run-command.con commit Merge branch 'js/rebase-am-options-fix' (fde566f)
   1#include "cache.h"
   2#include "run-command.h"
   3#include "exec-cmd.h"
   4#include "sigchain.h"
   5#include "argv-array.h"
   6#include "thread-utils.h"
   7#include "strbuf.h"
   8#include "string-list.h"
   9#include "quote.h"
  10
  11void child_process_init(struct child_process *child)
  12{
  13        memset(child, 0, sizeof(*child));
  14        argv_array_init(&child->args);
  15        argv_array_init(&child->env_array);
  16}
  17
  18void child_process_clear(struct child_process *child)
  19{
  20        argv_array_clear(&child->args);
  21        argv_array_clear(&child->env_array);
  22}
  23
  24struct child_to_clean {
  25        pid_t pid;
  26        struct child_process *process;
  27        struct child_to_clean *next;
  28};
  29static struct child_to_clean *children_to_clean;
  30static int installed_child_cleanup_handler;
  31
  32static void cleanup_children(int sig, int in_signal)
  33{
  34        struct child_to_clean *children_to_wait_for = NULL;
  35
  36        while (children_to_clean) {
  37                struct child_to_clean *p = children_to_clean;
  38                children_to_clean = p->next;
  39
  40                if (p->process && !in_signal) {
  41                        struct child_process *process = p->process;
  42                        if (process->clean_on_exit_handler) {
  43                                trace_printf(
  44                                        "trace: run_command: running exit handler for pid %"
  45                                        PRIuMAX, (uintmax_t)p->pid
  46                                );
  47                                process->clean_on_exit_handler(process);
  48                        }
  49                }
  50
  51                kill(p->pid, sig);
  52
  53                if (p->process && p->process->wait_after_clean) {
  54                        p->next = children_to_wait_for;
  55                        children_to_wait_for = p;
  56                } else {
  57                        if (!in_signal)
  58                                free(p);
  59                }
  60        }
  61
  62        while (children_to_wait_for) {
  63                struct child_to_clean *p = children_to_wait_for;
  64                children_to_wait_for = p->next;
  65
  66                while (waitpid(p->pid, NULL, 0) < 0 && errno == EINTR)
  67                        ; /* spin waiting for process exit or error */
  68
  69                if (!in_signal)
  70                        free(p);
  71        }
  72}
  73
  74static void cleanup_children_on_signal(int sig)
  75{
  76        cleanup_children(sig, 1);
  77        sigchain_pop(sig);
  78        raise(sig);
  79}
  80
  81static void cleanup_children_on_exit(void)
  82{
  83        cleanup_children(SIGTERM, 0);
  84}
  85
  86static void mark_child_for_cleanup(pid_t pid, struct child_process *process)
  87{
  88        struct child_to_clean *p = xmalloc(sizeof(*p));
  89        p->pid = pid;
  90        p->process = process;
  91        p->next = children_to_clean;
  92        children_to_clean = p;
  93
  94        if (!installed_child_cleanup_handler) {
  95                atexit(cleanup_children_on_exit);
  96                sigchain_push_common(cleanup_children_on_signal);
  97                installed_child_cleanup_handler = 1;
  98        }
  99}
 100
 101static void clear_child_for_cleanup(pid_t pid)
 102{
 103        struct child_to_clean **pp;
 104
 105        for (pp = &children_to_clean; *pp; pp = &(*pp)->next) {
 106                struct child_to_clean *clean_me = *pp;
 107
 108                if (clean_me->pid == pid) {
 109                        *pp = clean_me->next;
 110                        free(clean_me);
 111                        return;
 112                }
 113        }
 114}
 115
 116static inline void close_pair(int fd[2])
 117{
 118        close(fd[0]);
 119        close(fd[1]);
 120}
 121
 122int is_executable(const char *name)
 123{
 124        struct stat st;
 125
 126        if (stat(name, &st) || /* stat, not lstat */
 127            !S_ISREG(st.st_mode))
 128                return 0;
 129
 130#if defined(GIT_WINDOWS_NATIVE)
 131        /*
 132         * On Windows there is no executable bit. The file extension
 133         * indicates whether it can be run as an executable, and Git
 134         * has special-handling to detect scripts and launch them
 135         * through the indicated script interpreter. We test for the
 136         * file extension first because virus scanners may make
 137         * it quite expensive to open many files.
 138         */
 139        if (ends_with(name, ".exe"))
 140                return S_IXUSR;
 141
 142{
 143        /*
 144         * Now that we know it does not have an executable extension,
 145         * peek into the file instead.
 146         */
 147        char buf[3] = { 0 };
 148        int n;
 149        int fd = open(name, O_RDONLY);
 150        st.st_mode &= ~S_IXUSR;
 151        if (fd >= 0) {
 152                n = read(fd, buf, 2);
 153                if (n == 2)
 154                        /* look for a she-bang */
 155                        if (!strcmp(buf, "#!"))
 156                                st.st_mode |= S_IXUSR;
 157                close(fd);
 158        }
 159}
 160#endif
 161        return st.st_mode & S_IXUSR;
 162}
 163
 164/*
 165 * Search $PATH for a command.  This emulates the path search that
 166 * execvp would perform, without actually executing the command so it
 167 * can be used before fork() to prepare to run a command using
 168 * execve() or after execvp() to diagnose why it failed.
 169 *
 170 * The caller should ensure that file contains no directory
 171 * separators.
 172 *
 173 * Returns the path to the command, as found in $PATH or NULL if the
 174 * command could not be found.  The caller inherits ownership of the memory
 175 * used to store the resultant path.
 176 *
 177 * This should not be used on Windows, where the $PATH search rules
 178 * are more complicated (e.g., a search for "foo" should find
 179 * "foo.exe").
 180 */
 181static char *locate_in_PATH(const char *file)
 182{
 183        const char *p = getenv("PATH");
 184        struct strbuf buf = STRBUF_INIT;
 185
 186        if (!p || !*p)
 187                return NULL;
 188
 189        while (1) {
 190                const char *end = strchrnul(p, ':');
 191
 192                strbuf_reset(&buf);
 193
 194                /* POSIX specifies an empty entry as the current directory. */
 195                if (end != p) {
 196                        strbuf_add(&buf, p, end - p);
 197                        strbuf_addch(&buf, '/');
 198                }
 199                strbuf_addstr(&buf, file);
 200
 201                if (is_executable(buf.buf))
 202                        return strbuf_detach(&buf, NULL);
 203
 204                if (!*end)
 205                        break;
 206                p = end + 1;
 207        }
 208
 209        strbuf_release(&buf);
 210        return NULL;
 211}
 212
 213static int exists_in_PATH(const char *file)
 214{
 215        char *r = locate_in_PATH(file);
 216        free(r);
 217        return r != NULL;
 218}
 219
 220int sane_execvp(const char *file, char * const argv[])
 221{
 222        if (!execvp(file, argv))
 223                return 0; /* cannot happen ;-) */
 224
 225        /*
 226         * When a command can't be found because one of the directories
 227         * listed in $PATH is unsearchable, execvp reports EACCES, but
 228         * careful usability testing (read: analysis of occasional bug
 229         * reports) reveals that "No such file or directory" is more
 230         * intuitive.
 231         *
 232         * We avoid commands with "/", because execvp will not do $PATH
 233         * lookups in that case.
 234         *
 235         * The reassignment of EACCES to errno looks like a no-op below,
 236         * but we need to protect against exists_in_PATH overwriting errno.
