signal/allocrtsig.c

   1 /* Handle real-time signal allocation.  Generic version.
   2    Copyright (C) 1997-2022 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 <signal.h>
  20 #include <internal-signals.h>
  21
  22 /* In these variables we keep track of the used variables.  If the
  23    platform does not support any real-time signals we will define the
  24    values to some unreasonable value which will signal failing of all
  25    the functions below.  */
  26 #ifdef __SIGRTMIN
  27 static int current_rtmin = __SIGRTMIN + RESERVED_SIGRT;
  28 static int current_rtmax = __SIGRTMAX;
  29 #endif
  30
  31 /* Return number of available real-time signal with highest priority.  */
  32 int
  33 __libc_current_sigrtmin (void)
  34 {
  35 #ifdef __SIGRTMIN
  36   return current_rtmin;
  37 #else
  38   return -1;
  39 #endif
  40 }
  41 libc_hidden_def (__libc_current_sigrtmin)
  42
  43 /* Return number of available real-time signal with lowest priority.  */
  44 int
  45 __libc_current_sigrtmax (void)
  46 {
  47 #ifdef __SIGRTMIN
  48   return current_rtmax;
  49 #else
  50   return -1;
  51 #endif
  52 }
  53 libc_hidden_def (__libc_current_sigrtmax)
  54
  55 /* Allocate real-time signal with highest/lowest available
  56    priority.  Please note that we don't use a lock since we assume
  57    this function to be called at program start.  */
  58 int
  59 __libc_allocate_rtsig (int high)
  60 {
  61 #ifndef __SIGRTMIN
  62   return -1;
  63 #else
  64   if (current_rtmin == -1 || current_rtmin > current_rtmax)
  65     /* We don't have any more signals available.  */
  66     return -1;
  67
  68   return high ? current_rtmin++ : current_rtmax--;
  69 #endif
  70 }