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authorBenjamin Herrenschmidt <benh@kernel.crashing.org>2010-08-24 14:41:48 +1000
committerBenjamin Herrenschmidt <benh@kernel.crashing.org>2010-08-24 14:41:48 +1000
commit529b7307d804f649839b5b65b303442140266d26 (patch)
tree1fb7edf7770e27d1e596a1d0aa2a64c1b986938d
parentb1515af2911c4339ed34865a0594f4ad3392921a (diff)
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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>
-rw-r--r--arch/powerpc/include/asm/rwsem.h64
1 files changed, 37 insertions, 27 deletions
diff --git a/arch/powerpc/include/asm/rwsem.h b/arch/powerpc/include/asm/rwsem.h
index 24cd9281ec3..8447d89fbe7 100644
--- a/arch/powerpc/include/asm/rwsem.h
+++ b/arch/powerpc/include/asm/rwsem.h
@@ -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__ */