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For kernels using the CONFIG_RWSEM_GENERIC_SPINLOCK implementation nothing has changed. But if your kernel is building with arch specific rwsems rw_tryupgrade() has been disabled until it can be implemented correctly. In particular, the x86 implementation now leverages atomic primatives for serialization rather than spinlocks. So to get this working again it will need to be implemented as a cmpxchg for x86 and likely something similiar for other arches we are interested in. For now it's safest to simply disable it.
256 lines
9.8 KiB
C
256 lines
9.8 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) 2009 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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#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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/*
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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 will be
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* required so RW_COUNT() provides these semantics:
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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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#define SEM(rwp) ((struct rw_semaphore *)(rwp))
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#if defined(CONFIG_RWSEM_GENERIC_SPINLOCK)
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# define RW_COUNT(rwp) (SEM(rwp)->activity)
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# define rw_exit_locked(rwp) __up_read_locked(rwp)
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# define rw_tryenter_locked(rwp) __down_write_trylock_locked(rwp)
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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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#else
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/*
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* 2.6.x - 2.6.27 use guard macro _I386_RWSEM_H
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* 2.6.28 - 2.6.32+ use guard macro _ASM_X86_RWSEM_H
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*/
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# if defined(_I386_RWSEM_H) || defined(_ASM_X86_RWSEM_H)
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# define RW_COUNT(rwp) ((SEM(rwp)->count < 0) ? (-1) : \
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(SEM(rwp)->count & RWSEM_ACTIVE_MASK))
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# else
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# define RW_COUNT(rwp) (SEM(rwp)->count & RWSEM_ACTIVE_MASK)
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# endif
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# define rw_exit_locked(rwp) up_read(rwp)
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# define rw_tryenter_locked(rwp) down_write_trylock(rwp)
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#endif
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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 = ((RW_COUNT(rwp) > 0) && (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 = ((RW_COUNT(rwp) < 0) && (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 = (RW_COUNT(rwp) != 0);
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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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#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) && (RW_COUNT(rwp) == 1)) { \
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rw_exit_locked(SEM(rwp)); \
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VERIFY(_rc_ = rw_tryenter_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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* This can be done correctly but for each supported arch we will need
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* a custom cmpxchg() to atomically check and promote the rwsem. That's
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* not worth the trouble for now so rw_tryupgrade() will always fail.
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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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