/* Set current priority ceiling of pthread_mutex_t. Copyright (C) 2006, 2007 Free Software Foundation, Inc. This file is part of the GNU C Library. Contributed by Jakub Jelinek <jakub@redhat.com>, 2006. The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU Lesser General Public License as published by the Free Software Foundation; either version 2.1 of the License, or (at your option) any later version. The GNU C Library is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more details. You should have received a copy of the GNU Lesser General Public License along with the GNU C Library; if not, see <http://www.gnu.org/licenses/>. */ #include <stdbool.h> #include <errno.h> #include <pthreadP.h> int pthread_mutex_setprioceiling (mutex, prioceiling, old_ceiling) pthread_mutex_t *mutex; int prioceiling; int *old_ceiling; { /* The low bits of __kind aren't ever changed after pthread_mutex_init, so we don't need a lock yet. */ if ((mutex->__data.__kind & PTHREAD_MUTEX_PRIO_PROTECT_NP) == 0) return EINVAL; if (__sched_fifo_min_prio == -1) __init_sched_fifo_prio (); if (__builtin_expect (prioceiling < __sched_fifo_min_prio, 0) || __builtin_expect (prioceiling > __sched_fifo_max_prio, 0) || __builtin_expect ((prioceiling & (PTHREAD_MUTEXATTR_PRIO_CEILING_MASK >> PTHREAD_MUTEXATTR_PRIO_CEILING_SHIFT)) != prioceiling, 0)) return EINVAL; /* Check whether we already hold the mutex. */ bool locked = false; int kind = PTHREAD_MUTEX_TYPE (mutex); if (mutex->__data.__owner == THREAD_GETMEM (THREAD_SELF, tid)) { if (kind == PTHREAD_MUTEX_PP_ERRORCHECK_NP) return EDEADLK; if (kind == PTHREAD_MUTEX_PP_RECURSIVE_NP) locked = true; } int oldval = mutex->__data.__lock; if (! locked) do { /* Need to lock the mutex, but without obeying the priority protect protocol. */ int ceilval = (oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK); oldval = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock, ceilval | 1, ceilval); if (oldval == ceilval) break; do { oldval = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock, ceilval | 2, ceilval | 1); if ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval) break; if (oldval != ceilval) lll_futex_wait (&mutex->__data.__lock, ceilval | 2, PTHREAD_MUTEX_PSHARED (mutex)); } while (atomic_compare_and_exchange_val_acq (&mutex->__data.__lock, ceilval | 2, ceilval) != ceilval); if ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval) continue; } while (0); int oldprio = (oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) >> PTHREAD_MUTEX_PRIO_CEILING_SHIFT; if (locked) { int ret = __pthread_tpp_change_priority (oldprio, prioceiling); if (ret) return ret; } if (old_ceiling != NULL) *old_ceiling = oldprio; int newlock = 0; if (locked) newlock = (mutex->__data.__lock & ~PTHREAD_MUTEX_PRIO_CEILING_MASK); mutex->__data.__lock = newlock | (prioceiling << PTHREAD_MUTEX_PRIO_CEILING_SHIFT); atomic_full_barrier (); lll_futex_wake (&mutex->__data.__lock, INT_MAX, PTHREAD_MUTEX_PSHARED (mutex)); return 0; }