ae564c63b8
This implements an optimised mutex fastpath for powerpc, making use of acquire and release barrier semantics. This takes the mutex lock+unlock benchmark from 203 to 173 cycles on a G5. Signed-off-by: Nick Piggin <npiggin@suse.de> Signed-off-by: Paul Mackerras <paulus@samba.org>
134 lines
3.2 KiB
C
134 lines
3.2 KiB
C
/*
|
|
* Optimised mutex implementation of include/asm-generic/mutex-dec.h algorithm
|
|
*/
|
|
#ifndef _ASM_POWERPC_MUTEX_H
|
|
#define _ASM_POWERPC_MUTEX_H
|
|
|
|
static inline int __mutex_cmpxchg_lock(atomic_t *v, int old, int new)
|
|
{
|
|
int t;
|
|
|
|
__asm__ __volatile__ (
|
|
"1: lwarx %0,0,%1 # mutex trylock\n\
|
|
cmpw 0,%0,%2\n\
|
|
bne- 2f\n"
|
|
PPC405_ERR77(0,%1)
|
|
" stwcx. %3,0,%1\n\
|
|
bne- 1b"
|
|
ISYNC_ON_SMP
|
|
"\n\
|
|
2:"
|
|
: "=&r" (t)
|
|
: "r" (&v->counter), "r" (old), "r" (new)
|
|
: "cc", "memory");
|
|
|
|
return t;
|
|
}
|
|
|
|
static inline int __mutex_dec_return_lock(atomic_t *v)
|
|
{
|
|
int t;
|
|
|
|
__asm__ __volatile__(
|
|
"1: lwarx %0,0,%1 # mutex lock\n\
|
|
addic %0,%0,-1\n"
|
|
PPC405_ERR77(0,%1)
|
|
" stwcx. %0,0,%1\n\
|
|
bne- 1b"
|
|
ISYNC_ON_SMP
|
|
: "=&r" (t)
|
|
: "r" (&v->counter)
|
|
: "cc", "memory");
|
|
|
|
return t;
|
|
}
|
|
|
|
static inline int __mutex_inc_return_unlock(atomic_t *v)
|
|
{
|
|
int t;
|
|
|
|
__asm__ __volatile__(
|
|
LWSYNC_ON_SMP
|
|
"1: lwarx %0,0,%1 # mutex unlock\n\
|
|
addic %0,%0,1\n"
|
|
PPC405_ERR77(0,%1)
|
|
" stwcx. %0,0,%1 \n\
|
|
bne- 1b"
|
|
: "=&r" (t)
|
|
: "r" (&v->counter)
|
|
: "cc", "memory");
|
|
|
|
return t;
|
|
}
|
|
|
|
/**
|
|
* __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 <fail_fn> 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, void (*fail_fn)(atomic_t *))
|
|
{
|
|
if (unlikely(__mutex_dec_return_lock(count) < 0))
|
|
fail_fn(count);
|
|
}
|
|
|
|
/**
|
|
* __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 (*fail_fn)(atomic_t *))
|
|
{
|
|
if (unlikely(__mutex_dec_return_lock(count) < 0))
|
|
return fail_fn(count);
|
|
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 <fail_fn>.
|
|
* 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.
|
|
*/
|
|
static inline void
|
|
__mutex_fastpath_unlock(atomic_t *count, void (*fail_fn)(atomic_t *))
|
|
{
|
|
if (unlikely(__mutex_inc_return_unlock(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 0, and return 1 (success), or if the count
|
|
* was not 1, then return 0 (failure).
|
|
*/
|
|
static inline int
|
|
__mutex_fastpath_trylock(atomic_t *count, int (*fail_fn)(atomic_t *))
|
|
{
|
|
if (likely(__mutex_cmpxchg_lock(count, 1, 0) == 1))
|
|
return 1;
|
|
return 0;
|
|
}
|
|
|
|
#endif
|