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sparc64: Make rwsems 64-bit.

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Basically tip-off the powerpc code, use a 64-bit type and atomic64_t
interfaces for the implementation.

This gets us off of the by-hand asm code I wrote, which frankly I
think probably ruins I-cache hit rates.

The idea was the keep the call chains less deep, but anything taking
the rw-semaphores probably is also calling other stuff and therefore
already has allocated a stack-frame.  So no real stack frame savings
ever.

Ben H. has posted patches to make powerpc use 64-bit too and with some
abstractions we can probably use a shared header file somewhere.

With suggestions from Sam Ravnborg.

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2010-08-17 22:49:26 -07:00
parent b10f997bb0
commit 9b3bb86aca
4 changed files with 104 additions and 193 deletions
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12
arch/sparc/include/asm/rwsem-const.h
View File

@ -1,12 +0,0 @@
/* rwsem-const.h: RW semaphore counter constants. */
#ifndef _SPARC64_RWSEM_CONST_H
#define _SPARC64_RWSEM_CONST_H
#define RWSEM_UNLOCKED_VALUE 0x00000000
#define RWSEM_ACTIVE_BIAS 0x00000001
#define RWSEM_ACTIVE_MASK 0x0000ffff
#define RWSEM_WAITING_BIAS (-0x00010000)
#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
#endif /* _SPARC64_RWSEM_CONST_H */

120
arch/sparc/include/asm/rwsem.h
View File

@ -15,16 +15,21 @@
#include <linux/list.h>
#include <linux/spinlock.h>
#include <asm/rwsem-const.h>
struct rwsem_waiter;
struct rw_semaphore {
signed int count;
spinlock_t wait_lock;
struct list_head wait_list;
signed long count;
#define RWSEM_UNLOCKED_VALUE 0x00000000L
#define RWSEM_ACTIVE_BIAS 0x00000001L
#define RWSEM_ACTIVE_MASK 0xffffffffL
#define RWSEM_WAITING_BIAS (-RWSEM_ACTIVE_MASK-1)
#define RWSEM_ACTIVE_READ_BIAS RWSEM_ACTIVE_BIAS
#define RWSEM_ACTIVE_WRITE_BIAS (RWSEM_WAITING_BIAS + RWSEM_ACTIVE_BIAS)
spinlock_t wait_lock;
struct list_head wait_list;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lockdep_map dep_map;
struct lockdep_map dep_map;
#endif
};
@ -41,6 +46,11 @@ struct rw_semaphore {
#define DECLARE_RWSEM(name) \
struct rw_semaphore name = __RWSEM_INITIALIZER(name)
extern struct rw_semaphore *rwsem_down_read_failed(struct rw_semaphore *sem);
extern struct rw_semaphore *rwsem_down_write_failed(struct rw_semaphore *sem);
extern struct rw_semaphore *rwsem_wake(struct rw_semaphore *sem);
extern struct rw_semaphore *rwsem_downgrade_wake(struct rw_semaphore *sem);
extern void __init_rwsem(struct rw_semaphore *sem, const char *name,
struct lock_class_key *key);
@ -51,27 +61,103 @@ do { \
__init_rwsem((sem), #sem, &__key); \
} while (0)
extern void __down_read(struct rw_semaphore *sem);
extern int __down_read_trylock(struct rw_semaphore *sem);
extern void __down_write(struct rw_semaphore *sem);
extern int __down_write_trylock(struct rw_semaphore *sem);
extern void __up_read(struct rw_semaphore *sem);
extern void __up_write(struct rw_semaphore *sem);
extern void __downgrade_write(struct rw_semaphore *sem);
/*
* lock for reading
*/
static inline void __down_read(struct rw_semaphore *sem)
{
if (unlikely(atomic64_inc_return((atomic64_t *)(&sem->count)) <= 0L))
rwsem_down_read_failed(sem);
}
static inline int __down_read_trylock(struct rw_semaphore *sem)
{
long tmp;
while ((tmp = sem->count) >= 0L) {
if (tmp == cmpxchg(&sem->count, tmp,
tmp + RWSEM_ACTIVE_READ_BIAS)) {
return 1;
}
}
return 0;
}
/*
* lock for writing
*/
static inline void __down_write_nested(struct rw_semaphore *sem, int subclass)
{
__down_write(sem);
long tmp;
tmp = atomic64_add_return(RWSEM_ACTIVE_WRITE_BIAS,
(atomic64_t *)(&sem->count));
if (unlikely(tmp != RWSEM_ACTIVE_WRITE_BIAS))
rwsem_down_write_failed(sem);
}
static inline int rwsem_atomic_update(int delta, struct rw_semaphore *sem)
static inline void __down_write(struct rw_semaphore *sem)
{
return atomic_add_return(delta, (atomic_t *)(&sem->count));
__down_write_nested(sem, 0);
}
static inline void rwsem_atomic_add(int delta, struct rw_semaphore *sem)
static inline int __down_write_trylock(struct rw_semaphore *sem)
{
atomic_add(delta, (atomic_t *)(&sem->count));
long tmp;
tmp = cmpxchg(&sem->count, RWSEM_UNLOCKED_VALUE,
RWSEM_ACTIVE_WRITE_BIAS);
return tmp == RWSEM_UNLOCKED_VALUE;
}
/*
* unlock after reading
*/
static inline void __up_read(struct rw_semaphore *sem)
{
long tmp;
tmp = atomic64_dec_return((atomic64_t *)(&sem->count));
if (unlikely(tmp < -1L && (tmp & RWSEM_ACTIVE_MASK) == 0L))
rwsem_wake(sem);
}
/*
* unlock after writing
*/
static inline void __up_write(struct rw_semaphore *sem)
{
if (unlikely(atomic64_sub_return(RWSEM_ACTIVE_WRITE_BIAS,
(atomic64_t *)(&sem->count)) < 0L))
rwsem_wake(sem);
}
/*
* implement atomic add functionality
*/
static inline void rwsem_atomic_add(long delta, struct rw_semaphore *sem)
{
atomic64_add(delta, (atomic64_t *)(&sem->count));
}
/*
* downgrade write lock to read lock
*/
static inline void __downgrade_write(struct rw_semaphore *sem)
{
long tmp;
tmp = atomic64_add_return(-RWSEM_WAITING_BIAS, (atomic64_t *)(&sem->count));
if (tmp < 0L)
rwsem_downgrade_wake(sem);
}
/*
* implement exchange and add functionality
*/
static inline long rwsem_atomic_update(long delta, struct rw_semaphore *sem)
{
return atomic64_add_return(delta, (atomic64_t *)(&sem->count));
}
static inline int rwsem_is_locked(struct rw_semaphore *sem)

