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