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 int 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 '/' characters, we have exec attempt to invoke the command
 405          * 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                 } else {
 413                         argv_array_clear(out);
 414                         errno = ENOENT;
 415                         return -1;
 416                 }
 417         }
 418
 419         return 0;
 420 }
 421
 422 static char **prep_childenv(const char *const *deltaenv)
 423 {
 424         extern char **environ;
 425         char **childenv;
 426         struct string_list env = STRING_LIST_INIT_DUP;
 427         struct strbuf key = STRBUF_INIT;
 428         const char *const *p;
 429         int i;
 430
 431         /* Construct a sorted string list consisting of the current environ */
 432         for (p = (const char *const *) environ; p && *p; p++) {
 433                 const char *equals = strchr(*p, '=');
 434
 435                 if (equals) {
 436                         strbuf_reset(&key);
 437                         strbuf_add(&key, *p, equals - *p);
 438                         string_list_append(&env, key.buf)->util = (void *) *p;
 439                 } else {
 440                         string_list_append(&env, *p)->util = (void *) *p;
 441                 }
 442         }
 443         string_list_sort(&env);
 444
 445         /* Merge in 'deltaenv' with the current environ */
 446         for (p = deltaenv; p && *p; p++) {
 447                 const char *equals = strchr(*p, '=');
 448
 449                 if (equals) {
 450                         /* ('key=value'), insert or replace entry */
 451                         strbuf_reset(&key);
 452                         strbuf_add(&key, *p, equals - *p);
 453                         string_list_insert(&env, key.buf)->util = (void *) *p;
 454                 } else {
 455                         /* otherwise ('key') remove existing entry */
 456                         string_list_remove(&env, *p, 0);
 457                 }
 458         }
 459
 460         /* Create an array of 'char *' to be used as the childenv */
 461         ALLOC_ARRAY(childenv, env.nr + 1);
 462         for (i = 0; i < env.nr; i++)
 463                 childenv[i] = env.items[i].util;
 464         childenv[env.nr] = NULL;
 465
 466         string_list_clear(&env, 0);
 467         strbuf_release(&key);
 468         return childenv;
 469 }
 470
 471 struct atfork_state {
 472 #ifndef NO_PTHREADS
 473         int cs;
 474 #endif
 475         sigset_t old;
 476 };
 477
 478 #ifndef NO_PTHREADS
 479 static void bug_die(int err, const char *msg)
 480 {
 481         if (err) {
 482                 errno = err;
 483                 die_errno("BUG: %s", msg);
 484         }
 485 }
 486 #endif
 487
 488 static void atfork_prepare(struct atfork_state *as)
 489 {
 490         sigset_t all;
 491
 492         if (sigfillset(&all))
 493                 die_errno("sigfillset");
 494 #ifdef NO_PTHREADS
 495         if (sigprocmask(SIG_SETMASK, &all, &as->old))
 496                 die_errno("sigprocmask");
 497 #else
 498         bug_die(pthread_sigmask(SIG_SETMASK, &all, &as->old),
 499                 "blocking all signals");
 500         bug_die(pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &as->cs),
 501                 "disabling cancellation");
 502 #endif
 503 }
 504
 505 static void atfork_parent(struct atfork_state *as)
 506 {
 507 #ifdef NO_PTHREADS
 508         if (sigprocmask(SIG_SETMASK, &as->old, NULL))
 509                 die_errno("sigprocmask");
 510 #else
 511         bug_die(pthread_setcancelstate(as->cs, NULL),
 512                 "re-enabling cancellation");
 513         bug_die(pthread_sigmask(SIG_SETMASK, &as->old, NULL),
 514                 "restoring signal mask");
 515 #endif
 516 }
 517 #endif /* GIT_WINDOWS_NATIVE */
 518
 519 static inline void set_cloexec(int fd)
 520 {
 521         int flags = fcntl(fd, F_GETFD);
 522         if (flags >= 0)
 523                 fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
 524 }
 525
 526 static int wait_or_whine(pid_t pid, const char *argv0, int in_signal)
 527 {
 528         int status, code = -1;
 529         pid_t waiting;
 530         int failed_errno = 0;
 531
 532         while ((waiting = waitpid(pid, &status, 0)) < 0 && errno == EINTR)
 533                 ;       /* nothing */
 534         if (in_signal)
 535                 return 0;
 536
 537         if (waiting < 0) {
 538                 failed_errno = errno;
 539                 error_errno("waitpid for %s failed", argv0);
 540         } else if (waiting != pid) {
 541                 error("waitpid is confused (%s)", argv0);
 542         } else if (WIFSIGNALED(status)) {
 543                 code = WTERMSIG(status);
 544                 if (code != SIGINT && code != SIGQUIT && code != SIGPIPE)
 545                         error("%s died of signal %d", argv0, code);
 546                 /*
 547                  * This return value is chosen so that code & 0xff
 548                  * mimics the exit code that a POSIX shell would report for
 549                  * a program that died from this signal.
 550                  */
 551                 code += 128;
 552         } else if (WIFEXITED(status)) {
 553                 code = WEXITSTATUS(status);
 554         } else {
 555                 error("waitpid is confused (%s)", argv0);
 556         }
 557
 558         clear_child_for_cleanup(pid);
 559
 560         errno = failed_errno;
 561         return code;
 562 }
 563
 564 int start_command(struct child_process *cmd)
 565 {
 566         int need_in, need_out, need_err;
 567         int fdin[2], fdout[2], fderr[2];
 568         int failed_errno;
 569         char *str;
 570
 571         if (!cmd->argv)
 572                 cmd->argv = cmd->args.argv;
 573         if (!cmd->env)
 574                 cmd->env = cmd->env_array.argv;
 575
 576         /*
 577          * In case of errors we must keep the promise to close FDs
 578          * that have been passed in via ->in and ->out.
