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5a664d7ae8
The elision interfaces are closely aligned between the targets that implement them, so declare them in the generic <lowlevellock.h> file. Empty .c stubs are provided, so that fewer makefile updates under sysdeps are needed. Also simplify initialization via __libc_early_init. The symbols __lll_clocklock_elision, __lll_lock_elision, __lll_trylock_elision, __lll_unlock_elision, __pthread_force_elision move into libc. For the time being, non-hidden references are used from libpthread to access them, but once that part of libpthread is moved into libc, hidden symbols will be used again. (Hidden references seem desirable to reduce the likelihood of transactions aborts.)
459 lines
13 KiB
C
459 lines
13 KiB
C
/* Copyright (C) 2002-2021 Free Software Foundation, Inc.
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This file is part of the GNU C Library.
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Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
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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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<https://www.gnu.org/licenses/>. */
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#include <assert.h>
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#include <errno.h>
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#include <stdlib.h>
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#include "pthreadP.h"
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#include <lowlevellock.h>
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#include <futex-internal.h>
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int
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__pthread_mutex_trylock (pthread_mutex_t *mutex)
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{
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int oldval;
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pid_t id = THREAD_GETMEM (THREAD_SELF, tid);
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/* See concurrency notes regarding mutex type which is loaded from __kind
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in struct __pthread_mutex_s in sysdeps/nptl/bits/thread-shared-types.h. */
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switch (__builtin_expect (PTHREAD_MUTEX_TYPE_ELISION (mutex),
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PTHREAD_MUTEX_TIMED_NP))
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{
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/* Recursive mutex. */
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case PTHREAD_MUTEX_RECURSIVE_NP|PTHREAD_MUTEX_ELISION_NP:
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case PTHREAD_MUTEX_RECURSIVE_NP:
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/* Check whether we already hold the mutex. */
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if (mutex->__data.__owner == id)
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{
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/* Just bump the counter. */
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if (__glibc_unlikely (mutex->__data.__count + 1 == 0))
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/* Overflow of the counter. */
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return EAGAIN;
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++mutex->__data.__count;
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return 0;
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}
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if (lll_trylock (mutex->__data.__lock) == 0)
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{
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/* Record the ownership. */
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mutex->__data.__owner = id;
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mutex->__data.__count = 1;
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++mutex->__data.__nusers;
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return 0;
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}
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break;
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case PTHREAD_MUTEX_TIMED_ELISION_NP:
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elision: __attribute__((unused))
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if (lll_trylock_elision (mutex->__data.__lock,
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mutex->__data.__elision) != 0)
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break;
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/* Don't record the ownership. */
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return 0;
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case PTHREAD_MUTEX_TIMED_NP:
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FORCE_ELISION (mutex, goto elision);
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/*FALL THROUGH*/
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case PTHREAD_MUTEX_ADAPTIVE_NP:
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case PTHREAD_MUTEX_ERRORCHECK_NP:
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if (lll_trylock (mutex->__data.__lock) != 0)
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break;
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/* Record the ownership. */
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mutex->__data.__owner = id;
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++mutex->__data.__nusers;
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return 0;
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case PTHREAD_MUTEX_ROBUST_RECURSIVE_NP:
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case PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP:
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case PTHREAD_MUTEX_ROBUST_NORMAL_NP:
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case PTHREAD_MUTEX_ROBUST_ADAPTIVE_NP:
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THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
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&mutex->__data.__list.__next);
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/* We need to set op_pending before starting the operation. Also
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see comments at ENQUEUE_MUTEX. */
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__asm ("" ::: "memory");
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oldval = mutex->__data.__lock;
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do
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{
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again:
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if ((oldval & FUTEX_OWNER_DIED) != 0)
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{
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/* The previous owner died. Try locking the mutex. */
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int newval = id | (oldval & FUTEX_WAITERS);
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newval
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= atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
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newval, oldval);
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if (newval != oldval)
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{
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oldval = newval;
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goto again;
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}
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/* We got the mutex. */
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mutex->__data.__count = 1;
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/* But it is inconsistent unless marked otherwise. */
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mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;
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/* We must not enqueue the mutex before we have acquired it.