 237         */
 238        if (errno == EACCES && !strchr(file, '/'))
 239                errno = exists_in_PATH(file) ? EACCES : ENOENT;
 240        else if (errno == ENOTDIR && !strchr(file, '/'))
 241                errno = ENOENT;
 242        return -1;
 243}
 244
 245static const char **prepare_shell_cmd(struct argv_array *out, const char **argv)
 246{
 247        if (!argv[0])
 248                BUG("shell command is empty");
 249
 250        if (strcspn(argv[0], "|&;<>()$`\\\"' \t\n*?[#~=%") != strlen(argv[0])) {
 251#ifndef GIT_WINDOWS_NATIVE
 252                argv_array_push(out, SHELL_PATH);
 253#else
 254                argv_array_push(out, "sh");
 255#endif
 256                argv_array_push(out, "-c");
 257
 258                /*
 259                 * If we have no extra arguments, we do not even need to
 260                 * bother with the "$@" magic.
 261                 */
 262                if (!argv[1])
 263                        argv_array_push(out, argv[0]);
 264                else
 265                        argv_array_pushf(out, "%s \"$@\"", argv[0]);
 266        }
 267
 268        argv_array_pushv(out, argv);
 269        return out->argv;
 270}
 271
 272#ifndef GIT_WINDOWS_NATIVE
 273static int child_notifier = -1;
 274
 275enum child_errcode {
 276        CHILD_ERR_CHDIR,
 277        CHILD_ERR_DUP2,
 278        CHILD_ERR_CLOSE,
 279        CHILD_ERR_SIGPROCMASK,
 280        CHILD_ERR_ENOENT,
 281        CHILD_ERR_SILENT,
 282        CHILD_ERR_ERRNO
 283};
 284
 285struct child_err {
 286        enum child_errcode err;
 287        int syserr; /* errno */
 288};
 289
 290static void child_die(enum child_errcode err)
 291{
 292        struct child_err buf;
 293
 294        buf.err = err;
 295        buf.syserr = errno;
 296
 297        /* write(2) on buf smaller than PIPE_BUF (min 512) is atomic: */
 298        xwrite(child_notifier, &buf, sizeof(buf));
 299        _exit(1);
 300}
 301
 302static void child_dup2(int fd, int to)
 303{
 304        if (dup2(fd, to) < 0)
 305                child_die(CHILD_ERR_DUP2);
 306}
 307
 308static void child_close(int fd)
 309{
 310        if (close(fd))
 311                child_die(CHILD_ERR_CLOSE);
 312}
 313
 314static void child_close_pair(int fd[2])
 315{
 316        child_close(fd[0]);
 317        child_close(fd[1]);
 318}
 319
 320/*
 321 * parent will make it look like the child spewed a fatal error and died
 322 * this is needed to prevent changes to t0061.
 323 */
 324static void fake_fatal(const char *err, va_list params)
 325{
 326        vreportf("fatal: ", err, params);
 327}
 328
 329static void child_error_fn(const char *err, va_list params)
 330{
 331        const char msg[] = "error() should not be called in child\n";
 332        xwrite(2, msg, sizeof(msg) - 1);
 333}
 334
 335static void child_warn_fn(const char *err, va_list params)
 336{
 337        const char msg[] = "warn() should not be called in child\n";
 338        xwrite(2, msg, sizeof(msg) - 1);
 339}
 340
 341static void NORETURN child_die_fn(const char *err, va_list params)
 342{
 343        const char msg[] = "die() should not be called in child\n";
 344        xwrite(2, msg, sizeof(msg) - 1);
 345        _exit(2);
 346}
 347
 348/* this runs in the parent process */
 349static void child_err_spew(struct child_process *cmd, struct child_err *cerr)
 350{
 351        static void (*old_errfn)(const char *err, va_list params);
 352
 353        old_errfn = get_error_routine();
 354        set_error_routine(fake_fatal);
 355        errno = cerr->syserr;
 356
 357        switch (cerr->err) {
 358        case CHILD_ERR_CHDIR:
 359                error_errno("exec '%s': cd to '%s' failed",
 360                            cmd->argv[0], cmd->dir);
 361                break;
 362        case CHILD_ERR_DUP2:
 363                error_errno("dup2() in child failed");
 364                break;
 365        case CHILD_ERR_CLOSE:
 366                error_errno("close() in child failed");
 367                break;
 368        case CHILD_ERR_SIGPROCMASK:
 369                error_errno("sigprocmask failed restoring signals");
 370                break;
 371        case CHILD_ERR_ENOENT:
 372                error_errno("cannot run %s", cmd->argv[0]);
 373                break;
 374        case CHILD_ERR_SILENT:
 375                break;
 376        case CHILD_ERR_ERRNO:
 377                error_errno("cannot exec '%s'", cmd->argv[0]);
 378                break;
 379        }
 380        set_error_routine(old_errfn);
 381}
 382
 383static int prepare_cmd(struct argv_array *out, const struct child_process *cmd)
 384{
 385        if (!cmd->argv[0])
 386                BUG("command is empty");
 387
 388        /*
 389         * Add SHELL_PATH so in the event exec fails with ENOEXEC we can
 390         * attempt to interpret the command with 'sh'.
 391         */
 392        argv_array_push(out, SHELL_PATH);
 393
 394        if (cmd->git_cmd) {
 395                argv_array_push(out, "git");
 396                argv_array_pushv(out, cmd->argv);
 397        } else if (cmd->use_shell) {
 398                prepare_shell_cmd(out, cmd->argv);
 399        } else {
 400                argv_array_pushv(out, cmd->argv);
 401        }
 402
 403        /*
 404         * If there are no '/' characters in the command then perform a path
 405         * lookup and use the resolved path as the command to exec.  If there
 406         * are '/' characters, we have exec attempt to invoke the command
 407         * directly.
