974 int finish_command(struct child_process *cmd)
 975 {
 976         int ret = wait_or_whine(cmd->pid, cmd->args.v[0], 0);
 977         trace2_child_exit(cmd, ret);
 978         child_process_clear(cmd);
 979         invalidate_lstat_cache();
 980         return ret;
 981 }
 982
 983 int finish_command_in_signal(struct child_process *cmd)
 984 {
 985         int ret = wait_or_whine(cmd->pid, cmd->args.v[0], 1);
 986         if (ret != -1)
 987                 trace2_child_exit(cmd, ret);
 988         return ret;
 989 }
 990
 991
 992 int run_command(struct child_process *cmd)
 993 {
 994         int code;
 995
 996         if (cmd->out < 0 || cmd->err < 0)
 997                 BUG("run_command with a pipe can cause deadlock");
 998
 999         code = start_command(cmd);
1000         if (code)
1001                 return code;
1002         return finish_command(cmd);
1003 }
1004
1005 #ifndef NO_PTHREADS
1006 static pthread_t main_thread;
1007 static int main_thread_set;
1008 static pthread_key_t async_key;
1009 static pthread_key_t async_die_counter;
1010
1011 static void *run_thread(void *data)
1012 {
1013         struct async *async = data;
1014         intptr_t ret;
1015
1016         if (async->isolate_sigpipe) {
1017                 sigset_t mask;
1018                 sigemptyset(&mask);
1019                 sigaddset(&mask, SIGPIPE);
1020                 if (pthread_sigmask(SIG_BLOCK, &mask, NULL)) {
1021                         ret = error("unable to block SIGPIPE in async thread");
1022                         return (void *)ret;
1023                 }
1024         }
1025
1026         pthread_setspecific(async_key, async);
1027         ret = async->proc(async->proc_in, async->proc_out, async->data);
1028         return (void *)ret;
1029 }
1030
1031 static NORETURN void die_async(const char *err, va_list params)
1032 {
1033         report_fn die_message_fn = get_die_message_routine();
1034
1035         die_message_fn(err, params);
1036
1037         if (in_async()) {
1038                 struct async *async = pthread_getspecific(async_key);
1039                 if (async->proc_in >= 0)
1040                         close(async->proc_in);
1041                 if (async->proc_out >= 0)
1042                         close(async->proc_out);
1043                 pthread_exit((void *)128);
1044         }
1045
1046         exit(128);
1047 }
1048
1049 static int async_die_is_recursing(void)
1050 {
1051         void *ret = pthread_getspecific(async_die_counter);
1052         pthread_setspecific(async_die_counter, &async_die_counter); /* set to any non-NULL valid pointer */
1053         return ret != NULL;
1054 }
1055
1056 int in_async(void)
1057 {
1058         if (!main_thread_set)
1059                 return 0; /* no asyncs started yet */
1060         return !pthread_equal(main_thread, pthread_self());
1061 }
1062
1063 static void NORETURN async_exit(int code)
1064 {
1065         pthread_exit((void *)(intptr_t)code);
1066 }
1067
1068 #else
1069
1070 static struct {
1071         void (**handlers)(void);
1072         size_t nr;
1073         size_t alloc;
1074 } git_atexit_hdlrs;
1075
1076 static int git_atexit_installed;
1077
1078 static void git_atexit_dispatch(void)
1079 {
1080         size_t i;
1081
1082         for (i=git_atexit_hdlrs.nr ; i ; i--)
1083                 git_atexit_hdlrs.handlers[i-1]();
1084 }
1085
1086 static void git_atexit_clear(void)
1087 {
1088         free(git_atexit_hdlrs.handlers);
1089         memset(&git_atexit_hdlrs, 0, sizeof(git_atexit_hdlrs));
1090         git_atexit_installed = 0;
1091 }
1092
1093 #undef atexit
1094 int git_atexit(void (*handler)(void))
1095 {
