| Michael Trimarchi | 0c91223 | 2008-11-25 21:37:14 +0900 | [diff] [blame^] | 1 | /* |
| 2 | * arch/sh/include/asm/mutex-llsc.h |
| 3 | * |
| 4 | * SH-4A optimized mutex locking primitives |
| 5 | * |
| 6 | * Please look into asm-generic/mutex-xchg.h for a formal definition. |
| 7 | */ |
| 8 | #ifndef __ASM_SH_MUTEX_LLSC_H |
| 9 | #define __ASM_SH_MUTEX_LLSC_H |
| 10 | |
| 11 | /* |
| 12 | * Attempting to lock a mutex on SH4A is done like in ARMv6+ architecure. |
| 13 | * with a bastardized atomic decrement (it is not a reliable atomic decrement |
| 14 | * but it satisfies the defined semantics for our purpose, while being |
| 15 | * smaller and faster than a real atomic decrement or atomic swap. |
| 16 | * The idea is to attempt decrementing the lock value only once. If once |
| 17 | * decremented it isn't zero, or if its store-back fails due to a dispute |
| 18 | * on the exclusive store, we simply bail out immediately through the slow |
| 19 | * path where the lock will be reattempted until it succeeds. |
| 20 | */ |
| 21 | static inline void |
| 22 | __mutex_fastpath_lock(atomic_t *count, void (*fail_fn)(atomic_t *)) |
| 23 | { |
| 24 | int __res; |
| 25 | |
| 26 | __asm__ __volatile__ ( |
| 27 | "movli.l @%1, %0 \n" |
| 28 | "dt %0 \n" |
| 29 | "movco.l %0, @%1 \n" |
| 30 | : "=&z" (__res) |
| 31 | : "r" (&(count)->counter) |
| 32 | : "t"); |
| 33 | |
| 34 | if (unlikely(__res != 0)) |
| 35 | fail_fn(count); |
| 36 | } |
| 37 | |
| 38 | static inline int |
| 39 | __mutex_fastpath_lock_retval(atomic_t *count, int (*fail_fn)(atomic_t *)) |
| 40 | { |
| 41 | int __res; |
| 42 | |
| 43 | __asm__ __volatile__ ( |
| 44 | "movli.l @%1, %0 \n" |
| 45 | "dt %0 \n" |
| 46 | "movco.l %0, @%1 \n" |
| 47 | : "=&z" (__res) |
| 48 | : "r" (&(count)->counter) |
| 49 | : "t"); |
| 50 | |
| 51 | if (unlikely(__res != 0)) |
| 52 | __res = fail_fn(count); |
| 53 | |
| 54 | return __res; |
| 55 | } |
| 56 | |
| 57 | static inline void |
| 58 | __mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *)) |
| 59 | { |
| 60 | int __res; |
| 61 | |
| 62 | __asm__ __volatile__ ( |
| 63 | "1: movli.l @%1, %0 \n\t" |
| 64 | "add #1, %0 \n\t" |
| 65 | "movco.l %0, @%1 \n\t" |
| 66 | "bf 1b\n\t" |
| 67 | : "=&z" (__res) |
| 68 | : "r" (&(count)->counter) |
| 69 | : "t"); |
| 70 | |
| 71 | if (unlikely(__res <= 0)) |
| 72 | fail_fn(count); |
| 73 | } |
| 74 | |
| 75 | /* |
| 76 | * If the unlock was done on a contended lock, or if the unlock simply fails |
| 77 | * then the mutex remains locked. |
| 78 | */ |
| 79 | #define __mutex_slowpath_needs_to_unlock() 1 |
| 80 | |
| 81 | /* |
| 82 | * For __mutex_fastpath_trylock we do an atomic decrement and check the |
| 83 | * result and put it in the __res variable. |
| 84 | */ |
| 85 | static inline int |
| 86 | __mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *)) |
| 87 | { |
| 88 | int __res, __orig; |
| 89 | |
| 90 | __asm__ __volatile__ ( |
| 91 | "1: movli.l @%2, %0 \n\t" |
| 92 | "dt %0 \n\t" |
| 93 | "movco.l %0,@%2 \n\t" |
| 94 | "bf 1b \n\t" |
| 95 | "cmp/eq #0,%0 \n\t" |
| 96 | "bt 2f \n\t" |
| 97 | "mov #0, %1 \n\t" |
| 98 | "bf 3f \n\t" |
| 99 | "2: mov #1, %1 \n\t" |
| 100 | "3: " |
| 101 | : "=&z" (__orig), "=&r" (__res) |
| 102 | : "r" (&count->counter) |
| 103 | : "t"); |
| 104 | |
| 105 | return __res; |
| 106 | } |
| 107 | #endif /* __ASM_SH_MUTEX_LLSC_H */ |