 579          */
 580
 581         need_in = !cmd->no_stdin && cmd->in < 0;
 582         if (need_in) {
 583                 if (pipe(fdin) < 0) {
 584                         failed_errno = errno;
 585                         if (cmd->out > 0)
 586                                 close(cmd->out);
 587                         str = "standard input";
 588                         goto fail_pipe;
 589                 }
 590                 cmd->in = fdin[1];
 591         }
 592
 593         need_out = !cmd->no_stdout
 594                 && !cmd->stdout_to_stderr
 595                 && cmd->out < 0;
 596         if (need_out) {
 597                 if (pipe(fdout) < 0) {
 598                         failed_errno = errno;
 599                         if (need_in)
 600                                 close_pair(fdin);
 601                         else if (cmd->in)
 602                                 close(cmd->in);
 603                         str = "standard output";
 604                         goto fail_pipe;
 605                 }
 606                 cmd->out = fdout[0];
 607         }
 608
 609         need_err = !cmd->no_stderr && cmd->err < 0;
 610         if (need_err) {
 611                 if (pipe(fderr) < 0) {
 612                         failed_errno = errno;
 613                         if (need_in)
 614                                 close_pair(fdin);
 615                         else if (cmd->in)
 616                                 close(cmd->in);
 617                         if (need_out)
 618                                 close_pair(fdout);
 619                         else if (cmd->out)
 620                                 close(cmd->out);
 621                         str = "standard error";
 622 fail_pipe:
 623                         error("cannot create %s pipe for %s: %s",
 624                                 str, cmd->argv[0], strerror(failed_errno));
 625                         child_process_clear(cmd);
 626                         errno = failed_errno;
 627                         return -1;
 628                 }
 629                 cmd->err = fderr[0];
 630         }
 631
 632         trace_argv_printf(cmd->argv, "trace: run_command:");
 633         fflush(NULL);
 634
 635 #ifndef GIT_WINDOWS_NATIVE
 636 {
 637         int notify_pipe[2];
 638         int null_fd = -1;
 639         char **childenv;
 640         struct argv_array argv = ARGV_ARRAY_INIT;
 641         struct child_err cerr;
 642         struct atfork_state as;
 643
 644         if (prepare_cmd(&argv, cmd) < 0) {
 645                 failed_errno = errno;
 646                 cmd->pid = -1;
 647                 goto end_of_spawn;
 648         }
 649
 650         if (pipe(notify_pipe))
 651                 notify_pipe[0] = notify_pipe[1] = -1;
 652
 653         if (cmd->no_stdin || cmd->no_stdout || cmd->no_stderr) {
 654                 null_fd = open("/dev/null", O_RDWR | O_CLOEXEC);
 655                 if (null_fd < 0)
 656                         die_errno(_("open /dev/null failed"));
 657                 set_cloexec(null_fd);
 658         }
 659
 660         childenv = prep_childenv(cmd->env);
 661         atfork_prepare(&as);
 662
 663         /*
 664          * NOTE: In order to prevent deadlocking when using threads special
 665          * care should be taken with the function calls made in between the
 666          * fork() and exec() calls.  No calls should be made to functions which
 667          * require acquiring a lock (e.g. malloc) as the lock could have been
 668          * held by another thread at the time of forking, causing the lock to
 669          * never be released in the child process.  This means only
 670          * Async-Signal-Safe functions are permitted in the child.
 671          */
 672         cmd->pid = fork();
 673         failed_errno = errno;
 674         if (!cmd->pid) {
 675                 int sig;
 676                 /*
 677                  * Ensure the default die/error/warn routines do not get
 678                  * called, they can take stdio locks and malloc.
 679                  */
 680                 set_die_routine(child_die_fn);
 681                 set_error_routine(child_error_fn);
 682                 set_warn_routine(child_warn_fn);
 683
 684                 close(notify_pipe[0]);
 685                 set_cloexec(notify_pipe[1]);
 686                 child_notifier = notify_pipe[1];
 687
 688                 if (cmd->no_stdin)
 689                         child_dup2(null_fd, 0);
 690                 else if (need_in) {
 691                         child_dup2(fdin[0], 0);
 692                         child_close_pair(fdin);
 693                 } else if (cmd->in) {
 694                         child_dup2(cmd->in, 0);
 695                         child_close(cmd->in);
 696                 }
 697
 698                 if (cmd->no_stderr)
 699                         child_dup2(null_fd, 2);
 700                 else if (need_err) {
 701                         child_dup2(fderr[1], 2);
 702                         child_close_pair(fderr);
 703                 } else if (cmd->err > 1) {
 704                         child_dup2(cmd->err, 2);
 705                         child_close(cmd->err);
 706                 }
 707
 708                 if (cmd->no_stdout)
 709                         child_dup2(null_fd, 1);
 710                 else if (cmd->stdout_to_stderr)
 711                         child_dup2(2, 1);
 712                 else if (need_out) {
 713                         child_dup2(fdout[1], 1);
 714                         child_close_pair(fdout);
 715                 } else if (cmd->out > 1) {
 716                         child_dup2(cmd->out, 1);
 717                         child_close(cmd->out);
 718                 }
 719
 720                 if (cmd->dir && chdir(cmd->dir))
 721                         child_die(CHILD_ERR_CHDIR);
 722
 723                 /*
 724                  * restore default signal handlers here, in case
 725                  * we catch a signal right before execve below
 726                  */
 727                 for (sig = 1; sig < NSIG; sig++) {
 728                         /* ignored signals get reset to SIG_DFL on execve */
 729                         if (signal(sig, SIG_DFL) == SIG_IGN)
 730                                 signal(sig, SIG_IGN);
 731                 }
 732
 733                 if (sigprocmask(SIG_SETMASK, &as.old, NULL) != 0)
 734                         child_die(CHILD_ERR_SIGPROCMASK);
 735
 736                 /*
 737                  * Attempt to exec using the command and arguments starting at
 738                  * argv.argv[1].  argv.argv[0] contains SHELL_PATH which will
 739                  * be used in the event exec failed with ENOEXEC at which point
 740                  * we will try to interpret the command using 'sh'.