1096         ALLOC_GROW(git_atexit_hdlrs.handlers, git_atexit_hdlrs.nr + 1, git_atexit_hdlrs.alloc);
1097         git_atexit_hdlrs.handlers[git_atexit_hdlrs.nr++] = handler;
1098         if (!git_atexit_installed) {
1099                 if (atexit(&git_atexit_dispatch))
1100                         return -1;
1101                 git_atexit_installed = 1;
1102         }
1103         return 0;
1104 }
1105 #define atexit git_atexit
1106
1107 static int process_is_async;
1108 int in_async(void)
1109 {
1110         return process_is_async;
1111 }
1112
1113 static void NORETURN async_exit(int code)
1114 {
1115         exit(code);
1116 }
1117
1118 #endif
1119
1120 void check_pipe(int err)
1121 {
1122         if (err == EPIPE) {
1123                 if (in_async())
1124                         async_exit(141);
1125
1126                 signal(SIGPIPE, SIG_DFL);
1127                 raise(SIGPIPE);
1128                 /* Should never happen, but just in case... */
1129                 exit(141);
1130         }
1131 }
1132
1133 int start_async(struct async *async)
1134 {
1135         int need_in, need_out;
1136         int fdin[2], fdout[2];
1137         int proc_in, proc_out;
1138
1139         need_in = async->in < 0;
1140         if (need_in) {
1141                 if (pipe(fdin) < 0) {
1142                         if (async->out > 0)
1143                                 close(async->out);
1144                         return error_errno("cannot create pipe");
1145                 }
1146                 async->in = fdin[1];
1147         }
1148
1149         need_out = async->out < 0;
1150         if (need_out) {
1151                 if (pipe(fdout) < 0) {
1152                         if (need_in)
1153                                 close_pair(fdin);
1154                         else if (async->in)
1155                                 close(async->in);
1156                         return error_errno("cannot create pipe");
1157                 }
1158                 async->out = fdout[0];
1159         }
1160
1161         if (need_in)
1162                 proc_in = fdin[0];
1163         else if (async->in)
1164                 proc_in = async->in;
1165         else
1166                 proc_in = -1;
1167
1168         if (need_out)
1169                 proc_out = fdout[1];
1170         else if (async->out)
1171                 proc_out = async->out;
1172         else
1173                 proc_out = -1;
1174
1175 #ifdef NO_PTHREADS
1176         /* Flush stdio before fork() to avoid cloning buffers */
1177         fflush(NULL);
1178
1179         async->pid = fork();
1180         if (async->pid < 0) {
1181                 error_errno("fork (async) failed");
1182                 goto error;
1183         }
1184         if (!async->pid) {
1185                 if (need_in)
1186                         close(fdin[1]);
1187                 if (need_out)
1188                         close(fdout[0]);
1189                 git_atexit_clear();
1190                 process_is_async = 1;
1191                 exit(!!async->proc(proc_in, proc_out, async->data));
1192         }
1193
1194         mark_child_for_cleanup(async->pid, NULL);
1195
1196         if (need_in)
1197                 close(fdin[0]);
1198         else if (async->in)
1199                 close(async->in);
1200
1201         if (need_out)
1202                 close(fdout[1]);
1203         else if (async->out)
1204                 close(async->out);
1205 #else
1206         if (!main_thread_set) {
1207                 /*
1208                  * We assume that the first time that start_async is called
1209                  * it is from the main thread.
