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/* Copyright (C) 2016 Free Software Foundation, Inc.
Contributed by Agustina Arzille <avarzille@riseup.net>, 2016.
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU Library General Public License
as published by the Free Software Foundation; either
version 2 of the license, or (at your option) any later version.
This program 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 Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with this program; if not, see
<http://www.gnu.org/licenses/>.
*/
#include <pthread.h>
#include <pt-internal.h>
#include <bits/pt-atomic.h>
#include <hurdlock.h>
#include "pt-rwlock.h"
int __pthread_rwlock_wrlock (pthread_rwlock_t *rwp)
{
int flags = rwp->__flags & GSYNC_SHARED;
unsigned int self_id = early_pthread_self();
if (rwl_owned_p (rwp, self_id, flags))
return (EDEADLK);
while (1)
{
unsigned int *ptr = &rwl_oid (rwp->__oid_nrd);
atomic_read_barrier ();
unsigned int owner = *ptr;
if (owner == RWLOCK_UNOWNED)
{
if (atomic_compare_and_exchange_bool_acq (ptr, self_id, owner) == 0)
{
rwl_setown (rwp, flags);
return (0);
}
}
else
{
/* Wait on the address. We are only interested in the value of
* the OID field, but we need a different queue for writers.
* As such, we use 64-bit values, with the high word being
* the owner id. */
unsigned int nw = atomic_exchange_and_add (--ptr, 1);
lll_xwait (ptr, nw + 1, owner, flags);
atomic_decrement (ptr);
}
}
}
strong_alias (__pthread_rwlock_wrlock, pthread_rwlock_wrlock)
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