 741                  */
 742                 execve(argv.argv[1], (char *const *) argv.argv + 1,
 743                        (char *const *) childenv);
 744                 if (errno == ENOEXEC)
 745                         execve(argv.argv[0], (char *const *) argv.argv,
 746                                (char *const *) childenv);
 747
 748                 if (errno == ENOENT) {
 749                         if (cmd->silent_exec_failure)
 750                                 child_die(CHILD_ERR_SILENT);
 751                         child_die(CHILD_ERR_ENOENT);
 752                 } else {
 753                         child_die(CHILD_ERR_ERRNO);
 754                 }
 755         }
 756         atfork_parent(&as);
 757         if (cmd->pid < 0)
 758                 error_errno("cannot fork() for %s", cmd->argv[0]);
 759         else if (cmd->clean_on_exit)
 760                 mark_child_for_cleanup(cmd->pid, cmd);
 761
 762         /*
 763          * Wait for child's exec. If the exec succeeds (or if fork()
 764          * failed), EOF is seen immediately by the parent. Otherwise, the
 765          * child process sends a child_err struct.
 766          * Note that use of this infrastructure is completely advisory,
 767          * therefore, we keep error checks minimal.
 768          */
 769         close(notify_pipe[1]);
 770         if (xread(notify_pipe[0], &cerr, sizeof(cerr)) == sizeof(cerr)) {
 771                 /*
 772                  * At this point we know that fork() succeeded, but exec()
 773                  * failed. Errors have been reported to our stderr.
 774                  */
 775                 wait_or_whine(cmd->pid, cmd->argv[0], 0);
 776                 child_err_spew(cmd, &cerr);
 777                 failed_errno = errno;
 778                 cmd->pid = -1;
 779         }
 780         close(notify_pipe[0]);
 781
 782         if (null_fd >= 0)
 783                 close(null_fd);
 784         argv_array_clear(&argv);
 785         free(childenv);
 786 }
 787 end_of_spawn:
 788
 789 #else
 790 {
 791         int fhin = 0, fhout = 1, fherr = 2;
 792         const char **sargv = cmd->argv;
 793         struct argv_array nargv = ARGV_ARRAY_INIT;
 794
 795         if (cmd->no_stdin)
 796                 fhin = open("/dev/null", O_RDWR);
 797         else if (need_in)
 798                 fhin = dup(fdin[0]);
 799         else if (cmd->in)
 800                 fhin = dup(cmd->in);
 801
 802         if (cmd->no_stderr)
 803                 fherr = open("/dev/null", O_RDWR);
 804         else if (need_err)
 805                 fherr = dup(fderr[1]);
 806         else if (cmd->err > 2)
 807                 fherr = dup(cmd->err);
 808
 809         if (cmd->no_stdout)
 810                 fhout = open("/dev/null", O_RDWR);
 811         else if (cmd->stdout_to_stderr)
 812                 fhout = dup(fherr);
 813         else if (need_out)
 814                 fhout = dup(fdout[1]);
 815         else if (cmd->out > 1)
 816                 fhout = dup(cmd->out);
 817
 818         if (cmd->git_cmd)
 819                 cmd->argv = prepare_git_cmd(&nargv, cmd->argv);
 820         else if (cmd->use_shell)
 821                 cmd->argv = prepare_shell_cmd(&nargv, cmd->argv);
 822
 823         cmd->pid = mingw_spawnvpe(cmd->argv[0], cmd->argv, (char**) cmd->env,
 824                         cmd->dir, fhin, fhout, fherr);
 825         failed_errno = errno;
 826         if (cmd->pid < 0 && (!cmd->silent_exec_failure || errno != ENOENT))
 827                 error_errno("cannot spawn %s", cmd->argv[0]);
 828         if (cmd->clean_on_exit && cmd->pid >= 0)
 829                 mark_child_for_cleanup(cmd->pid, cmd);
 830
 831         argv_array_clear(&nargv);
 832         cmd->argv = sargv;
 833         if (fhin != 0)
 834                 close(fhin);
 835         if (fhout != 1)
 836                 close(fhout);
 837         if (fherr != 2)
 838                 close(fherr);
 839 }
 840 #endif
 841
 842         if (cmd->pid < 0) {
 843                 if (need_in)
 844                         close_pair(fdin);
 845                 else if (cmd->in)
 846                         close(cmd->in);
 847                 if (need_out)
 848                         close_pair(fdout);
 849                 else if (cmd->out)
 850                         close(cmd->out);
 851                 if (need_err)
 852                         close_pair(fderr);
 853                 else if (cmd->err)
 854                         close(cmd->err);
 855                 child_process_clear(cmd);
 856                 errno = failed_errno;
 857                 return -1;
 858         }
 859
 860         if (need_in)
 861                 close(fdin[0]);
 862         else if (cmd->in)
 863                 close(cmd->in);
 864
 865         if (need_out)
 866                 close(fdout[1]);
 867         else if (cmd->out)
 868                 close(cmd->out);
 869
 870         if (need_err)
 871                 close(fderr[1]);
 872         else if (cmd->err)
 873                 close(cmd->err);
 874
 875         return 0;
 876 }
 877
 878 int finish_command(struct child_process *cmd)
 879 {
 880         int ret = wait_or_whine(cmd->pid, cmd->argv[0], 0);
 881         child_process_clear(cmd);