1210                  */
1211                 main_thread_set = 1;
1212                 main_thread = pthread_self();
1213                 pthread_key_create(&async_key, NULL);
1214                 pthread_key_create(&async_die_counter, NULL);
1215                 set_die_routine(die_async);
1216                 set_die_is_recursing_routine(async_die_is_recursing);
1217         }
1218
1219         if (proc_in >= 0)
1220                 set_cloexec(proc_in);
1221         if (proc_out >= 0)
1222                 set_cloexec(proc_out);
1223         async->proc_in = proc_in;
1224         async->proc_out = proc_out;
1225         {
1226                 int err = pthread_create(&async->tid, NULL, run_thread, async);
1227                 if (err) {
1228                         error(_("cannot create async thread: %s"), strerror(err));
1229                         goto error;
1230                 }
1231         }
1232 #endif
1233         return 0;
1234
1235 error:
1236         if (need_in)
1237                 close_pair(fdin);
1238         else if (async->in)
1239                 close(async->in);
1240
1241         if (need_out)
1242                 close_pair(fdout);
1243         else if (async->out)
1244                 close(async->out);
1245         return -1;
1246 }
1247
1248 int finish_async(struct async *async)
1249 {
1250 #ifdef NO_PTHREADS
1251         int ret = wait_or_whine(async->pid, "child process", 0);
1252
1253         invalidate_lstat_cache();
1254
1255         return ret;
1256 #else
1257         void *ret = (void *)(intptr_t)(-1);
1258
1259         if (pthread_join(async->tid, &ret))
1260                 error("pthread_join failed");
1261         invalidate_lstat_cache();
1262         return (int)(intptr_t)ret;
1263
1264 #endif
1265 }
1266
1267 int async_with_fork(void)
1268 {
1269 #ifdef NO_PTHREADS
1270         return 1;
1271 #else
1272         return 0;
1273 #endif
1274 }
1275
1276 struct io_pump {
1277         /* initialized by caller */
1278         int fd;
1279         int type; /* POLLOUT or POLLIN */
1280         union {
1281                 struct {
1282                         const char *buf;
1283                         size_t len;
1284                 } out;
1285                 struct {
1286                         struct strbuf *buf;
1287                         size_t hint;
1288                 } in;
1289         } u;
1290
1291         /* returned by pump_io */
1292         int error; /* 0 for success, otherwise errno */
1293
1294         /* internal use */
1295         struct pollfd *pfd;
1296 };
1297
1298 static int pump_io_round(struct io_pump *slots, int nr, struct pollfd *pfd)
1299 {
1300         int pollsize = 0;
1301         int i;
1302
1303         for (i = 0; i < nr; i++) {
1304                 struct io_pump *io = &slots[i];
1305                 if (io->fd < 0)
1306                         continue;
1307                 pfd[pollsize].fd = io->fd;
1308                 pfd[pollsize].events = io->type;
1309                 io->pfd = &pfd[pollsize++];
1310         }
1311
1312         if (!pollsize)
1313                 return 0;
1314
1315         if (poll(pfd, pollsize, -1) < 0) {
1316                 if (errno == EINTR)
1317                         return 1;
1318                 die_errno("poll failed");
1319         }
1320
1321         for (i = 0; i < nr; i++) {
1322                 struct io_pump *io = &slots[i];
1323
1324                 if (io->fd < 0)
1325                         continue;
1326
1327                 if (!(io->pfd->revents & (POLLOUT|POLLIN|POLLHUP|POLLERR|POLLNVAL)))
1328                         continue;
1329
1330                 if (io->type == POLLOUT) {
1331                         ssize_t len;
1332
1333                         /*
1334                          * Don't use xwrite() here. It loops forever on EAGAIN,
1335                          * and we're in our own poll() loop here.
1336                          *
1337                          * Note that we lose xwrite()'s handling of MAX_IO_SIZE
1338                          * and EINTR, so we have to implement those ourselves.
1339                          */
1340                         len = write(io->fd, io->u.out.buf,
1341                                     io->u.out.len <= MAX_IO_SIZE ?
