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123 lines
3.6 KiB
C
123 lines
3.6 KiB
C
/* Set current priority ceiling of pthread_mutex_t.
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Copyright (C) 2006-2019 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Jakub Jelinek <jakub@redhat.com>, 2006.
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The GNU C Library is free software; you can redistribute it and/or
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modify it under the terms of the GNU Lesser General Public
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License as published by the Free Software Foundation; either
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version 2.1 of the License, or (at your option) any later version.
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The GNU C Library is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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Lesser General Public License for more details.
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You should have received a copy of the GNU Lesser General Public
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License along with the GNU C Library; if not, see
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<http://www.gnu.org/licenses/>. */
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#include <stdbool.h>
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#include <errno.h>
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#include <pthreadP.h>
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#include <atomic.h>
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int
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pthread_mutex_setprioceiling (pthread_mutex_t *mutex, int prioceiling,
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int *old_ceiling)
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{
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/* See concurrency notes regarding __kind in struct __pthread_mutex_s
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in sysdeps/nptl/bits/thread-shared-types.h. */
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if ((atomic_load_relaxed (&(mutex->__data.__kind))
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& PTHREAD_MUTEX_PRIO_PROTECT_NP) == 0)
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return EINVAL;
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/* See __init_sched_fifo_prio. */
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if (atomic_load_relaxed (&__sched_fifo_min_prio) == -1
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|| atomic_load_relaxed (&__sched_fifo_max_prio) == -1)
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__init_sched_fifo_prio ();
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if (__glibc_unlikely (prioceiling
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< atomic_load_relaxed (&__sched_fifo_min_prio))
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|| __glibc_unlikely (prioceiling
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> atomic_load_relaxed (&__sched_fifo_max_prio))
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|| __glibc_unlikely ((prioceiling
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& (PTHREAD_MUTEXATTR_PRIO_CEILING_MASK
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>> PTHREAD_MUTEXATTR_PRIO_CEILING_SHIFT))
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!= prioceiling))
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return EINVAL;
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/* Check whether we already hold the mutex. */
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bool locked = false;
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int kind = PTHREAD_MUTEX_TYPE (mutex);
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if (mutex->__data.__owner == THREAD_GETMEM (THREAD_SELF, tid))
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{
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if (kind == PTHREAD_MUTEX_PP_ERRORCHECK_NP)
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return EDEADLK;
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if (kind == PTHREAD_MUTEX_PP_RECURSIVE_NP)
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locked = true;
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}
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int oldval = mutex->__data.__lock;
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if (! locked)
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do
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{
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/* Need to lock the mutex, but without obeying the priority
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protect protocol. */
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int ceilval = (oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK);
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oldval = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
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ceilval | 1, ceilval);
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if (oldval == ceilval)
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break;
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do
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{
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oldval
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= atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
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ceilval | 2,
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ceilval | 1);
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if ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval)
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break;
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if (oldval != ceilval)
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lll_futex_wait (&mutex->__data.__lock, ceilval | 2,
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PTHREAD_MUTEX_PSHARED (mutex));
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}
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while (atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
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ceilval | 2, ceilval)
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!= ceilval);
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if ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval)
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continue;
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}
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while (0);
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int oldprio = (oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK)
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>> PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
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if (locked)
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{
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int ret = __pthread_tpp_change_priority (oldprio, prioceiling);
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if (ret)
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return ret;
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}
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if (old_ceiling != NULL)
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*old_ceiling = oldprio;
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int newlock = 0;
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if (locked)
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newlock = (mutex->__data.__lock & ~PTHREAD_MUTEX_PRIO_CEILING_MASK);
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mutex->__data.__lock = newlock
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atomic_full_barrier ();
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lll_futex_wake (&mutex->__data.__lock, INT_MAX,
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PTHREAD_MUTEX_PSHARED (mutex));
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return 0;
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}
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