 882         return ret;
 883 }
 884
 885 int finish_command_in_signal(struct child_process *cmd)
 886 {
 887         return wait_or_whine(cmd->pid, cmd->argv[0], 1);
 888 }
 889
 890
 891 int run_command(struct child_process *cmd)
 892 {
 893         int code;
 894
 895         if (cmd->out < 0 || cmd->err < 0)
 896                 die("BUG: run_command with a pipe can cause deadlock");
 897
 898         code = start_command(cmd);
 899         if (code)
 900                 return code;
 901         return finish_command(cmd);
 902 }
 903
 904 int run_command_v_opt(const char **argv, int opt)
 905 {
 906         return run_command_v_opt_cd_env(argv, opt, NULL, NULL);
 907 }
 908
 909 int run_command_v_opt_cd_env(const char **argv, int opt, const char *dir, const char *const *env)
 910 {
 911         struct child_process cmd = CHILD_PROCESS_INIT;
 912         cmd.argv = argv;
 913         cmd.no_stdin = opt & RUN_COMMAND_NO_STDIN ? 1 : 0;
 914         cmd.git_cmd = opt & RUN_GIT_CMD ? 1 : 0;
 915         cmd.stdout_to_stderr = opt & RUN_COMMAND_STDOUT_TO_STDERR ? 1 : 0;
 916         cmd.silent_exec_failure = opt & RUN_SILENT_EXEC_FAILURE ? 1 : 0;
 917         cmd.use_shell = opt & RUN_USING_SHELL ? 1 : 0;
 918         cmd.clean_on_exit = opt & RUN_CLEAN_ON_EXIT ? 1 : 0;
 919         cmd.dir = dir;
 920         cmd.env = env;
 921         return run_command(&cmd);
 922 }
 923
 924 #ifndef NO_PTHREADS
 925 static pthread_t main_thread;
 926 static int main_thread_set;
 927 static pthread_key_t async_key;
 928 static pthread_key_t async_die_counter;
 929
 930 static void *run_thread(void *data)
 931 {
 932         struct async *async = data;
 933         intptr_t ret;
 934
 935         if (async->isolate_sigpipe) {
 936                 sigset_t mask;
 937                 sigemptyset(&mask);
 938                 sigaddset(&mask, SIGPIPE);
 939                 if (pthread_sigmask(SIG_BLOCK, &mask, NULL) < 0) {
 940                         ret = error("unable to block SIGPIPE in async thread");
 941                         return (void *)ret;
 942                 }
 943         }
 944
 945         pthread_setspecific(async_key, async);
 946         ret = async->proc(async->proc_in, async->proc_out, async->data);
 947         return (void *)ret;
 948 }
 949
 950 static NORETURN void die_async(const char *err, va_list params)
 951 {
 952         vreportf("fatal: ", err, params);
 953
 954         if (in_async()) {
 955                 struct async *async = pthread_getspecific(async_key);
 956                 if (async->proc_in >= 0)
 957                         close(async->proc_in);
 958                 if (async->proc_out >= 0)
 959                         close(async->proc_out);
 960                 pthread_exit((void *)128);
 961         }
 962
 963         exit(128);
 964 }
 965
 966 static int async_die_is_recursing(void)
 967 {
 968         void *ret = pthread_getspecific(async_die_counter);
 969         pthread_setspecific(async_die_counter, (void *)1);
 970         return ret != NULL;
 971 }
 972
 973 int in_async(void)
 974 {
 975         if (!main_thread_set)
 976                 return 0; /* no asyncs started yet */
 977         return !pthread_equal(main_thread, pthread_self());
 978 }
 979
 980 static void NORETURN async_exit(int code)
 981 {
 982         pthread_exit((void *)(intptr_t)code);
 983 }
 984
 985 #else
 986
 987 static struct {
 988         void (**handlers)(void);
 989         size_t nr;
 990         size_t alloc;
 991 } git_atexit_hdlrs;
 992
 993 static int git_atexit_installed;
 994
 995 static void git_atexit_dispatch(void)
 996 {
 997         size_t i;
 998
 999         for (i=git_atexit_hdlrs.nr ; i ; i--)
1000                 git_atexit_hdlrs.handlers[i-1]();
1001 }
1002
1003 static void git_atexit_clear(void)
1004 {
1005         free(git_atexit_hdlrs.handlers);
1006         memset(&git_atexit_hdlrs, 0, sizeof(git_atexit_hdlrs));
1007         git_atexit_installed = 0;
1008 }
1009
1010 #undef atexit
1011 int git_atexit(void (*handler)(void))
1012 {
1013         ALLOC_GROW(git_atexit_hdlrs.handlers, git_atexit_hdlrs.nr + 1, git_atexit_hdlrs.alloc);
1014         git_atexit_hdlrs.handlers[git_atexit_hdlrs.nr++] = handler;
1015         if (!git_atexit_installed) {
1016                 if (atexit(&git_atexit_dispatch))
1017                         return -1;
1018                 git_atexit_installed = 1;
1019         }
1020         return 0;
1021 }
1022 #define atexit git_atexit
1023
1024 static int process_is_async;
1025 int in_async(void)
1026 {
1027         return process_is_async;
1028 }
1029
1030 static void NORETURN async_exit(int code)
1031 {
1032         exit(code);
1033 }
1034
1035 #endif
1036
1037 void check_pipe(int err)
1038 {
1039         if (err == EPIPE) {
1040                 if (in_async())
1041                         async_exit(141);
1042
1043                 signal(SIGPIPE, SIG_DFL);
1044                 raise(SIGPIPE);
1045                 /* Should never happen, but just in case... */
1046                 exit(141);
1047         }
1048 }
1049
1050 int start_async(struct async *async)
1051 {
1052         int need_in, need_out;
1053         int fdin[2], fdout[2];
1054         int proc_in, proc_out;
1055
