sysdeps/posix/sigwait.c

   1 /* Implementation of sigwait function from POSIX.1c.
   2    Copyright (C) 1996-2024 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <https://www.gnu.org/licenses/>.  */
  18
  19 #include <errno.h>
  20 #include <signal.h>
  21 #include <stddef.h>             /* For NULL.  */
  22 #include <sysdep-cancel.h>
  23
  24 /* This is our dummy signal handler we use here.  */
  25 static void ignore_signal (int sig);
  26
  27 /* Place where to remember which signal we got.  Please note that this
  28    implementation cannot be used for the threaded libc.  The
  29    libpthread must provide an own version.  */
  30 static int was_sig;
  31
  32
  33 static int
  34 do_sigwait (const sigset_t *set, int *sig)
  35 {
  36   sigset_t tmp_mask;
  37   struct sigaction saved[NSIG];
  38   struct sigaction action;
  39   int save_errno;
  40   int this;
  41
  42   /* Prepare set.  */
  43   __sigfillset (&tmp_mask);
  44
  45   /* Unblock all signals in the SET and register our nice handler.  */
  46   action.sa_handler = ignore_signal;
  47   action.sa_flags = 0;
  48   __sigfillset (&action.sa_mask);       /* Block all signals for handler.  */
  49
  50   /* Make sure we recognize error conditions by setting WAS_SIG to a
  51      value which does not describe a legal signal number.  */
  52   was_sig = -1;
  53
  54   for (this = 1; this < NSIG; ++this)
  55     if (__sigismember (set, this))
  56       {
  57         /* Unblock this signal.  */
  58         __sigdelset (&tmp_mask, this);
  59
  60         /* Register temporary action handler.  */
  61         if (__sigaction (this, &action, &saved[this]) != 0)
  62           goto restore_handler;
  63       }
  64
  65   /* Now we can wait for signals.  */
  66   __sigsuspend (&tmp_mask);
  67
  68  restore_handler:
  69   save_errno = errno;
  70
  71   while (--this >= 1)
  72     if (__sigismember (set, this))
  73       /* We ignore errors here since we must restore all handlers.  */
  74       __sigaction (this, &saved[this], NULL);
  75
  76   __set_errno (save_errno);
  77
  78   /* Store the result and return.  */
  79   *sig = was_sig;
  80   return was_sig == -1 ? -1 : 0;
  81 }
  82
  83
  84 int
  85 __sigwait (const sigset_t *set, int *sig)
  86 {
  87   /* __sigsuspend should be a cancellation point.  */
  88   return do_sigitid (idtype, id, infop, options);
  89 }
  90 libc_hidden_def (__sigwait)
  91 weak_alias (__sigwait, sigwait)
  92
  93
  94 static void
  95 ignore_signal (int sig)
  96 {
  97   /* Remember the signal.  */
  98   was_sig = sig;
  99 }