/src/git/run-command.c

Source
#define DISABLE_SIGN_COMPARE_WARNINGS

#include "git-compat-util.h"
#include "run-command.h"
#include "environment.h"
#include "exec-cmd.h"
#include "gettext.h"
#include "sigchain.h"
#include "strvec.h"
#include "symlinks.h"
#include "thread-utils.h"
#include "strbuf.h"
#include "string-list.h"
#include "trace.h"
#include "trace2.h"
#include "quote.h"
#include "config.h"
#include "packfile.h"
#include "compat/nonblock.h"

void child_process_init(struct child_process *child)
{
  struct child_process blank = CHILD_PROCESS_INIT;
  memcpy(child, &blank, sizeof(*child));
}

void child_process_clear(struct child_process *child)
{
  strvec_clear(&child->args);
  strvec_clear(&child->env);
}

struct child_to_clean {
  pid_t pid;
  struct child_process *process;
  struct child_to_clean *next;
};
static struct child_to_clean *children_to_clean;
static int installed_child_cleanup_handler;

static void cleanup_children(int sig, int in_signal)
{
  struct child_to_clean *children_to_wait_for = NULL;

  while (children_to_clean) {
    struct child_to_clean *p = children_to_clean;
    children_to_clean = p->next;

    if (p->process && !in_signal) {
      struct child_process *process = p->process;
      if (process->clean_on_exit_handler) {
        trace_printf(
          "trace: run_command: running exit handler for pid %"
          PRIuMAX, (uintmax_t)p->pid
        );
        process->clean_on_exit_handler(process);
      }
    }

    kill(p->pid, sig);

    if (p->process && p->process->wait_after_clean) {
      p->next = children_to_wait_for;
      children_to_wait_for = p;
    } else {
      if (!in_signal)
        free(p);
    }
  }

  while (children_to_wait_for) {
    struct child_to_clean *p = children_to_wait_for;
    children_to_wait_for = p->next;

    while (waitpid(p->pid, NULL, 0) < 0 && errno == EINTR)
      ; /* spin waiting for process exit or error */

    if (!in_signal)
      free(p);
  }
}

static void cleanup_children_on_signal(int sig)
{
  cleanup_children(sig, 1);
  sigchain_pop(sig);
  raise(sig);
}

static void cleanup_children_on_exit(void)
{
  cleanup_children(SIGTERM, 0);
}

static void mark_child_for_cleanup(pid_t pid, struct child_process *process)
{
  struct child_to_clean *p = xmalloc(sizeof(*p));
  p->pid = pid;
  p->process = process;
  p->next = children_to_clean;
  children_to_clean = p;

  if (!installed_child_cleanup_handler) {
    atexit(cleanup_children_on_exit);
    sigchain_push_common(cleanup_children_on_signal);
    installed_child_cleanup_handler = 1;
  }
}

static void clear_child_for_cleanup(pid_t pid)
{
  struct child_to_clean **pp;

  for (pp = &children_to_clean; *pp; pp = &(*pp)->next) {
    struct child_to_clean *clean_me = *pp;

    if (clean_me->pid == pid) {
      *pp = clean_me->next;
      free(clean_me);
      return;
    }
  }
}

static inline void close_pair(int fd[2])
{
  close(fd[0]);
  close(fd[1]);
}

int is_executable(const char *name)
{
  struct stat st;

  if (stat(name, &st) || /* stat, not lstat */
      !S_ISREG(st.st_mode))
    return 0;

#if defined(GIT_WINDOWS_NATIVE)
  /*
   * On Windows there is no executable bit. The file extension
   * indicates whether it can be run as an executable, and Git
   * has special-handling to detect scripts and launch them
   * through the indicated script interpreter. We test for the
   * file extension first because virus scanners may make
   * it quite expensive to open many files.
   */
  if (ends_with(name, ".exe"))
    return S_IXUSR;

{
  /*
   * Now that we know it does not have an executable extension,
   * peek into the file instead.
   */
  char buf[3] = { 0 };
  int n;
  int fd = open(name, O_RDONLY);
  st.st_mode &= ~S_IXUSR;
  if (fd >= 0) {
    n = read(fd, buf, 2);
    if (n == 2)
      /* look for a she-bang */
      if (!strcmp(buf, "#!"))
        st.st_mode |= S_IXUSR;
    close(fd);
  }
}
#endif
  return st.st_mode & S_IXUSR;
}

#ifndef locate_in_PATH
/*
 * Search $PATH for a command.  This emulates the path search that
 * execvp would perform, without actually executing the command so it
 * can be used before fork() to prepare to run a command using
 * execve() or after execvp() to diagnose why it failed.
 *
 * The caller should ensure that file contains no directory
 * separators.
 *
 * Returns the path to the command, as found in $PATH or NULL if the
 * command could not be found.  The caller inherits ownership of the memory
 * used to store the resultant path.
 *
 * This should not be used on Windows, where the $PATH search rules
 * are more complicated (e.g., a search for "foo" should find
 * "foo.exe").
 */
static char *locate_in_PATH(const char *file)
{
  const char *p = getenv("PATH");
  struct strbuf buf = STRBUF_INIT;

  if (!p || !*p)
    return NULL;

  while (1) {
    const char *end = strchrnul(p, ':');

    strbuf_reset(&buf);

    /* POSIX specifies an empty entry as the current directory. */
    if (end != p) {
      strbuf_add(&buf, p, end - p);
      strbuf_addch(&buf, '/');
    }
    strbuf_addstr(&buf, file);

    if (is_executable(buf.buf))
      return strbuf_detach(&buf, NULL);

    if (!*end)
      break;
    p = end + 1;
  }

  strbuf_release(&buf);
  return NULL;
}
#endif

int exists_in_PATH(const char *command)
{
  char *r = locate_in_PATH(command);
  int found = r != NULL;
  free(r);
  return found;
}

int sane_execvp(const char *file, char * const argv[])
{
#ifndef GIT_WINDOWS_NATIVE
  /*
   * execvp() doesn't return, so we all we can do is tell trace2
   * what we are about to do and let it leave a hint in the log
   * (unless of course the execvp() fails).
   *
   * we skip this for Windows because the compat layer already
   * has to emulate the execvp() call anyway.
   */
  int exec_id = trace2_exec(file, (const char **)argv);
#endif

  if (!execvp(file, argv))
    return 0; /* cannot happen ;-) */

#ifndef GIT_WINDOWS_NATIVE
  {
    int ec = errno;
    trace2_exec_result(exec_id, ec);
    errno = ec;
  }
#endif

  /*
   * When a command can't be found because one of the directories
   * listed in $PATH is unsearchable, execvp reports EACCES, but
   * careful usability testing (read: analysis of occasional bug
   * reports) reveals that "No such file or directory" is more
   * intuitive.
   *
   * We avoid commands with "/", because execvp will not do $PATH
   * lookups in that case.
   *
   * The reassignment of EACCES to errno looks like a no-op below,
   * but we need to protect against exists_in_PATH overwriting errno.
   */
  if (errno == EACCES && !strchr(file, '/'))
    errno = exists_in_PATH(file) ? EACCES : ENOENT;
  else if (errno == ENOTDIR && !strchr(file, '/'))
    errno = ENOENT;
  return -1;
}

char *git_shell_path(void)
{
#ifndef GIT_WINDOWS_NATIVE
  return xstrdup(SHELL_PATH);
#else
  char *p = locate_in_PATH("sh");
  convert_slashes(p);
  return p;
#endif
}

static const char **prepare_shell_cmd(struct strvec *out, const char **argv)
{
  if (!argv[0])
    BUG("shell command is empty");

  if (strcspn(argv[0], "|&;<>()$`\\\"' \t\n*?[#~=%") != strlen(argv[0])) {
    strvec_push_nodup(out, git_shell_path());
    strvec_push(out, "-c");

