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

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