1342                                     io->u.out.len : MAX_IO_SIZE);
1343                         if (len < 0) {
1344                                 if (errno != EINTR && errno != EAGAIN &&
1345                                     errno != ENOSPC) {
1346                                         io->error = errno;
1347                                         close(io->fd);
1348                                         io->fd = -1;
1349                                 }
1350                         } else {
1351                                 io->u.out.buf += len;
1352                                 io->u.out.len -= len;
1353                                 if (!io->u.out.len) {
1354                                         close(io->fd);
1355                                         io->fd = -1;
1356                                 }
1357                         }
1358                 }
1359
1360                 if (io->type == POLLIN) {
1361                         ssize_t len = strbuf_read_once(io->u.in.buf,
1362                                                        io->fd, io->u.in.hint);
1363                         if (len < 0)
1364                                 io->error = errno;
1365                         if (len <= 0) {
1366                                 close(io->fd);
1367                                 io->fd = -1;
1368                         }
1369                 }
1370         }
1371
1372         return 1;
1373 }
1374
1375 static int pump_io(struct io_pump *slots, int nr)
1376 {
1377         struct pollfd *pfd;
1378         int i;
1379
1380         for (i = 0; i < nr; i++)
1381                 slots[i].error = 0;
1382
1383         ALLOC_ARRAY(pfd, nr);
1384         while (pump_io_round(slots, nr, pfd))
1385                 ; /* nothing */
1386         free(pfd);
1387
1388         /* There may be multiple errno values, so just pick the first. */
1389         for (i = 0; i < nr; i++) {
1390                 if (slots[i].error) {
1391                         errno = slots[i].error;
1392                         return -1;
1393                 }
1394         }
1395         return 0;
1396 }
1397
1398
1399 int pipe_command(struct child_process *cmd,
1400                  const char *in, size_t in_len,
1401                  struct strbuf *out, size_t out_hint,
1402                  struct strbuf *err, size_t err_hint)
1403 {
1404         struct io_pump io[3];
1405         int nr = 0;
1406
1407         if (in)
1408                 cmd->in = -1;
1409         if (out)
1410                 cmd->out = -1;
1411         if (err)
1412                 cmd->err = -1;
1413
1414         if (start_command(cmd) < 0)
1415                 return -1;
1416
1417         if (in) {
1418                 if (enable_pipe_nonblock(cmd->in) < 0) {
1419                         error_errno("unable to make pipe non-blocking");
1420                         close(cmd->in);
1421                         if (out)
1422                                 close(cmd->out);
1423                         if (err)
1424                                 close(cmd->err);
1425                         return -1;
1426                 }
1427                 io[nr].fd = cmd->in;
1428                 io[nr].type = POLLOUT;
1429                 io[nr].u.out.buf = in;
1430                 io[nr].u.out.len = in_len;
1431                 nr++;
1432         }
1433         if (out) {
1434                 io[nr].fd = cmd->out;
1435                 io[nr].type = POLLIN;
1436                 io[nr].u.in.buf = out;
1437                 io[nr].u.in.hint = out_hint;
1438                 nr++;
1439         }
1440         if (err) {
1441                 io[nr].fd = cmd->err;
1442                 io[nr].type = POLLIN;
1443                 io[nr].u.in.buf = err;
1444                 io[nr].u.in.hint = err_hint;
1445                 nr++;
1446         }
1447
1448         if (pump_io(io, nr) < 0) {
1449                 finish_command(cmd); /* throw away exit code */
1450                 return -1;
1451         }
1452
1453         return finish_command(cmd);
1454 }
1455
1456 enum child_state {
1457         GIT_CP_FREE,
1458         GIT_CP_WORKING,
1459         GIT_CP_WAIT_CLEANUP,
1460 };
1461
1462 struct parallel_processes {
1463         size_t nr_processes;
1464
1465         struct {
1466                 enum child_state state;
1467                 struct child_process process;
1468                 struct strbuf err;
1469                 void *data;
1470         } *children;
1471         /*
1472          * The struct pollfd is logically part of *children,
1473          * but the system call expects it as its own array.
