libc/signal/sigwait.c

   1 /* sigwait
   2  *
   3  * Copyright (C) 2006 by Steven J. Hill <sjhill@realitydiluted.com>
   4  * Copyright (C) 2003-2005 by Erik Andersen <andersen@uclibc.org>
   5  *
   6  * This program 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; see the file COPYING.LIB.  If
  18  * not, see <http://www.gnu.org/licenses/>.
  19  */
  20
  21 #define __need_NULL
  22 #include <stddef.h>
  23 #include <sys/syscall.h>
  24 #include <signal.h>
  25 #include <cancel.h>
  26
  27 #if defined __NR_rt_sigtimedwait && defined __UCLIBC_HAS_REALTIME__
  28
  29 #include <string.h>
  30
  31 /* Return any pending signal or wait for one for the given time.  */
  32 static int __NC(sigwait)(const sigset_t *set, int *sig)
  33 {
  34         int ret;
  35
  36         do
  37                 /* we might as well use sigtimedwait and do not care about cancellation */
  38                 ret = __NC(sigtimedwait)(set, NULL, NULL);
  39         while (ret == -1 && errno == EINTR);
  40         if (ret != -1) {
  41                 *sig = ret;
  42                 ret = 0;
  43         } else
  44                 ret = errno;
  45
  46         return ret;
  47 }
  48
  49 #else /* __NR_rt_sigtimedwait */
  50
  51 /* variant without REALTIME extensions */
  52 #include <unistd.h>     /* smallint */
  53
  54 static smallint was_sig; /* obviously not thread-safe */
  55
  56 static void ignore_signal(int sig)
  57 {
  58         was_sig = sig;
  59 }
  60
  61 static int __NC(sigwait)(const sigset_t *set, int *sig)
  62 {
  63   sigset_t tmp_mask;
  64   struct sigaction saved[NSIG];
  65   struct sigaction action;
  66   int save_errno;
  67   int this;
  68
  69   /* Prepare set.  */
  70   __sigfillset (&tmp_mask);
  71
  72   /* Unblock all signals in the SET and register our nice handler.  */
  73   action.sa_handler = ignore_signal;
  74   action.sa_flags = 0;
  75   __sigfillset (&action.sa_mask);       /* Block all signals for handler.  */
  76
  77   /* Make sure we recognize error conditions by setting WAS_SIG to a
  78      value which does not describe a legal signal number.  */
  79   was_sig = -1;
  80
  81   for (this = 1; this < NSIG; ++this)
  82     if (__sigismember (set, this))
  83       {
  84         /* Unblock this signal.  */
  85         __sigdelset (&tmp_mask, this);
  86
  87         /* Register temporary action handler.  */
  88         /* In Linux (as of 2.6.25), fails only if sig is SIGKILL or SIGSTOP */
  89         /* (so, will it work correctly if set has, say, SIGSTOP?) */
  90         if (sigaction (this, &action, &saved[this]) != 0)
  91           goto restore_handler;
  92       }
  93
  94   /* Now we can wait for signals.  */
  95   __NC(sigsuspend)(&tmp_mask);
  96
  97  restore_handler:
  98   save_errno = errno;
  99
 100   while (--this >= 1)
 101     if (__sigismember (set, this))
 102       /* We ignore errors here since we must restore all handlers.  */
 103       sigaction (this, &saved[this], NULL);
 104
 105   __set_errno (save_errno);
 106
 107   /* Store the result and return.  */
 108   *sig = was_sig;
 109   return was_sig == -1 ? -1 : 0;
 110 }
 111 #endif /* __NR_rt_sigtimedwait */
 112
 113 CANCELLABLE_SYSCALL(int, sigwait, (const sigset_t *set, int *sig), (set, sig))