From 529b7307d804f649839b5b65b303442140266d26 Mon Sep 17 00:00:00 2001 From: Benjamin Herrenschmidt Date: Tue, 24 Aug 2010 14:41:48 +1000 Subject: [PATCH] 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 --- arch/powerpc/include/asm/rwsem.h | 64 ++++++++++++++++++-------------- 1 file changed, 37 insertions(+), 27 deletions(-) diff --git a/arch/powerpc/include/asm/rwsem.h b/arch/powerpc/include/asm/rwsem.h index 24cd9281ec37..8447d89fbe72 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__ */ -- 2.30.2