 408         */
 409        if (!strchr(out->argv[1], '/')) {
 410                char *program = locate_in_PATH(out->argv[1]);
 411                if (program) {
 412                        free((char *)out->argv[1]);
 413                        out->argv[1] = program;
 414                } else {
 415                        argv_array_clear(out);
 416                        errno = ENOENT;
 417                        return -1;
 418                }
 419        }
 420
 421        return 0;
 422}
 423
 424static char **prep_childenv(const char *const *deltaenv)
 425{
 426        extern char **environ;
 427        char **childenv;
 428        struct string_list env = STRING_LIST_INIT_DUP;
 429        struct strbuf key = STRBUF_INIT;
 430        const char *const *p;
 431        int i;
 432
 433        /* Construct a sorted string list consisting of the current environ */
 434        for (p = (const char *const *) environ; p && *p; p++) {
 435                const char *equals = strchr(*p, '=');
 436
 437                if (equals) {
 438                        strbuf_reset(&key);
 439                        strbuf_add(&key, *p, equals - *p);
 440                        string_list_append(&env, key.buf)->util = (void *) *p;
 441                } else {
 442                        string_list_append(&env, *p)->util = (void *) *p;
 443                }
 444        }
 445        string_list_sort(&env);
 446
 447        /* Merge in 'deltaenv' with the current environ */
 448        for (p = deltaenv; p && *p; p++) {
 449                const char *equals = strchr(*p, '=');
 450
 451                if (equals) {
 452                        /* ('key=value'), insert or replace entry */
 453                        strbuf_reset(&key);
 454                        strbuf_add(&key, *p, equals - *p);
 455                        string_list_insert(&env, key.buf)->util = (void *) *p;
 456                } else {
 457                        /* otherwise ('key') remove existing entry */
 458                        string_list_remove(&env, *p, 0);
 459                }
 460        }
 461
 462        /* Create an array of 'char *' to be used as the childenv */
 463        ALLOC_ARRAY(childenv, env.nr + 1);
 464        for (i = 0; i < env.nr; i++)
 465                childenv[i] = env.items[i].util;
 466        childenv[env.nr] = NULL;
 467
 468        string_list_clear(&env, 0);
 469        strbuf_release(&key);
 470        return childenv;
 471}
 472
 473struct atfork_state {
 474#ifndef NO_PTHREADS
 475        int cs;
 476#endif
 477        sigset_t old;
 478};
 479
 480#define CHECK_BUG(err, msg) \
 481        do { \
 482                int e = (err); \
 483                if (e) \
 484                        BUG("%s: %s", msg, strerror(e)); \
 485        } while(0)
 486
 487static void atfork_prepare(struct atfork_state *as)
 488{
 489        sigset_t all;
 490
 491        if (sigfillset(&all))
 492                die_errno("sigfillset");
 493#ifdef NO_PTHREADS
 494        if (sigprocmask(SIG_SETMASK, &all, &as->old))
 495                die_errno("sigprocmask");
 496#else
 497        CHECK_BUG(pthread_sigmask(SIG_SETMASK, &all, &as->old),
 498                "blocking all signals");
 499        CHECK_BUG(pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &as->cs),
 500                "disabling cancellation");
 501#endif
 502}
 503
 504static void atfork_parent(struct atfork_state *as)
 505{
 506#ifdef NO_PTHREADS
 507        if (sigprocmask(SIG_SETMASK, &as->old, NULL))
 508                die_errno("sigprocmask");
 509#else
 510        CHECK_BUG(pthread_setcancelstate(as->cs, NULL),
 511                "re-enabling cancellation");
 512        CHECK_BUG(pthread_sigmask(SIG_SETMASK, &as->old, NULL),
 513                "restoring signal mask");
 514#endif
 515}
 516#endif /* GIT_WINDOWS_NATIVE */
 517
 518static inline void set_cloexec(int fd)
 519{
 520        int flags = fcntl(fd, F_GETFD);
 521        if (flags >= 0)
 522                fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
 523}
 524
 525static int wait_or_whine(pid_t pid, const char *argv0, int in_signal)
 526{
 527        int status, code = -1;
 528        pid_t waiting;
 529        int failed_errno = 0;
 530
 531        while ((waiting = waitpid(pid, &status, 0)) < 0 && errno == EINTR)
 532                ;       /* nothing */
 533        if (in_signal)
 534                return 0;
 535
 536        if (waiting < 0) {
 537                failed_errno = errno;
 538                error_errno("waitpid for %s failed", argv0);
 539        } else if (waiting != pid) {
 540                error("waitpid is confused (%s)", argv0);
 541        } else if (WIFSIGNALED(status)) {
 542                code = WTERMSIG(status);
 543                if (code != SIGINT && code != SIGQUIT && code != SIGPIPE)
 544                        error("%s died of signal %d", argv0, code);
 545                /*
 546                 * This return value is chosen so that code & 0xff
 547                 * mimics the exit code that a POSIX shell would report for
 548                 * a program that died from this signal.
 549                 */
 550                code += 128;
 551        } else if (WIFEXITED(status)) {
 552                code = WEXITSTATUS(status);
 553        } else {
 554                error("waitpid is confused (%s)", argv0);
 555        }
 556
 557        clear_child_for_cleanup(pid);
 558
 559        errno = failed_errno;
 560        return code;
 561}
 562
 563static void trace_add_env(struct strbuf *dst, const char *const *deltaenv)
 564{
 565        struct string_list envs = STRING_LIST_INIT_DUP;
 566        const char *const *e;
 567        int i;
 568        int printed_unset = 0;
 569
 570        /* Last one wins, see run-command.c:prep_childenv() for context */
 571        for (e = deltaenv; e && *e; e++) {
 572                struct strbuf key = STRBUF_INIT;
 573                char *equals = strchr(*e, '=');
 574
 575                if (equals) {
 576                        strbuf_add(&key, *e, equals - *e);
 577                        string_list_insert(&envs, key.buf)->util = equals + 1;
 578                } else {
 579                        string_list_insert(&envs, *e)->util = NULL;
 580                }
 581                strbuf_release(&key);
 582        }
 583
 584        /* "unset X Y...;" */
 585        for (i = 0; i < envs.nr; i++) {
 586                const char *var = envs.items[i].string;
 587                const char *val = envs.items[i].util;
 588
 589                if (val || !getenv(var))
 590                        continue;
 591
 592                if (!printed_unset) {
 593                        strbuf_addstr(dst, " unset");
 594                        printed_unset = 1;
 595                }
 596                strbuf_addf(dst, " %s", var);
 597        }
 598        if (printed_unset)
 599                strbuf_addch(dst, ';');
 600
 601        /* ... followed by "A=B C=D ..." */
 602        for (i = 0; i < envs.nr; i++) {
 603                const char *var = envs.items[i].string;
 604                const char *val = envs.items[i].util;
 605                const char *oldval;
 606
 607                if (!val)
 608                        continue;
 609
 610                oldval = getenv(var);
 611                if (oldval && !strcmp(val, oldval))
 612                        continue;
 613
 614                strbuf_addf(dst, " %s=", var);
 615                sq_quote_buf_pretty(dst, val);
 616        }
 617        string_list_clear(&envs, 0);
 618}
 619
 620static void trace_run_command(const struct child_process *cp)
 621{
 622        struct strbuf buf = STRBUF_INIT;
 623
 624        if (!trace_want(&trace_default_key))
 625                return;
 626
 627        strbuf_addstr(&buf, "trace: run_command:");
 628        if (cp->dir) {
 629                strbuf_addstr(&buf, " cd ");
 630                sq_quote_buf_pretty(&buf, cp->dir);
 631                strbuf_addch(&buf, ';');
 632        }
 633        /*
 634         * The caller is responsible for initializing cp->env from
 635         * cp->env_array if needed. We only check one place.
 636         */
 637        if (cp->env)
 638                trace_add_env(&buf, cp->env);
 639        if (cp->git_cmd)
 640                strbuf_addstr(&buf, " git");
 641        sq_quote_argv_pretty(&buf, cp->argv);
 642
 643        trace_printf("%s", buf.buf);
 644        strbuf_release(&buf);
 645}
 646
 647int start_command(struct child_process *cmd)
 648{
 649        int need_in, need_out, need_err;
 650        int fdin[2], fdout[2], fderr[2];
 651        int failed_errno;
 652        char *str;
 653
 654        if (!cmd->argv)
 655                cmd->argv = cmd->args.argv;
 656        if (!cmd->env)
 657                cmd->env = cmd->env_array.argv;
 658
 659        /*
 660         * In case of errors we must keep the promise to close FDs
 661         * that have been passed in via ->in and ->out.
