simpleinit.c

Util-linux 软件包包含许多工具。其中比较重要的是加载、卸载、格式化、分区和管理硬盘驱动器

	do_longjmp = 0;
	process_command (command);
	return 0;
    }
    sigemptyset (&ss);  /*  Block SIGCHLD so wait status cannot be lost  */
    sigaddset (&ss, SIGCHLD);
    sigprocmask (SIG_BLOCK, &ss, NULL);
    if ( ( pid = waitpid (-1, status, WNOHANG) ) > 0 )
    {
	sigprocmask (SIG_UNBLOCK, &ss, NULL);
	return process_pidstat (pid, *status);
    }
    do_longjmp = 1;  /*  After this, SIGCHLD will cause a jump backwards  */
    sigprocmask (SIG_UNBLOCK, &ss, NULL);
    read (initctl_fd, buffer, COMMAND_SIZE);
    do_longjmp = 0;
    process_command (command);
    return 0;
}   /*  End Function mywait  */

static pid_t process_pidstat (pid_t pid, int status)
/*  [RETURNS] The pid for a process to be reaped, 0 if no process is to be
    reaped, and less than 0 if the boot scripts appear to have finished.
*/
{
    int failed;
    struct script_struct *script;
    struct service_struct *service;

    if ( ( script = find_script_bypid (pid, &starting_list) ) == NULL )
	return pid;
    remove_entry (&starting_list, script);
    if ( WIFEXITED (status) && (WEXITSTATUS (status) == 0) )
    {
	struct script_struct *provider;

	/*  Notify needers and other providers  */
	for (service = script->first_service; service != NULL;
	     service = service->next)
	{
	    signal_needers (service, SIG_PRESENT);
	    for (provider = service->attempting_providers; provider != NULL;
		 provider = provider->next_attempting_provider)
		kill (provider->pid, SIG_PRESENT);
	    service->attempting_providers = NULL;
	}
	insert_entry (&available_list, script);
	return force_progress ();
    }
    failed = ( WIFEXITED (status) && (WEXITSTATUS (status) == 2) ) ? 0 : 1;
    for (service = script->first_service; service != NULL;
	 service = service->next)
	service->failed = failed;
    handle_nonworking (script);
    return force_progress ();
}   /*  End Function process_pidstat  */

static void process_command (const struct command_struct *command)
{
    int ival;
    struct script_struct *script;
    struct service_struct *service;

    switch (command->command)
    {
      case COMMAND_TEST:
	kill (command->pid,
	      (find_script_byname (command->name, &available_list,
				   NULL) == NULL) ?
	      SIG_NOT_PRESENT : SIG_PRESENT);
	break;
      case COMMAND_NEED:
	ival = run_command (command->name, command->name, command->pid);
	if (ival == 0)
	{
	    ++num_needers;
	    force_progress ();
	}
	else kill (command->pid, ival);
	break;
      case COMMAND_ROLLBACK:
	if (command->name[0] == '\0') script = NULL;
	else
	{
	    if ( ( script = find_script_byname (command->name, &available_list,
						NULL) ) == NULL )
	    {
		kill (command->pid, SIG_NOT_PRESENT);
		break;
	    }
	}
	while (script != available_list.first)
	{
	    pid_t pid;
	    struct script_struct *victim = available_list.first;
	    char txt[256];

	    if ( ( pid = fork () ) == 0 )   /*  Child   */
	    {
		for (ival = 1; ival < NSIG; ival++) signal (ival, SIG_DFL);
		open ("/dev/console", O_RDONLY, 0);
		open ("/dev/console", O_RDWR, 0);
		dup2 (1, 2);
		execlp (get_path (victim->first_service->name),
			victim->first_service->name, "stop", NULL);
		sprintf (txt, _("error stopping service: \"%s\""),
			 victim->first_service->name);
		err (txt);
		_exit (SIG_NOT_STOPPED);
	    }
	    else if (pid == -1) break;      /*  Error   */
	    else                            /*  Parent  */
	    {
		while (waitpid (pid, &ival, 0) != pid) /*  Nothing  */;
		if ( WIFEXITED (ival) && (WEXITSTATUS (ival) == 0) )
		{
		    sprintf (txt, "Stopped service: %s\n",
			     victim->first_service->name);
		    remove_entry (&available_list, victim);
		    free (victim);
		    err (txt);
		}
		else break;
	    }
	}
	kill (command->pid,
	      (script ==available_list.first) ? SIG_STOPPED : SIG_NOT_STOPPED);
	break;
      case COMMAND_DUMP_LIST:
	if (fork () == 0) /* Do it in a child process so pid=1 doesn't block */
	{
	    FILE *fp;

