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/* Copyright (C) 2002, 2003, 2005, 2006 Free Software Foundation, Inc.
This file is part of the GNU C Library.
Contributed by Ulrich Drepper <drepper@redhat.com>, 2002.
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, write to the Free
Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
02111-1307 USA. */
#include <assert.h>
#include <errno.h>
#include <stdlib.h>
#include "pthreadP.h"
#include <lowlevellock.h>
int
__pthread_mutex_trylock (mutex)
pthread_mutex_t *mutex;
{
int oldval;
pid_t id = THREAD_GETMEM (THREAD_SELF, tid);
switch (__builtin_expect (mutex->__data.__kind, PTHREAD_MUTEX_TIMED_NP))
{
/* Recursive mutex. */
case PTHREAD_MUTEX_RECURSIVE_NP:
/* Check whether we already hold the mutex. */
if (mutex->__data.__owner == id)
{
/* Just bump the counter. */
if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
/* Overflow of the counter. */
return EAGAIN;
++mutex->__data.__count;
return 0;
}
if (lll_mutex_trylock (mutex->__data.__lock) == 0)
{
/* Record the ownership. */
mutex->__data.__owner = id;
mutex->__data.__count = 1;
++mutex->__data.__nusers;
return 0;
}
break;
case PTHREAD_MUTEX_ERRORCHECK_NP:
/* Check whether we already hold the mutex. */
if (__builtin_expect (mutex->__data.__owner == id, 0))
return EDEADLK;
/* FALLTHROUGH */
case PTHREAD_MUTEX_TIMED_NP:
case PTHREAD_MUTEX_ADAPTIVE_NP:
/* Normal mutex. */
if (lll_mutex_trylock (mutex->__data.__lock) != 0)
break;
/* Record the ownership. */
mutex->__data.__owner = id;
++mutex->__data.__nusers;
return 0;
case PTHREAD_MUTEX_ROBUST_RECURSIVE_NP:
case PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP:
case PTHREAD_MUTEX_ROBUST_NORMAL_NP:
case PTHREAD_MUTEX_ROBUST_ADAPTIVE_NP:
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
&mutex->__data.__list.__next);
oldval = mutex->__data.__lock;
do
{
again:
if ((oldval & FUTEX_OWNER_DIED) != 0)
{
/* The previous owner died. Try locking the mutex. */
int newval
= atomic_compare_and_exchange_val_acq (&mutex->__data.__lock,
id, oldval);
if (newval != oldval)
{
oldval = newval;
goto again;
}
/* We got the mutex. */
mutex->__data.__count = 1;
/* But it is inconsistent unless marked otherwise. */
mutex->__data.__owner = PTHREAD_MUTEX_INCONSISTENT;
ENQUEUE_MUTEX (mutex);
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
/* Note that we deliberately exist here. If we fall
through to the end of the function __nusers would be
incremented which is not correct because the old
owner has to be discounted. */
return EOWNERDEAD;
}
/* Check whether we already hold the mutex. */
if (__builtin_expect ((oldval & FUTEX_TID_MASK) == id, 0))
{
if (mutex->__data.__kind
== PTHREAD_MUTEX_ROBUST_ERRORCHECK_NP)
{
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
NULL);
return EDEADLK;
}
if (mutex->__data.__kind
== PTHREAD_MUTEX_ROBUST_RECURSIVE_NP)
{
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending,
NULL);
/* Just bump the counter. */
if (__builtin_expect (mutex->__data.__count + 1 == 0, 0))
/* Overflow of the counter. */
return EAGAIN;
++mutex->__data.__count;
return 0;
}
}
oldval = lll_robust_mutex_trylock (mutex->__data.__lock, id);
if (oldval != 0 && (oldval & FUTEX_OWNER_DIED) == 0)
{
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
return EBUSY;
}
robust:
if (__builtin_expect (mutex->__data.__owner
== PTHREAD_MUTEX_NOTRECOVERABLE, 0))
{
/* This mutex is now not recoverable. */
mutex->__data.__count = 0;
if (oldval == id)
lll_mutex_unlock (mutex->__data.__lock);
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
return ENOTRECOVERABLE;
}
}
while ((oldval & FUTEX_OWNER_DIED) != 0);
ENQUEUE_MUTEX (mutex);
THREAD_SETMEM (THREAD_SELF, robust_head.list_op_pending, NULL);
mutex->__data.__owner = id;
++mutex->__data.__nusers;
mutex->__data.__count = 1;
return 0;
default:
/* Correct code cannot set any other type. */
return EINVAL;
}
return EBUSY;
}
strong_alias (__pthread_mutex_trylock, pthread_mutex_trylock)
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