1474          */
1475         struct pollfd *pfd;
1476
1477         unsigned shutdown : 1;
1478
1479         size_t output_owner;
1480         struct strbuf buffered_output; /* of finished children */
1481 };
1482
1483 struct parallel_processes_for_signal {
1484         const struct run_process_parallel_opts *opts;
1485         const struct parallel_processes *pp;
1486 };
1487
1488 static void kill_children(const struct parallel_processes *pp,
1489                           const struct run_process_parallel_opts *opts,
1490                           int signo)
1491 {
1492         for (size_t i = 0; i < opts->processes; i++)
1493                 if (pp->children[i].state == GIT_CP_WORKING)
1494                         kill(pp->children[i].process.pid, signo);
1495 }
1496
1497 static void kill_children_signal(const struct parallel_processes_for_signal *pp_sig,
1498                                  int signo)
1499 {
1500         kill_children(pp_sig->pp, pp_sig->opts, signo);
1501 }
1502
1503 static struct parallel_processes_for_signal *pp_for_signal;
1504
1505 static void handle_children_on_signal(int signo)
1506 {
1507         kill_children_signal(pp_for_signal, signo);
1508         sigchain_pop(signo);
1509         raise(signo);
1510 }
1511
1512 static void pp_init(struct parallel_processes *pp,
1513                     const struct run_process_parallel_opts *opts,
1514                     struct parallel_processes_for_signal *pp_sig)
1515 {
1516         const size_t n = opts->processes;
1517
1518         if (!n)
1519                 BUG("you must provide a non-zero number of processes!");
1520
1521         trace_printf("run_processes_parallel: preparing to run up to %"PRIuMAX" tasks",
1522                      (uintmax_t)n);
1523
1524         if (!opts->get_next_task)
1525                 BUG("you need to specify a get_next_task function");
1526
1527         CALLOC_ARRAY(pp->children, n);
1528         if (!opts->ungroup)
1529                 CALLOC_ARRAY(pp->pfd, n);
1530
1531         for (size_t i = 0; i < n; i++) {
1532                 strbuf_init(&pp->children[i].err, 0);
1533                 child_process_init(&pp->children[i].process);
1534                 if (pp->pfd) {
1535                         pp->pfd[i].events = POLLIN | POLLHUP;
1536                         pp->pfd[i].fd = -1;
1537                 }
1538         }
1539
1540         pp_sig->pp = pp;
1541         pp_sig->opts = opts;
1542         pp_for_signal = pp_sig;
1543         sigchain_push_common(handle_children_on_signal);
1544 }
1545
1546 static void pp_cleanup(struct parallel_processes *pp,
1547                        const struct run_process_parallel_opts *opts)
1548 {
1549         trace_printf("run_processes_parallel: done");
1550         for (size_t i = 0; i < opts->processes; i++) {
1551                 strbuf_release(&pp->children[i].err);
1552                 child_process_clear(&pp->children[i].process);
1553         }
1554
1555         free(pp->children);
1556         free(pp->pfd);
1557
1558         /*
1559          * When get_next_task added messages to the buffer in its last
1560          * iteration, the buffered output is non empty.
1561          */
1562         strbuf_write(&pp->buffered_output, stderr);
1563         strbuf_release(&pp->buffered_output);
1564
1565         sigchain_pop_common();
1566 }
1567
1568 /* returns
1569  *  0 if a new task was started.
1570  *  1 if no new jobs was started (get_next_task ran out of work, non critical
1571  *    problem with starting a new command)
1572  * <0 no new job was started, user wishes to shutdown early. Use negative code
1573  *    to signal the children.
1574  */
1575 static int pp_start_one(struct parallel_processes *pp,
1576                         const struct run_process_parallel_opts *opts)
1577 {
1578         size_t i;
1579         int code;
1580
1581         for (i = 0; i < opts->processes; i++)
1582                 if (pp->children[i].state == GIT_CP_FREE)
1583                         break;
1584         if (i == opts->processes)
1585                 BUG("bookkeeping is hard");
1586
1587         /*
1588          * By default, do not inherit stdin from the parent process - otherwise,
1589          * all children would share stdin! Users may overwrite this to provide
1590          * something to the child's stdin by having their 'get_next_task'
1591          * callback assign 0 to .no_stdin and an appropriate integer to .in.