 662         */
 663
 664        need_in = !cmd->no_stdin && cmd->in < 0;
 665        if (need_in) {
 666                if (pipe(fdin) < 0) {
 667                        failed_errno = errno;
 668                        if (cmd->out > 0)
 669                                close(cmd->out);
 670                        str = "standard input";
 671                        goto fail_pipe;
 672                }
 673                cmd->in = fdin[1];
 674        }
 675
 676        need_out = !cmd->no_stdout
 677                && !cmd->stdout_to_stderr
 678                && cmd->out < 0;
 679        if (need_out) {
 680                if (pipe(fdout) < 0) {
 681                        failed_errno = errno;
 682                        if (need_in)
 683                                close_pair(fdin);
 684                        else if (cmd->in)
 685                                close(cmd->in);
 686                        str = "standard output";
 687                        goto fail_pipe;
 688                }
 689                cmd->out = fdout[0];
 690        }
 691
 692        need_err = !cmd->no_stderr && cmd->err < 0;
 693        if (need_err) {
 694                if (pipe(fderr) < 0) {
 695                        failed_errno = errno;
 696                        if (need_in)
 697                                close_pair(fdin);
 698                        else if (cmd->in)
 699                                close(cmd->in);
 700                        if (need_out)
 701                                close_pair(fdout);
 702                        else if (cmd->out)
 703                                close(cmd->out);
 704                        str = "standard error";
 705fail_pipe:
 706                        error("cannot create %s pipe for %s: %s",
 707                                str, cmd->argv[0], strerror(failed_errno));
 708                        child_process_clear(cmd);
 709                        errno = failed_errno;
 710                        return -1;
 711                }
 712                cmd->err = fderr[0];
 713        }
 714
 715        trace_run_command(cmd);
 716
 717        fflush(NULL);
 718
 719#ifndef GIT_WINDOWS_NATIVE
 720{
 721        int notify_pipe[2];
 722        int null_fd = -1;
 723        char **childenv;
 724        struct argv_array argv = ARGV_ARRAY_INIT;
 725        struct child_err cerr;
 726        struct atfork_state as;
 727
 728        if (prepare_cmd(&argv, cmd) < 0) {
 729                failed_errno = errno;
 730                cmd->pid = -1;
 731                goto end_of_spawn;
 732        }
 733
 734        if (pipe(notify_pipe))
 735                notify_pipe[0] = notify_pipe[1] = -1;
 736
 737        if (cmd->no_stdin || cmd->no_stdout || cmd->no_stderr) {
 738                null_fd = open("/dev/null", O_RDWR | O_CLOEXEC);
 739                if (null_fd < 0)
 740                        die_errno(_("open /dev/null failed"));
 741                set_cloexec(null_fd);
 742        }
 743
 744        childenv = prep_childenv(cmd->env);
 745        atfork_prepare(&as);
 746
 747        /*
 748         * NOTE: In order to prevent deadlocking when using threads special
 749         * care should be taken with the function calls made in between the
 750         * fork() and exec() calls.  No calls should be made to functions which
 751         * require acquiring a lock (e.g. malloc) as the lock could have been
 752         * held by another thread at the time of forking, causing the lock to
 753         * never be released in the child process.  This means only
 754         * Async-Signal-Safe functions are permitted in the child.
 755         */
 756        cmd->pid = fork();
 757        failed_errno = errno;
 758        if (!cmd->pid) {
 759                int sig;
 760                /*
 761                 * Ensure the default die/error/warn routines do not get
 762                 * called, they can take stdio locks and malloc.
 763                 */
 764                set_die_routine(child_die_fn);
 765                set_error_routine(child_error_fn);
 766                set_warn_routine(child_warn_fn);
 767
 768                close(notify_pipe[0]);
 769                set_cloexec(notify_pipe[1]);
 770                child_notifier = notify_pipe[1];
 771
 772                if (cmd->no_stdin)
 773                        child_dup2(null_fd, 0);
 774                else if (need_in) {
 775                        child_dup2(fdin[0], 0);
 776                        child_close_pair(fdin);
 777                } else if (cmd->in) {
 778                        child_dup2(cmd->in, 0);
 779                        child_close(cmd->in);
 780                }
 781
 782                if (cmd->no_stderr)
 783                        child_dup2(null_fd, 2);
 784                else if (need_err) {
 785                        child_dup2(fderr[1], 2);
 786                        child_close_pair(fderr);
 787                } else if (cmd->err > 1) {
 788                        child_dup2(cmd->err, 2);
 789                        child_close(cmd->err);
 790                }
 791
 792                if (cmd->no_stdout)
 793                        child_dup2(null_fd, 1);
 794                else if (cmd->stdout_to_stderr)
 795                        child_dup2(2, 1);
 796                else if (need_out) {
 797                        child_dup2(fdout[1], 1);
 798                        child_close_pair(fdout);
 799                } else if (cmd->out > 1) {
 800                        child_dup2(cmd->out, 1);
 801                        child_close(cmd->out);
 802                }
 803
 804                if (cmd->dir && chdir(cmd->dir))
 805                        child_die(CHILD_ERR_CHDIR);
 806
 807                /*
 808                 * restore default signal handlers here, in case
 809                 * we catch a signal right before execve below
 810                 */
 811                for (sig = 1; sig < NSIG; sig++) {
 812                        /* ignored signals get reset to SIG_DFL on execve */
 813                        if (signal(sig, SIG_DFL) == SIG_IGN)
 814                                signal(sig, SIG_IGN);
 815                }
 816
 817                if (sigprocmask(SIG_SETMASK, &as.old, NULL) != 0)
 818                        child_die(CHILD_ERR_SIGPROCMASK);
 819
 820                /*
 821                 * Attempt to exec using the command and arguments starting at
 822                 * argv.argv[1].  argv.argv[0] contains SHELL_PATH which will
 823                 * be used in the event exec failed with ENOEXEC at which point
 824                 * we will try to interpret the command using 'sh'.
 825                 */
 826                execve(argv.argv[1], (char *const *) argv.argv + 1,
 827                       (char *const *) childenv);
 828                if (errno == ENOEXEC)
 829                        execve(argv.argv[0], (char *const *) argv.argv,
 830                               (char *const *) childenv);
 831
 832                if (errno == ENOENT) {
 833                        if (cmd->silent_exec_failure)
 834                                child_die(CHILD_ERR_SILENT);
 835                        child_die(CHILD_ERR_ENOENT);
 836                } else {
 837                        child_die(CHILD_ERR_ERRNO);
 838                }
 839        }
 840        atfork_parent(&as);
 841        if (cmd->pid < 0)
 842                error_errno("cannot fork() for %s", cmd->argv[0]);
 843        else if (cmd->clean_on_exit)
 844                mark_child_for_cleanup(cmd->pid, cmd);
 845
 846        /*
 847         * Wait for child's exec. If the exec succeeds (or if fork()
 848         * failed), EOF is seen immediately by the parent. Otherwise, the
 849         * child process sends a child_err struct.
 850         * Note that use of this infrastructure is completely advisory,
 851         * therefore, we keep error checks minimal.
 852         */
 853        close(notify_pipe[1]);
 854        if (xread(notify_pipe[0], &cerr, sizeof(cerr)) == sizeof(cerr)) {
 855                /*
 856                 * At this point we know that fork() succeeded, but exec()
 857                 * failed. Errors have been reported to our stderr.
