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locking, rwsem: Annotate inner lock as raw
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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: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
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Thomas Gleixner authored and Ingo Molnar committed Sep 13, 2011
1 parent 8292c9e commit ddb6c9b
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Showing 4 changed files with 33 additions and 31 deletions.
2 changes: 1 addition & 1 deletion include/linux/rwsem-spinlock.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down
10 changes: 6 additions & 4 deletions include/linux/rwsem.h
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Original file line number Diff line number Diff line change
Expand Up @@ -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;
Expand Down Expand Up @@ -56,9 +56,11 @@ static inline int rwsem_is_locked(struct rw_semaphore *sem)
# define __RWSEM_DEP_MAP_INIT(lockname)
#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) }
#define __RWSEM_INITIALIZER(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)
Expand Down
38 changes: 19 additions & 19 deletions lib/rwsem-spinlock.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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;
}
Expand All @@ -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);
Expand Down Expand Up @@ -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;
}

Expand All @@ -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 (;;) {
Expand All @@ -189,15 +189,15 @@ 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 */
sem->activity++;
ret = 1;
}

spin_unlock_irqrestore(&sem->wait_lock, flags);
raw_spin_unlock_irqrestore(&sem->wait_lock, flags);

return ret;
}
Expand All @@ -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;
}

Expand All @@ -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 (;;) {
Expand Down Expand Up @@ -260,15 +260,15 @@ 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 */
sem->activity = -1;
ret = 1;
}

spin_unlock_irqrestore(&sem->wait_lock, flags);
raw_spin_unlock_irqrestore(&sem->wait_lock, flags);

return ret;
}
Expand All @@ -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);
}

/*
Expand All @@ -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);
}

/*
Expand All @@ -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);
}

14 changes: 7 additions & 7 deletions lib/rwsem.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -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);
}

Expand Down Expand Up @@ -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);
Expand All @@ -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 (;;) {
Expand Down Expand Up @@ -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;
}
Expand All @@ -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;
}
Expand Down

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