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/*****************************************************************************\
* Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
* Copyright (C) 2007 The Regents of the University of California.
* Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
* Written by Brian Behlendorf <behlendorf1@llnl.gov>.
* UCRL-CODE-235197
*
* This file is part of the SPL, Solaris Porting Layer.
* For details, see <http://zfsonlinux.org/>.
*
* The SPL is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
* Free Software Foundation; either version 2 of the License, or (at your
* option) any later version.
*
* The SPL 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 General Public License
* for more details.
*
* You should have received a copy of the GNU General Public License along
* with the SPL. If not, see <http://www.gnu.org/licenses/>.
*****************************************************************************
* Solaris Porting Layer (SPL) Reader/Writer Lock Implementation.
\*****************************************************************************/
#include <sys/rwlock.h>
#ifdef DEBUG_SUBSYSTEM
#undef DEBUG_SUBSYSTEM
#endif
#define DEBUG_SUBSYSTEM S_RWLOCK
#ifdef CONFIG_RWSEM_GENERIC_SPINLOCK
/*
* From lib/rwsem-spinlock.c but modified such that the caller is
* responsible for acquiring and dropping the sem->wait_lock.
*/
struct rwsem_waiter {
struct list_head list;
struct task_struct *task;
unsigned int flags;
#define RWSEM_WAITING_FOR_READ 0x00000001
#define RWSEM_WAITING_FOR_WRITE 0x00000002
};
/* wake a single writer */
static struct rw_semaphore *
__rwsem_wake_one_writer_locked(struct rw_semaphore *sem)
{
struct rwsem_waiter *waiter;
struct task_struct *tsk;
sem->activity = -1;
waiter = list_entry(sem->wait_list.next, struct rwsem_waiter, list);
list_del(&waiter->list);
tsk = waiter->task;
smp_mb();
waiter->task = NULL;
wake_up_process(tsk);
put_task_struct(tsk);
return sem;
}
/* release a read lock on the semaphore */
void
__up_read_locked(struct rw_semaphore *sem)
{
if (--sem->activity == 0 && !list_empty(&sem->wait_list))
(void)__rwsem_wake_one_writer_locked(sem);
}
EXPORT_SYMBOL(__up_read_locked);
/* trylock for writing -- returns 1 if successful, 0 if contention */
int
__down_write_trylock_locked(struct rw_semaphore *sem)
{
int ret = 0;
if (sem->activity == 0 && list_empty(&sem->wait_list)) {
sem->activity = -1;
ret = 1;
}
return ret;
}
EXPORT_SYMBOL(__down_write_trylock_locked);
#endif
int spl_rw_init(void) { return 0; }
void spl_rw_fini(void) { }
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