signal/allocrtsig.c

   1 /* Handle real-time signal allocation.  Generic version.
   2    Copyright (C) 1997-2021 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
   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    <https://www.gnu.org/licenses/>.  */
  19
  20 #include <signal.h>
  21 #include <internal-signals.h>
  22
  23 /* In these variables we keep track of the used variables.  If the
  24    platform does not support any real-time signals we will define the
  25    values to some unreasonable value which will signal failing of all
  26    the functions below.  */
  27 #ifdef __SIGRTMIN
  28 static int current_rtmin = __SIGRTMIN + RESERVED_SIGRT;
  29 static int current_rtmax = __SIGRTMAX;
  30 #endif
  31
  32 /* Return number of available real-time signal with highest priority.  */
  33 int
  34 __libc_current_sigrtmin (void)
  35 {
  36 #ifdef __SIGRTMIN
  37   return current_rtmin;
  38 #else
  39   return -1;
  40 #endif
  41 }
  42 libc_hidden_def (__libc_current_sigrtmin)
  43
  44 /* Return number of available real-time signal with lowest priority.  */
  45 int
  46 __libc_current_sigrtmax (void)
  47 {
  48 #ifdef __SIGRTMIN
  49   return current_rtmax;
  50 #else
  51   return -1;
  52 #endif
  53 }
  54 libc_hidden_def (__libc_current_sigrtmax)
  55
  56 /* Allocate real-time signal with highest/lowest available
  57    priority.  Please note that we don't use a lock since we assume
  58    this function to be called at program start.  */
  59 int
  60 __libc_allocate_rtsig (int high)
  61 {
  62 #ifndef __SIGRTMIN
  63   return -1;
  64 #else
  65   if (current_rtmin == -1 || current_rtmin > current_rtmax)
  66     /* We don't have any more signals available.  */
  67     return -1;
  68
  69   return high ? current_rtmin++ : current_rtmax--;
  70 #endif
  71 }