    /*
     * If we have no extra arguments, we do not even need to
     * bother with the "$@" magic.
     */
    if (!argv[1])
      strvec_push(out, argv[0]);
    else
      strvec_pushf(out, "%s \"$@\"", argv[0]);
  }

  strvec_pushv(out, argv);
  return out->v;
}

#ifndef GIT_WINDOWS_NATIVE
static int child_notifier = -1;

enum child_errcode {
  CHILD_ERR_CHDIR,
  CHILD_ERR_DUP2,
  CHILD_ERR_CLOSE,
  CHILD_ERR_SIGPROCMASK,
  CHILD_ERR_SILENT,
  CHILD_ERR_ERRNO
};

struct child_err {
  enum child_errcode err;
  int syserr; /* errno */
};

static void child_die(enum child_errcode err)
{
  struct child_err buf;

  buf.err = err;
  buf.syserr = errno;

  /* write(2) on buf smaller than PIPE_BUF (min 512) is atomic: */
  xwrite(child_notifier, &buf, sizeof(buf));
  _exit(1);
}

static void child_dup2(int fd, int to)
{
  if (dup2(fd, to) < 0)
    child_die(CHILD_ERR_DUP2);
}

static void child_close(int fd)
{
  if (close(fd))
    child_die(CHILD_ERR_CLOSE);
}

static void child_close_pair(int fd[2])
{
  child_close(fd[0]);
  child_close(fd[1]);
}

static void child_error_fn(const char *err UNUSED, va_list params UNUSED)
{
  const char msg[] = "error() should not be called in child\n";
  xwrite(2, msg, sizeof(msg) - 1);
}

static void child_warn_fn(const char *err UNUSED, va_list params UNUSED)
{
  const char msg[] = "warn() should not be called in child\n";
  xwrite(2, msg, sizeof(msg) - 1);
}

static void NORETURN child_die_fn(const char *err UNUSED, va_list params UNUSED)
{
  const char msg[] = "die() should not be called in child\n";
  xwrite(2, msg, sizeof(msg) - 1);
  _exit(2);
}

/* this runs in the parent process */
static void child_err_spew(struct child_process *cmd, struct child_err *cerr)
{
  static void (*old_errfn)(const char *err, va_list params);
  report_fn die_message_routine = get_die_message_routine();

  old_errfn = get_error_routine();
  set_error_routine(die_message_routine);
  errno = cerr->syserr;

  switch (cerr->err) {
  case CHILD_ERR_CHDIR:
    error_errno("exec '%s': cd to '%s' failed",
          cmd->args.v[0], cmd->dir);
    break;
  case CHILD_ERR_DUP2:
    error_errno("dup2() in child failed");
    break;
  case CHILD_ERR_CLOSE:
    error_errno("close() in child failed");
    break;
  case CHILD_ERR_SIGPROCMASK:
    error_errno("sigprocmask failed restoring signals");
    break;
  case CHILD_ERR_SILENT:
    break;
  case CHILD_ERR_ERRNO:
    error_errno("cannot exec '%s'", cmd->args.v[0]);
    break;
  }
  set_error_routine(old_errfn);
}

static int prepare_cmd(struct strvec *out, const struct child_process *cmd)
{
  if (!cmd->args.v[0])
    BUG("command is empty");

  /*
   * Add SHELL_PATH so in the event exec fails with ENOEXEC we can
   * attempt to interpret the command with 'sh'.
   */
  strvec_push(out, SHELL_PATH);

  if (cmd->git_cmd) {
    prepare_git_cmd(out, cmd->args.v);
  } else if (cmd->use_shell) {
    prepare_shell_cmd(out, cmd->args.v);
  } else {
    strvec_pushv(out, cmd->args.v);
  }

  /*
   * If there are no dir separator characters in the command then perform
   * a path lookup and use the resolved path as the command to exec. If
   * there are dir separator characters, we have exec attempt to invoke
   * the command directly.
   */
  if (!has_dir_sep(out->v[1])) {
    char *program = locate_in_PATH(out->v[1]);
    if (program) {
      free((char *)out->v[1]);
      out->v[1] = program;
    } else {
      strvec_clear(out);
      errno = ENOENT;
      return -1;
    }
  }

  return 0;
}

static char **prep_childenv(const char *const *deltaenv)
{
  extern char **environ;
  char **childenv;
  struct string_list env = STRING_LIST_INIT_DUP;
  struct strbuf key = STRBUF_INIT;
  const char *const *p;
  int i;

  /* Construct a sorted string list consisting of the current environ */
  for (p = (const char *const *) environ; p && *p; p++) {
    const char *equals = strchr(*p, '=');

    if (equals) {
      strbuf_reset(&key);
      strbuf_add(&key, *p, equals - *p);
      string_list_append(&env, key.buf)->util = (void *) *p;
    } else {
      string_list_append(&env, *p)->util = (void *) *p;
    }
  }
  string_list_sort(&env);

  /* Merge in 'deltaenv' with the current environ */
  for (p = deltaenv; p && *p; p++) {
    const char *equals = strchr(*p, '=');

    if (equals) {
      /* ('key=value'), insert or replace entry */
      strbuf_reset(&key);
      strbuf_add(&key, *p, equals - *p);
      string_list_insert(&env, key.buf)->util = (void *) *p;
    } else {
      /* otherwise ('key') remove existing entry */
      string_list_remove(&env, *p, 0);
    }
  }

  /* Create an array of 'char *' to be used as the childenv */
  ALLOC_ARRAY(childenv, env.nr + 1);
  for (i = 0; i < env.nr; i++)
    childenv[i] = env.items[i].util;
  childenv[env.nr] = NULL;

  string_list_clear(&env, 0);
  strbuf_release(&key);
  return childenv;
}

struct atfork_state {
#ifndef NO_PTHREADS
  int cs;
#endif
  sigset_t old;
};

#define CHECK_BUG(err, msg) \
  do { \
    int e = (err); \
    if (e) \
      BUG("%s: %s", msg, strerror(e)); \
  } while(0)

static void atfork_prepare(struct atfork_state *as)
{
  sigset_t all;