1592          */
1593         pp->children[i].process.no_stdin = 1;
1594
1595         code = opts->get_next_task(&pp->children[i].process,
1596                                    opts->ungroup ? NULL : &pp->children[i].err,
1597                                    opts->data,
1598                                    &pp->children[i].data);
1599         if (!code) {
1600                 if (!opts->ungroup) {
1601                         strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1602                         strbuf_reset(&pp->children[i].err);
1603                 }
1604                 return 1;
1605         }
1606         if (!opts->ungroup) {
1607                 pp->children[i].process.err = -1;
1608                 pp->children[i].process.stdout_to_stderr = 1;
1609         }
1610
1611         if (start_command(&pp->children[i].process)) {
1612                 if (opts->start_failure)
1613                         code = opts->start_failure(opts->ungroup ? NULL :
1614                                                    &pp->children[i].err,
1615                                                    opts->data,
1616                                                    pp->children[i].data);
1617                 else
1618                         code = 0;
1619
1620                 if (!opts->ungroup) {
1621                         strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1622                         strbuf_reset(&pp->children[i].err);
1623                 }
1624                 if (code)
1625                         pp->shutdown = 1;
1626                 return code;
1627         }
1628
1629         pp->nr_processes++;
1630         pp->children[i].state = GIT_CP_WORKING;
1631         if (pp->pfd)
1632                 pp->pfd[i].fd = pp->children[i].process.err;
1633         return 0;
1634 }
1635
1636 static void pp_buffer_stderr(struct parallel_processes *pp,
1637                              const struct run_process_parallel_opts *opts,
1638                              int output_timeout)
1639 {
1640         while (poll(pp->pfd, opts->processes, output_timeout) < 0) {
1641                 if (errno == EINTR)
1642                         continue;
1643                 pp_cleanup(pp, opts);
1644                 die_errno("poll");
1645         }
1646
1647         /* Buffer output from all pipes. */
1648         for (size_t i = 0; i < opts->processes; i++) {
1649                 if (pp->children[i].state == GIT_CP_WORKING &&
1650                     pp->pfd[i].revents & (POLLIN | POLLHUP)) {
1651                         int n = strbuf_read_once(&pp->children[i].err,
1652                                                  pp->children[i].process.err, 0);
1653                         if (n == 0) {
1654                                 close(pp->children[i].process.err);
1655                                 pp->children[i].state = GIT_CP_WAIT_CLEANUP;
1656                         } else if (n < 0)
1657                                 if (errno != EAGAIN)
1658                                         die_errno("read");
1659                 }
1660         }
1661 }
1662
1663 static void pp_output(const struct parallel_processes *pp)
1664 {
1665         size_t i = pp->output_owner;
1666
1667         if (pp->children[i].state == GIT_CP_WORKING &&
1668             pp->children[i].err.len) {
1669                 strbuf_write(&pp->children[i].err, stderr);
1670                 strbuf_reset(&pp->children[i].err);
1671         }
1672 }
1673
1674 static int pp_collect_finished(struct parallel_processes *pp,
1675                                const struct run_process_parallel_opts *opts)
1676 {
1677         int code;
1678         size_t i;
1679         int result = 0;
1680
1681         while (pp->nr_processes > 0) {
1682                 for (i = 0; i < opts->processes; i++)
1683                         if (pp->children[i].state == GIT_CP_WAIT_CLEANUP)
1684                                 break;
1685                 if (i == opts->processes)
1686                         break;
1687
1688                 code = finish_command(&pp->children[i].process);
1689
1690                 if (opts->task_finished)
1691                         code = opts->task_finished(code, opts->ungroup ? NULL :
1692                                                    &pp->children[i].err, opts->data,
1693                                                    pp->children[i].data);
1694                 else
1695                         code = 0;
1696
1697                 if (code)
1698                         result = code;
1699                 if (code < 0)
1700                         break;
1701
1702                 pp->nr_processes--;
1703                 pp->children[i].state = GIT_CP_FREE;
1704                 if (pp->pfd)
1705                         pp->pfd[i].fd = -1;
1706                 child_process_init(&pp->children[i].process);
1707
1708                 if (opts->ungroup) {
1709                         ; /* no strbuf_*() work to do here */
1710                 } else if (i != pp->output_owner) {
1711                         strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1712                         strbuf_reset(&pp->children[i].err);
1713                 } else {
1714                         const size_t n = opts->processes;
1715
1716                         strbuf_write(&pp->children[i].err, stderr);
1717                         strbuf_reset(&pp->children[i].err);
1718
1719                         /* Output all other finished child processes */
1720                         strbuf_write(&pp->buffered_output, stderr);
1721                         strbuf_reset(&pp->buffered_output);
1722
1723                         /*
1724                          * Pick next process to output live.
