sysdeps/mach/hurd/setsid.c

   1 /* Copyright (C) 1993-2015 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <http://www.gnu.org/licenses/>.  */
  17
  18 #include <errno.h>
  19 #include <unistd.h>
  20 #include <hurd.h>
  21 #include <hurd/port.h>
  22 #include <hurd/fd.h>
  23
  24 /* Create a new session with the calling process as its leader.
  25    The process group IDs of the session and the calling process
  26    are set to the process ID of the calling process, which is returned.  */
  27 pid_t
  28 __setsid (void)
  29 {
  30   error_t err;
  31   unsigned int stamp;
  32
  33   HURD_CRITICAL_BEGIN;
  34   __mutex_lock (&_hurd_dtable_lock);
  35
  36   stamp = _hurd_pids_changed_stamp; /* Atomic fetch.  */
  37
  38   /* Tell the proc server we want to start a new session.  */
  39   err = __USEPORT (PROC, __proc_setsid (port));
  40   if (err)
  41     __mutex_unlock (&_hurd_dtable_lock);
  42   else
  43     {
  44       /* Punt our current ctty, and update the dtable accordingly.  We hold
  45          the dtable lock from before the proc_setsid call through clearing
  46          the cttyid port and processing the dtable, so that we can be sure
  47          that it's all done by the time the signal thread processes the
  48          pgrp change notification.  */
  49       _hurd_locked_install_cttyid (MACH_PORT_NULL);
  50
  51       /* Synchronize with the signal thread to make sure we have received
  52          and processed proc_newids before returning to the user.
  53          This is necessary to ensure that _hurd_pgrp (and thus the value
  54          returned by `getpgrp ()' in other threads) has been updated before
  55          we return.  */
  56       while (_hurd_pids_changed_stamp == stamp)
  57         {
  58 #ifdef noteven
  59           /* XXX we have no need for a mutex, but cthreads demands one.  */
  60           __condition_wait (&_hurd_pids_changed_sync, NULL);
  61 #else
  62           __swtch_pri (0);
  63 #endif
  64         }
  65     }
  66
  67   HURD_CRITICAL_END;
  68
  69   return err ? __hurd_fail (err) : _hurd_pgrp;
  70 }
  71
  72 weak_alias (__setsid, setsid)