nptl/pthread_mutex_getprioceiling.c

   1 /* Get current priority ceiling of pthread_mutex_t.
   2    Copyright (C) 2006-2021 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 <errno.h>
  21 #include <pthreadP.h>
  22
  23
  24 int
  25 pthread_mutex_getprioceiling (const pthread_mutex_t *mutex, int *prioceiling)
  26 {
  27   /* See concurrency notes regarding __kind in struct __pthread_mutex_s
  28      in sysdeps/nptl/bits/thread-shared-types.h.  */
  29   if (__builtin_expect ((atomic_load_relaxed (&(mutex->__data.__kind))
  30                          & PTHREAD_MUTEX_PRIO_PROTECT_NP) == 0, 0))
  31     return EINVAL;
  32
  33   *prioceiling = (mutex->__data.__lock & PTHREAD_MUTEX_PRIO_CEILING_MASK)
  34                  >> PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
  35
  36   return 0;
  37 }