 858                 */
 859                wait_or_whine(cmd->pid, cmd->argv[0], 0);
 860                child_err_spew(cmd, &cerr);
 861                failed_errno = errno;
 862                cmd->pid = -1;
 863        }
 864        close(notify_pipe[0]);
 865
 866        if (null_fd >= 0)
 867                close(null_fd);
 868        argv_array_clear(&argv);
 869        free(childenv);
 870}
 871end_of_spawn:
 872
 873#else
 874{
 875        int fhin = 0, fhout = 1, fherr = 2;
 876        const char **sargv = cmd->argv;
 877        struct argv_array nargv = ARGV_ARRAY_INIT;
 878
 879        if (cmd->no_stdin)
 880                fhin = open("/dev/null", O_RDWR);
 881        else if (need_in)
 882                fhin = dup(fdin[0]);
 883        else if (cmd->in)
 884                fhin = dup(cmd->in);
 885
 886        if (cmd->no_stderr)
 887                fherr = open("/dev/null", O_RDWR);
 888        else if (need_err)
 889                fherr = dup(fderr[1]);
 890        else if (cmd->err > 2)
 891                fherr = dup(cmd->err);
 892
 893        if (cmd->no_stdout)
 894                fhout = open("/dev/null", O_RDWR);
 895        else if (cmd->stdout_to_stderr)
 896                fhout = dup(fherr);
 897        else if (need_out)
 898                fhout = dup(fdout[1]);
 899        else if (cmd->out > 1)
 900                fhout = dup(cmd->out);
 901
 902        if (cmd->git_cmd)
 903                cmd->argv = prepare_git_cmd(&nargv, cmd->argv);
 904        else if (cmd->use_shell)
 905                cmd->argv = prepare_shell_cmd(&nargv, cmd->argv);
 906
 907        cmd->pid = mingw_spawnvpe(cmd->argv[0], cmd->argv, (char**) cmd->env,
 908                        cmd->dir, fhin, fhout, fherr);
 909        failed_errno = errno;
 910        if (cmd->pid < 0 && (!cmd->silent_exec_failure || errno != ENOENT))
 911                error_errno("cannot spawn %s", cmd->argv[0]);
 912        if (cmd->clean_on_exit && cmd->pid >= 0)
 913                mark_child_for_cleanup(cmd->pid, cmd);
 914
 915        argv_array_clear(&nargv);
 916        cmd->argv = sargv;
 917        if (fhin != 0)
 918                close(fhin);
 919        if (fhout != 1)
 920                close(fhout);
 921        if (fherr != 2)
 922                close(fherr);
 923}
 924#endif
 925
 926        if (cmd->pid < 0) {
 927                if (need_in)
 928                        close_pair(fdin);
 929                else if (cmd->in)
 930                        close(cmd->in);
 931                if (need_out)
 932                        close_pair(fdout);
 933                else if (cmd->out)
 934                        close(cmd->out);
 935                if (need_err)
 936                        close_pair(fderr);
 937                else if (cmd->err)
 938                        close(cmd->err);
 939                child_process_clear(cmd);
 940                errno = failed_errno;
 941                return -1;
 942        }
 943
 944        if (need_in)
 945                close(fdin[0]);
 946        else if (cmd->in)
 947                close(cmd->in);
 948
 949        if (need_out)
 950                close(fdout[1]);
 951        else if (cmd->out)
 952                close(cmd->out);
 953
 954        if (need_err)
 955                close(fderr[1]);
 956        else if (cmd->err)
 957                close(cmd->err);
 958
 959        return 0;
 960}
 961
 962int finish_command(struct child_process *cmd)
 963{
 964        int ret = wait_or_whine(cmd->pid, cmd->argv[0], 0);
 965        child_process_clear(cmd);
 966        return ret;
 967}
 968
 969int finish_command_in_signal(struct child_process *cmd)
 970{
 971        return wait_or_whine(cmd->pid, cmd->argv[0], 1);
 972}
 973
 974
 975int run_command(struct child_process *cmd)
 976{
 977        int code;
 978
 979        if (cmd->out < 0 || cmd->err < 0)
 980                BUG("run_command with a pipe can cause deadlock");
 981
 982        code = start_command(cmd);
 983        if (code)
 984                return code;
 985        return finish_command(cmd);
 986}
 987
 988int run_command_v_opt(const char **argv, int opt)
 989{
 990        return run_command_v_opt_cd_env(argv, opt, NULL, NULL);
 991}
 992
 993int run_command_v_opt_cd_env(const char **argv, int opt, const char *dir, const char *const *env)
 994{
 995        struct child_process cmd = CHILD_PROCESS_INIT;
 996        cmd.argv = argv;
 997        cmd.no_stdin = opt & RUN_COMMAND_NO_STDIN ? 1 : 0;
 998        cmd.git_cmd = opt & RUN_GIT_CMD ? 1 : 0;
 999        cmd.stdout_to_stderr = opt & RUN_COMMAND_STDOUT_TO_STDERR ? 1 : 0;
1000        cmd.silent_exec_failure = opt & RUN_SILENT_EXEC_FAILURE ? 1 : 0;
1001        cmd.use_shell = opt & RUN_USING_SHELL ? 1 : 0;
1002        cmd.clean_on_exit = opt & RUN_CLEAN_ON_EXIT ? 1 : 0;
1003        cmd.dir = dir;
1004        cmd.env = env;
1005        return run_command(&cmd);
1006}
1007
1008#ifndef NO_PTHREADS
1009static pthread_t main_thread;
1010static int main_thread_set;
1011static pthread_key_t async_key;
1012static pthread_key_t async_die_counter;
1013
1014static void *run_thread(void *data)
1015{
1016        struct async *async = data;
1017        intptr_t ret;
1018
1019        if (async->isolate_sigpipe) {
1020                sigset_t mask;
1021                sigemptyset(&mask);
1022                sigaddset(&mask, SIGPIPE);
1023                if (pthread_sigmask(SIG_BLOCK, &mask, NULL) < 0) {
1024                        ret = error("unable to block SIGPIPE in async thread");
1025                        return (void *)ret;
1026                }
1027        }
1028
1029        pthread_setspecific(async_key, async);
1030        ret = async->proc(async->proc_in, async->proc_out, async->data);
1031        return (void *)ret;
1032}
1033
1034static NORETURN void die_async(const char *err, va_list params)
1035{
1036        vreportf("fatal: ", err, params);
1037
1038        if (in_async()) {
1039                struct async *async = pthread_getspecific(async_key);
1040                if (async->proc_in >= 0)
1041                        close(async->proc_in);
1042                if (async->proc_out >= 0)
1043                        close(async->proc_out);
1044                pthread_exit((void *)128);
1045        }
1046
1047        exit(128);
1048}
1049
1050static int async_die_is_recursing(void)
1051{
1052        void *ret = pthread_getspecific(async_die_counter);
1053        pthread_setspecific(async_die_counter, (void *)1);
1054        return ret != NULL;
1055}
1056
1057int in_async(void)
1058{
1059        if (!main_thread_set)
1060                return 0; /* no asyncs started yet */
1061        return !pthread_equal(main_thread, pthread_self());
1062}
1063
1064static void NORETURN async_exit(int code)
1065{
1066        pthread_exit((void *)(intptr_t)code);
1067}
1068
1069#else
1070
1071static struct {
1072        void (**handlers)(void);
1073        size_t nr;
1074        size_t alloc;
1075} git_atexit_hdlrs;
1076
1077static int git_atexit_installed;
1078
1079static void git_atexit_dispatch(void)
1080{
1081        size_t i;
1082
1083        for (i=git_atexit_hdlrs.nr ; i ; i--)
1084                git_atexit_hdlrs.handlers[i-1]();
1085}
1086
1087static void git_atexit_clear(void)
1088{
1089        free(git_atexit_hdlrs.handlers);
1090        memset(&git_atexit_hdlrs, 0, sizeof(git_atexit_hdlrs));
1091        git_atexit_installed = 0;
