run-command.con commit Merge branch 'bw/forking-and-threading' into maint (e350625)
   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
   9void 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
  16void child_process_clear(struct child_process *child)
  17{
  18        argv_array_clear(&child->args);
  19        argv_array_clear(&child->env_array);
  20}
  21
  22struct child_to_clean {
  23        pid_t pid;
  24        struct child_process *process;
  25        struct child_to_clean *next;
  26};
  27static struct child_to_clean *children_to_clean;
  28static int installed_child_cleanup_handler;
  29
  30static 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
  72static void cleanup_children_on_signal(int sig)
  73{
  74        cleanup_children(sig, 1);
  75        sigchain_pop(sig);
  76        raise(sig);
  77}
  78
  79static void cleanup_children_on_exit(void)
  80{
  81        cleanup_children(SIGTERM, 0);
  82}
  83
  84static 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
  99static 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
 114static inline void close_pair(int fd[2])
 115{
 116        close(fd[0]);
 117        close(fd[1]);
 118}
 119
 120int 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 */
 179static 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
 211static int exists_in_PATH(const char *file)
 212{
 213        char *r = locate_in_PATH(file);
 214        free(r);
 215        return r != NULL;
 216}
 217
 218int 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 $PATH
 231         * lookups in that case.
 232         *
 233         * The reassignment of EACCES to errno looks like a no-op below,
 234         * but we need to protect against exists_in_PATH overwriting errno.
 235         */
 236        if (errno == EACCES && !strchr(file, '/'))
 237                errno = exists_in_PATH(file) ? EACCES : ENOENT;
 238        else if (errno == ENOTDIR && !strchr(file, '/'))
 239                errno = ENOENT;
 240        return -1;
 241}
 242
 243static const char **prepare_shell_cmd(struct argv_array *out, const char **argv)
 244{
 245        if (!argv[0])
 246                die("BUG: shell command is empty");
 247
 248        if (strcspn(argv[0], "|&;<>()$`\\\"' \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
 271static int child_notifier = -1;
 272
 273enum 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
 283struct child_err {
 284        enum child_errcode err;
 285        int syserr; /* errno */
 286};
 287
 288static 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
 300static void child_dup2(int fd, int to)
 301{
 302        if (dup2(fd, to) < 0)
 303                child_die(CHILD_ERR_DUP2);
 304}
 305
 306static void child_close(int fd)
 307{
 308        if (close(fd))
 309                child_die(CHILD_ERR_CLOSE);
 310}
 311
 312static 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 */
 322static void fake_fatal(const char *err, va_list params)
 323{
 324        vreportf("fatal: ", err, params);
 325}
 326
 327static 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
 333static 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
 339static 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 */
 347static 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
 381static 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
 416static 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        childenv = xmalloc((env.nr + 1) * sizeof(char *));
 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
 465struct atfork_state {
 466#ifndef NO_PTHREADS
 467        int cs;
 468#endif
 469        sigset_t old;
 470};
 471
 472#ifndef NO_PTHREADS
 473static 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
 482static 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
 499static 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
 513static 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
 520static 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
 558int 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";
 616fail_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
 865int 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
 872int finish_command_in_signal(struct child_process *cmd)
 873{
 874        return wait_or_whine(cmd->pid, cmd->argv[0], 1);
 875}
 876
 877
 878int 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
 891int run_command_v_opt(const char **argv, int opt)
 892{
 893        return run_command_v_opt_cd_env(argv, opt, NULL, NULL);
 894}
 895
 896int 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
 912static pthread_t main_thread;
 913static int main_thread_set;
 914static pthread_key_t async_key;
 915static pthread_key_t async_die_counter;
 916
 917static 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
 937static 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
 953static 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
 960int 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
 967static void NORETURN async_exit(int code)
 968{
 969        pthread_exit((void *)(intptr_t)code);
 970}
 971
 972#else
 973
 974static struct {
 975        void (**handlers)(void);
 976        size_t nr;
 977        size_t alloc;
 978} git_atexit_hdlrs;
 979
 980static int git_atexit_installed;
 981
 982static 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
 990static 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
 998int 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
1011static int process_is_async;
1012int in_async(void)
1013{
1014        return process_is_async;
1015}
1016
1017static void NORETURN async_exit(int code)
1018{
1019        exit(code);
1020}
1021
1022#endif
1023
1024void 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
1037int 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
1139error:
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
1152int 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
1165const 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
1182int 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
1201int 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
1213struct 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
1235static 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
1299static 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
1323int 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
1371enum child_state {
1372        GIT_CP_FREE,
1373        GIT_CP_WORKING,
1374        GIT_CP_WAIT_CLEANUP,
1375};
1376
1377struct 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
1405static int default_start_failure(struct strbuf *out,
1406                                 void *pp_cb,
1407                                 void *pp_task_cb)
1408{
1409        return 0;
1410}
1411
1412static 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
1420static 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
1429static struct parallel_processes *pp_for_signal;
1430
1431static void handle_children_on_signal(int signo)
1432{
1433        kill_children(pp_for_signal, signo);
1434        sigchain_pop(signo);
1435        raise(signo);
1436}
1437
1438static 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
1480static 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 */
1510static 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
1550static 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
1577static 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
1587static 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
1644int 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}