1056         need_in = async->in < 0;
1057         if (need_in) {
1058                 if (pipe(fdin) < 0) {
1059                         if (async->out > 0)
1060                                 close(async->out);
1061                         return error_errno("cannot create pipe");
1062                 }
1063                 async->in = fdin[1];
1064         }
1065
1066         need_out = async->out < 0;
1067         if (need_out) {
1068                 if (pipe(fdout) < 0) {
1069                         if (need_in)
1070                                 close_pair(fdin);
1071                         else if (async->in)
1072                                 close(async->in);
1073                         return error_errno("cannot create pipe");
1074                 }
1075                 async->out = fdout[0];
1076         }
1077
1078         if (need_in)
1079                 proc_in = fdin[0];
1080         else if (async->in)
1081                 proc_in = async->in;
1082         else
1083                 proc_in = -1;
1084
1085         if (need_out)
1086                 proc_out = fdout[1];
1087         else if (async->out)
1088                 proc_out = async->out;
1089         else
1090                 proc_out = -1;
1091
1092 #ifdef NO_PTHREADS
1093         /* Flush stdio before fork() to avoid cloning buffers */
1094         fflush(NULL);
1095
1096         async->pid = fork();
1097         if (async->pid < 0) {
1098                 error_errno("fork (async) failed");
1099                 goto error;
1100         }
1101         if (!async->pid) {
1102                 if (need_in)
1103                         close(fdin[1]);
1104                 if (need_out)
1105                         close(fdout[0]);
1106                 git_atexit_clear();
1107                 process_is_async = 1;
1108                 exit(!!async->proc(proc_in, proc_out, async->data));
1109         }
1110
1111         mark_child_for_cleanup(async->pid, NULL);
1112
1113         if (need_in)
1114                 close(fdin[0]);
1115         else if (async->in)
1116                 close(async->in);
1117
1118         if (need_out)
1119                 close(fdout[1]);
1120         else if (async->out)
1121                 close(async->out);
1122 #else
1123         if (!main_thread_set) {
1124                 /*
1125                  * We assume that the first time that start_async is called
1126                  * it is from the main thread.
1127                  */
1128                 main_thread_set = 1;
1129                 main_thread = pthread_self();
1130                 pthread_key_create(&async_key, NULL);
1131                 pthread_key_create(&async_die_counter, NULL);
1132                 set_die_routine(die_async);
1133                 set_die_is_recursing_routine(async_die_is_recursing);
1134         }
1135
1136         if (proc_in >= 0)
1137                 set_cloexec(proc_in);
1138         if (proc_out >= 0)
1139                 set_cloexec(proc_out);
1140         async->proc_in = proc_in;
1141         async->proc_out = proc_out;
1142         {
1143                 int err = pthread_create(&async->tid, NULL, run_thread, async);
1144                 if (err) {
1145                         error_errno("cannot create thread");
1146                         goto error;
1147                 }
1148         }
1149 #endif
1150         return 0;
1151
1152 error:
1153         if (need_in)
1154                 close_pair(fdin);
1155         else if (async->in)
1156                 close(async->in);
1157
1158         if (need_out)
1159                 close_pair(fdout);
1160         else if (async->out)
1161                 close(async->out);
1162         return -1;
1163 }
1164
1165 int finish_async(struct async *async)
1166 {
1167 #ifdef NO_PTHREADS
1168         return wait_or_whine(async->pid, "child process", 0);
1169 #else
1170         void *ret = (void *)(intptr_t)(-1);
1171
1172         if (pthread_join(async->tid, &ret))
1173                 error("pthread_join failed");
1174         return (int)(intptr_t)ret;
1175 #endif
1176 }
1177
1178 const char *find_hook(const char *name)
1179 {
1180         static struct strbuf path = STRBUF_INIT;
1181
1182         strbuf_reset(&path);
1183         strbuf_git_path(&path, "hooks/%s", name);
1184         if (access(path.buf, X_OK) < 0) {
1185 #ifdef STRIP_EXTENSION
1186                 strbuf_addstr(&path, STRIP_EXTENSION);
1187                 if (access(path.buf, X_OK) >= 0)
1188                         return path.buf;
1189 #endif
1190                 return NULL;
1191         }
1192         return path.buf;
1193 }
1194
1195 int run_hook_ve(const char *const *env, const char *name, va_list args)
1196 {
1197         struct child_process hook = CHILD_PROCESS_INIT;
1198         const char *p;
1199
1200         p = find_hook(name);
1201         if (!p)
1202                 return 0;
1203
1204         argv_array_push(&hook.args, p);
1205         while ((p = va_arg(args, const char *)))
1206                 argv_array_push(&hook.args, p);
1207         hook.env = env;
1208         hook.no_stdin = 1;
1209         hook.stdout_to_stderr = 1;
1210
1211         return run_command(&hook);
1212 }
1213
1214 int run_hook_le(const char *const *env, const char *name, ...)
