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Commit ddb6c9b5 authored by Thomas Gleixner's avatar Thomas Gleixner Committed by Ingo Molnar
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locking, rwsem: Annotate inner lock as raw 



There is no reason to allow the lock protecting rwsems (the
ownerless variant) to be preemptible on -rt. Convert it to raw.

In mainline this change documents the low level nature of
the lock - otherwise there's no functional difference. Lockdep
and Sparse checking will work as usual.

Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 8292c9e1

include/linux/rwsem-spinlock.h

+1 −1
Original line number Diff line number Diff line
@@ -22,7 +22,7 @@ 
 */

struct rw_semaphore {

	__s32			activity;

	spinlock_t		wait_lock;

	raw_spinlock_t		wait_lock;

	struct list_head	wait_list;

#ifdef CONFIG_DEBUG_LOCK_ALLOC

	struct lockdep_map dep_map;

include/linux/rwsem.h

+6 −4
Original line number Diff line number Diff line
@@ -25,7 +25,7 @@ struct rw_semaphore; 
/* All arch specific implementations share the same struct */

struct rw_semaphore {

	long			count;

	spinlock_t		wait_lock;

	raw_spinlock_t		wait_lock;

	struct list_head	wait_list;

#ifdef CONFIG_DEBUG_LOCK_ALLOC

	struct lockdep_map	dep_map;
@@ -57,8 +57,10 @@ static inline int rwsem_is_locked(struct rw_semaphore *sem) 
#endif



#define __RWSEM_INITIALIZER(name)			\

	{ RWSEM_UNLOCKED_VALUE, __SPIN_LOCK_UNLOCKED(name.wait_lock),	\

	  LIST_HEAD_INIT((name).wait_list) __RWSEM_DEP_MAP_INIT(name) }

	{ RWSEM_UNLOCKED_VALUE,				\

	  __RAW_SPIN_LOCK_UNLOCKED(name.wait_lock),	\

	  LIST_HEAD_INIT((name).wait_list)		\

	  __RWSEM_DEP_MAP_INIT(name) }



#define DECLARE_RWSEM(name) \

	struct rw_semaphore name = __RWSEM_INITIALIZER(name)

lib/rwsem-spinlock.c

+19 −19
Original line number Diff line number Diff line
@@ -22,9 +22,9 @@ int rwsem_is_locked(struct rw_semaphore *sem) 
	int ret = 1;

	unsigned long flags;



	if (spin_trylock_irqsave(&sem->wait_lock, flags)) {

	if (raw_spin_trylock_irqsave(&sem->wait_lock, flags)) {

		ret = (sem->activity != 0);

		spin_unlock_irqrestore(&sem->wait_lock, flags);

		raw_spin_unlock_irqrestore(&sem->wait_lock, flags);

	}

	return ret;

}
@@ -44,7 +44,7 @@ void __init_rwsem(struct rw_semaphore *sem, const char *name, 
	lockdep_init_map(&sem->dep_map, name, key, 0);

#endif

	sem->activity = 0;

	spin_lock_init(&sem->wait_lock);

	raw_spin_lock_init(&sem->wait_lock);

	INIT_LIST_HEAD(&sem->wait_list);

}

EXPORT_SYMBOL(__init_rwsem);
@@ -145,12 +145,12 @@ void __sched __down_read(struct rw_semaphore *sem) 
	struct task_struct *tsk;

	unsigned long flags;



	spin_lock_irqsave(&sem->wait_lock, flags);

	raw_spin_lock_irqsave(&sem->wait_lock, flags);



	if (sem->activity >= 0 && list_empty(&sem->wait_list)) {

		/* granted */

		sem->activity++;

		spin_unlock_irqrestore(&sem->wait_lock, flags);

		raw_spin_unlock_irqrestore(&sem->wait_lock, flags);

		goto out;

	}
@@ -165,7 +165,7 @@ void __sched __down_read(struct rw_semaphore *sem) 
	list_add_tail(&waiter.list, &sem->wait_list);



	/* we don't need to touch the semaphore struct anymore */

	spin_unlock_irqrestore(&sem->wait_lock, flags);

	raw_spin_unlock_irqrestore(&sem->wait_lock, flags);



	/* wait to be given the lock */

	for (;;) {
@@ -189,7 +189,7 @@ int __down_read_trylock(struct rw_semaphore *sem) 
	int ret = 0;





	spin_lock_irqsave(&sem->wait_lock, flags);

	raw_spin_lock_irqsave(&sem->wait_lock, flags);



	if (sem->activity >= 0 && list_empty(&sem->wait_list)) {

		/* granted */
@@ -197,7 +197,7 @@ int __down_read_trylock(struct rw_semaphore *sem) 
		ret = 1;

	}



	spin_unlock_irqrestore(&sem->wait_lock, flags);

	raw_spin_unlock_irqrestore(&sem->wait_lock, flags);



	return ret;

}
@@ -212,12 +212,12 @@ void __sched __down_write_nested(struct rw_semaphore *sem, int subclass) 
	struct task_struct *tsk;

	unsigned long flags;



	spin_lock_irqsave(&sem->wait_lock, flags);

	raw_spin_lock_irqsave(&sem->wait_lock, flags);



	if (sem->activity == 0 && list_empty(&sem->wait_list)) {

		/* granted */

		sem->activity = -1;

		spin_unlock_irqrestore(&sem->wait_lock, flags);

		raw_spin_unlock_irqrestore(&sem->wait_lock, flags);

		goto out;

