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/* Set current priority ceiling of pthread_mutex_t.
Copyright (C) 2006-2019 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
<https://www.gnu.org/licenses/>. */
#include <stdbool.h>
#include <errno.h>
#include <pthreadP.h>
#include <atomic.h>
int
pthread_mutex_setprioceiling (pthread_mutex_t *mutex, int prioceiling,
int *old_ceiling)
{
/* See concurrency notes regarding __kind in struct __pthread_mutex_s
in sysdeps/nptl/bits/thread-shared-types.h. */
if ((atomic_load_relaxed (&(mutex->__data.__kind))
& PTHREAD_MUTEX_PRIO_PROTECT_NP) == 0)
return EINVAL;
/* See __init_sched_fifo_prio. */
if (atomic_load_relaxed (&__sched_fifo_min_prio) == -1
|| atomic_load_relaxed (&__sched_fifo_max_prio) == -1)
__init_sched_fifo_prio ();
if (__glibc_unlikely (prioceiling
< atomic_load_relaxed (&__sched_fifo_min_prio))
|| __glibc_unlikely (prioceiling
> atomic_load_relaxed (&__sched_fifo_max_prio))
|| __glibc_unlikely ((prioceiling
& (PTHREAD_MUTEXATTR_PRIO_CEILING_MASK
>> PTHREAD_MUTEXATTR_PRIO_CEILING_SHIFT))
!= prioceiling))
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;
}
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