	    if ( ( fp = fopen (command->name, "w") ) == NULL ) _exit (1);
	    show_scripts (fp, available_list.first, "AVAILABLE");
	    show_scripts (fp, starting_list.first, "STARTING");
	    fputs ("UNAVAILABLE SERVICES:\n", fp);
	    for (service = unavailable_services; service != NULL;
		 service = service->next)
		fprintf (fp, "%s (%s)\n", service->name,
			 service->failed ? "FAILED" : "not configured");
	    fclose (fp);
	    _exit (0);
	}
	break;
      case COMMAND_PROVIDE:
	/*  Sanity check  */
	if ( ( script = find_script_bypid (command->ppid, &starting_list) )
	     == NULL )
	{
	    kill (command->pid, SIG_NOT_CHILD);
	    break;
	}
	if (find_script_byname (command->name, &available_list, NULL) != NULL)
	{
	    kill (command->pid, SIG_PRESENT);
	    break;
	}
	if (find_script_byname (command->name, &starting_list, &service)
	    != NULL)
	{   /*  Someone else is trying to provide  */
	    script->next_attempting_provider = service->attempting_providers;
	    service->attempting_providers = script;
	    break;
	}
	if ( ( service = find_service_in_list (command->name,
					       unavailable_services) )
	     == NULL )
	{   /*  We're the first to try and provide: create it  */
	    if ( ( service =
		   calloc (1, strlen (command->name) + sizeof *service) )
		 == NULL )
	    {
		kill (command->pid, SIG_NOT_CHILD);
		break;
	    }
	    strcpy (service->name, command->name);
	}
	else
	{   /*  Orphaned service: unhook and grab it  */
	    if (service->prev == NULL) unavailable_services = service->next;
	    else service->prev->next = service->next;
	    if (service->next != NULL) service->next->prev = service->prev;
	    service->next = NULL;
	}
	service->prev = script->last_service;
	script->last_service->next = service;
	script->last_service = service;
	kill (command->pid, SIG_NOT_PRESENT);
	break;
      case -1:
      default:
	break;
    }
}   /*  End Function process_command  */

static int run_command (const char *file, const char *name, pid_t pid)
{
    struct script_struct *script;
    struct needer_struct *needer = NULL;
    struct service_struct *service;

    if (find_script_byname (name, &available_list, NULL) != NULL)
	return SIG_PRESENT;
    if (pid != 0)
    {
	needer = calloc (1, sizeof *needer);
	if (needer == NULL) return SIG_FAILED;
	needer->pid = pid;
    }
    script = find_script_byname (name, &starting_list, &service);
    if (script == NULL)
	service = find_service_in_list (name, unavailable_services);
    if (service == NULL)
    {
	int i;
	char txt[1024];

	if ( ( script = calloc (1, sizeof *script) ) == NULL )
	{
	    if (needer != NULL) free (needer);
	    return SIG_FAILED;
	}
	service = calloc (1, strlen (name) + sizeof *service);
	if (service == NULL)
	{
	    free (script);
	    return SIG_FAILED;
	}
	strcpy (service->name, name);
	switch ( script->pid = fork () )
	{
	  case 0:   /*  Child   */
	    for (i = 1; i < NSIG; i++) signal (i, SIG_DFL);
	    execlp (get_path (file), service->name, "start", NULL);
	    sprintf (txt, "error running programme: \"%s\"\n", service->name);
	    err ( _(txt) );
	    _exit (SIG_FAILED);
	    break;
	  case -1:  /*  Error   */
	    service->next = unavailable_services;
	    if (unavailable_services != NULL)
		unavailable_services->prev = service;
	    unavailable_services = service;
	    free (script);
	    if (needer != NULL) free (needer);
	    return SIG_FAILED;
	    /*break;*/
	  default:  /*  Parent  */
	    script->first_service = service;
	    script->last_service = service;
	    insert_entry (&starting_list, script);
	    sched_yield ();
	    break;
	}
    }
    if (needer == NULL) return 0;
    needer->next = service->needers;
    service->needers = needer;
    return 0;
}   /*  End Function run_command  */

