nptl/pthread_mutexattr_getprioceiling.c

   1 /* Get priority ceiling setting from pthread_mutexattr_t.
   2    Copyright (C) 2006-2020 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Jakub Jelinek <jakub@redhat.com>, 2006.
   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 <pthreadP.h>
  21 #include <atomic.h>
  22
  23
  24 int
  25 pthread_mutexattr_getprioceiling (const pthread_mutexattr_t *attr,
  26                                   int *prioceiling)
  27 {
  28   const struct pthread_mutexattr *iattr;
  29   int ceiling;
  30
  31   iattr = (const struct pthread_mutexattr *) attr;
  32
  33   ceiling = ((iattr->mutexkind & PTHREAD_MUTEXATTR_PRIO_CEILING_MASK)
  34              >> PTHREAD_MUTEXATTR_PRIO_CEILING_SHIFT);
  35
  36   if (! ceiling)
  37     {
  38       /* See __init_sched_fifo_prio.  */
  39       if (atomic_load_relaxed (&__sched_fifo_min_prio) == -1)
  40         __init_sched_fifo_prio ();
  41       if (ceiling < atomic_load_relaxed (&__sched_fifo_min_prio))
  42         ceiling = atomic_load_relaxed (&__sched_fifo_min_prio);
  43     }
  44
  45   *prioceiling = ceiling;
  46
  47   return 0;
  48 }