2021-08-15 21:28:27 +00:00
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// SPDX-License-Identifier: GPL-2.0-only
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/*
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* PREEMPT_RT substitution for spin/rw_locks
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*
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* spinlocks and rwlocks on RT are based on rtmutexes, with a few twists to
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* resemble the non RT semantics:
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*
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* - Contrary to plain rtmutexes, spinlocks and rwlocks are state
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* preserving. The task state is saved before blocking on the underlying
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* rtmutex, and restored when the lock has been acquired. Regular wakeups
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* during that time are redirected to the saved state so no wake up is
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* missed.
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*
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* - Non RT spin/rwlocks disable preemption and eventually interrupts.
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* Disabling preemption has the side effect of disabling migration and
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* preventing RCU grace periods.
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*
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* The RT substitutions explicitly disable migration and take
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* rcu_read_lock() across the lock held section.
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*/
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#include <linux/spinlock.h>
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#include <linux/export.h>
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#define RT_MUTEX_BUILD_SPINLOCKS
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#include "rtmutex.c"
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static __always_inline void rtlock_lock(struct rt_mutex_base *rtm)
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{
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if (unlikely(!rt_mutex_cmpxchg_acquire(rtm, NULL, current)))
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rtlock_slowlock(rtm);
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}
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static __always_inline void __rt_spin_lock(spinlock_t *lock)
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{
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___might_sleep(__FILE__, __LINE__, 0);
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rtlock_lock(&lock->lock);
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rcu_read_lock();
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migrate_disable();
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}
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void __sched rt_spin_lock(spinlock_t *lock)
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{
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spin_acquire(&lock->dep_map, 0, 0, _RET_IP_);
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__rt_spin_lock(lock);
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}
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EXPORT_SYMBOL(rt_spin_lock);
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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void __sched rt_spin_lock_nested(spinlock_t *lock, int subclass)
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{
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spin_acquire(&lock->dep_map, subclass, 0, _RET_IP_);
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__rt_spin_lock(lock);
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}
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EXPORT_SYMBOL(rt_spin_lock_nested);
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void __sched rt_spin_lock_nest_lock(spinlock_t *lock,
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struct lockdep_map *nest_lock)
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{
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spin_acquire_nest(&lock->dep_map, 0, 0, nest_lock, _RET_IP_);
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__rt_spin_lock(lock);
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}
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EXPORT_SYMBOL(rt_spin_lock_nest_lock);
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#endif
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void __sched rt_spin_unlock(spinlock_t *lock)
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{
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spin_release(&lock->dep_map, _RET_IP_);
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migrate_enable();
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rcu_read_unlock();
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if (unlikely(!rt_mutex_cmpxchg_release(&lock->lock, current, NULL)))
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rt_mutex_slowunlock(&lock->lock);
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}
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EXPORT_SYMBOL(rt_spin_unlock);
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/*
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* Wait for the lock to get unlocked: instead of polling for an unlock
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* (like raw spinlocks do), lock and unlock, to force the kernel to
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* schedule if there's contention:
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*/
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void __sched rt_spin_lock_unlock(spinlock_t *lock)
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{
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spin_lock(lock);
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spin_unlock(lock);
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}
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EXPORT_SYMBOL(rt_spin_lock_unlock);
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static __always_inline int __rt_spin_trylock(spinlock_t *lock)
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{
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int ret = 1;
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if (unlikely(!rt_mutex_cmpxchg_acquire(&lock->lock, NULL, current)))
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ret = rt_mutex_slowtrylock(&lock->lock);
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if (ret) {
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spin_acquire(&lock->dep_map, 0, 1, _RET_IP_);
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rcu_read_lock();
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migrate_disable();
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}
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return ret;
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}
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int __sched rt_spin_trylock(spinlock_t *lock)
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{
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return __rt_spin_trylock(lock);
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}
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EXPORT_SYMBOL(rt_spin_trylock);
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int __sched rt_spin_trylock_bh(spinlock_t *lock)
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{
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int ret;
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local_bh_disable();
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ret = __rt_spin_trylock(lock);
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if (!ret)
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local_bh_enable();
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return ret;
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}
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EXPORT_SYMBOL(rt_spin_trylock_bh);
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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void __rt_spin_lock_init(spinlock_t *lock, const char *name,
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2021-08-15 21:29:27 +00:00
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struct lock_class_key *key, bool percpu)
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2021-08-15 21:28:27 +00:00
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{
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2021-08-15 21:29:27 +00:00
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u8 type = percpu ? LD_LOCK_PERCPU : LD_LOCK_NORMAL;
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2021-08-15 21:28:27 +00:00
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debug_check_no_locks_freed((void *)lock, sizeof(*lock));
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2021-08-15 21:29:27 +00:00