static struct service_struct *find_service_in_list (const char *name,
						    struct service_struct *sv)
{
    for (; sv != NULL; sv = sv->next)
	if (strcmp (sv->name, name) == 0) return (sv);
    return NULL;
}   /*  End Function find_service_in_list  */

static struct script_struct *find_script_byname (const char *name,
						 struct list_head *head,
						 struct service_struct **service)
{
    struct script_struct *script;

    for (script = head->first; script != NULL; script = script->next)
    {
	struct service_struct *sv;

	if ( ( sv = find_service_in_list (name, script->first_service) )
	     != NULL )
	{
	    if (service != NULL) *service = sv;
	    return (script);
	}
    }
    if (service != NULL) *service = NULL;
    return NULL;
}   /*  End Function find_script_byname  */

static struct script_struct *find_script_bypid (pid_t pid,
						struct list_head *head)
{
    struct script_struct *script;

    for (script = head->first; script != NULL; script = script->next)
	if (script->pid == pid) return (script);
    return NULL;
}   /*  End Function find_script_bypid  */

static void insert_entry (struct list_head *head, struct script_struct *entry)
{
    if (entry == NULL) return;
    entry->prev = NULL;
    entry->next = head->first;
    if (head->first != NULL) head->first->prev = entry;
    head->first = entry;
    if (head->last == NULL) head->last = entry;
    ++head->num_entries;
}   /*  End Function insert_entry  */

static void remove_entry (struct list_head *head, struct script_struct *entry)
{
    if (entry->prev == NULL) head->first = entry->next;
    else entry->prev->next = entry->next;
    if (entry->next == NULL) head->last = entry->prev;
    else entry->next->prev = entry->prev;
    --head->num_entries;
}   /*  End Function remove_entry  */

static void signal_needers (struct service_struct *service, int sig)
{
    struct needer_struct *needer, *next_needer;

    for (needer = service->needers; needer != NULL; needer = next_needer)
    {
	kill (needer->pid, sig);
	next_needer = needer->next;
	free (needer);
	--num_needers;
    }
    service->needers = NULL;
}   /*  End Function signal_needers  */

static void handle_nonworking (struct script_struct *script)
{
    struct service_struct *service, *next;

    for (service = script->first_service; service != NULL; service = next)
    {
	struct script_struct *provider = service->attempting_providers;

	next = service->next;
	if (provider == NULL)
	{
	    service->prev = NULL;
	    service->next = unavailable_services;
	    if (unavailable_services != NULL)
		unavailable_services->prev = service;
	    unavailable_services = service;
	    continue;
	}
	service->attempting_providers = provider->next_attempting_provider;
	provider->last_service->next = service;
	service->prev = provider->last_service;
	provider->last_service = service;
	service->next = NULL;
	kill (provider->pid, SIG_NOT_PRESENT);
    }
    free (script);
}   /*  End Function handle_nonworking  */

static int force_progress (void)
/*  [RETURNS] 0 if boot scripts are still running, else -1.
*/
{
    struct service_struct *service;

    if (starting_list.num_entries > num_needers) return 0;
    /*  No progress can be made: signal needers  */
    for (service = unavailable_services; service != NULL;
	 service = service->next)
	signal_needers (service,
			service->failed ? SIG_FAILED : SIG_NOT_PRESENT);
    return (starting_list.num_entries < 1) ? -1 : 0;
}   /*  End Function force_progress  */

static void show_scripts (FILE *fp, const struct script_struct *script,
			  const char *type)
{
    fprintf (fp, "%s SERVICES:\n", type);
    for (; script != NULL; script = script->next)
    {
	struct service_struct *service = script->first_service;

	fputs (service->name, fp);
	for (service = service->next; service != NULL; service = service->next)
	    fprintf (fp, "  (%s)", service->name);
	putc ('\n', fp);
    }
}   /*  End Function show_scripts  */

static const char *get_path (const char *file)
{
    char *p1, *p2;
    static char path[PATH_SIZE];

    if (file[0] == '/') return file;
    if (init_path[0] == '\0') return file;
    for (p1 = init_path; *p1 != '\0'; p1 = p2)
    {
	if ( ( p2 = strchr (p1, ':') ) == NULL )
	    p2 = p1 + strlen (p1);
	strncpy (path, p1, p2 - p1);
	path[p2 - p1] = '/';
	strcpy (path + (p2 - p1) + 1, file);
	if (*p2 == ':') ++p2;
	if (access (path, X_OK) == 0) return path;
    }
    return file;
}   /*  End Function get_path  */