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| Rev | Author | Line No. | Line |
|---|---|---|---|
| 422 | giacomo | 1 | /* rwsem.h: R/W semaphores, public interface |
| 2 | * |
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| 3 | * Written by David Howells (dhowells@redhat.com). |
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| 4 | * Derived from asm-i386/semaphore.h |
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| 5 | */ |
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| 6 | |||
| 7 | #ifndef _LINUX_RWSEM_H |
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| 8 | #define _LINUX_RWSEM_H |
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| 9 | |||
| 10 | #include <linux/linkage.h> |
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| 11 | |||
| 12 | #define RWSEM_DEBUG 0 |
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| 13 | |||
| 14 | #ifdef __KERNEL__ |
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| 15 | |||
| 16 | #include <linux/config.h> |
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| 17 | #include <linux/types.h> |
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| 18 | #include <linux/kernel.h> |
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| 19 | #include <asm/system.h> |
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| 20 | #include <asm/atomic.h> |
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| 21 | |||
| 22 | struct rw_semaphore; |
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| 23 | |||
| 24 | #ifdef CONFIG_RWSEM_GENERIC_SPINLOCK |
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| 25 | #include <linux/rwsem-spinlock.h> /* use a generic implementation */ |
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| 26 | #else |
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| 27 | #include <asm/rwsem.h> /* use an arch-specific implementation */ |
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| 28 | #endif |
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| 29 | |||
| 30 | #ifndef rwsemtrace |
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| 31 | #if RWSEM_DEBUG |
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| 32 | extern void FASTCALL(rwsemtrace(struct rw_semaphore *sem, const char *str)); |
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| 33 | #else |
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| 34 | #define rwsemtrace(SEM,FMT) |
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| 35 | #endif |
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| 36 | #endif |
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| 37 | |||
| 38 | /* |
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| 39 | * lock for reading |
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| 40 | */ |
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| 41 | static inline void down_read(struct rw_semaphore *sem) |
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| 42 | { |
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| 43 | might_sleep(); |
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| 44 | rwsemtrace(sem,"Entering down_read"); |
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| 45 | __down_read(sem); |
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| 46 | rwsemtrace(sem,"Leaving down_read"); |
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| 47 | } |
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| 48 | |||
| 49 | /* |
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| 50 | * trylock for reading -- returns 1 if successful, 0 if contention |
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| 51 | */ |
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| 52 | static inline int down_read_trylock(struct rw_semaphore *sem) |
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| 53 | { |
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| 54 | int ret; |
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| 55 | rwsemtrace(sem,"Entering down_read_trylock"); |
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| 56 | ret = __down_read_trylock(sem); |
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| 57 | rwsemtrace(sem,"Leaving down_read_trylock"); |
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| 58 | return ret; |
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| 59 | } |
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| 60 | |||
| 61 | /* |
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| 62 | * lock for writing |
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| 63 | */ |
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| 64 | static inline void down_write(struct rw_semaphore *sem) |
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| 65 | { |
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| 66 | might_sleep(); |
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| 67 | rwsemtrace(sem,"Entering down_write"); |
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| 68 | __down_write(sem); |
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| 69 | rwsemtrace(sem,"Leaving down_write"); |
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| 70 | } |
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| 71 | |||
| 72 | /* |
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| 73 | * trylock for writing -- returns 1 if successful, 0 if contention |
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| 74 | */ |
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| 75 | static inline int down_write_trylock(struct rw_semaphore *sem) |
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| 76 | { |
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| 77 | int ret; |
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| 78 | rwsemtrace(sem,"Entering down_write_trylock"); |
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| 79 | ret = __down_write_trylock(sem); |
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| 80 | rwsemtrace(sem,"Leaving down_write_trylock"); |
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| 81 | return ret; |
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| 82 | } |
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| 83 | |||
| 84 | /* |
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| 85 | * release a read lock |
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| 86 | */ |
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| 87 | static inline void up_read(struct rw_semaphore *sem) |
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| 88 | { |
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| 89 | rwsemtrace(sem,"Entering up_read"); |
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| 90 | __up_read(sem); |
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| 91 | rwsemtrace(sem,"Leaving up_read"); |
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| 92 | } |
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| 93 | |||
| 94 | /* |
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| 95 | * release a write lock |
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| 96 | */ |
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| 97 | static inline void up_write(struct rw_semaphore *sem) |
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| 98 | { |
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| 99 | rwsemtrace(sem,"Entering up_write"); |
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| 100 | __up_write(sem); |
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| 101 | rwsemtrace(sem,"Leaving up_write"); |
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| 102 | } |
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| 103 | |||
| 104 | /* |
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| 105 | * downgrade write lock to read lock |
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| 106 | */ |
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| 107 | static inline void downgrade_write(struct rw_semaphore *sem) |
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| 108 | { |
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| 109 | rwsemtrace(sem,"Entering downgrade_write"); |
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| 110 | __downgrade_write(sem); |
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| 111 | rwsemtrace(sem,"Leaving downgrade_write"); |
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| 112 | } |
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| 113 | |||
| 114 | #endif /* __KERNEL__ */ |
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| 115 | #endif /* _LINUX_RWSEM_H */ |