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Also see comments at ENQUEUE_MUTEX. */
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__asm ("" ::: "memory");
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ENQUEUE_MUTEX (mutex);
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/* We need to clear op_pending after we enqueue the mutex. */
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__asm ("" ::: "memory");
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THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
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/* Note that we deliberately exit here. If we fall
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through to the end of the function __nusers would be
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incremented which is not correct because the old
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owner has to be discounted. */
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return EOWNERDEAD;
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}
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/* Check whether we already hold the mutex. */
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if (__glibc_unlikely ((oldval & FUTEX_TID_MASK) == id))
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{
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int kind = PTHREAD_MUTEX_TYPE (mutex);
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if (kind == PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP)
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{
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/* We do not need to ensure ordering wrt another memory
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access. Also see comments at ENQUEUE_MUTEX. */
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THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
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NULL);
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return EDEADLK;
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}
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if (kind == PTHREAD_MUTEX_ROBUST_RECURSIVE_NP)
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{
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/* We do not need to ensure ordering wrt another memory
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access. */
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THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
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NULL);
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/* Just bump the counter. */
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if (__glibc_unlikely (mutex->__data.__count + 1 == 0))
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/* Overflow of the counter. */
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return EAGAIN;
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++mutex->__data.__count;
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return 0;
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}
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}
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oldval = atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
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id, 0);
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if (oldval != 0 && (oldval & FUTEX_OWNER_DIED) == 0)
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{
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/* We haven't acquired the lock as it is already acquired by
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another owner. We do not need to ensure ordering wrt another
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memory access. */
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THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
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return EBUSY;
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}
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if (__builtin_expect (mutex->__data.__owner
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== PTHREAD_MUTEX_NOTRECOVERABLE, 0))
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{
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/* This mutex is now not recoverable. */
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mutex->__data.__count = 0;
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if (oldval == id)
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lll_unlock (mutex->__data.__lock,
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PTHREAD_ROBUST_MUTEX_PSHARED (mutex));
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/* FIXME This violates the mutex destruction requirements. See
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__pthread_mutex_unlock_full. */
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THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
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return ENOTRECOVERABLE;
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}
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}
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while ((oldval & FUTEX_OWNER_DIED) != 0);
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/* We must not enqueue the mutex before we have acquired it.
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Also see comments at ENQUEUE_MUTEX. */
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__asm ("" ::: "memory");
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ENQUEUE_MUTEX (mutex);
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/* We need to clear op_pending after we enqueue the mutex. */
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__asm ("" ::: "memory");
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THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
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mutex->__data.__owner = id;
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++mutex->__data.__nusers;
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mutex->__data.__count = 1;
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return 0;
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/* The PI support requires the Linux futex system call. If that's not
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available, pthread_mutex_init should never have allowed the type to
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be set. So it will get the default case for an invalid type. */
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#ifdef __NR_futex
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case PTHREAD_MUTEX_PI_RECURSIVE_NP:
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case PTHREAD_MUTEX_PI_ERRORCHECK_NP:
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case PTHREAD_MUTEX_PI_NORMAL_NP:
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case PTHREAD_MUTEX_PI_ADAPTIVE_NP:
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case PTHREAD_MUTEX_PI_ROBUST_RECURSIVE_NP:
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case PTHREAD_MUTEX_PI_ROBUST_ERRORCHECK_NP:
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case PTHREAD_MUTEX_PI_ROBUST_NORMAL_NP:
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case PTHREAD_MUTEX_PI_ROBUST_ADAPTIVE_NP:
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{
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int kind, robust;
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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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int mutex_kind = atomic_load_relaxed (&(mutex->__data.__kind));
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kind = mutex_kind & PTHREAD_MUTEX_KIND_MASK_NP;
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robust = mutex_kind & PTHREAD_MUTEX_ROBUST_NORMAL_NP;
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}
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if (robust)
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{
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/* Note: robust PI futexes are signaled by setting bit 0. */
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THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
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(void *) (((uintptr_t) &mutex->__data.__list.__next)
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| 1));
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/* We need to set op_pending before starting the operation. Also
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see comments at ENQUEUE_MUTEX. */
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__asm ("" ::: "memory");
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}
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oldval = mutex->__data.__lock;
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/* Check whether we already hold the mutex. */
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if (__glibc_unlikely ((oldval & FUTEX_TID_MASK) == id))
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{
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if (kind == PTHREAD_MUTEX_ERRORCHECK_NP)
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{
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/* We do not need to ensure ordering wrt another memory
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access. */
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THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
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return EDEADLK;
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}
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if (kind == PTHREAD_MUTEX_RECURSIVE_NP)
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{
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/* We do not need to ensure ordering wrt another memory
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access. */
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THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
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/* Just bump the counter. */
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if (__glibc_unlikely (mutex->__data.__count + 1 == 0))
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/* Overflow of the counter. */
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return EAGAIN;
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++mutex->__data.__count;
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return 0;
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}
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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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id, 0);
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if (oldval != 0)
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{
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if ((oldval & FUTEX_OWNER_DIED) == 0)
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{
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/* We haven't acquired the lock as it is already acquired by
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another owner. We do not need to ensure ordering wrt another
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memory access. */
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THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
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return EBUSY;
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}
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assert (robust);
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/* The mutex owner died. The kernel will now take care of
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everything. */
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int private = (robust
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? PTHREAD_ROBUST_MUTEX_PSHARED (mutex)
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: PTHREAD_MUTEX_PSHARED (mutex));
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int e = INTERNAL_SYSCALL_CALL (futex, &mutex->__data.__lock,
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__lll_private_flag (FUTEX_TRYLOCK_PI,
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private), 0, 0);
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if (INTERNAL_SYSCALL_ERROR_P (e)
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&& INTERNAL_SYSCALL_ERRNO (e) == EWOULDBLOCK)
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{
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/* The kernel has not yet finished the mutex owner death.
