sysdeps/posix/sigwait.c

   1 /* Implementation of sigwait function from POSIX.1c.
   2    Copyright (C) 1996-2015 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1996.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #include <errno.h>
  21 #include <signal.h>
  22 #include <stddef.h>             /* For NULL.  */
  23 #include <sysdep-cancel.h>
  24
  25 /* This is our dummy signal handler we use here.  */
  26 static void ignore_signal (int sig);
  27
  28 /* Place where to remember which signal we got.  Please note that this
  29    implementation cannot be used for the threaded libc.  The
  30    libpthread must provide an own version.  */
  31 static int was_sig;
  32
  33
  34 static int
  35 do_sigwait (const sigset_t *set, int *sig)
  36 {
  37   sigset_t tmp_mask;
  38   struct sigaction saved[NSIG];
  39   struct sigaction action;
  40   int save_errno;
  41   int this;
  42
  43   /* Prepare set.  */
  44   __sigfillset (&tmp_mask);
  45
  46   /* Unblock all signals in the SET and register our nice handler.  */
  47   action.sa_handler = ignore_signal;
  48   action.sa_flags = 0;
  49   __sigfillset (&action.sa_mask);       /* Block all signals for handler.  */
  50
  51   /* Make sure we recognize error conditions by setting WAS_SIG to a
  52      value which does not describe a legal signal number.  */
  53   was_sig = -1;
  54
  55   for (this = 1; this < NSIG; ++this)
  56     if (__sigismember (set, this))
  57       {
  58         /* Unblock this signal.  */
  59         __sigdelset (&tmp_mask, this);
  60
  61         /* Register temporary action handler.  */
  62         if (__sigaction (this, &action, &saved[this]) != 0)
  63           goto restore_handler;
  64       }
  65
  66   /* Now we can wait for signals.  */
  67   __sigsuspend (&tmp_mask);
  68
  69  restore_handler:
  70   save_errno = errno;
  71
  72   while (--this >= 1)
  73     if (__sigismember (set, this))
  74       /* We ignore errors here since we must restore all handlers.  */
  75       __sigaction (this, &saved[this], NULL);
  76
  77   __set_errno (save_errno);
  78
  79   /* Store the result and return.  */
  80   *sig = was_sig;
  81   return was_sig == -1 ? -1 : 0;
  82 }
  83
  84
  85 int
  86 __sigwait (const sigset_t *set, int *sig)
  87 {
  88   if (SINGLE_THREAD_P)
  89     return do_sigwait (set, sig);
  90
  91   int oldtype = LIBC_CANCEL_ASYNC ();
  92
  93   int result = do_sigwait (set, sig);
  94
  95   LIBC_CANCEL_RESET (oldtype);
  96
  97   return result;
  98 }
  99 libc_hidden_def (__sigwait)
 100 weak_alias (__sigwait, sigwait)
 101
 102
 103 static void
 104 ignore_signal (int sig)
 105 {
 106   /* Remember the signal.  */
 107   was_sig = sig;
 108 }