1215 {
1216         va_list args;
1217         int ret;
1218
1219         va_start(args, name);
1220         ret = run_hook_ve(env, name, args);
1221         va_end(args);
1222
1223         return ret;
1224 }
1225
1226 struct io_pump {
1227         /* initialized by caller */
1228         int fd;
1229         int type; /* POLLOUT or POLLIN */
1230         union {
1231                 struct {
1232                         const char *buf;
1233                         size_t len;
1234                 } out;
1235                 struct {
1236                         struct strbuf *buf;
1237                         size_t hint;
1238                 } in;
1239         } u;
1240
1241         /* returned by pump_io */
1242         int error; /* 0 for success, otherwise errno */
1243
1244         /* internal use */
1245         struct pollfd *pfd;
1246 };
1247
1248 static int pump_io_round(struct io_pump *slots, int nr, struct pollfd *pfd)
1249 {
1250         int pollsize = 0;
1251         int i;
1252
1253         for (i = 0; i < nr; i++) {
1254                 struct io_pump *io = &slots[i];
1255                 if (io->fd < 0)
1256                         continue;
1257                 pfd[pollsize].fd = io->fd;
1258                 pfd[pollsize].events = io->type;
1259                 io->pfd = &pfd[pollsize++];
1260         }
1261
1262         if (!pollsize)
1263                 return 0;
1264
1265         if (poll(pfd, pollsize, -1) < 0) {
1266                 if (errno == EINTR)
1267                         return 1;
1268                 die_errno("poll failed");
1269         }
1270
1271         for (i = 0; i < nr; i++) {
1272                 struct io_pump *io = &slots[i];
1273
1274                 if (io->fd < 0)
1275                         continue;
1276
1277                 if (!(io->pfd->revents & (POLLOUT|POLLIN|POLLHUP|POLLERR|POLLNVAL)))
1278                         continue;
1279
1280                 if (io->type == POLLOUT) {
1281                         ssize_t len = xwrite(io->fd,
1282                                              io->u.out.buf, io->u.out.len);
1283                         if (len < 0) {
1284                                 io->error = errno;
1285                                 close(io->fd);
1286                                 io->fd = -1;
1287                         } else {
1288                                 io->u.out.buf += len;
1289                                 io->u.out.len -= len;
1290                                 if (!io->u.out.len) {
1291                                         close(io->fd);
1292                                         io->fd = -1;
1293                                 }
1294                         }
1295                 }
1296
1297                 if (io->type == POLLIN) {
1298                         ssize_t len = strbuf_read_once(io->u.in.buf,
1299                                                        io->fd, io->u.in.hint);
1300                         if (len < 0)
1301                                 io->error = errno;
1302                         if (len <= 0) {
1303                                 close(io->fd);
1304                                 io->fd = -1;
1305                         }
1306                 }
1307         }
1308
1309         return 1;
1310 }
1311
1312 static int pump_io(struct io_pump *slots, int nr)
1313 {
1314         struct pollfd *pfd;
1315         int i;
1316
1317         for (i = 0; i < nr; i++)
1318                 slots[i].error = 0;
1319
1320         ALLOC_ARRAY(pfd, nr);
1321         while (pump_io_round(slots, nr, pfd))
1322                 ; /* nothing */
1323         free(pfd);
1324
1325         /* There may be multiple errno values, so just pick the first. */
1326         for (i = 0; i < nr; i++) {
1327                 if (slots[i].error) {
1328                         errno = slots[i].error;
1329                         return -1;
1330                 }
1331         }
1332         return 0;
1333 }
1334
1335
1336 int pipe_command(struct child_process *cmd,
1337                  const char *in, size_t in_len,
1338                  struct strbuf *out, size_t out_hint,
1339                  struct strbuf *err, size_t err_hint)
1340 {
1341         struct io_pump io[3];
1342         int nr = 0;
1343
1344         if (in)
1345                 cmd->in = -1;
1346         if (out)
1347                 cmd->out = -1;
1348         if (err)
1349                 cmd->err = -1;
1350
1351         if (start_command(cmd) < 0)
1352                 return -1;
1353
1354         if (in) {
1355                 io[nr].fd = cmd->in;
1356                 io[nr].type = POLLOUT;
1357                 io[nr].u.out.buf = in;
1358                 io[nr].u.out.len = in_len;
1359                 nr++;
1360         }
1361         if (out) {
1362                 io[nr].fd = cmd->out;
1363                 io[nr].type = POLLIN;
1364                 io[nr].u.in.buf = out;
1365                 io[nr].u.in.hint = out_hint;
1366                 nr++;
1367         }
1368         if (err) {
1369                 io[nr].fd = cmd->err;
1370                 io[nr].type = POLLIN;
1371                 io[nr].u.in.buf = err;
1372                 io[nr].u.in.hint = err_hint;
1373                 nr++;
1374         }
1375
1376         if (pump_io(io, nr) < 0) {
1377                 finish_command(cmd); /* throw away exit code */
1378                 return -1;
1379         }
1380
1381         return finish_command(cmd);
1382 }
1383
1384 enum child_state {
1385         GIT_CP_FREE,
1386         GIT_CP_WORKING,
1387         GIT_CP_WAIT_CLEANUP,
1388 };
1389
1390 struct parallel_processes {
1391         void *data;
1392
1393         int max_processes;
1394         int nr_processes;
1395
1396         get_next_task_fn get_next_task;
1397         start_failure_fn start_failure;
1398         task_finished_fn task_finished;
1399
1400         struct {
1401                 enum child_state state;
1402                 struct child_process process;
1403                 struct strbuf err;
1404                 void *data;
1405         } *children;
1406         /*
1407          * The struct pollfd is logically part of *children,
1408          * but the system call expects it as its own array.