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We do not need to ensure ordering wrt another memory
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access. */
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THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
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return EBUSY;
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}
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oldval = mutex->__data.__lock;
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}
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if (__glibc_unlikely (oldval & FUTEX_OWNER_DIED))
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{
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atomic_and (&mutex->__data.__lock, ~FUTEX_OWNER_DIED);
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/* We got the mutex. */
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mutex->__data.__count = 1;
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/* But it is inconsistent unless marked otherwise. */
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mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;
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/* We must not enqueue the mutex before we have acquired it.
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Also see comments at ENQUEUE_MUTEX. */
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__asm ("" ::: "memory");
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ENQUEUE_MUTEX (mutex);
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/* We need to clear op_pending after we enqueue the mutex. */
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__asm ("" ::: "memory");
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THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
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/* Note that we deliberately exit here. If we fall
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through to the end of the function __nusers would be
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incremented which is not correct because the old owner
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has to be discounted. */
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return EOWNERDEAD;
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}
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if (robust
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&& __builtin_expect (mutex->__data.__owner
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== PTHREAD_MUTEX_NOTRECOVERABLE, 0))
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{
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/* This mutex is now not recoverable. */
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mutex->__data.__count = 0;
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futex_unlock_pi ((unsigned int *) &mutex->__data.__lock,
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PTHREAD_ROBUST_MUTEX_PSHARED (mutex));
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/* To the kernel, this will be visible after the kernel has
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acquired the mutex in the syscall. */
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THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
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return ENOTRECOVERABLE;
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}
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if (robust)
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{
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/* We must not enqueue the mutex before we have acquired it.
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Also see comments at ENQUEUE_MUTEX. */
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__asm ("" ::: "memory");
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ENQUEUE_MUTEX_PI (mutex);
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/* We need to clear op_pending after we enqueue the mutex. */
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__asm ("" ::: "memory");
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THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
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}
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mutex->__data.__owner = id;
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++mutex->__data.__nusers;
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mutex->__data.__count = 1;
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return 0;
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}
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#endif /* __NR_futex. */
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case PTHREAD_MUTEX_PP_RECURSIVE_NP:
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case PTHREAD_MUTEX_PP_ERRORCHECK_NP:
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case PTHREAD_MUTEX_PP_NORMAL_NP:
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case PTHREAD_MUTEX_PP_ADAPTIVE_NP:
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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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int kind = atomic_load_relaxed (&(mutex->__data.__kind))
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& PTHREAD_MUTEX_KIND_MASK_NP;
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oldval = mutex->__data.__lock;
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/* Check whether we already hold the mutex. */
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if (mutex->__data.__owner == id)
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{
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if (kind == PTHREAD_MUTEX_ERRORCHECK_NP)
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return EDEADLK;
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if (kind == PTHREAD_MUTEX_RECURSIVE_NP)
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{
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/* Just bump the counter. */
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if (__glibc_unlikely (mutex->__data.__count + 1 == 0))
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/* Overflow of the counter. */
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return EAGAIN;
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++mutex->__data.__count;
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return 0;
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}
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}
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int oldprio = -1, ceilval;
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do
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{
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int ceiling = (oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK)
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>> PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
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if (__pthread_current_priority () > ceiling)
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{
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if (oldprio != -1)
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__pthread_tpp_change_priority (oldprio, -1);
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return EINVAL;
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}
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int retval = __pthread_tpp_change_priority (oldprio, ceiling);
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if (retval)
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return retval;
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ceilval = ceiling << PTHREAD_MUTEX_PRIO_CEILING_SHIFT;
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oldprio = ceiling;
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oldval
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= 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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}
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while ((oldval & PTHREAD_MUTEX_PRIO_CEILING_MASK) != ceilval);
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if (oldval != ceilval)
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{
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__pthread_tpp_change_priority (oldprio, -1);
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break;
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}
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assert (mutex->__data.__owner == 0);
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/* Record the ownership. */
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mutex->__data.__owner = id;
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++mutex->__data.__nusers;
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mutex->__data.__count = 1;
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return 0;
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}
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break;
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default:
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/* Correct code cannot set any other type. */
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return EINVAL;
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}
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return EBUSY;
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}
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#ifndef __pthread_mutex_trylock
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#ifndef pthread_mutex_trylock
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weak_alias (__pthread_mutex_trylock, pthread_mutex_trylock)
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hidden_def (__pthread_mutex_trylock)
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#endif
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#endif
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