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