1725                          * NEEDSWORK:
1726                          * For now we pick it randomly by doing a round
1727                          * robin. Later we may want to pick the one with
1728                          * the most output or the longest or shortest
1729                          * running process time.
1730                          */
1731                         for (i = 0; i < n; i++)
1732                                 if (pp->children[(pp->output_owner + i) % n].state == GIT_CP_WORKING)
1733                                         break;
1734                         pp->output_owner = (pp->output_owner + i) % n;
1735                 }
1736         }
1737         return result;
1738 }
1739
1740 void run_processes_parallel(const struct run_process_parallel_opts *opts)
1741 {
1742         int i, code;
1743         int output_timeout = 100;
1744         int spawn_cap = 4;
1745         struct parallel_processes_for_signal pp_sig;
1746         struct parallel_processes pp = {
1747                 .buffered_output = STRBUF_INIT,
1748         };
1749         /* options */
1750         const char *tr2_category = opts->tr2_category;
1751         const char *tr2_label = opts->tr2_label;
1752         const int do_trace2 = tr2_category && tr2_label;
1753
1754         if (do_trace2)
1755                 trace2_region_enter_printf(tr2_category, tr2_label, NULL,
1756                                            "max:%d", opts->processes);
1757
1758         pp_init(&pp, opts, &pp_sig);
1759         while (1) {
1760                 for (i = 0;
1761                     i < spawn_cap && !pp.shutdown &&
1762                     pp.nr_processes < opts->processes;
1763                     i++) {
1764                         code = pp_start_one(&pp, opts);
1765                         if (!code)
1766                                 continue;
1767                         if (code < 0) {
1768                                 pp.shutdown = 1;
1769                                 kill_children(&pp, opts, -code);
1770                         }
1771                         break;
1772                 }
1773                 if (!pp.nr_processes)
1774                         break;
1775                 if (opts->ungroup) {
1776                         for (size_t i = 0; i < opts->processes; i++)
1777                                 pp.children[i].state = GIT_CP_WAIT_CLEANUP;
1778                 } else {
1779                         pp_buffer_stderr(&pp, opts, output_timeout);
1780                         pp_output(&pp);
1781                 }
1782                 code = pp_collect_finished(&pp, opts);
1783                 if (code) {
1784                         pp.shutdown = 1;
1785                         if (code < 0)
1786                                 kill_children(&pp, opts,-code);
1787                 }
1788         }
1789
1790         pp_cleanup(&pp, opts);
1791
1792         if (do_trace2)
1793                 trace2_region_leave(tr2_category, tr2_label, NULL);
1794 }
1795
1796 int run_auto_maintenance(int quiet)
1797 {
1798         int enabled;
1799         struct child_process maint = CHILD_PROCESS_INIT;
1800
1801         if (!git_config_get_bool("maintenance.auto", &enabled) &&
1802             !enabled)
1803                 return 0;
1804
1805         maint.git_cmd = 1;
1806         maint.close_object_store = 1;
1807         strvec_pushl(&maint.args, "maintenance", "run", "--auto", NULL);
1808         strvec_push(&maint.args, quiet ? "--quiet" : "--no-quiet");
1809
1810         return run_command(&maint);
1811 }
1812
1813 void prepare_other_repo_env(struct strvec *env, const char *new_git_dir)
1814 {
1815         const char * const *var;
1816
1817         for (var = local_repo_env; *var; var++) {
1818                 if (strcmp(*var, CONFIG_DATA_ENVIRONMENT) &&
1819                     strcmp(*var, CONFIG_COUNT_ENVIRONMENT))
1820                         strvec_push(env, *var);
1821         }
1822         strvec_pushf(env, "%s=%s", GIT_DIR_ENVIRONMENT, new_git_dir);
1823 }
1824
1825 enum start_bg_result start_bg_command(struct child_process *cmd,
1826                                       start_bg_wait_cb *wait_cb,
1827                                       void *cb_data,
1828                                       unsigned int timeout_sec)
1829 {
1830         enum start_bg_result sbgr = SBGR_ERROR;
1831         int ret;
1832         int wait_status;
1833         pid_t pid_seen;
1834         time_t time_limit;
1835
1836         /*
1837          * We do not allow clean-on-exit because the child process
1838          * should persist in the background and possibly/probably
1839          * after this process exits.  So we don't want to kill the
1840          * child during our atexit routine.
