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| -rw-r--r-- | include/asm-x86_64/mutex.h | 113 |
1 files changed, 113 insertions, 0 deletions
diff --git a/include/asm-x86_64/mutex.h b/include/asm-x86_64/mutex.h new file mode 100644 index 00000000000..818abfd262d --- /dev/null +++ b/include/asm-x86_64/mutex.h @@ -0,0 +1,113 @@ +/* + * Assembly implementation of the mutex fastpath, based on atomic + * decrement/increment. + * + * started by Ingo Molnar: + * + * Copyright (C) 2004, 2005, 2006 Red Hat, Inc., Ingo Molnar <mingo@redhat.com> + */ +#ifndef _ASM_MUTEX_H +#define _ASM_MUTEX_H + +/** + * __mutex_fastpath_lock - decrement and call function if negative + * @v: pointer of type atomic_t + * @fail_fn: function to call if the result is negative + * + * Atomically decrements @v and calls <fail_fn> if the result is negative. + */ +#define __mutex_fastpath_lock(v, fail_fn) \ +do { \ + unsigned long dummy; \ + \ + typecheck(atomic_t *, v); \ + typecheck_fn(fastcall void (*)(atomic_t *), fail_fn); \ + \ + __asm__ __volatile__( \ + LOCK " decl (%%rdi) \n" \ + " js 2f \n" \ + "1: \n" \ + \ + LOCK_SECTION_START("") \ + "2: call "#fail_fn" \n" \ + " jmp 1b \n" \ + LOCK_SECTION_END \ + \ + :"=D" (dummy) \ + : "D" (v) \ + : "rax", "rsi", "rdx", "rcx", \ + "r8", "r9", "r10", "r11", "memory"); \ +} while (0) + +/** + * __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 <fail_fn> 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, + int fastcall (*fail_fn)(atomic_t *)) +{ + if (unlikely(atomic_dec_return(count) < 0)) + return fail_fn(count); + else + return 0; +} + +/** + * __mutex_fastpath_unlock - increment and call function if nonpositive + * @v: pointer of type atomic_t + * @fail_fn: function to call if the result is nonpositive + * + * Atomically increments @v and calls <fail_fn> if the result is nonpositive. + */ +#define __mutex_fastpath_unlock(v, fail_fn) \ +do { \ + unsigned long dummy; \ + \ + typecheck(atomic_t *, v); \ + typecheck_fn(fastcall void (*)(atomic_t *), fail_fn); \ + \ + __asm__ __volatile__( \ + LOCK " incl (%%rdi) \n" \ + " jle 2f \n" \ + "1: \n" \ + \ + LOCK_SECTION_START("") \ + "2: call "#fail_fn" \n" \ + " jmp 1b \n" \ + LOCK_SECTION_END \ + \ + :"=D" (dummy) \ + : "D" (v) \ + : "rax", "rsi", "rdx", "rcx", \ + "r8", "r9", "r10", "r11", "memory"); \ +} while (0) + +#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 0 and return 1 (success), or return 0 (failure) + * if it wasn't 1 originally. [the fallback function is never used on + * x86_64, because all x86_64 CPUs have a CMPXCHG instruction.] + */ +static inline int +__mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *)) +{ + if (likely(atomic_cmpxchg(count, 1, 0)) == 1) + return 1; + else + return 0; +} + +#endif |