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powerpc: Make rwsem use "long" type 

This makes the 64-bit kernel use 64-bit signed integers for the counter
(effectively supporting 32-bit of active count in the semaphore), thus
avoiding things like overflow of the mmap_sem if you use a really crazy
number of threads

Note: Ideally the type in the structure should be atomic_long_t rather
than "long". However, there's some nasty issues with that. It needs to
be initialized statically -and- lib/rwsem.c does things like

        sem->count = RWSEM_UNLOCKED_VALUE;

Now, if you mix in the fact that atomic_* types are actually structures
with one member and note typedefs of a scalar, it makes its really nasty.

So I stuck to what we did before using a long and casts for now.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Benjamin Herrenschmidt 2010-08-24 14:41:48 +10:00
parent b1515af291
commit 529b7307d8
1 changed files with 37 additions and 27 deletions
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64
arch/powerpc/include/asm/rwsem.h
View File

@ -21,15 +21,20 @@
/*
* the semaphore definition
*/
struct rw_semaphore {
/* XXX this should be able to be an atomic_t -- paulus */
signed int count;
#define RWSEM_UNLOCKED_VALUE 0x00000000
#define RWSEM_ACTIVE_BIAS 0x00000001
#define RWSEM_ACTIVE_MASK 0x0000ffff
#define RWSEM_WAITING_BIAS (-0x00010000)
#ifdef CONFIG_PPC64
# define RWSEM_ACTIVE_MASK 0xffffffffL
#else
# define RWSEM_ACTIVE_MASK 0x0000ffffL
#endif
#define RWSEM_UNLOCKED_VALUE 0x00000000L
#define RWSEM_ACTIVE_BIAS 0x00000001L
#define RWSEM_WAITING_BIAS (-RWSEM_ACTIVE_MASK-1)
#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
struct rw_semaphore {
long count;
spinlock_t wait_lock;
struct list_head wait_list;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
@ -43,9 +48,13 @@ struct rw_semaphore {
# 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, \
__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)
@ -70,13 +79,13 @@ extern void __init_rwsem(struct rw_semaphore *sem, const char *name,
*/
static inline void __down_read(struct rw_semaphore *sem)
{
if (unlikely(atomic_inc_return((atomic_t *)(&sem->count)) <= 0))
if (unlikely(atomic_long_inc_return((atomic_long_t *)&sem->count) <= 0))
rwsem_down_read_failed(sem);
}
static inline int __down_read_trylock(struct rw_semaphore *sem)
{
int tmp;
long tmp;
while ((tmp = sem->count) >= 0) {
if (tmp == cmpxchg(&sem->count, tmp,
@ -92,10 +101,10 @@ static inline int __down_read_trylock(struct rw_semaphore *sem)
*/
static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
{
int tmp;
long tmp;
tmp = atomic_add_return(RWSEM_ACTIVE_WRITE_BIAS,
(atomic_t *)(&sem->count));
tmp = atomic_long_add_return(RWSEM_ACTIVE_WRITE_BIAS,
(atomic_long_t *)&sem->count);
if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
rwsem_down_write_failed(sem);
}
@ -107,7 +116,7 @@ static inline void __down_write(struct rw_semaphore *sem)
static inline int __down_write_trylock(struct rw_semaphore *sem)
{
int tmp;
long tmp;
tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
RWSEM_ACTIVE_WRITE_BIAS);
@ -119,9 +128,9 @@ static inline int __down_write_trylock(struct rw_semaphore *sem)
*/
static inline void __up_read(struct rw_semaphore *sem)
{
int tmp;
long tmp;
tmp = atomic_dec_return((atomic_t *)(&sem->count));
tmp = atomic_long_dec_return((atomic_long_t *)&sem->count);
if (unlikely(tmp < -1 && (tmp & RWSEM_ACTIVE_MASK) == 0))
rwsem_wake(sem);
}
@ -131,17 +140,17 @@ static inline void __up_read(struct rw_semaphore *sem)
*/
static inline void __up_write(struct rw_semaphore *sem)
{
if (unlikely(atomic_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
(atomic_t *)(&sem->count)) < 0))
if (unlikely(atomic_long_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
(atomic_long_t *)&sem->count) < 0))
rwsem_wake(sem);
}
/*
* implement atomic add functionality
*/
static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
static inline void rwsem_atomic_add(long delta, struct rw_semaphore *sem)
{
atomic_add(delta, (atomic_t *)(&sem->count));
atomic_long_add(delta, (atomic_long_t *)&sem->count);
}
/*
@ -149,9 +158,10 @@ static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
*/
static inline void __downgrade_write(struct rw_semaphore *sem)
{
int tmp;
long tmp;
tmp = atomic_add_return(-RWSEM_WAITING_BIAS, (atomic_t *)(&sem->count));
tmp = atomic_long_add_return(-RWSEM_WAITING_BIAS,
(atomic_long_t *)&sem->count);
if (tmp < 0)
rwsem_downgrade_wake(sem);
}
@ -159,14 +169,14 @@ static inline void __downgrade_write(struct rw_semaphore *sem)
/*
* implement exchange and add functionality
*/
static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
static inline long rwsem_atomic_update(long delta, struct rw_semaphore *sem)
{
return atomic_add_return(delta, (atomic_t *)(&sem->count));
return atomic_long_add_return(delta, (atomic_long_t *)&sem->count);
}
static inline int rwsem_is_locked(struct rw_semaphore *sem)
{
return (sem->count != 0);
return sem->count != 0;
}
#endif /* __KERNEL__ */