  /*
   * POSIX says sigfillset() can fail, but an overly clever
   * compiler can see through the header files and decide
   * it cannot fail on a particular platform it is compiling for,
   * triggering -Wunreachable-code false positive.
   */
  if (NOT_CONSTANT(sigfillset(&all)))
    die_errno("sigfillset");
#ifdef NO_PTHREADS
  if (sigprocmask(SIG_SETMASK, &all, &as->old))
    die_errno("sigprocmask");
#else
  CHECK_BUG(pthread_sigmask(SIG_SETMASK, &all, &as->old),
    "blocking all signals");
  CHECK_BUG(pthread_setcancelstate(PTHREAD_CANCEL_DISABLE, &as->cs),
    "disabling cancellation");
#endif
}

static void atfork_parent(struct atfork_state *as)
{
#ifdef NO_PTHREADS
  if (sigprocmask(SIG_SETMASK, &as->old, NULL))
    die_errno("sigprocmask");
#else
  CHECK_BUG(pthread_setcancelstate(as->cs, NULL),
    "re-enabling cancellation");
  CHECK_BUG(pthread_sigmask(SIG_SETMASK, &as->old, NULL),
    "restoring signal mask");
#endif
}
#endif /* GIT_WINDOWS_NATIVE */

static inline void set_cloexec(int fd)
{
  int flags = fcntl(fd, F_GETFD);
  if (flags >= 0)
    fcntl(fd, F_SETFD, flags | FD_CLOEXEC);
}

static int wait_or_whine(pid_t pid, const char *argv0, int in_signal)
{
  int status, code = -1;
  pid_t waiting;
  int failed_errno = 0;

  while ((waiting = waitpid(pid, &status, 0)) < 0 && errno == EINTR)
    ;  /* nothing */

  if (waiting < 0) {
    failed_errno = errno;
    if (!in_signal)
      error_errno("waitpid for %s failed", argv0);
  } else if (waiting != pid) {
    if (!in_signal)
      error("waitpid is confused (%s)", argv0);
  } else if (WIFSIGNALED(status)) {
    code = WTERMSIG(status);
    if (!in_signal && code != SIGINT && code != SIGQUIT && code != SIGPIPE)
      error("%s died of signal %d", argv0, code);
    /*
     * This return value is chosen so that code & 0xff
     * mimics the exit code that a POSIX shell would report for
     * a program that died from this signal.
     */
    code += 128;
  } else if (WIFEXITED(status)) {
    code = WEXITSTATUS(status);
  } else {
    if (!in_signal)
      error("waitpid is confused (%s)", argv0);
  }

  if (!in_signal)
    clear_child_for_cleanup(pid);

  errno = failed_errno;
  return code;
}

static void trace_add_env(struct strbuf *dst, const char *const *deltaenv)
{
  struct string_list envs = STRING_LIST_INIT_DUP;
  const char *const *e;
  int i;
  int printed_unset = 0;

  /* Last one wins, see run-command.c:prep_childenv() for context */
  for (e = deltaenv; e && *e; e++) {
    struct strbuf key = STRBUF_INIT;
    char *equals = strchr(*e, '=');

    if (equals) {
      strbuf_add(&key, *e, equals - *e);
      string_list_insert(&envs, key.buf)->util = equals + 1;
    } else {
      string_list_insert(&envs, *e)->util = NULL;
    }
    strbuf_release(&key);
  }

  /* "unset X Y...;" */
  for (i = 0; i < envs.nr; i++) {
    const char *var = envs.items[i].string;
    const char *val = envs.items[i].util;

    if (val || !getenv(var))
      continue;

    if (!printed_unset) {
      strbuf_addstr(dst, " unset");
      printed_unset = 1;
    }
    strbuf_addf(dst, " %s", var);
  }
  if (printed_unset)
    strbuf_addch(dst, ';');

  /* ... followed by "A=B C=D ..." */
  for (i = 0; i < envs.nr; i++) {
    const char *var = envs.items[i].string;
    const char *val = envs.items[i].util;
    const char *oldval;

    if (!val)
      continue;

    oldval = getenv(var);
    if (oldval && !strcmp(val, oldval))
      continue;

    strbuf_addf(dst, " %s=", var);
    sq_quote_buf_pretty(dst, val);
  }
  string_list_clear(&envs, 0);
}

static void trace_run_command(const struct child_process *cp)
{
  struct strbuf buf = STRBUF_INIT;

  if (!trace_want(&trace_default_key))
    return;

  strbuf_addstr(&buf, "trace: run_command:");
  if (cp->dir) {
    strbuf_addstr(&buf, " cd ");
    sq_quote_buf_pretty(&buf, cp->dir);
    strbuf_addch(&buf, ';');
  }
  trace_add_env(&buf, cp->env.v);
  if (cp->git_cmd)
    strbuf_addstr(&buf, " git");
  sq_quote_argv_pretty(&buf, cp->args.v);

  trace_printf("%s", buf.buf);
  strbuf_release(&buf);
}

int start_command(struct child_process *cmd)
{
  int need_in, need_out, need_err;
  int fdin[2], fdout[2], fderr[2];
  int failed_errno;
  const char *str;

  /*
   * In case of errors we must keep the promise to close FDs
   * that have been passed in via ->in and ->out.
   */

  need_in = !cmd->no_stdin && cmd->in < 0;
  if (need_in) {
    if (pipe(fdin) < 0) {
      failed_errno = errno;
      if (cmd->out > 0)
        close(cmd->out);
      str = "standard input";
      goto fail_pipe;
    }
    cmd->in = fdin[1];
  }

  need_out = !cmd->no_stdout
    && !cmd->stdout_to_stderr
    && cmd->out < 0;
  if (need_out) {
    if (pipe(fdout) < 0) {
      failed_errno = errno;
      if (need_in)
        close_pair(fdin);
      else if (cmd->in)
        close(cmd->in);
      str = "standard output";
      goto fail_pipe;
    }
    cmd->out = fdout[0];
  }

  need_err = !cmd->no_stderr && cmd->err < 0;
  if (need_err) {
    if (pipe(fderr) < 0) {
      failed_errno = errno;
      if (need_in)
        close_pair(fdin);
      else if (cmd->in)
        close(cmd->in);
      if (need_out)
        close_pair(fdout);
      else if (cmd->out)
        close(cmd->out);
      str = "standard error";
fail_pipe:
      error("cannot create %s pipe for %s: %s",
        str, cmd->args.v[0], strerror(failed_errno));
      child_process_clear(cmd);
      errno = failed_errno;
      return -1;
    }
    cmd->err = fderr[0];
  }

  trace2_child_start(cmd);
  trace_run_command(cmd);

  fflush(NULL);

  if (cmd->odb_to_close)
    odb_close(cmd->odb_to_close);

#ifndef GIT_WINDOWS_NATIVE
{
  int notify_pipe[2];
  int null_fd = -1;
  char **childenv;
  struct strvec argv = STRVEC_INIT;
  struct child_err cerr;
  struct atfork_state as;

  if (prepare_cmd(&argv, cmd) < 0) {
    failed_errno = errno;
    cmd->pid = -1;
    if (!cmd->silent_exec_failure)
      error_errno("cannot run %s", cmd->args.v[0]);
    goto end_of_spawn;
  }

  trace_argv_printf(&argv.v[1], "trace: start_command:");

  if (pipe(notify_pipe))
    notify_pipe[0] = notify_pipe[1] = -1;

  if (cmd->no_stdin || cmd->no_stdout || cmd->no_stderr) {
    null_fd = xopen("/dev/null", O_RDWR | O_CLOEXEC);
    set_cloexec(null_fd);
  }

  childenv = prep_childenv(cmd->env.v);
  atfork_prepare(&as);