1092}
1093
1094#undef atexit
1095int git_atexit(void (*handler)(void))
1096{
1097        ALLOC_GROW(git_atexit_hdlrs.handlers, git_atexit_hdlrs.nr + 1, git_atexit_hdlrs.alloc);
1098        git_atexit_hdlrs.handlers[git_atexit_hdlrs.nr++] = handler;
1099        if (!git_atexit_installed) {
1100                if (atexit(&git_atexit_dispatch))
1101                        return -1;
1102                git_atexit_installed = 1;
1103        }
1104        return 0;
1105}
1106#define atexit git_atexit
1107
1108static int process_is_async;
1109int in_async(void)
1110{
1111        return process_is_async;
1112}
1113
1114static void NORETURN async_exit(int code)
1115{
1116        exit(code);
1117}
1118
1119#endif
1120
1121void check_pipe(int err)
1122{
1123        if (err == EPIPE) {
1124                if (in_async())
1125                        async_exit(141);
1126
1127                signal(SIGPIPE, SIG_DFL);
1128                raise(SIGPIPE);
1129                /* Should never happen, but just in case... */
1130                exit(141);
1131        }
1132}
1133
1134int start_async(struct async *async)
1135{
1136        int need_in, need_out;
1137        int fdin[2], fdout[2];
1138        int proc_in, proc_out;
1139
1140        need_in = async->in < 0;
1141        if (need_in) {
1142                if (pipe(fdin) < 0) {
1143                        if (async->out > 0)
1144                                close(async->out);
1145                        return error_errno("cannot create pipe");
1146                }
1147                async->in = fdin[1];
1148        }
1149
1150        need_out = async->out < 0;
1151        if (need_out) {
1152                if (pipe(fdout) < 0) {
1153                        if (need_in)
1154                                close_pair(fdin);
1155                        else if (async->in)
1156                                close(async->in);
1157                        return error_errno("cannot create pipe");
1158                }
1159                async->out = fdout[0];
1160        }
1161
1162        if (need_in)
1163                proc_in = fdin[0];
1164        else if (async->in)
1165                proc_in = async->in;
1166        else
1167                proc_in = -1;
1168
1169        if (need_out)
1170                proc_out = fdout[1];
1171        else if (async->out)
1172                proc_out = async->out;
1173        else
1174                proc_out = -1;
1175
1176#ifdef NO_PTHREADS
1177        /* Flush stdio before fork() to avoid cloning buffers */
1178        fflush(NULL);
1179
1180        async->pid = fork();
1181        if (async->pid < 0) {
1182                error_errno("fork (async) failed");
1183                goto error;
1184        }
1185        if (!async->pid) {
1186                if (need_in)
1187                        close(fdin[1]);
1188                if (need_out)
1189                        close(fdout[0]);
1190                git_atexit_clear();
1191                process_is_async = 1;
1192                exit(!!async->proc(proc_in, proc_out, async->data));
1193        }
1194
1195        mark_child_for_cleanup(async->pid, NULL);
1196
1197        if (need_in)
1198                close(fdin[0]);
1199        else if (async->in)
1200                close(async->in);
1201
1202        if (need_out)
1203                close(fdout[1]);
1204        else if (async->out)
1205                close(async->out);
1206#else
1207        if (!main_thread_set) {
1208                /*
1209                 * We assume that the first time that start_async is called
1210                 * it is from the main thread.
1211                 */
1212                main_thread_set = 1;
1213                main_thread = pthread_self();
1214                pthread_key_create(&async_key, NULL);
1215                pthread_key_create(&async_die_counter, NULL);
1216                set_die_routine(die_async);
1217                set_die_is_recursing_routine(async_die_is_recursing);
1218        }
1219
1220        if (proc_in >= 0)
1221                set_cloexec(proc_in);
1222        if (proc_out >= 0)
1223                set_cloexec(proc_out);
1224        async->proc_in = proc_in;
1225        async->proc_out = proc_out;
1226        {
1227                int err = pthread_create(&async->tid, NULL, run_thread, async);
1228                if (err) {
1229                        error(_("cannot create async thread: %s"), strerror(err));
1230                        goto error;
1231                }
1232        }
1233#endif
1234        return 0;
1235
1236error:
1237        if (need_in)
1238                close_pair(fdin);
1239        else if (async->in)
1240                close(async->in);
1241
1242        if (need_out)
1243                close_pair(fdout);
1244        else if (async->out)
1245                close(async->out);
1246        return -1;
1247}
1248
1249int finish_async(struct async *async)
1250{
1251#ifdef NO_PTHREADS
1252        return wait_or_whine(async->pid, "child process", 0);
1253#else
1254        void *ret = (void *)(intptr_t)(-1);
1255
1256        if (pthread_join(async->tid, &ret))
1257                error("pthread_join failed");
1258        return (int)(intptr_t)ret;
1259#endif
1260}
1261
1262int async_with_fork(void)
1263{
1264#ifdef NO_PTHREADS
1265        return 1;
1266#else
1267        return 0;
1268#endif
1269}
1270
1271const char *find_hook(const char *name)
1272{
1273        static struct strbuf path = STRBUF_INIT;
1274
1275        strbuf_reset(&path);
1276        strbuf_git_path(&path, "hooks/%s", name);
1277        if (access(path.buf, X_OK) < 0) {
1278                int err = errno;
1279
1280#ifdef STRIP_EXTENSION
1281                strbuf_addstr(&path, STRIP_EXTENSION);
1282                if (access(path.buf, X_OK) >= 0)
1283                        return path.buf;
1284                if (errno == EACCES)
1285                        err = errno;
1286#endif
1287
1288                if (err == EACCES && advice_ignored_hook) {
1289                        static struct string_list advise_given = STRING_LIST_INIT_DUP;
1290
1291                        if (!string_list_lookup(&advise_given, name)) {
1292                                string_list_insert(&advise_given, name);
1293                                advise(_("The '%s' hook was ignored because "
1294                                         "it's not set as executable.\n"
1295                                         "You can disable this warning with "
1296                                         "`git config advice.ignoredHook false`."),
1297                                       path.buf);
1298                        }
1299                }
1300                return NULL;
1301        }
1302        return path.buf;
1303}
1304
1305int run_hook_ve(const char *const *env, const char *name, va_list args)
1306{
1307        struct child_process hook = CHILD_PROCESS_INIT;
1308        const char *p;
1309
1310        p = find_hook(name);
1311        if (!p)
1312                return 0;
1313
1314        argv_array_push(&hook.args, p);
1315        while ((p = va_arg(args, const char *)))
1316                argv_array_push(&hook.args, p);
1317        hook.env = env;
1318        hook.no_stdin = 1;
1319        hook.stdout_to_stderr = 1;
1320
1321        return run_command(&hook);
1322}
1323
1324int run_hook_le(const char *const *env, const char *name, ...)
