97 lines
2.7 KiB
C
97 lines
2.7 KiB
C
/*
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* This file is part of the SPL: Solaris Porting Layer.
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*
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* Copyright (c) 2008 Lawrence Livermore National Security, LLC.
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* Produced at Lawrence Livermore National Laboratory
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* Written by:
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* Brian Behlendorf <behlendorf1@llnl.gov>,
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* Herb Wartens <wartens2@llnl.gov>,
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* Jim Garlick <garlick@llnl.gov>
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* UCRL-CODE-235197
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*
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* This 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
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This 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 this program; if not, write to the Free Software Foundation, Inc.,
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* 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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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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