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The RT rwsem implementation was changed to allow multiple readers as of the 4.9.20-rt16 patch set. This results in a build failure because the existing implementation was forced to directly access the rwsem structure which has changed. While this could be accommodated by adding additional compatibility code. This patch resolves the build issue by simply assuming the rwsem can never be upgraded. This functionality is a performance optimization and all callers must already handle this case. Converting the last remaining use of __SPIN_LOCK_UNLOCKED to spin_lock_init() was additionally required to get a clean build. Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov> Closes #7589
275 lines
7.0 KiB
C
275 lines
7.0 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://zfsonlinux.org/>.
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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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#include <linux/sched.h>
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/* Linux kernel compatibility */
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#if defined(CONFIG_PREEMPT_RT_FULL)
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#define SPL_RWSEM_SINGLE_READER_VALUE (1)
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#define SPL_RWSEM_SINGLE_WRITER_VALUE (0)
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#elif defined(CONFIG_RWSEM_GENERIC_SPINLOCK)
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#define SPL_RWSEM_SINGLE_READER_VALUE (1)
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#define SPL_RWSEM_SINGLE_WRITER_VALUE (-1)
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#else
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#define SPL_RWSEM_SINGLE_READER_VALUE (RWSEM_ACTIVE_READ_BIAS)
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#define SPL_RWSEM_SINGLE_WRITER_VALUE (RWSEM_ACTIVE_WRITE_BIAS)
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#endif
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/* Linux 3.16 changed activity to count for rwsem-spinlock */
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#if defined(CONFIG_PREEMPT_RT_FULL)
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#define RWSEM_COUNT(sem) sem->read_depth
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#elif defined(HAVE_RWSEM_ACTIVITY)
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#define RWSEM_COUNT(sem) sem->activity
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/* Linux 4.8 changed count to an atomic_long_t for !rwsem-spinlock */
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#elif defined(HAVE_RWSEM_ATOMIC_LONG_COUNT)
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#define RWSEM_COUNT(sem) atomic_long_read(&(sem)->count)
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#else
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#define RWSEM_COUNT(sem) sem->count
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#endif
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#if defined(RWSEM_SPINLOCK_IS_RAW)
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#define spl_rwsem_lock_irqsave(lk, fl) raw_spin_lock_irqsave(lk, fl)
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#define spl_rwsem_unlock_irqrestore(lk, fl) \
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raw_spin_unlock_irqrestore(lk, fl)
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#define spl_rwsem_trylock_irqsave(lk, fl) raw_spin_trylock_irqsave(lk, fl)
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#else
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#define spl_rwsem_lock_irqsave(lk, fl) spin_lock_irqsave(lk, fl)
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#define spl_rwsem_unlock_irqrestore(lk, fl) spin_unlock_irqrestore(lk, fl)
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#define spl_rwsem_trylock_irqsave(lk, fl) spin_trylock_irqsave(lk, fl)
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#endif /* RWSEM_SPINLOCK_IS_RAW */
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#define spl_rwsem_is_locked(rwsem) rwsem_is_locked(rwsem)
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typedef enum {
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RW_DRIVER = 2,
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RW_DEFAULT = 4,
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RW_NOLOCKDEP = 5
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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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/*
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* If CONFIG_RWSEM_SPIN_ON_OWNER is defined, rw_semaphore will have an owner
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* field, so we don't need our own.
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*/
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typedef struct {
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struct rw_semaphore rw_rwlock;
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#ifndef CONFIG_RWSEM_SPIN_ON_OWNER
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kthread_t *rw_owner;
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#endif
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#ifdef CONFIG_LOCKDEP
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krw_type_t rw_type;
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#endif /* CONFIG_LOCKDEP */
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} krwlock_t;
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#define SEM(rwp) (&(rwp)->rw_rwlock)
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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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/*
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* If CONFIG_RWSEM_SPIN_ON_OWNER is defined, down_write, up_write,
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* downgrade_write and __init_rwsem will set/clear owner for us.
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*/
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#ifndef CONFIG_RWSEM_SPIN_ON_OWNER
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rwp->rw_owner = current;
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#endif
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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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#ifndef CONFIG_RWSEM_SPIN_ON_OWNER
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rwp->rw_owner = NULL;
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#endif
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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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#ifdef CONFIG_RWSEM_SPIN_ON_OWNER
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return (SEM(rwp)->owner);
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#else
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return (rwp->rw_owner);
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#endif
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}
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#ifdef CONFIG_LOCKDEP
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static inline void
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spl_rw_set_type(krwlock_t *rwp, krw_type_t type)
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{
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rwp->rw_type = type;
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}
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static inline void
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spl_rw_lockdep_off_maybe(krwlock_t *rwp) \
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{ \
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if (rwp && rwp->rw_type == RW_NOLOCKDEP) \
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lockdep_off(); \
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}
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static inline void
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spl_rw_lockdep_on_maybe(krwlock_t *rwp) \
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{ \
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if (rwp && rwp->rw_type == RW_NOLOCKDEP) \
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lockdep_on(); \
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}
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#else /* CONFIG_LOCKDEP */
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#define spl_rw_set_type(rwp, type)
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#define spl_rw_lockdep_off_maybe(rwp)
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#define spl_rw_lockdep_on_maybe(rwp)
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#endif /* CONFIG_LOCKDEP */
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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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/*
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* Linux 4.8 will set owner to 1 when read held instead of leave it
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* NULL. So we check whether owner <= 1.
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*/
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return (spl_rwsem_is_locked(SEM(rwp)) &&
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(unsigned long)rw_owner(rwp) <= 1);
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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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return (rw_owner(rwp) == current);
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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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return (spl_rwsem_is_locked(SEM(rwp)));
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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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/* BEGIN CSTYLED */
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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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ASSERT(type == RW_DEFAULT || type == RW_NOLOCKDEP); \
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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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spl_rw_set_type(rwp, type); \
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})
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/*
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* The Linux rwsem implementation does not require a matching destroy.
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*/
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#define rw_destroy(rwp) ((void) 0)
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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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spl_rw_lockdep_off_maybe(rwp); \
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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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VERIFY(0); \
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} \
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spl_rw_lockdep_on_maybe(rwp); \
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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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spl_rw_lockdep_off_maybe(rwp); \
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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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VERIFY(0); \
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} \
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spl_rw_lockdep_on_maybe(rwp); \
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})
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#define rw_exit(rwp) \
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({ \
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spl_rw_lockdep_off_maybe(rwp); \
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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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spl_rw_lockdep_on_maybe(rwp); \
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})
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#define rw_downgrade(rwp) \
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({ \
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spl_rw_lockdep_off_maybe(rwp); \
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spl_rw_clear_owner(rwp); \
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downgrade_write(SEM(rwp)); \
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spl_rw_lockdep_on_maybe(rwp); \
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})
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#define rw_tryupgrade(rwp) \
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({ \
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int _rc_ = 0; \
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\
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if (RW_WRITE_HELD(rwp)) { \
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_rc_ = 1; \
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} else { \
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spl_rw_lockdep_off_maybe(rwp); \
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if ((_rc_ = rwsem_tryupgrade(SEM(rwp)))) \
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spl_rw_set_owner(rwp); \
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spl_rw_lockdep_on_maybe(rwp); \
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} \
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_rc_; \
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})
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/* END CSTYLED */
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int spl_rw_init(void);
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void spl_rw_fini(void);
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int rwsem_tryupgrade(struct rw_semaphore *rwsem);
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#endif /* _SPL_RWLOCK_H */
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