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author | Linus Torvalds <torvalds@g5.osdl.org> | 2006-01-10 01:31:38 (GMT) |
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committer | Linus Torvalds <torvalds@g5.osdl.org> | 2006-01-10 01:31:38 (GMT) |
commit | 80c0531514516e43ae118ddf38424e06e5c3cb3c (patch) | |
tree | 2eef8cf8fdf505b18f83078d1eb41167e98f5b54 /include/asm-arm | |
parent | a457aa6c2bdd743bbbffd3f9e4fdbd8c71f8af1b (diff) | |
parent | 11b751ae8c8ca3fa24c85bd5a3e51dd9f95cda17 (diff) | |
download | linux-fsl-qoriq-80c0531514516e43ae118ddf38424e06e5c3cb3c.tar.xz |
Merge master.kernel.org:/pub/scm/linux/kernel/git/mingo/mutex-2.6
Diffstat (limited to 'include/asm-arm')
-rw-r--r-- | include/asm-arm/atomic.h | 2 | ||||
-rw-r--r-- | include/asm-arm/mutex.h | 128 |
2 files changed, 130 insertions, 0 deletions
diff --git a/include/asm-arm/atomic.h b/include/asm-arm/atomic.h index f72b633..3d7283d 100644 --- a/include/asm-arm/atomic.h +++ b/include/asm-arm/atomic.h @@ -175,6 +175,8 @@ static inline void atomic_clear_mask(unsigned long mask, unsigned long *addr) #endif /* __LINUX_ARM_ARCH__ */ +#define atomic_xchg(v, new) (xchg(&((v)->counter), new)) + static inline int atomic_add_unless(atomic_t *v, int a, int u) { int c, old; diff --git a/include/asm-arm/mutex.h b/include/asm-arm/mutex.h new file mode 100644 index 0000000..6caa59f --- /dev/null +++ b/include/asm-arm/mutex.h @@ -0,0 +1,128 @@ +/* + * include/asm-arm/mutex.h + * + * ARM optimized mutex locking primitives + * + * Please look into asm-generic/mutex-xchg.h for a formal definition. + */ +#ifndef _ASM_MUTEX_H +#define _ASM_MUTEX_H + +#if __LINUX_ARM_ARCH__ < 6 +/* On pre-ARMv6 hardware the swp based implementation is the most efficient. */ +# include <asm-generic/mutex-xchg.h> +#else + +/* + * Attempting to lock a mutex on ARMv6+ can be done with a bastardized + * atomic decrement (it is not a reliable atomic decrement but it satisfies + * the defined semantics for our purpose, while being smaller and faster + * than a real atomic decrement or atomic swap. The idea is to attempt + * decrementing the lock value only once. If once decremented it isn't zero, + * or if its store-back fails due to a dispute on the exclusive store, we + * simply bail out immediately through the slow path where the lock will be + * reattempted until it succeeds. + */ +#define __mutex_fastpath_lock(count, fail_fn) \ +do { \ + int __ex_flag, __res; \ + \ + typecheck(atomic_t *, count); \ + typecheck_fn(fastcall void (*)(atomic_t *), fail_fn); \ + \ + __asm__ ( \ + "ldrex %0, [%2] \n" \ + "sub %0, %0, #1 \n" \ + "strex %1, %0, [%2] \n" \ + \ + : "=&r" (__res), "=&r" (__ex_flag) \ + : "r" (&(count)->counter) \ + : "cc","memory" ); \ + \ + if (unlikely(__res || __ex_flag)) \ + fail_fn(count); \ +} while (0) + +#define __mutex_fastpath_lock_retval(count, fail_fn) \ +({ \ + int __ex_flag, __res; \ + \ + typecheck(atomic_t *, count); \ + typecheck_fn(fastcall int (*)(atomic_t *), fail_fn); \ + \ + __asm__ ( \ + "ldrex %0, [%2] \n" \ + "sub %0, %0, #1 \n" \ + "strex %1, %0, [%2] \n" \ + \ + : "=&r" (__res), "=&r" (__ex_flag) \ + : "r" (&(count)->counter) \ + : "cc","memory" ); \ + \ + __res |= __ex_flag; \ + if (unlikely(__res != 0)) \ + __res = fail_fn(count); \ + __res; \ +}) + +/* + * Same trick is used for the unlock fast path. However the original value, + * rather than the result, is used to test for success in order to have + * better generated assembly. + */ +#define __mutex_fastpath_unlock(count, fail_fn) \ +do { \ + int __ex_flag, __res, __orig; \ + \ + typecheck(atomic_t *, count); \ + typecheck_fn(fastcall void (*)(atomic_t *), fail_fn); \ + \ + __asm__ ( \ + "ldrex %0, [%3] \n" \ + "add %1, %0, #1 \n" \ + "strex %2, %1, [%3] \n" \ + \ + : "=&r" (__orig), "=&r" (__res), "=&r" (__ex_flag) \ + : "r" (&(count)->counter) \ + : "cc","memory" ); \ + \ + if (unlikely(__orig || __ex_flag)) \ + fail_fn(count); \ +} while (0) + +/* + * If the unlock was done on a contended lock, or if the unlock simply fails + * then the mutex remains locked. + */ +#define __mutex_slowpath_needs_to_unlock() 1 + +/* + * For __mutex_fastpath_trylock we use another construct which could be + * described as a "single value cmpxchg". + * + * This provides the needed trylock semantics like cmpxchg would, but it is + * lighter and less generic than a true cmpxchg implementation. + */ +static inline int +__mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *)) +{ + int __ex_flag, __res, __orig; + + __asm__ ( + + "1: ldrex %0, [%3] \n" + "subs %1, %0, #1 \n" + "strexeq %2, %1, [%3] \n" + "movlt %0, #0 \n" + "cmpeq %2, #0 \n" + "bgt 1b \n" + + : "=&r" (__orig), "=&r" (__res), "=&r" (__ex_flag) + : "r" (&count->counter) + : "cc", "memory" ); + + return __orig; +} + +#endif +#endif |