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/* Acquire a rwlock for reading. Generic version.
Copyright (C) 2002, 2005 Free Software Foundation, Inc.
This file is part of the GNU C Library.
The GNU C Library 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.
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
Library General Public License for more details.
You should have received a copy of the GNU Library General Public
License along with the GNU C Library; see the file COPYING.LIB. If not,
write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330,
Boston, MA 02111-1307, USA. */
#include <pthread.h>
#include <assert.h>
#include <pt-internal.h>
/* Acquire the rwlock *RWLOCK for reading blocking until *ABSTIME if
it is already held. As a GNU extension, if TIMESPEC is NULL then
wait forever. */
int
__pthread_rwlock_timedrdlock_internal (struct __pthread_rwlock *rwlock,
const struct timespec *abstime)
{
struct __pthread *self;
__pthread_spin_lock (&rwlock->__lock);
if (__pthread_spin_trylock (&rwlock->__held) == 0)
/* Successfully acquired the lock. */
{
assert (rwlock->readerqueue == 0);
assert (rwlock->writerqueue == 0);
assert (rwlock->readers == 0);
rwlock->readers = 1;
__pthread_spin_unlock (&rwlock->__lock);
return 0;
}
else
/* Lock is held, but is held by a reader? */
if (rwlock->readers > 0)
/* Just add ourself to number of readers. */
{
assert (rwlock->readerqueue == 0);
rwlock->readers ++;
__pthread_spin_unlock (&rwlock->__lock);
return 0;
}
/* The lock is busy. */
/* Better be blocked by a writer. */
assert (rwlock->readers == 0);
if (abstime && (abstime->tv_nsec < 0 || abstime->tv_nsec >= 1000000000))
return EINVAL;
self = _pthread_self ();
/* Add ourself to the queue. */
__pthread_enqueue (&rwlock->readerqueue, self);
__pthread_spin_unlock (&rwlock->__lock);
/* Block the thread. */
if (abstime)
{
error_t err;
err = __pthread_timedblock (self, abstime);
if (err)
/* We timed out. We may need to disconnect ourself from the
waiter queue.
FIXME: What do we do if we get a wakeup message before we
disconnect ourself? It may remain until the next time we
block. */
{
assert (err == ETIMEDOUT);
__pthread_spin_lock (&rwlock->__lock);
if (self->prevp)
/* Disconnect ourself. */
__pthread_dequeue (self);
__pthread_spin_unlock (&rwlock->__lock);
return err;
}
}
else
__pthread_block (self);
/* The reader count has already been increment by whoever woke us
up. */
assert (rwlock->readers > 0);
return 0;
}
int
pthread_rwlock_timedrdlock (struct __pthread_rwlock *rwlock,
const struct timespec *abstime)
{
return __pthread_rwlock_timedrdlock_internal (rwlock, abstime);
}
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