git.oblomov.eu Git - git/blob - run-command.c

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