  /*
   * NOTE: In order to prevent deadlocking when using threads special
   * care should be taken with the function calls made in between the
   * fork() and exec() calls.  No calls should be made to functions which
   * require acquiring a lock (e.g. malloc) as the lock could have been
   * held by another thread at the time of forking, causing the lock to
   * never be released in the child process.  This means only
   * Async-Signal-Safe functions are permitted in the child.
   */
  cmd->pid = fork();
  failed_errno = errno;
  if (!cmd->pid) {
    int sig;
    /*
     * Ensure the default die/error/warn routines do not get
     * called, they can take stdio locks and malloc.
     */
    set_die_routine(child_die_fn);
    set_error_routine(child_error_fn);
    set_warn_routine(child_warn_fn);

    close(notify_pipe[0]);
    set_cloexec(notify_pipe[1]);
    child_notifier = notify_pipe[1];

    if (cmd->no_stdin)
      child_dup2(null_fd, 0);
    else if (need_in) {
      child_dup2(fdin[0], 0);
      child_close_pair(fdin);
    } else if (cmd->in) {
      child_dup2(cmd->in, 0);
      child_close(cmd->in);
    }

    if (cmd->no_stderr)
      child_dup2(null_fd, 2);
    else if (need_err) {
      child_dup2(fderr[1], 2);
      child_close_pair(fderr);
    } else if (cmd->err > 1) {
      child_dup2(cmd->err, 2);
      child_close(cmd->err);
    }

    if (cmd->no_stdout)
      child_dup2(null_fd, 1);
    else if (cmd->stdout_to_stderr)
      child_dup2(2, 1);
    else if (need_out) {
      child_dup2(fdout[1], 1);
      child_close_pair(fdout);
    } else if (cmd->out > 1) {
      child_dup2(cmd->out, 1);
      child_close(cmd->out);
    }

    if (cmd->dir && chdir(cmd->dir))
      child_die(CHILD_ERR_CHDIR);

    /*
     * restore default signal handlers here, in case
     * we catch a signal right before execve below
     */
    for (sig = 1; sig < NSIG; sig++) {
      /* ignored signals get reset to SIG_DFL on execve */
      if (signal(sig, SIG_DFL) == SIG_IGN)
        signal(sig, SIG_IGN);
    }

    if (sigprocmask(SIG_SETMASK, &as.old, NULL) != 0)
      child_die(CHILD_ERR_SIGPROCMASK);

    /*
     * Attempt to exec using the command and arguments starting at
     * argv.argv[1].  argv.argv[0] contains SHELL_PATH which will
     * be used in the event exec failed with ENOEXEC at which point
     * we will try to interpret the command using 'sh'.
     */
    execve(argv.v[1], (char *const *) argv.v + 1,
           (char *const *) childenv);
    if (errno == ENOEXEC)
      execve(argv.v[0], (char *const *) argv.v,
             (char *const *) childenv);

    if (cmd->silent_exec_failure && errno == ENOENT)
      child_die(CHILD_ERR_SILENT);
    child_die(CHILD_ERR_ERRNO);
  }
  atfork_parent(&as);
  if (cmd->pid < 0)
    error_errno("cannot fork() for %s", cmd->args.v[0]);
  else if (cmd->clean_on_exit)
    mark_child_for_cleanup(cmd->pid, cmd);

  /*
   * Wait for child's exec. If the exec succeeds (or if fork()
   * failed), EOF is seen immediately by the parent. Otherwise, the
   * child process sends a child_err struct.
   * Note that use of this infrastructure is completely advisory,
   * therefore, we keep error checks minimal.
   */
  close(notify_pipe[1]);
  if (xread(notify_pipe[0], &cerr, sizeof(cerr)) == sizeof(cerr)) {
    /*
     * At this point we know that fork() succeeded, but exec()
     * failed. Errors have been reported to our stderr.
     */
    wait_or_whine(cmd->pid, cmd->args.v[0], 0);
    child_err_spew(cmd, &cerr);
    failed_errno = errno;
    cmd->pid = -1;
  }
  close(notify_pipe[0]);

  if (null_fd >= 0)
    close(null_fd);
  strvec_clear(&argv);
  free(childenv);
}
end_of_spawn:

#else
{
  int fhin = 0, fhout = 1, fherr = 2;
  const char **sargv = cmd->args.v;
  struct strvec nargv = STRVEC_INIT;

  if (cmd->no_stdin)
    fhin = open("/dev/null", O_RDWR);
  else if (need_in)
    fhin = dup(fdin[0]);
  else if (cmd->in)
    fhin = dup(cmd->in);

  if (cmd->no_stderr)
    fherr = open("/dev/null", O_RDWR);
  else if (need_err)
    fherr = dup(fderr[1]);
  else if (cmd->err > 2)
    fherr = dup(cmd->err);

  if (cmd->no_stdout)
    fhout = open("/dev/null", O_RDWR);
  else if (cmd->stdout_to_stderr)
    fhout = dup(fherr);
  else if (need_out)
    fhout = dup(fdout[1]);
  else if (cmd->out > 1)
    fhout = dup(cmd->out);

  if (cmd->git_cmd)
    cmd->args.v = prepare_git_cmd(&nargv, sargv);
  else if (cmd->use_shell)
    cmd->args.v = prepare_shell_cmd(&nargv, sargv);

  trace_argv_printf(cmd->args.v, "trace: start_command:");
  cmd->pid = mingw_spawnvpe(cmd->args.v[0], cmd->args.v,
          (char**) cmd->env.v,
          cmd->dir, fhin, fhout, fherr);
  failed_errno = errno;
  if (cmd->pid < 0 && (!cmd->silent_exec_failure || errno != ENOENT))
    error_errno("cannot spawn %s", cmd->args.v[0]);
  if (cmd->clean_on_exit && cmd->pid >= 0)
    mark_child_for_cleanup(cmd->pid, cmd);

  strvec_clear(&nargv);
  cmd->args.v = sargv;
  if (fhin != 0)
    close(fhin);
  if (fhout != 1)
    close(fhout);
  if (fherr != 2)
    close(fherr);
}
#endif

  if (cmd->pid < 0) {
    trace2_child_exit(cmd, -1);

    if (need_in)
      close_pair(fdin);
    else if (cmd->in)
      close(cmd->in);
    if (need_out)
      close_pair(fdout);
    else if (cmd->out)
      close(cmd->out);
    if (need_err)
      close_pair(fderr);
    else if (cmd->err)
      close(cmd->err);
    child_process_clear(cmd);
    errno = failed_errno;
    return -1;
  }

  if (need_in)
    close(fdin[0]);
  else if (cmd->in)
    close(cmd->in);

  if (need_out)
    close(fdout[1]);
  else if (cmd->out)
    close(cmd->out);

  if (need_err)
    close(fderr[1]);
  else if (cmd->err)
    close(cmd->err);

  return 0;
}

int finish_command(struct child_process *cmd)
{
  int ret = wait_or_whine(cmd->pid, cmd->args.v[0], 0);
  trace2_child_exit(cmd, ret);
  child_process_clear(cmd);
  invalidate_lstat_cache();
  return ret;
}

int finish_command_in_signal(struct child_process *cmd)
{
  int ret = wait_or_whine(cmd->pid, cmd->args.v[0], 1);
  if (ret != -1)
    trace2_child_exit(cmd, ret);
  return ret;
}


int run_command(struct child_process *cmd)
{
  int code;

  if (cmd->out < 0 || cmd->err < 0)
    BUG("run_command with a pipe can cause deadlock");

  code = start_command(cmd);
  if (code)
    return code;
  return finish_command(cmd);
}