1841          */
1842         if (cmd->clean_on_exit)
1843                 BUG("start_bg_command() does not allow non-zero clean_on_exit");
1844
1845         if (!cmd->trace2_child_class)
1846                 cmd->trace2_child_class = "background";
1847
1848         ret = start_command(cmd);
1849         if (ret) {
1850                 /*
1851                  * We assume that if `start_command()` fails, we
1852                  * either get a complete `trace2_child_start() /
1853                  * trace2_child_exit()` pair or it fails before the
1854                  * `trace2_child_start()` is emitted, so we do not
1855                  * need to worry about it here.
1856                  *
1857                  * We also assume that `start_command()` does not add
1858                  * us to the cleanup list.  And that it calls
1859                  * `child_process_clear()`.
1860                  */
1861                 sbgr = SBGR_ERROR;
1862                 goto done;
1863         }
1864
1865         time(&time_limit);
1866         time_limit += timeout_sec;
1867
1868 wait:
1869         pid_seen = waitpid(cmd->pid, &wait_status, WNOHANG);
1870
1871         if (!pid_seen) {
1872                 /*
1873                  * The child is currently running.  Ask the callback
1874                  * if the child is ready to do work or whether we
1875                  * should keep waiting for it to boot up.
1876                  */
1877                 ret = (*wait_cb)(cmd, cb_data);
1878                 if (!ret) {
1879                         /*
1880                          * The child is running and "ready".
1881                          */
1882                         trace2_child_ready(cmd, "ready");
1883                         sbgr = SBGR_READY;
1884                         goto done;
1885                 } else if (ret > 0) {
1886                         /*
1887                          * The callback said to give it more time to boot up
1888                          * (subject to our timeout limit).
1889                          */
1890                         time_t now;
1891
1892                         time(&now);
1893                         if (now < time_limit)
1894                                 goto wait;
1895
1896                         /*
1897                          * Our timeout has expired.  We don't try to
1898                          * kill the child, but rather let it continue
1899                          * (hopefully) trying to startup.
1900                          */
1901                         trace2_child_ready(cmd, "timeout");
1902                         sbgr = SBGR_TIMEOUT;
1903                         goto done;
1904                 } else {
1905                         /*
1906                          * The cb gave up on this child.  It is still running,
1907                          * but our cb got an error trying to probe it.
1908                          */
1909                         trace2_child_ready(cmd, "error");
1910                         sbgr = SBGR_CB_ERROR;
1911                         goto done;
1912                 }
1913         }
1914
1915         else if (pid_seen == cmd->pid) {
1916                 int child_code = -1;
1917
1918                 /*
1919                  * The child started, but exited or was terminated
1920                  * before becoming "ready".
1921                  *
1922                  * We try to match the behavior of `wait_or_whine()`
1923                  * WRT the handling of WIFSIGNALED() and WIFEXITED()
1924                  * and convert the child's status to a return code for
1925                  * tracing purposes and emit the `trace2_child_exit()`
1926                  * event.
1927                  *
1928                  * We do not want the wait_or_whine() error message
1929                  * because we will be called by client-side library
1930                  * routines.
1931                  */
1932                 if (WIFEXITED(wait_status))
1933                         child_code = WEXITSTATUS(wait_status);
1934                 else if (WIFSIGNALED(wait_status))
1935                         child_code = WTERMSIG(wait_status) + 128;
1936                 trace2_child_exit(cmd, child_code);
1937
1938                 sbgr = SBGR_DIED;
1939                 goto done;
1940         }
1941
1942         else if (pid_seen < 0 && errno == EINTR)
1943                 goto wait;
1944
1945         trace2_child_exit(cmd, -1);
1946         sbgr = SBGR_ERROR;
1947
1948 done:
1949         child_process_clear(cmd);
1950         invalidate_lstat_cache();
1951         return sbgr;
1952 }