1409          */
1410         struct pollfd *pfd;
1411
1412         unsigned shutdown : 1;
1413
1414         int output_owner;
1415         struct strbuf buffered_output; /* of finished children */
1416 };
1417
1418 static int default_start_failure(struct strbuf *out,
1419                                  void *pp_cb,
1420                                  void *pp_task_cb)
1421 {
1422         return 0;
1423 }
1424
1425 static int default_task_finished(int result,
1426                                  struct strbuf *out,
1427                                  void *pp_cb,
1428                                  void *pp_task_cb)
1429 {
1430         return 0;
1431 }
1432
1433 static void kill_children(struct parallel_processes *pp, int signo)
1434 {
1435         int i, n = pp->max_processes;
1436
1437         for (i = 0; i < n; i++)
1438                 if (pp->children[i].state == GIT_CP_WORKING)
1439                         kill(pp->children[i].process.pid, signo);
1440 }
1441
1442 static struct parallel_processes *pp_for_signal;
1443
1444 static void handle_children_on_signal(int signo)
1445 {
1446         kill_children(pp_for_signal, signo);
1447         sigchain_pop(signo);
1448         raise(signo);
1449 }
1450
1451 static void pp_init(struct parallel_processes *pp,
1452                     int n,
1453                     get_next_task_fn get_next_task,
1454                     start_failure_fn start_failure,
1455                     task_finished_fn task_finished,
1456                     void *data)
1457 {
1458         int i;
1459
1460         if (n < 1)
1461                 n = online_cpus();
1462
1463         pp->max_processes = n;
1464
1465         trace_printf("run_processes_parallel: preparing to run up to %d tasks", n);
1466
1467         pp->data = data;
1468         if (!get_next_task)
1469                 die("BUG: you need to specify a get_next_task function");
1470         pp->get_next_task = get_next_task;
1471
1472         pp->start_failure = start_failure ? start_failure : default_start_failure;
1473         pp->task_finished = task_finished ? task_finished : default_task_finished;
1474
1475         pp->nr_processes = 0;
1476         pp->output_owner = 0;
1477         pp->shutdown = 0;
1478         pp->children = xcalloc(n, sizeof(*pp->children));
1479         pp->pfd = xcalloc(n, sizeof(*pp->pfd));
1480         strbuf_init(&pp->buffered_output, 0);
1481
1482         for (i = 0; i < n; i++) {
1483                 strbuf_init(&pp->children[i].err, 0);
1484                 child_process_init(&pp->children[i].process);
1485                 pp->pfd[i].events = POLLIN | POLLHUP;
1486                 pp->pfd[i].fd = -1;
1487         }
1488
1489         pp_for_signal = pp;
1490         sigchain_push_common(handle_children_on_signal);
1491 }
1492
1493 static void pp_cleanup(struct parallel_processes *pp)
1494 {
1495         int i;
1496
1497         trace_printf("run_processes_parallel: done");
1498         for (i = 0; i < pp->max_processes; i++) {
1499                 strbuf_release(&pp->children[i].err);
1500                 child_process_clear(&pp->children[i].process);
1501         }
1502
1503         free(pp->children);
1504         free(pp->pfd);
1505
1506         /*
1507          * When get_next_task added messages to the buffer in its last
1508          * iteration, the buffered output is non empty.
1509          */
1510         strbuf_write(&pp->buffered_output, stderr);
1511         strbuf_release(&pp->buffered_output);
1512
1513         sigchain_pop_common();
1514 }
1515
1516 /* returns
1517  *  0 if a new task was started.
1518  *  1 if no new jobs was started (get_next_task ran out of work, non critical
1519  *    problem with starting a new command)
1520  * <0 no new job was started, user wishes to shutdown early. Use negative code
1521  *    to signal the children.