1325{
1326        va_list args;
1327        int ret;
1328
1329        va_start(args, name);
1330        ret = run_hook_ve(env, name, args);
1331        va_end(args);
1332
1333        return ret;
1334}
1335
1336struct io_pump {
1337        /* initialized by caller */
1338        int fd;
1339        int type; /* POLLOUT or POLLIN */
1340        union {
1341                struct {
1342                        const char *buf;
1343                        size_t len;
1344                } out;
1345                struct {
1346                        struct strbuf *buf;
1347                        size_t hint;
1348                } in;
1349        } u;
1350
1351        /* returned by pump_io */
1352        int error; /* 0 for success, otherwise errno */
1353
1354        /* internal use */
1355        struct pollfd *pfd;
1356};
1357
1358static int pump_io_round(struct io_pump *slots, int nr, struct pollfd *pfd)
1359{
1360        int pollsize = 0;
1361        int i;
1362
1363        for (i = 0; i < nr; i++) {
1364                struct io_pump *io = &slots[i];
1365                if (io->fd < 0)
1366                        continue;
1367                pfd[pollsize].fd = io->fd;
1368                pfd[pollsize].events = io->type;
1369                io->pfd = &pfd[pollsize++];
1370        }
1371
1372        if (!pollsize)
1373                return 0;
1374
1375        if (poll(pfd, pollsize, -1) < 0) {
1376                if (errno == EINTR)
1377                        return 1;
1378                die_errno("poll failed");
1379        }
1380
1381        for (i = 0; i < nr; i++) {
1382                struct io_pump *io = &slots[i];
1383
1384                if (io->fd < 0)
1385                        continue;
1386
1387                if (!(io->pfd->revents & (POLLOUT|POLLIN|POLLHUP|POLLERR|POLLNVAL)))
1388                        continue;
1389
1390                if (io->type == POLLOUT) {
1391                        ssize_t len = xwrite(io->fd,
1392                                             io->u.out.buf, io->u.out.len);
1393                        if (len < 0) {
1394                                io->error = errno;
1395                                close(io->fd);
1396                                io->fd = -1;
1397                        } else {
1398                                io->u.out.buf += len;
1399                                io->u.out.len -= len;
1400                                if (!io->u.out.len) {
1401                                        close(io->fd);
1402                                        io->fd = -1;
1403                                }
1404                        }
1405                }
1406
1407                if (io->type == POLLIN) {
1408                        ssize_t len = strbuf_read_once(io->u.in.buf,
1409                                                       io->fd, io->u.in.hint);
1410                        if (len < 0)
1411                                io->error = errno;
1412                        if (len <= 0) {
1413                                close(io->fd);
1414                                io->fd = -1;
1415                        }
1416                }
1417        }
1418
1419        return 1;
1420}
1421
1422static int pump_io(struct io_pump *slots, int nr)
1423{
1424        struct pollfd *pfd;
1425        int i;
1426
1427        for (i = 0; i < nr; i++)
1428                slots[i].error = 0;
1429
1430        ALLOC_ARRAY(pfd, nr);
1431        while (pump_io_round(slots, nr, pfd))
1432                ; /* nothing */
1433        free(pfd);
1434
1435        /* There may be multiple errno values, so just pick the first. */
1436        for (i = 0; i < nr; i++) {
1437                if (slots[i].error) {
1438                        errno = slots[i].error;
1439                        return -1;
1440                }
1441        }
1442        return 0;
1443}
1444
1445
1446int pipe_command(struct child_process *cmd,
1447                 const char *in, size_t in_len,
1448                 struct strbuf *out, size_t out_hint,
1449                 struct strbuf *err, size_t err_hint)
1450{
1451        struct io_pump io[3];
1452        int nr = 0;
1453
1454        if (in)
1455                cmd->in = -1;
1456        if (out)
1457                cmd->out = -1;
1458        if (err)
1459                cmd->err = -1;
1460
1461        if (start_command(cmd) < 0)
1462                return -1;
1463
1464        if (in) {
1465                io[nr].fd = cmd->in;
1466                io[nr].type = POLLOUT;
1467                io[nr].u.out.buf = in;
1468                io[nr].u.out.len = in_len;
1469                nr++;
1470        }
1471        if (out) {
1472                io[nr].fd = cmd->out;
1473                io[nr].type = POLLIN;
1474                io[nr].u.in.buf = out;
1475                io[nr].u.in.hint = out_hint;
1476                nr++;
1477        }
1478        if (err) {
1479                io[nr].fd = cmd->err;
1480                io[nr].type = POLLIN;
1481                io[nr].u.in.buf = err;
1482                io[nr].u.in.hint = err_hint;
1483                nr++;
1484        }
1485
1486        if (pump_io(io, nr) < 0) {
1487                finish_command(cmd); /* throw away exit code */
1488                return -1;
1489        }
1490
1491        return finish_command(cmd);
1492}
1493
1494enum child_state {
1495        GIT_CP_FREE,
1496        GIT_CP_WORKING,
1497        GIT_CP_WAIT_CLEANUP,
1498};
1499
1500struct parallel_processes {
1501        void *data;
1502
1503        int max_processes;
1504        int nr_processes;
1505
1506        get_next_task_fn get_next_task;
1507        start_failure_fn start_failure;
1508        task_finished_fn task_finished;
1509
1510        struct {
1511                enum child_state state;
1512                struct child_process process;
1513                struct strbuf err;
1514                void *data;
1515        } *children;
1516        /*
1517         * The struct pollfd is logically part of *children,
1518         * but the system call expects it as its own array.
1519         */
1520        struct pollfd *pfd;
1521
1522        unsigned shutdown : 1;
1523
1524        int output_owner;
1525        struct strbuf buffered_output; /* of finished children */
1526};
1527
1528static int default_start_failure(struct strbuf *out,
1529                                 void *pp_cb,
1530                                 void *pp_task_cb)
1531{
1532        return 0;
1533}
1534
1535static int default_task_finished(int result,
1536                                 struct strbuf *out,
1537                                 void *pp_cb,
1538                                 void *pp_task_cb)
1539{
1540        return 0;
1541}
1542
1543static void kill_children(struct parallel_processes *pp, int signo)
1544{
1545        int i, n = pp->max_processes;
1546
1547        for (i = 0; i < n; i++)
1548                if (pp->children[i].state == GIT_CP_WORKING)
1549                        kill(pp->children[i].process.pid, signo);
1550}
1551
1552static struct parallel_processes *pp_for_signal;
1553
1554static void handle_children_on_signal(int signo)
1555{
1556        kill_children(pp_for_signal, signo);
1557        sigchain_pop(signo);
1558        raise(signo);
1559}
1560
1561static void pp_init(struct parallel_processes *pp,
1562                    int n,
1563                    get_next_task_fn get_next_task,
1564                    start_failure_fn start_failure,
1565                    task_finished_fn task_finished,
1566                    void *data)
1567{
1568        int i;
1569
1570        if (n < 1)
1571                n = online_cpus();
1572
1573        pp->max_processes = n;
1574
1575        trace_printf("run_processes_parallel: preparing to run up to %d tasks", n);
1576
1577        pp->data = data;
1578        if (!get_next_task)
1579                BUG("you need to specify a get_next_task function");
1580        pp->get_next_task = get_next_task;
1581
1582        pp->start_failure = start_failure ? start_failure : default_start_failure;
1583        pp->task_finished = task_finished ? task_finished : default_task_finished;
1584
1585        pp->nr_processes = 0;
1586        pp->output_owner = 0;
1587        pp->shutdown = 0;
1588        pp->children = xcalloc(n, sizeof(*pp->children));
1589        pp->pfd = xcalloc(n, sizeof(*pp->pfd));
1590        strbuf_init(&pp->buffered_output, 0);
1591
1592        for (i = 0; i < n; i++) {
1593                strbuf_init(&pp->children[i].err, 0);
1594                child_process_init(&pp->children[i].process);
1595                pp->pfd[i].events = POLLIN | POLLHUP;
1596                pp->pfd[i].fd = -1;
1597        }
1598
1599        pp_for_signal = pp;
1600        sigchain_push_common(handle_children_on_signal);
1601}
1602
1603static void pp_cleanup(struct parallel_processes *pp)
1604{
1605        int i;
1606
1607        trace_printf("run_processes_parallel: done");
1608        for (i = 0; i < pp->max_processes; i++) {
1609                strbuf_release(&pp->children[i].err);
1610                child_process_clear(&pp->children[i].process);
1611        }
1612
1613        free(pp->children);
1614        free(pp->pfd);
1615
1616        /*
1617         * When get_next_task added messages to the buffer in its last
1618         * iteration, the buffered output is non empty.
