309 lines
8.1 KiB
C
309 lines
8.1 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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#elif defined(RWSEM_ACTIVE_MASK)
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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_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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static inline int
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RW_READ_HELD(krwlock_t *rwp)
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{
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if (!RW_LOCK_HELD(rwp))
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return (0);
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/*
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* rw_semaphore cheat sheet:
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*
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* < 3.16:
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* There's no rw_semaphore.owner, so use rwp.owner instead.
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* If rwp.owner == NULL then it's a reader
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*
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* 3.16 - 4.7:
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* rw_semaphore.owner added (https://lwn.net/Articles/596656/)
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* and CONFIG_RWSEM_SPIN_ON_OWNER introduced.
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* If rw_semaphore.owner == NULL then it's a reader
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*
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* 4.8 - 4.16.16:
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* RWSEM_READER_OWNED added as an internal #define.
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* (https://lore.kernel.org/patchwork/patch/678590/)
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* If rw_semaphore.owner == 1 then it's a reader
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*
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* 4.16.17 - 4.19:
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* RWSEM_OWNER_UNKNOWN introduced as ((struct task_struct *)-1L)
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* (https://do-db2.lkml.org/lkml/2018/5/15/985)
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* If rw_semaphore.owner == 1 then it's a reader.
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*
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* 4.20+:
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* RWSEM_OWNER_UNKNOWN changed to ((struct task_struct *)-2L)
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* (https://lkml.org/lkml/2018/9/6/986)
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* If rw_semaphore.owner & 1 then it's a reader, and also the reader's
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* task_struct may be embedded in rw_semaphore->owner.
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*/
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#if defined(CONFIG_RWSEM_SPIN_ON_OWNER) && defined(RWSEM_OWNER_UNKNOWN)
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if (RWSEM_OWNER_UNKNOWN == (struct task_struct *)-2L) {
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/* 4.20+ kernels with CONFIG_RWSEM_SPIN_ON_OWNER */
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return ((unsigned long) SEM(rwp)->owner & 1);
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}
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#endif
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/* < 4.20 kernel or !CONFIG_RWSEM_SPIN_ON_OWNER */
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return (rw_owner(rwp) == NULL || (unsigned long) rw_owner(rwp) == 1);
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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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