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32f5faff69
Remove RW_COUNT() from the rwlock implementation. The idea was that it could be used as a generic wrapper for getting at the internal state of a rwlock. While a good idea it's proven problematic to keep it correct for multiple archs and internal implementation changes. In short it hasn't been worth the trouble. With that and simplicity in mind things have been updated to use the rwsem_is_locked() function instead of RW_COUNT for the RW_*_HELD() functions. As for rw_upgrade() it remains only implemented for the generic rwsem implemenation. It remains to be determined if its worth the effort of adding a custom implementation for each arch.
239 lines
9.3 KiB
C
239 lines
9.3 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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#ifndef _SPL_RWLOCK_H
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#define _SPL_RWLOCK_H
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#include <sys/types.h>
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#include <linux/rwsem.h>
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typedef enum {
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RW_DRIVER = 2,
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RW_DEFAULT = 4
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} krw_type_t;
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typedef enum {
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RW_NONE = 0,
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RW_WRITER = 1,
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RW_READER = 2
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} krw_t;
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typedef struct {
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struct rw_semaphore rw_rwlock;
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kthread_t *rw_owner;
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} krwlock_t;
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#define SEM(rwp) ((struct rw_semaphore *)(rwp))
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static inline kthread_t *
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spl_rw_get_owner(krwlock_t *rwp)
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{
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return rwp->rw_owner;
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}
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static inline void
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spl_rw_set_owner(krwlock_t *rwp)
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{
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unsigned long flags;
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spin_lock_irqsave(&SEM(rwp)->wait_lock, flags);
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rwp->rw_owner = current;
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spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
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}
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static inline void
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spl_rw_clear_owner(krwlock_t *rwp)
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{
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unsigned long flags;
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spin_lock_irqsave(&SEM(rwp)->wait_lock, flags);
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rwp->rw_owner = NULL;
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spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
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}
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static inline kthread_t *
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rw_owner(krwlock_t *rwp)
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{
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unsigned long flags;
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kthread_t *owner;
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spin_lock_irqsave(&SEM(rwp)->wait_lock, flags);
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owner = spl_rw_get_owner(rwp);
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spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
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return owner;
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}
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static inline int
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RW_READ_HELD(krwlock_t *rwp)
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{
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unsigned long flags;
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int rc;
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spin_lock_irqsave(&SEM(rwp)->wait_lock, flags);
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rc = (rwsem_is_locked(SEM(rwp)) && spl_rw_get_owner(rwp) == NULL);
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spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
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return rc;
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}
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static inline int
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RW_WRITE_HELD(krwlock_t *rwp)
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{
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unsigned long flags;
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int rc;
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spin_lock_irqsave(&SEM(rwp)->wait_lock, flags);
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rc = (rwsem_is_locked(SEM(rwp)) && spl_rw_get_owner(rwp) == current);
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spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
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return rc;
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}
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static inline int
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RW_LOCK_HELD(krwlock_t *rwp)
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{
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unsigned long flags;
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int rc;
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spin_lock_irqsave(&SEM(rwp)->wait_lock, flags);
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rc = rwsem_is_locked(SEM(rwp));
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spin_unlock_irqrestore(&SEM(rwp)->wait_lock, flags);
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return rc;
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}
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/*
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* The following functions must be a #define and not static inline.
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* This ensures that the native linux semaphore functions (down/up)
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* will be correctly located in the users code which is important
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* for the built in kernel lock analysis tools
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*/
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#define rw_init(rwp, name, type, arg) \
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({ \
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static struct lock_class_key __key; \
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\
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__init_rwsem(SEM(rwp), #rwp, &__key); \
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spl_rw_clear_owner(rwp); \
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})
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#define rw_destroy(rwp) \
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({ \
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VERIFY(!RW_LOCK_HELD(rwp)); \
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})
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#define rw_tryenter(rwp, rw) \
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({ \
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int _rc_ = 0; \
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\
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switch (rw) { \
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case RW_READER: \
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_rc_ = down_read_trylock(SEM(rwp)); \
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break; \
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case RW_WRITER: \
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if ((_rc_ = down_write_trylock(SEM(rwp)))) \
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spl_rw_set_owner(rwp); \
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break; \
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default: \
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SBUG(); \
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} \
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_rc_; \
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})
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#define rw_enter(rwp, rw) \
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({ \
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switch (rw) { \
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case RW_READER: \
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down_read(SEM(rwp)); \
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break; \
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case RW_WRITER: \
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down_write(SEM(rwp)); \
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spl_rw_set_owner(rwp); \
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break; \
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default: \
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SBUG(); \
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} \
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})
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#define rw_exit(rwp) \
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({ \
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if (RW_WRITE_HELD(rwp)) { \
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spl_rw_clear_owner(rwp); \
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up_write(SEM(rwp)); \
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} else { \
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ASSERT(RW_READ_HELD(rwp)); \
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up_read(SEM(rwp)); \
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} \
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})
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#define rw_downgrade(rwp) \
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({ \
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spl_rw_clear_owner(rwp); \
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downgrade_write(SEM(rwp)); \
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})
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#if defined(CONFIG_RWSEM_GENERIC_SPINLOCK)
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/*
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* For the generic implementations of rw-semaphores the following is
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* true. If your semaphore implementation internally represents the
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* semaphore state differently then special case handling is required.
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* - if activity/count is 0 then there are no active readers or writers
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* - if activity/count is +ve then that is the number of active readers
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* - if activity/count is -1 then there is one active writer
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*/
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extern void __up_read_locked(struct rw_semaphore *);
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extern int __down_write_trylock_locked(struct rw_semaphore *);
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#define rw_tryupgrade(rwp) \
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({ \
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unsigned long _flags_; \
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int _rc_ = 0; \
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\
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spin_lock_irqsave(&SEM(rwp)->wait_lock, _flags_); \
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if ((list_empty(&SEM(rwp)->wait_list)) && \
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(SEM(rwp)->activity == 1)) { \
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__up_read_locked(SEM(rwp)); \
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VERIFY(_rc_ = __down_write_trylock_locked(SEM(rwp))); \
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(rwp)->rw_owner = current; \
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} \
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spin_unlock_irqrestore(&SEM(rwp)->wait_lock, _flags_); \
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_rc_; \
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})
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#else
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/*
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* rw_tryupgrade() can be implemented correctly but for each supported
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* arch we will need a custom implementation. For the x86 implementation
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* it looks like a custom cmpxchg() to atomically check and promote the
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* rwsem would be safe. For now that's not worth the trouble so in this
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* case rw_tryupgrade() has just been disabled.
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*/
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#define rw_tryupgrade(rwp) ({ 0; })
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#endif
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int spl_rw_init(void);
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void spl_rw_fini(void);
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#endif /* _SPL_RWLOCK_H */
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