#ifndef NO_PTHREADS
static pthread_t main_thread;
static int main_thread_set;
static pthread_key_t async_key;
static pthread_key_t async_die_counter;

static void *run_thread(void *data)
{
  struct async *async = data;
  intptr_t ret;

  if (async->isolate_sigpipe) {
    sigset_t mask;
    sigemptyset(&mask);
    sigaddset(&mask, SIGPIPE);
    if (pthread_sigmask(SIG_BLOCK, &mask, NULL)) {
      ret = error("unable to block SIGPIPE in async thread");
      return (void *)ret;
    }
  }

  pthread_setspecific(async_key, async);
  ret = async->proc(async->proc_in, async->proc_out, async->data);
  return (void *)ret;
}

static NORETURN void die_async(const char *err, va_list params)
{
  report_fn die_message_fn = get_die_message_routine();

  die_message_fn(err, params);

  if (in_async()) {
    struct async *async = pthread_getspecific(async_key);
    if (async->proc_in >= 0)
      close(async->proc_in);
    if (async->proc_out >= 0)
      close(async->proc_out);
    pthread_exit((void *)128);
  }

  exit(128);
}

static int async_die_is_recursing(void)
{
  void *ret = pthread_getspecific(async_die_counter);
  pthread_setspecific(async_die_counter, &async_die_counter); /* set to any non-NULL valid pointer */
  return ret != NULL;
}

int in_async(void)
{
  if (!main_thread_set)
    return 0; /* no asyncs started yet */
  return !pthread_equal(main_thread, pthread_self());
}

static void NORETURN async_exit(int code)
{
  pthread_exit((void *)(intptr_t)code);
}

#else

static struct {
  void (**handlers)(void);
  size_t nr;
  size_t alloc;
} git_atexit_hdlrs;

static int git_atexit_installed;

static void git_atexit_dispatch(void)
{
  size_t i;

  for (i=git_atexit_hdlrs.nr ; i ; i--)
    git_atexit_hdlrs.handlers[i-1]();
}

static void git_atexit_clear(void)
{
  free(git_atexit_hdlrs.handlers);
  memset(&git_atexit_hdlrs, 0, sizeof(git_atexit_hdlrs));
  git_atexit_installed = 0;
}

#undef atexit
int git_atexit(void (*handler)(void))
{
  ALLOC_GROW(git_atexit_hdlrs.handlers, git_atexit_hdlrs.nr + 1, git_atexit_hdlrs.alloc);
  git_atexit_hdlrs.handlers[git_atexit_hdlrs.nr++] = handler;
  if (!git_atexit_installed) {
    if (atexit(&git_atexit_dispatch))
      return -1;
    git_atexit_installed = 1;
  }
  return 0;
}
#define atexit git_atexit

static int process_is_async;
int in_async(void)
{
  return process_is_async;
}

static void NORETURN async_exit(int code)
{
  exit(code);
}

#endif

void check_pipe(int err)
{
  if (err == EPIPE) {
    if (in_async())
      async_exit(141);

    signal(SIGPIPE, SIG_DFL);
    raise(SIGPIPE);
    /* Should never happen, but just in case... */
    exit(141);
  }
}

int start_async(struct async *async)
{
  int need_in, need_out;
  int fdin[2], fdout[2];
  int proc_in, proc_out;

  need_in = async->in < 0;
  if (need_in) {
    if (pipe(fdin) < 0) {
      if (async->out > 0)
        close(async->out);
      return error_errno("cannot create pipe");
    }
    async->in = fdin[1];
  }

  need_out = async->out < 0;
  if (need_out) {
    if (pipe(fdout) < 0) {
      if (need_in)
        close_pair(fdin);
      else if (async->in)
        close(async->in);
      return error_errno("cannot create pipe");
    }
    async->out = fdout[0];
  }

  if (need_in)
    proc_in = fdin[0];
  else if (async->in)
    proc_in = async->in;
  else
    proc_in = -1;

  if (need_out)
    proc_out = fdout[1];
  else if (async->out)
    proc_out = async->out;
  else
    proc_out = -1;

#ifdef NO_PTHREADS
  /* Flush stdio before fork() to avoid cloning buffers */
  fflush(NULL);

  async->pid = fork();
  if (async->pid < 0) {
    error_errno("fork (async) failed");
    goto error;
  }
  if (!async->pid) {
    if (need_in)
      close(fdin[1]);
    if (need_out)
      close(fdout[0]);
    git_atexit_clear();
    process_is_async = 1;
    exit(!!async->proc(proc_in, proc_out, async->data));
  }

  mark_child_for_cleanup(async->pid, NULL);

  if (need_in)
    close(fdin[0]);
  else if (async->in)
    close(async->in);

  if (need_out)
    close(fdout[1]);
  else if (async->out)
    close(async->out);
#else
  if (!main_thread_set) {
    /*
     * We assume that the first time that start_async is called
     * it is from the main thread.
     */
    main_thread_set = 1;
    main_thread = pthread_self();
    pthread_key_create(&async_key, NULL);
    pthread_key_create(&async_die_counter, NULL);
    set_die_routine(die_async);
    set_die_is_recursing_routine(async_die_is_recursing);
  }

  if (proc_in >= 0)
    set_cloexec(proc_in);
  if (proc_out >= 0)
    set_cloexec(proc_out);
  async->proc_in = proc_in;
  async->proc_out = proc_out;
  {
    int err = pthread_create(&async->tid, NULL, run_thread, async);
    if (err) {
      error(_("cannot create async thread: %s"), strerror(err));
      goto error;
    }
  }
#endif
  return 0;

error:
  if (need_in)
    close_pair(fdin);
  else if (async->in)
    close(async->in);

  if (need_out)
    close_pair(fdout);
  else if (async->out)
    close(async->out);
  return -1;
}

int finish_async(struct async *async)
{
#ifdef NO_PTHREADS
  int ret = wait_or_whine(async->pid, "child process", 0);

  invalidate_lstat_cache();

  return ret;
#else
  void *ret = (void *)(intptr_t)(-1);

  if (pthread_join(async->tid, &ret))
    error("pthread_join failed");
  invalidate_lstat_cache();
  return (int)(intptr_t)ret;

#endif
}

int async_with_fork(void)
{
#ifdef NO_PTHREADS
  return 1;
#else
  return 0;
#endif
}

struct io_pump {
  /* initialized by caller */
  int fd;
  int type; /* POLLOUT or POLLIN */
  union {
    struct {
      const char *buf;
      size_t len;
    } out;
    struct {
      struct strbuf *buf;
      size_t hint;
    } in;
  } u;

  /* returned by pump_io */
  int error; /* 0 for success, otherwise errno */

  /* internal use */
  struct pollfd *pfd;
};

static int pump_io_round(struct io_pump *slots, int nr, struct pollfd *pfd)
{
  int pollsize = 0;
  int i;

  for (i = 0; i < nr; i++) {
    struct io_pump *io = &slots[i];
    if (io->fd < 0)
      continue;
    pfd[pollsize].fd = io->fd;
    pfd[pollsize].events = io->type;
    io->pfd = &pfd[pollsize++];
  }

  if (!pollsize)
    return 0;

  if (poll(pfd, pollsize, -1) < 0) {
    if (errno == EINTR)
      return 1;
    die_errno("poll failed");
  }

  for (i = 0; i < nr; i++) {
    struct io_pump *io = &slots[i];

    if (io->fd < 0)
      continue;

    if (!(io->pfd->revents & (POLLOUT|POLLIN|POLLHUP|POLLERR|POLLNVAL)))
      continue;

    if (io->type == POLLOUT) {
      ssize_t len;

