716154c592
Updated AUTHORS, COPYING, DISCLAIMER, and INSTALL files. Added standardized headers to all source file to clearly indicate the copyright, license, and to give credit where credit is due.
97 lines
2.9 KiB
C
97 lines
2.9 KiB
C
/*****************************************************************************\
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* Copyright (C) 2007-2010 Lawrence Livermore National Security, LLC.
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* Copyright (C) 2007 The Regents of the University of California.
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* Produced at Lawrence Livermore National Laboratory (cf, DISCLAIMER).
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* Written by Brian Behlendorf <behlendorf1@llnl.gov>.
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* UCRL-CODE-235197
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*
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* This file is part of the SPL, Solaris Porting Layer.
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* For details, see <http://github.com/behlendorf/spl/>.
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*
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* The SPL is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License as published by the
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* Free Software Foundation; either version 2 of the License, or (at your
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* option) any later version.
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*
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* The SPL is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* for more details.
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*
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* You should have received a copy of the GNU General Public License along
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* with the SPL. If not, see <http://www.gnu.org/licenses/>.
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*****************************************************************************
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* Solaris Porting Layer (SPL) Reader/Writer Lock Implementation.
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\*****************************************************************************/
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#include <sys/rwlock.h>
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#ifdef DEBUG_SUBSYSTEM
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#undef DEBUG_SUBSYSTEM
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#endif
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#define DEBUG_SUBSYSTEM S_RWLOCK
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#ifdef CONFIG_RWSEM_GENERIC_SPINLOCK
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/*
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* From lib/rwsem-spinlock.c but modified such that the caller is
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* responsible for acquiring and dropping the sem->wait_lock.
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*/
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struct rwsem_waiter {
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struct list_head list;
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struct task_struct *task;
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unsigned int flags;
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#define RWSEM_WAITING_FOR_READ 0x00000001
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#define RWSEM_WAITING_FOR_WRITE 0x00000002
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};
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/* wake a single writer */
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static struct rw_semaphore *
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__rwsem_wake_one_writer_locked(struct rw_semaphore *sem)
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{
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struct rwsem_waiter *waiter;
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struct task_struct *tsk;
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sem->activity = -1;
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waiter = list_entry(sem->wait_list.next, struct rwsem_waiter, list);
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list_del(&waiter->list);
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tsk = waiter->task;
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smp_mb();
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waiter->task = NULL;
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wake_up_process(tsk);
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put_task_struct(tsk);
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return sem;
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}
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/* release a read lock on the semaphore */
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void
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__up_read_locked(struct rw_semaphore *sem)
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{
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if (--sem->activity == 0 && !list_empty(&sem->wait_list))
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(void)__rwsem_wake_one_writer_locked(sem);
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}
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EXPORT_SYMBOL(__up_read_locked);
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/* trylock for writing -- returns 1 if successful, 0 if contention */
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int
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__down_write_trylock_locked(struct rw_semaphore *sem)
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{
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int ret = 0;
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if (sem->activity == 0 && list_empty(&sem->wait_list)) {
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sem->activity = -1;
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ret = 1;
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}
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return ret;
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}
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EXPORT_SYMBOL(__down_write_trylock_locked);
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#endif
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int spl_rw_init(void) { return 0; }
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void spl_rw_fini(void) { }
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