File diff 052c0cbc4bbf → 85642093068c
BLD/build/HEADERS/CUR-92-vmkdrivers-asm-x64/vmkernel64/release/asm/mutex.h
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new file 100644
 
/*
 
 * 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_PREFIX "   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_PREFIX "   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