      /*
       * Don't use xwrite() here. It loops forever on EAGAIN,
       * and we're in our own poll() loop here.
       *
       * Note that we lose xwrite()'s handling of MAX_IO_SIZE
       * and EINTR, so we have to implement those ourselves.
       */
      len = write(io->fd, io->u.out.buf,
            io->u.out.len <= MAX_IO_SIZE ?
            io->u.out.len : MAX_IO_SIZE);
      if (len < 0) {
        if (errno != EINTR && errno != EAGAIN &&
            errno != ENOSPC) {
          io->error = errno;
          close(io->fd);
          io->fd = -1;
        }
      } else {
        io->u.out.buf += len;
        io->u.out.len -= len;
        if (!io->u.out.len) {
          close(io->fd);
          io->fd = -1;
        }
      }
    }

    if (io->type == POLLIN) {
      ssize_t len = strbuf_read_once(io->u.in.buf,
                   io->fd, io->u.in.hint);
      if (len < 0)
        io->error = errno;
      if (len <= 0) {
        close(io->fd);
        io->fd = -1;
      }
    }
  }

  return 1;
}

static int pump_io(struct io_pump *slots, int nr)
{
  struct pollfd *pfd;
  int i;

  for (i = 0; i < nr; i++)
    slots[i].error = 0;

  ALLOC_ARRAY(pfd, nr);
  while (pump_io_round(slots, nr, pfd))
    ; /* nothing */
  free(pfd);

  /* There may be multiple errno values, so just pick the first. */
  for (i = 0; i < nr; i++) {
    if (slots[i].error) {
      errno = slots[i].error;
      return -1;
    }
  }
  return 0;
}


int pipe_command(struct child_process *cmd,
     const char *in, size_t in_len,
     struct strbuf *out, size_t out_hint,
     struct strbuf *err, size_t err_hint)
{
  struct io_pump io[3];
  int nr = 0;

  if (in)
    cmd->in = -1;
  if (out)
    cmd->out = -1;
  if (err)
    cmd->err = -1;

  if (start_command(cmd) < 0)
    return -1;

  if (in) {
    if (enable_pipe_nonblock(cmd->in) < 0) {
      error_errno("unable to make pipe non-blocking");
      close(cmd->in);
      if (out)
        close(cmd->out);
      if (err)
        close(cmd->err);
      return -1;
    }
    io[nr].fd = cmd->in;
    io[nr].type = POLLOUT;
    io[nr].u.out.buf = in;
    io[nr].u.out.len = in_len;
    nr++;
  }
  if (out) {
    io[nr].fd = cmd->out;
    io[nr].type = POLLIN;
    io[nr].u.in.buf = out;
    io[nr].u.in.hint = out_hint;
    nr++;
  }
  if (err) {
    io[nr].fd = cmd->err;
    io[nr].type = POLLIN;
    io[nr].u.in.buf = err;
    io[nr].u.in.hint = err_hint;
    nr++;
  }

  if (pump_io(io, nr) < 0) {
    finish_command(cmd); /* throw away exit code */
    return -1;
  }

  return finish_command(cmd);
}

enum child_state {
  GIT_CP_FREE,
  GIT_CP_WORKING,
  GIT_CP_WAIT_CLEANUP,
};

struct parallel_child {
  enum child_state state;
  struct child_process process;
  struct strbuf err;
  void *data;
};

static int child_is_working(const struct parallel_child *pp_child)
{
  return pp_child->state == GIT_CP_WORKING;
}

static int child_is_ready_for_cleanup(const struct parallel_child *pp_child)
{
  return child_is_working(pp_child) && !pp_child->process.in;
}

static int child_is_receiving_input(const struct parallel_child *pp_child)
{
  return child_is_working(pp_child) && pp_child->process.in > 0;
}
static int child_is_sending_output(const struct parallel_child *pp_child)
{
  /*
   * all pp children which buffer output through run_command via ungroup=0
   * redirect stdout to stderr, so we just need to check process.err.
   */
  return child_is_working(pp_child) && pp_child->process.err > 0;
}

struct parallel_processes {
  size_t nr_processes;

  struct parallel_child *children;
  /*
   * The struct pollfd is logically part of *children,
   * but the system call expects it as its own array.
   */
  struct pollfd *pfd;

  unsigned shutdown : 1;

  size_t output_owner;
  struct strbuf buffered_output; /* of finished children */
};

struct parallel_processes_for_signal {
  const struct run_process_parallel_opts *opts;
  const struct parallel_processes *pp;
};

static void kill_children(const struct parallel_processes *pp,
        const struct run_process_parallel_opts *opts,
        int signo)
{
  for (size_t i = 0; i < opts->processes; i++)
    if (child_is_working(&pp->children[i]))
      kill(pp->children[i].process.pid, signo);
}

static void kill_children_signal(const struct parallel_processes_for_signal *pp_sig,
         int signo)
{
  kill_children(pp_sig->pp, pp_sig->opts, signo);
}

static struct parallel_processes_for_signal *pp_for_signal;

static void handle_children_on_signal(int signo)
{
  kill_children_signal(pp_for_signal, signo);
  sigchain_pop(signo);
  raise(signo);
}

static void pp_init(struct parallel_processes *pp,
        const struct run_process_parallel_opts *opts,
        struct parallel_processes_for_signal *pp_sig)
{
  const size_t n = opts->processes;

  if (!n)
    BUG("you must provide a non-zero number of processes!");

  trace_printf("run_processes_parallel: preparing to run up to %"PRIuMAX" tasks",
         (uintmax_t)n);

  if (!opts->get_next_task)
    BUG("you need to specify a get_next_task function");

  CALLOC_ARRAY(pp->children, n);
  if (!opts->ungroup)
    CALLOC_ARRAY(pp->pfd, n * 2);

  for (size_t i = 0; i < n; i++) {
    strbuf_init(&pp->children[i].err, 0);
    child_process_init(&pp->children[i].process);
    if (pp->pfd) {
      pp->pfd[i].events = POLLIN | POLLHUP;
      pp->pfd[i].fd = -1;
    }
  }

  pp_sig->pp = pp;
  pp_sig->opts = opts;
  pp_for_signal = pp_sig;
  sigchain_push_common(handle_children_on_signal);
}

static void pp_cleanup(struct parallel_processes *pp,
           const struct run_process_parallel_opts *opts)
{
  trace_printf("run_processes_parallel: done");
  for (size_t i = 0; i < opts->processes; i++) {
    strbuf_release(&pp->children[i].err);
    child_process_clear(&pp->children[i].process);
  }

  free(pp->children);
  free(pp->pfd);

  /*
   * When get_next_task added messages to the buffer in its last
   * iteration, the buffered output is non empty.
   */
  strbuf_write(&pp->buffered_output, stderr);
  strbuf_release(&pp->buffered_output);

  sigchain_pop_common();
}

/* returns
 *  0 if a new task was started.
 *  1 if no new jobs was started (get_next_task ran out of work, non critical
 *    problem with starting a new command)
 * <0 no new job was started, user wishes to shutdown early. Use negative code
 *    to signal the children.
 */
static int pp_start_one(struct parallel_processes *pp,
      const struct run_process_parallel_opts *opts)
{
  size_t i;
  int code;

  for (i = 0; i < opts->processes; i++)
    if (pp->children[i].state == GIT_CP_FREE)
      break;
  if (i == opts->processes)
    BUG("bookkeeping is hard");