	}
@@ -232,7 +232,7 @@ void __sched __down_write_nested(struct rw_semaphore *sem, int subclass) 
	list_add_tail(&waiter.list, &sem->wait_list);



	/* we don't need to touch the semaphore struct anymore */

	spin_unlock_irqrestore(&sem->wait_lock, flags);

	raw_spin_unlock_irqrestore(&sem->wait_lock, flags);



	/* wait to be given the lock */

	for (;;) {
@@ -260,7 +260,7 @@ int __down_write_trylock(struct rw_semaphore *sem) 
	unsigned long flags;

	int ret = 0;



	spin_lock_irqsave(&sem->wait_lock, flags);

	raw_spin_lock_irqsave(&sem->wait_lock, flags);



	if (sem->activity == 0 && list_empty(&sem->wait_list)) {

		/* granted */
@@ -268,7 +268,7 @@ int __down_write_trylock(struct rw_semaphore *sem) 
		ret = 1;

	}



	spin_unlock_irqrestore(&sem->wait_lock, flags);

	raw_spin_unlock_irqrestore(&sem->wait_lock, flags);



	return ret;

}
@@ -280,12 +280,12 @@ void __up_read(struct rw_semaphore *sem) 
{

	unsigned long flags;



	spin_lock_irqsave(&sem->wait_lock, flags);

	raw_spin_lock_irqsave(&sem->wait_lock, flags);



	if (--sem->activity == 0 && !list_empty(&sem->wait_list))

		sem = __rwsem_wake_one_writer(sem);



	spin_unlock_irqrestore(&sem->wait_lock, flags);

	raw_spin_unlock_irqrestore(&sem->wait_lock, flags);

}



/*
@@ -295,13 +295,13 @@ void __up_write(struct rw_semaphore *sem) 
{

	unsigned long flags;



	spin_lock_irqsave(&sem->wait_lock, flags);

	raw_spin_lock_irqsave(&sem->wait_lock, flags);



	sem->activity = 0;

	if (!list_empty(&sem->wait_list))

		sem = __rwsem_do_wake(sem, 1);



	spin_unlock_irqrestore(&sem->wait_lock, flags);

	raw_spin_unlock_irqrestore(&sem->wait_lock, flags);

}



/*
@@ -312,12 +312,12 @@ void __downgrade_write(struct rw_semaphore *sem) 
{

	unsigned long flags;



	spin_lock_irqsave(&sem->wait_lock, flags);

	raw_spin_lock_irqsave(&sem->wait_lock, flags);



	sem->activity = 1;

	if (!list_empty(&sem->wait_list))

		sem = __rwsem_do_wake(sem, 0);



	spin_unlock_irqrestore(&sem->wait_lock, flags);

	raw_spin_unlock_irqrestore(&sem->wait_lock, flags);

}

lib/rwsem.c

+7 −7
Original line number Diff line number Diff line
@@ -22,7 +22,7 @@ void __init_rwsem(struct rw_semaphore *sem, const char *name, 
	lockdep_init_map(&sem->dep_map, name, key, 0);

#endif

	sem->count = RWSEM_UNLOCKED_VALUE;

	spin_lock_init(&sem->wait_lock);

	raw_spin_lock_init(&sem->wait_lock);

	INIT_LIST_HEAD(&sem->wait_list);

}
@@ -180,7 +180,7 @@ rwsem_down_failed_common(struct rw_semaphore *sem, 
	set_task_state(tsk, TASK_UNINTERRUPTIBLE);



	/* set up my own style of waitqueue */

	spin_lock_irq(&sem->wait_lock);

	raw_spin_lock_irq(&sem->wait_lock);

	waiter.task = tsk;

	waiter.flags = flags;

	get_task_struct(tsk);
@@ -204,7 +204,7 @@ rwsem_down_failed_common(struct rw_semaphore *sem, 
		 adjustment == -RWSEM_ACTIVE_WRITE_BIAS)

		sem = __rwsem_do_wake(sem, RWSEM_WAKE_READ_OWNED);



	spin_unlock_irq(&sem->wait_lock);

	raw_spin_unlock_irq(&sem->wait_lock);



	/* wait to be given the lock */

	for (;;) {
@@ -245,13 +245,13 @@ struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem) 
{

	unsigned long flags;



	spin_lock_irqsave(&sem->wait_lock, flags);

	raw_spin_lock_irqsave(&sem->wait_lock, flags);



	/* do nothing if list empty */

	if (!list_empty(&sem->wait_list))

		sem = __rwsem_do_wake(sem, RWSEM_WAKE_ANY);



	spin_unlock_irqrestore(&sem->wait_lock, flags);

	raw_spin_unlock_irqrestore(&sem->wait_lock, flags);



	return sem;

}
@@ -265,13 +265,13 @@ struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem) 
{

	unsigned long flags;



	spin_lock_irqsave(&sem->wait_lock, flags);

	raw_spin_lock_irqsave(&sem->wait_lock, flags);



	/* do nothing if list empty */

	if (!list_empty(&sem->wait_list))

		sem = __rwsem_do_wake(sem, RWSEM_WAKE_READ_OWNED);



	spin_unlock_irqrestore(&sem->wait_lock, flags);

	raw_spin_unlock_irqrestore(&sem->wait_lock, flags);



	return sem;

}