1522  */
1523 static int pp_start_one(struct parallel_processes *pp)
1524 {
1525         int i, code;
1526
1527         for (i = 0; i < pp->max_processes; i++)
1528                 if (pp->children[i].state == GIT_CP_FREE)
1529                         break;
1530         if (i == pp->max_processes)
1531                 die("BUG: bookkeeping is hard");
1532
1533         code = pp->get_next_task(&pp->children[i].process,
1534                                  &pp->children[i].err,
1535                                  pp->data,
1536                                  &pp->children[i].data);
1537         if (!code) {
1538                 strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1539                 strbuf_reset(&pp->children[i].err);
1540                 return 1;
1541         }
1542         pp->children[i].process.err = -1;
1543         pp->children[i].process.stdout_to_stderr = 1;
1544         pp->children[i].process.no_stdin = 1;
1545
1546         if (start_command(&pp->children[i].process)) {
1547                 code = pp->start_failure(&pp->children[i].err,
1548                                          pp->data,
1549                                          pp->children[i].data);
1550                 strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1551                 strbuf_reset(&pp->children[i].err);
1552                 if (code)
1553                         pp->shutdown = 1;
1554                 return code;
1555         }
1556
1557         pp->nr_processes++;
1558         pp->children[i].state = GIT_CP_WORKING;
1559         pp->pfd[i].fd = pp->children[i].process.err;
1560         return 0;
1561 }
1562
1563 static void pp_buffer_stderr(struct parallel_processes *pp, int output_timeout)
1564 {
1565         int i;
1566
1567         while ((i = poll(pp->pfd, pp->max_processes, output_timeout)) < 0) {
1568                 if (errno == EINTR)
1569                         continue;
1570                 pp_cleanup(pp);
1571                 die_errno("poll");
1572         }
1573
1574         /* Buffer output from all pipes. */
1575         for (i = 0; i < pp->max_processes; i++) {
1576                 if (pp->children[i].state == GIT_CP_WORKING &&
1577                     pp->pfd[i].revents & (POLLIN | POLLHUP)) {
1578                         int n = strbuf_read_once(&pp->children[i].err,
1579                                                  pp->children[i].process.err, 0);
1580                         if (n == 0) {
1581                                 close(pp->children[i].process.err);
1582                                 pp->children[i].state = GIT_CP_WAIT_CLEANUP;
1583                         } else if (n < 0)
1584                                 if (errno != EAGAIN)
1585                                         die_errno("read");
1586                 }
1587         }
1588 }
1589
1590 static void pp_output(struct parallel_processes *pp)
1591 {
1592         int i = pp->output_owner;
1593         if (pp->children[i].state == GIT_CP_WORKING &&
1594             pp->children[i].err.len) {
1595                 strbuf_write(&pp->children[i].err, stderr);
1596                 strbuf_reset(&pp->children[i].err);
1597         }
1598 }
1599
1600 static int pp_collect_finished(struct parallel_processes *pp)
1601 {
1602         int i, code;
1603         int n = pp->max_processes;
1604         int result = 0;
1605
1606         while (pp->nr_processes > 0) {
1607                 for (i = 0; i < pp->max_processes; i++)
1608                         if (pp->children[i].state == GIT_CP_WAIT_CLEANUP)
1609                                 break;
1610                 if (i == pp->max_processes)
1611                         break;
1612
1613                 code = finish_command(&pp->children[i].process);
1614
1615                 code = pp->task_finished(code,
1616                                          &pp->children[i].err, pp->data,
1617                                          pp->children[i].data);
1618
1619                 if (code)
1620                         result = code;
1621                 if (code < 0)
1622                         break;
1623
1624                 pp->nr_processes--;
1625                 pp->children[i].state = GIT_CP_FREE;
1626                 pp->pfd[i].fd = -1;
1627                 child_process_init(&pp->children[i].process);
1628
1629                 if (i != pp->output_owner) {
1630                         strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1631                         strbuf_reset(&pp->children[i].err);
1632                 } else {
1633                         strbuf_write(&pp->children[i].err, stderr);
1634                         strbuf_reset(&pp->children[i].err);
1635
1636                         /* Output all other finished child processes */
1637                         strbuf_write(&pp->buffered_output, stderr);
1638                         strbuf_reset(&pp->buffered_output);
1639
1640                         /*
1641                          * Pick next process to output live.
1642                          * NEEDSWORK:
1643                          * For now we pick it randomly by doing a round
1644                          * robin. Later we may want to pick the one with
1645                          * the most output or the longest or shortest
1646                          * running process time.
1647                          */
1648                         for (i = 0; i < n; i++)
1649                                 if (pp->children[(pp->output_owner + i) % n].state == GIT_CP_WORKING)
1650                                         break;
1651                         pp->output_owner = (pp->output_owner + i) % n;
1652                 }
1653         }
1654         return result;
1655 }
1656
1657 int run_processes_parallel(int n,
1658                            get_next_task_fn get_next_task,
1659                            start_failure_fn start_failure,
1660                            task_finished_fn task_finished,
1661                            void *pp_cb)
1662 {
1663         int i, code;
1664         int output_timeout = 100;
1665         int spawn_cap = 4;
1666         struct parallel_processes pp;
1667
1668         pp_init(&pp, n, get_next_task, start_failure, task_finished, pp_cb);
1669         while (1) {
1670                 for (i = 0;
1671                     i < spawn_cap && !pp.shutdown &&
1672                     pp.nr_processes < pp.max_processes;
1673                     i++) {
1674                         code = pp_start_one(&pp);
1675                         if (!code)
1676                                 continue;
1677                         if (code < 0) {
1678                                 pp.shutdown = 1;
1679                                 kill_children(&pp, -code);
1680                         }
1681                         break;
1682                 }
1683                 if (!pp.nr_processes)
1684                         break;
1685                 pp_buffer_stderr(&pp, output_timeout);
1686                 pp_output(&pp);
1687                 code = pp_collect_finished(&pp);
1688                 if (code) {
1689                         pp.shutdown = 1;
1690                         if (code < 0)
1691                                 kill_children(&pp, -code);
1692                 }
1693         }
1694
1695         pp_cleanup(&pp);
1696         return 0;
1697 }