  /*
   * By default, do not inherit stdin from the parent process - otherwise,
   * all children would share stdin! Users may overwrite this to provide
   * something to the child's stdin by having their 'get_next_task'
   * callback assign 0 to .no_stdin and an appropriate integer to .in.
   */
  pp->children[i].process.no_stdin = 1;

  code = opts->get_next_task(&pp->children[i].process,
           opts->ungroup ? NULL : &pp->children[i].err,
           opts->data,
           &pp->children[i].data);
  if (!code) {
    if (!opts->ungroup) {
      strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
      strbuf_reset(&pp->children[i].err);
    }
    return 1;
  }
  if (!opts->ungroup) {
    pp->children[i].process.err = -1;
    pp->children[i].process.stdout_to_stderr = 1;
  }

  if (start_command(&pp->children[i].process)) {
    if (opts->start_failure)
      code = opts->start_failure(opts->ungroup ? NULL :
               &pp->children[i].err,
               opts->data,
               pp->children[i].data);
    else
      code = 0;

    if (!opts->ungroup) {
      strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
      strbuf_reset(&pp->children[i].err);
    }
    if (code)
      pp->shutdown = 1;
    return code;
  }

  pp->nr_processes++;
  pp->children[i].state = GIT_CP_WORKING;
  if (pp->pfd)
    pp->pfd[i].fd = pp->children[i].process.err;
  return 0;
}

static void pp_buffer_stdin(struct parallel_processes *pp,
          const struct run_process_parallel_opts *opts)
{
  /* Buffer stdin for each pipe. */
  for (size_t i = 0; i < opts->processes; i++) {
    struct child_process *proc = &pp->children[i].process;
    int ret;

    if (!child_is_receiving_input(&pp->children[i]))
      continue;

    /*
     * child input is provided via path_to_stdin when the feed_pipe cb is
     * missing, so we just signal an EOF.
     */
    if (!opts->feed_pipe) {
      close(proc->in);
      proc->in = 0;
      continue;
    }

    /**
     * Feed the pipe:
     *   ret < 0 means error
     *   ret == 0 means there is more data to be fed
     *   ret > 0 means feeding finished
     */
    ret = opts->feed_pipe(proc->in, opts->data, pp->children[i].data);
    if (ret < 0)
      die_errno("feed_pipe");

    if (ret) {
      close(proc->in);
      proc->in = 0;
    }
  }
}

static void pp_buffer_io(struct parallel_processes *pp,
       const struct run_process_parallel_opts *opts,
       int timeout)
{
  /* for each potential child slot, prepare two pollfd entries */
  for (size_t i = 0; i < opts->processes; i++) {
    if (child_is_sending_output(&pp->children[i])) {
      pp->pfd[2*i].fd = pp->children[i].process.err;
      pp->pfd[2*i].events = POLLIN | POLLHUP;
    } else {
      pp->pfd[2*i].fd = -1;
    }

    if (child_is_receiving_input(&pp->children[i])) {
      pp->pfd[2*i+1].fd = pp->children[i].process.in;
      pp->pfd[2*i+1].events = POLLOUT;
    } else {
      pp->pfd[2*i+1].fd = -1;
    }
  }

  while (poll(pp->pfd, opts->processes * 2, timeout) < 0) {
    if (errno == EINTR)
      continue;
    pp_cleanup(pp, opts);
    die_errno("poll");
  }

  for (size_t i = 0; i < opts->processes; i++) {
    /* Handle input feeding (stdin) */
    if (pp->pfd[2*i+1].revents & (POLLOUT | POLLHUP | POLLERR)) {
      if (opts->feed_pipe) {
        int ret = opts->feed_pipe(pp->children[i].process.in,
                opts->data,
                pp->children[i].data);
        if (ret < 0)
          die_errno("feed_pipe");
        if (ret) {
          /* done feeding */
          close(pp->children[i].process.in);
          pp->children[i].process.in = 0;
        }
      } else {
        /*
         * No feed_pipe means there is nothing to do, so
         * close the fd. Child input can be fed by other
         * methods, such as opts->path_to_stdin which
         * slurps a file via dup2, so clean up here.
         */
        close(pp->children[i].process.in);
        pp->children[i].process.in = 0;
      }
    }

    /* Handle output reading (stderr) */
    if (child_is_working(&pp->children[i]) &&
        pp->pfd[2*i].revents & (POLLIN | POLLHUP)) {
      int n = strbuf_read_once(&pp->children[i].err,
             pp->children[i].process.err, 0);
      if (n == 0) {
        close(pp->children[i].process.err);
        pp->children[i].state = GIT_CP_WAIT_CLEANUP;
      } else if (n < 0)
        if (errno != EAGAIN)
          die_errno("read");
    }
  }
}

static void pp_output(const struct parallel_processes *pp)
{
  size_t i = pp->output_owner;

  if (child_is_working(&pp->children[i]) &&
      pp->children[i].err.len) {
    strbuf_write(&pp->children[i].err, stderr);
    strbuf_reset(&pp->children[i].err);
  }
}

static int pp_collect_finished(struct parallel_processes *pp,
             const struct run_process_parallel_opts *opts)
{
  int code;
  size_t i;
  int result = 0;

  while (pp->nr_processes > 0) {
    for (i = 0; i < opts->processes; i++)
      if (pp->children[i].state == GIT_CP_WAIT_CLEANUP)
        break;
    if (i == opts->processes)
      break;

    code = finish_command(&pp->children[i].process);

    if (opts->task_finished)
      code = opts->task_finished(code, opts->ungroup ? NULL :
               &pp->children[i].err, opts->data,
               pp->children[i].data);
    else
      code = 0;

    if (code)
      result = code;
    if (code < 0)
      break;

    pp->nr_processes--;
    pp->children[i].state = GIT_CP_FREE;
    if (pp->pfd)
      pp->pfd[i].fd = -1;
    pp->children[i].process.in = 0;
    child_process_init(&pp->children[i].process);

    if (opts->ungroup) {
      ; /* no strbuf_*() work to do here */
    } else if (i != pp->output_owner) {
      strbuf_addbuf(&pp->buffered_output, &pp->children[i].err);
      strbuf_reset(&pp->children[i].err);
    } else {
      const size_t n = opts->processes;

      strbuf_write(&pp->children[i].err, stderr);
      strbuf_reset(&pp->children[i].err);

      /* Output all other finished child processes */
      strbuf_write(&pp->buffered_output, stderr);
      strbuf_reset(&pp->buffered_output);

      /*
       * Pick next process to output live.
       * NEEDSWORK:
       * For now we pick it randomly by doing a round
       * robin. Later we may want to pick the one with
       * the most output or the longest or shortest
       * running process time.
       */
      for (i = 0; i < n; i++)
        if (child_is_working(&pp->children[(pp->output_owner + i) % n]))
          break;
      pp->output_owner = (pp->output_owner + i) % n;
    }
  }
  return result;
}

static void pp_handle_child_IO(struct parallel_processes *pp,
        const struct run_process_parallel_opts *opts,
        int timeout)
{
  if (opts->ungroup) {
    pp_buffer_stdin(pp, opts);
    for (size_t i = 0; i < opts->processes; i++)
      if (child_is_ready_for_cleanup(&pp->children[i]))
        pp->children[i].state = GIT_CP_WAIT_CLEANUP;
  } else {
    pp_buffer_io(pp, opts, timeout);
    pp_output(pp);
  }
}

void run_processes_parallel(const struct run_process_parallel_opts *opts)
{
  int i, code;
  int timeout = 100;
  int spawn_cap = 4;
  struct parallel_processes_for_signal pp_sig;
  struct parallel_processes pp = {
    .buffered_output = STRBUF_INIT,
  };
  /* options */
  const char *tr2_category = opts->tr2_category;
  const char *tr2_label = opts->tr2_label;
  const int do_trace2 = tr2_category && tr2_label;

  if (do_trace2)
    trace2_region_enter_printf(tr2_category, tr2_label, NULL,
             "max:%"PRIuMAX,
             (uintmax_t)opts->processes);