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lockdep_init_map_type(&lock->dep_map, name, key, 0, LD_WAIT_CONFIG,
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LD_WAIT_INV, type);
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2021-08-15 21:28:27 +00:00
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}
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EXPORT_SYMBOL(__rt_spin_lock_init);
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#endif
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2021-08-15 21:28:28 +00:00
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/*
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* RT-specific reader/writer locks
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*/
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#define rwbase_set_and_save_current_state(state) \
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current_save_and_set_rtlock_wait_state()
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#define rwbase_restore_current_state() \
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current_restore_rtlock_saved_state()
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static __always_inline int
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rwbase_rtmutex_lock_state(struct rt_mutex_base *rtm, unsigned int state)
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{
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if (unlikely(!rt_mutex_cmpxchg_acquire(rtm, NULL, current)))
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rtlock_slowlock(rtm);
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return 0;
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}
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static __always_inline int
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rwbase_rtmutex_slowlock_locked(struct rt_mutex_base *rtm, unsigned int state)
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{
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rtlock_slowlock_locked(rtm);
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return 0;
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}
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static __always_inline void rwbase_rtmutex_unlock(struct rt_mutex_base *rtm)
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{
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if (likely(rt_mutex_cmpxchg_acquire(rtm, current, NULL)))
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return;
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rt_mutex_slowunlock(rtm);
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}
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static __always_inline int rwbase_rtmutex_trylock(struct rt_mutex_base *rtm)
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{
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if (likely(rt_mutex_cmpxchg_acquire(rtm, NULL, current)))
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return 1;
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return rt_mutex_slowtrylock(rtm);
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}
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#define rwbase_signal_pending_state(state, current) (0)
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#define rwbase_schedule() \
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schedule_rtlock()
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#include "rwbase_rt.c"
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/*
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* The common functions which get wrapped into the rwlock API.
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*/
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int __sched rt_read_trylock(rwlock_t *rwlock)
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{
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int ret;
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ret = rwbase_read_trylock(&rwlock->rwbase);
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if (ret) {
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rwlock_acquire_read(&rwlock->dep_map, 0, 1, _RET_IP_);
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rcu_read_lock();
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migrate_disable();
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}
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return ret;
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}
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EXPORT_SYMBOL(rt_read_trylock);
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int __sched rt_write_trylock(rwlock_t *rwlock)
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{
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int ret;
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ret = rwbase_write_trylock(&rwlock->rwbase);
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if (ret) {
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rwlock_acquire(&rwlock->dep_map, 0, 1, _RET_IP_);
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rcu_read_lock();
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migrate_disable();
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}
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return ret;
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}
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EXPORT_SYMBOL(rt_write_trylock);
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void __sched rt_read_lock(rwlock_t *rwlock)
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{
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___might_sleep(__FILE__, __LINE__, 0);
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rwlock_acquire_read(&rwlock->dep_map, 0, 0, _RET_IP_);
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rwbase_read_lock(&rwlock->rwbase, TASK_RTLOCK_WAIT);
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rcu_read_lock();
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migrate_disable();
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}
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EXPORT_SYMBOL(rt_read_lock);
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void __sched rt_write_lock(rwlock_t *rwlock)
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{
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___might_sleep(__FILE__, __LINE__, 0);
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rwlock_acquire(&rwlock->dep_map, 0, 0, _RET_IP_);
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rwbase_write_lock(&rwlock->rwbase, TASK_RTLOCK_WAIT);
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rcu_read_lock();
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migrate_disable();
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}
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EXPORT_SYMBOL(rt_write_lock);
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void __sched rt_read_unlock(rwlock_t *rwlock)
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{
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rwlock_release(&rwlock->dep_map, _RET_IP_);
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migrate_enable();
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rcu_read_unlock();
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rwbase_read_unlock(&rwlock->rwbase, TASK_RTLOCK_WAIT);
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}
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EXPORT_SYMBOL(rt_read_unlock);
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void __sched rt_write_unlock(rwlock_t *rwlock)
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{
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rwlock_release(&rwlock->dep_map, _RET_IP_);
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rcu_read_unlock();
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migrate_enable();
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rwbase_write_unlock(&rwlock->rwbase);
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}
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EXPORT_SYMBOL(rt_write_unlock);
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int __sched rt_rwlock_is_contended(rwlock_t *rwlock)
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{
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return rw_base_is_contended(&rwlock->rwbase);
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}
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EXPORT_SYMBOL(rt_rwlock_is_contended);
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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void __rt_rwlock_init(rwlock_t *rwlock, const char *name,
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struct lock_class_key *key)
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{
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debug_check_no_locks_freed((void *)rwlock, sizeof(*rwlock));
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lockdep_init_map_wait(&rwlock->dep_map, name, key, 0, LD_WAIT_CONFIG);
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}
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EXPORT_SYMBOL(__rt_rwlock_init);
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#endif
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