1619         */
1620        strbuf_write(&pp->buffered_output, stderr);
1621        strbuf_release(&pp->buffered_output);
1622
1623        sigchain_pop_common();
1624}
1625
1626/* returns
1627 *  0 if a new task was started.
1628 *  1 if no new jobs was started (get_next_task ran out of work, non critical
1629 *    problem with starting a new command)
1630 * <0 no new job was started, user wishes to shutdown early. Use negative code
1631 *    to signal the children.
1632 */
1633static int pp_start_one(struct parallel_processes *pp)
1634{
1635        int i, code;
1636
1637        for (i = 0; i < pp->max_processes; i++)
1638                if (pp->children[i].state == GIT_CP_FREE)
1639                        break;
1640        if (i == pp->max_processes)
1641                BUG("bookkeeping is hard");
1642
1643        code = pp->get_next_task(&pp->children[i].process,
1644                                 &pp->children[i].err,
1645                                 pp->data,
1646                                 &pp->children[i].data);
1647        if (!code) {
1648                strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1649                strbuf_reset(&pp->children[i].err);
1650                return 1;
1651        }
1652        pp->children[i].process.err = -1;
1653        pp->children[i].process.stdout_to_stderr = 1;
1654        pp->children[i].process.no_stdin = 1;
1655
1656        if (start_command(&pp->children[i].process)) {
1657                code = pp->start_failure(&pp->children[i].err,
1658                                         pp->data,
1659                                         pp->children[i].data);
1660                strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1661                strbuf_reset(&pp->children[i].err);
1662                if (code)
1663                        pp->shutdown = 1;
1664                return code;
1665        }
1666
1667        pp->nr_processes++;
1668        pp->children[i].state = GIT_CP_WORKING;
1669        pp->pfd[i].fd = pp->children[i].process.err;
1670        return 0;
1671}
1672
1673static void pp_buffer_stderr(struct parallel_processes *pp, int output_timeout)
1674{
1675        int i;
1676
1677        while ((i = poll(pp->pfd, pp->max_processes, output_timeout)) < 0) {
1678                if (errno == EINTR)
1679                        continue;
1680                pp_cleanup(pp);
1681                die_errno("poll");
1682        }
1683
1684        /* Buffer output from all pipes. */
1685        for (i = 0; i < pp->max_processes; i++) {
1686                if (pp->children[i].state == GIT_CP_WORKING &&
1687                    pp->pfd[i].revents & (POLLIN | POLLHUP)) {
1688                        int n = strbuf_read_once(&pp->children[i].err,
1689                                                 pp->children[i].process.err, 0);
1690                        if (n == 0) {
1691                                close(pp->children[i].process.err);
1692                                pp->children[i].state = GIT_CP_WAIT_CLEANUP;
1693                        } else if (n < 0)
1694                                if (errno != EAGAIN)
1695                                        die_errno("read");
1696                }
1697        }
1698}
1699
1700static void pp_output(struct parallel_processes *pp)
1701{
1702        int i = pp->output_owner;
1703        if (pp->children[i].state == GIT_CP_WORKING &&
1704            pp->children[i].err.len) {
1705                strbuf_write(&pp->children[i].err, stderr);
1706                strbuf_reset(&pp->children[i].err);
1707        }
1708}
1709
1710static int pp_collect_finished(struct parallel_processes *pp)
1711{
1712        int i, code;
1713        int n = pp->max_processes;
1714        int result = 0;
1715
1716        while (pp->nr_processes > 0) {
1717                for (i = 0; i < pp->max_processes; i++)
1718                        if (pp->children[i].state == GIT_CP_WAIT_CLEANUP)
1719                                break;
1720                if (i == pp->max_processes)
1721                        break;
1722
1723                code = finish_command(&pp->children[i].process);
1724
1725                code = pp->task_finished(code,
1726                                         &pp->children[i].err, pp->data,
1727                                         pp->children[i].data);
1728
1729                if (code)
1730                        result = code;
1731                if (code < 0)
1732                        break;
1733
1734                pp->nr_processes--;
1735                pp->children[i].state = GIT_CP_FREE;
1736                pp->pfd[i].fd = -1;
1737                child_process_init(&pp->children[i].process);
1738
1739                if (i != pp->output_owner) {
1740                        strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
1741                        strbuf_reset(&pp->children[i].err);
1742                } else {
1743                        strbuf_write(&pp->children[i].err, stderr);
1744                        strbuf_reset(&pp->children[i].err);
1745
1746                        /* Output all other finished child processes */
1747                        strbuf_write(&pp->buffered_output, stderr);
1748                        strbuf_reset(&pp->buffered_output);
1749
1750                        /*
1751                         * Pick next process to output live.
1752                         * NEEDSWORK:
1753                         * For now we pick it randomly by doing a round
1754                         * robin. Later we may want to pick the one with
1755                         * the most output or the longest or shortest
1756                         * running process time.
1757                         */
1758                        for (i = 0; i < n; i++)
1759                                if (pp->children[(pp->output_owner + i) % n].state == GIT_CP_WORKING)
1760                                        break;
1761                        pp->output_owner = (pp->output_owner + i) % n;
1762                }
1763        }
1764        return result;
1765}
1766
1767int run_processes_parallel(int n,
1768                           get_next_task_fn get_next_task,
1769                           start_failure_fn start_failure,
1770                           task_finished_fn task_finished,
1771                           void *pp_cb)
1772{
1773        int i, code;
1774        int output_timeout = 100;
1775        int spawn_cap = 4;
1776        struct parallel_processes pp;
1777
1778        pp_init(&pp, n, get_next_task, start_failure, task_finished, pp_cb);
1779        while (1) {
1780                for (i = 0;
1781                    i < spawn_cap && !pp.shutdown &&
1782                    pp.nr_processes < pp.max_processes;
1783                    i++) {
1784                        code = pp_start_one(&pp);
1785                        if (!code)
1786                                continue;
1787                        if (code < 0) {
1788                                pp.shutdown = 1;
1789                                kill_children(&pp, -code);
1790                        }
1791                        break;
1792                }
1793                if (!pp.nr_processes)
1794                        break;
1795                pp_buffer_stderr(&pp, output_timeout);
1796                pp_output(&pp);
1797                code = pp_collect_finished(&pp);
1798                if (code) {
1799                        pp.shutdown = 1;
1800                        if (code < 0)
1801                                kill_children(&pp, -code);
1802                }
1803        }
1804
1805        pp_cleanup(&pp);
1806        return 0;
1807}