libc/signal/sigwait.c

   1 /* vi: set sw=4 ts=4: */
   2 /* sigwait
   3  *
   4  * Copyright (C) 2006 by Steven J. Hill <sjhill@realitydiluted.com>
   5  * Copyright (C) 2003-2005 by Erik Andersen <andersen@uclibc.org>
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * The GNU C Library is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with the GNU C Library; see the file COPYING.LIB.  If
  19  * not, see <http://www.gnu.org/licenses/>.
  20  */
  21
  22 #define __need_NULL
  23 #include <stddef.h>
  24 #include <sys/syscall.h>
  25 #include <signal.h>
  26 #include <cancel.h>
  27
  28 #if defined __NR_rt_sigtimedwait && defined __UCLIBC_HAS_REALTIME__
  29
  30 #include <string.h>
  31
  32 /* Return any pending signal or wait for one for the given time.  */
  33 static int __NC(sigwait)(const sigset_t *set, int *sig)
  34 {
  35         int ret;
  36
  37         do
  38                 /* we might as well use sigtimedwait and do not care about cancellation */
  39                 ret = __NC(sigtimedwait)(set, NULL, NULL);
  40         while (ret == -1 && errno == EINTR);
  41         if (ret != -1) {
  42                 *sig = ret;
  43                 ret = 0;
  44         } else
  45                 ret = errno;
  46
  47         return ret;
  48 }
  49
  50 #else /* __NR_rt_sigtimedwait */
  51
  52 /* variant without REALTIME extensions */
  53 #include <unistd.h>     /* smallint */
  54
  55 static smallint was_sig; /* obviously not thread-safe */
  56
  57 static void ignore_signal(int sig)
  58 {
  59         was_sig = sig;
  60 }
  61
  62 static int __NC(sigwait)(const sigset_t *set, int *sig)
  63 {
  64   sigset_t tmp_mask;
  65   struct sigaction saved[NSIG];
  66   struct sigaction action;
  67   int save_errno;
  68   int this;
  69
  70   /* Prepare set.  */
  71   __sigfillset (&tmp_mask);
  72
  73   /* Unblock all signals in the SET and register our nice handler.  */
  74   action.sa_handler = ignore_signal;
  75   action.sa_flags = 0;
  76   __sigfillset (&action.sa_mask);       /* Block all signals for handler.  */
  77
  78   /* Make sure we recognize error conditions by setting WAS_SIG to a
  79      value which does not describe a legal signal number.  */
  80   was_sig = -1;
  81
  82   for (this = 1; this < NSIG; ++this)
  83     if (__sigismember (set, this))
  84       {
  85         /* Unblock this signal.  */
  86         __sigdelset (&tmp_mask, this);
  87
  88         /* Register temporary action handler.  */
  89         /* In Linux (as of 2.6.25), fails only if sig is SIGKILL or SIGSTOP */
  90         /* (so, will it work correctly if set has, say, SIGSTOP?) */
  91         if (sigaction (this, &action, &saved[this]) != 0)
  92           goto restore_handler;
  93       }
  94
  95   /* Now we can wait for signals.  */
  96   __NC(sigsuspend)(&tmp_mask);
  97
  98  restore_handler:
  99   save_errno = errno;
 100
 101   while (--this >= 1)
 102     if (__sigismember (set, this))
 103       /* We ignore errors here since we must restore all handlers.  */
 104       sigaction (this, &saved[this], NULL);
 105
 106   __set_errno (save_errno);
 107
 108   /* Store the result and return.  */
 109   *sig = was_sig;
 110   return was_sig == -1 ? -1 : 0;
 111 }
 112 #endif /* __NR_rt_sigtimedwait */
 113
 114 CANCELLABLE_SYSCALL(int, sigwait, (const sigset_t *set, int *sig), (set, sig))