From 6b3087c64a92a36ae20d33479b4df6d7afc910d4 Mon Sep 17 00:00:00 2001 From: Graf Yang Date: Wed, 7 Jan 2009 23:14:39 +0800 Subject: Blackfin arch: SMP supporting patchset: Blackfin header files and machine common code Blackfin dual core BF561 processor can support SMP like features. https://docs.blackfin.uclinux.org/doku.php?id=linux-kernel:smp-like In this patch, we provide SMP extend to Blackfin header files and machine common code Signed-off-by: Graf Yang Signed-off-by: Bryan Wu --- arch/blackfin/include/asm/mutex-dec.h | 112 ++++++++++++++++++++++++++++++++++ 1 file changed, 112 insertions(+) create mode 100644 arch/blackfin/include/asm/mutex-dec.h (limited to 'arch/blackfin/include/asm/mutex-dec.h') diff --git a/arch/blackfin/include/asm/mutex-dec.h b/arch/blackfin/include/asm/mutex-dec.h new file mode 100644 index 000000000000..0134151656af --- /dev/null +++ b/arch/blackfin/include/asm/mutex-dec.h @@ -0,0 +1,112 @@ +/* + * include/asm-generic/mutex-dec.h + * + * Generic implementation of the mutex fastpath, based on atomic + * decrement/increment. + */ +#ifndef _ASM_GENERIC_MUTEX_DEC_H +#define _ASM_GENERIC_MUTEX_DEC_H + +/** + * __mutex_fastpath_lock - try to take the lock by moving the count + * from 1 to a 0 value + * @count: pointer of type atomic_t + * @fail_fn: function to call if the original value was not 1 + * + * Change the count from 1 to a value lower than 1, and call if + * it wasn't 1 originally. This function MUST leave the value lower than + * 1 even when the "1" assertion wasn't true. + */ +static inline void +__mutex_fastpath_lock(atomic_t *count, fastcall void (*fail_fn)(atomic_t *)) +{ + if (unlikely(atomic_dec_return(count) < 0)) + fail_fn(count); + else + smp_mb(); +} + +/** + * __mutex_fastpath_lock_retval - try to take the lock by moving the count + * from 1 to a 0 value + * @count: pointer of type atomic_t + * @fail_fn: function to call if the original value was not 1 + * + * Change the count from 1 to a value lower than 1, and call if + * it wasn't 1 originally. This function returns 0 if the fastpath succeeds, + * or anything the slow path function returns. + */ +static inline int +__mutex_fastpath_lock_retval(atomic_t *count, fastcall int (*fail_fn)(atomic_t *)) +{ + if (unlikely(atomic_dec_return(count) < 0)) + return fail_fn(count); + else { + smp_mb(); + return 0; + } +} + +/** + * __mutex_fastpath_unlock - try to promote the count from 0 to 1 + * @count: pointer of type atomic_t + * @fail_fn: function to call if the original value was not 0 + * + * Try to promote the count from 0 to 1. If it wasn't 0, call . + * In the failure case, this function is allowed to either set the value to + * 1, or to set it to a value lower than 1. + * + * If the implementation sets it to a value of lower than 1, then the + * __mutex_slowpath_needs_to_unlock() macro needs to return 1, it needs + * to return 0 otherwise. + */ +static inline void +__mutex_fastpath_unlock(atomic_t *count, fastcall void (*fail_fn)(atomic_t *)) +{ + smp_mb(); + if (unlikely(atomic_inc_return(count) <= 0)) + fail_fn(count); +} + +#define __mutex_slowpath_needs_to_unlock() 1 + +/** + * __mutex_fastpath_trylock - try to acquire the mutex, without waiting + * + * @count: pointer of type atomic_t + * @fail_fn: fallback function + * + * Change the count from 1 to a value lower than 1, and return 0 (failure) + * if it wasn't 1 originally, or return 1 (success) otherwise. This function + * MUST leave the value lower than 1 even when the "1" assertion wasn't true. + * Additionally, if the value was < 0 originally, this function must not leave + * it to 0 on failure. + * + * If the architecture has no effective trylock variant, it should call the + * spinlock-based trylock variant unconditionally. + */ +static inline int +__mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *)) +{ + /* + * We have two variants here. The cmpxchg based one is the best one + * because it never induce a false contention state. It is included + * here because architectures using the inc/dec algorithms over the + * xchg ones are much more likely to support cmpxchg natively. + * + * If not we fall back to the spinlock based variant - that is + * just as efficient (and simpler) as a 'destructive' probing of + * the mutex state would be. + */ +#ifdef __HAVE_ARCH_CMPXCHG + if (likely(atomic_cmpxchg(count, 1, 0) == 1)) { + smp_mb(); + return 1; + } + return 0; +#else + return fail_fn(count); +#endif +} + +#endif -- cgit v1.2.3-59-g8ed1b