  /*
   * Child tasks might receive input via stdin, terminating early (or not), so
   * ignore the default SIGPIPE which gets handled by each feed_pipe_fn which
   * actually writes the data to children stdin fds.
   */
  sigchain_push(SIGPIPE, SIG_IGN);

  pp_init(&pp, opts, &pp_sig);
  while (1) {
    for (i = 0;
        i < spawn_cap && !pp.shutdown &&
        pp.nr_processes < opts->processes;
        i++) {
      code = pp_start_one(&pp, opts);
      if (!code)
        continue;
      if (code < 0) {
        pp.shutdown = 1;
        kill_children(&pp, opts, -code);
      }
      break;
    }
    if (!pp.nr_processes)
      break;
    pp_handle_child_IO(&pp, opts, timeout);
    code = pp_collect_finished(&pp, opts);
    if (code) {
      pp.shutdown = 1;
      if (code < 0)
        kill_children(&pp, opts,-code);
    }
  }

  pp_cleanup(&pp, opts);

  sigchain_pop(SIGPIPE);

  if (do_trace2)
    trace2_region_leave(tr2_category, tr2_label, NULL);
}

int prepare_auto_maintenance(struct repository *r, int quiet,
           struct child_process *maint)
{
  int enabled, auto_detach;

  if (!repo_config_get_bool(r, "maintenance.auto", &enabled) &&
      !enabled)
    return 0;

  /*
   * When `maintenance.autoDetach` isn't set, then we fall back to
   * honoring `gc.autoDetach`. This is somewhat weird, but required to
   * retain behaviour from when we used to run git-gc(1) here.
   */
  if (repo_config_get_bool(r, "maintenance.autodetach", &auto_detach) &&
      repo_config_get_bool(r, "gc.autodetach", &auto_detach))
    auto_detach = git_env_bool("GIT_TEST_MAINT_AUTO_DETACH", true);

  maint->git_cmd = 1;
  maint->odb_to_close = r->objects;
  strvec_pushl(&maint->args, "maintenance", "run", "--auto", NULL);
  strvec_push(&maint->args, quiet ? "--quiet" : "--no-quiet");
  strvec_push(&maint->args, auto_detach ? "--detach" : "--no-detach");

  return 1;
}

int run_auto_maintenance(struct repository *r, int quiet)
{
  struct child_process maint = CHILD_PROCESS_INIT;
  if (!prepare_auto_maintenance(r, quiet, &maint))
    return 0;
  return run_command(&maint);
}

void sanitize_repo_env(struct strvec *env)
{
  const char * const *var;

  for (var = local_repo_env; *var; var++) {
    if (strcmp(*var, CONFIG_DATA_ENVIRONMENT) &&
        strcmp(*var, CONFIG_COUNT_ENVIRONMENT))
      strvec_push(env, *var);
  }
}

void prepare_other_repo_env(struct strvec *env, const char *new_git_dir)
{
  sanitize_repo_env(env);
  strvec_pushf(env, "%s=%s", GIT_DIR_ENVIRONMENT, new_git_dir);
}

enum start_bg_result start_bg_command(struct child_process *cmd,
              start_bg_wait_cb *wait_cb,
              void *cb_data,
              unsigned int timeout_sec)
{
  enum start_bg_result sbgr = SBGR_ERROR;
  int ret;
  int wait_status;
  pid_t pid_seen;
  time_t time_limit;

  /*
   * We do not allow clean-on-exit because the child process
   * should persist in the background and possibly/probably
   * after this process exits.  So we don't want to kill the
   * child during our atexit routine.
   */
  if (cmd->clean_on_exit)
    BUG("start_bg_command() does not allow non-zero clean_on_exit");

  if (!cmd->trace2_child_class)
    cmd->trace2_child_class = "background";

  ret = start_command(cmd);
  if (ret) {
    /*
     * We assume that if `start_command()` fails, we
     * either get a complete `trace2_child_start() /
     * trace2_child_exit()` pair or it fails before the
     * `trace2_child_start()` is emitted, so we do not
     * need to worry about it here.
     *
     * We also assume that `start_command()` does not add
     * us to the cleanup list.  And that it calls
     * `child_process_clear()`.
     */
    sbgr = SBGR_ERROR;
    goto done;
  }

  time(&time_limit);
  time_limit += timeout_sec;

wait:
  pid_seen = waitpid(cmd->pid, &wait_status, WNOHANG);

  if (!pid_seen) {
    /*
     * The child is currently running.  Ask the callback
     * if the child is ready to do work or whether we
     * should keep waiting for it to boot up.
     */
    ret = (*wait_cb)(cmd, cb_data);
    if (!ret) {
      /*
       * The child is running and "ready".
       */
      trace2_child_ready(cmd, "ready");
      sbgr = SBGR_READY;
      goto done;
    } else if (ret > 0) {
      /*
       * The callback said to give it more time to boot up
       * (subject to our timeout limit).
       */
      time_t now;

      time(&now);
      if (now < time_limit)
        goto wait;

      /*
       * Our timeout has expired.  We don't try to
       * kill the child, but rather let it continue
       * (hopefully) trying to startup.
       */
      trace2_child_ready(cmd, "timeout");
      sbgr = SBGR_TIMEOUT;
      goto done;
    } else {
      /*
       * The cb gave up on this child.  It is still running,
       * but our cb got an error trying to probe it.
       */
      trace2_child_ready(cmd, "error");
      sbgr = SBGR_CB_ERROR;
      goto done;
    }
  }

  else if (pid_seen == cmd->pid) {
    int child_code = -1;

    /*
     * The child started, but exited or was terminated
     * before becoming "ready".
     *
     * We try to match the behavior of `wait_or_whine()`
     * WRT the handling of WIFSIGNALED() and WIFEXITED()
     * and convert the child's status to a return code for
     * tracing purposes and emit the `trace2_child_exit()`
     * event.
     *
     * We do not want the wait_or_whine() error message
     * because we will be called by client-side library
     * routines.
     */
    if (WIFEXITED(wait_status))
      child_code = WEXITSTATUS(wait_status);
    else if (WIFSIGNALED(wait_status))
      child_code = WTERMSIG(wait_status) + 128;
    trace2_child_exit(cmd, child_code);

    sbgr = SBGR_DIED;
    goto done;
  }

  else if (pid_seen < 0 && errno == EINTR)
    goto wait;

  trace2_child_exit(cmd, -1);
  sbgr = SBGR_ERROR;

done:
  child_process_clear(cmd);
  invalidate_lstat_cache();
  return sbgr;
}

Coverage Report

Created: 2026-03-31 06:24