2
arch/sparc/lib/Makefile
View File

@ -15,7 +15,7 @@ lib-$(CONFIG_SPARC32) += divdi3.o udivdi3.o
lib-$(CONFIG_SPARC32) += copy_user.o locks.o
lib-y += atomic_$(BITS).o
lib-$(CONFIG_SPARC32) += lshrdi3.o ashldi3.o
lib-y += rwsem_$(BITS).o
lib-$(CONFIG_SPARC32) += rwsem_32.o
lib-$(CONFIG_SPARC32) += muldi3.o bitext.o cmpdi2.o
lib-$(CONFIG_SPARC64) += copy_page.o clear_page.o bzero.o

163
arch/sparc/lib/rwsem_64.S
View File

@ -1,163 +0,0 @@
/* rwsem.S: RW semaphore assembler.
*
* Written by David S. Miller (davem@redhat.com), 2001.
* Derived from asm-i386/rwsem.h
*/
#include <asm/rwsem-const.h>
.section .sched.text, "ax"
.globl __down_read
__down_read:
1: lduw [%o0], %g1
add %g1, 1, %g7
cas [%o0], %g1, %g7
cmp %g1, %g7
bne,pn %icc, 1b
add %g7, 1, %g7
cmp %g7, 0
bl,pn %icc, 3f
nop
2:
retl
nop
3:
save %sp, -192, %sp
call rwsem_down_read_failed
mov %i0, %o0
ret
restore
.size __down_read, .-__down_read
.globl __down_read_trylock
__down_read_trylock:
1: lduw [%o0], %g1
add %g1, 1, %g7
cmp %g7, 0
bl,pn %icc, 2f
mov 0, %o1
cas [%o0], %g1, %g7
cmp %g1, %g7
bne,pn %icc, 1b
mov 1, %o1
2: retl
mov %o1, %o0
.size __down_read_trylock, .-__down_read_trylock
.globl __down_write
__down_write:
sethi %hi(RWSEM_ACTIVE_WRITE_BIAS), %g1
or %g1, %lo(RWSEM_ACTIVE_WRITE_BIAS), %g1
1:
lduw [%o0], %g3
add %g3, %g1, %g7
cas [%o0], %g3, %g7
cmp %g3, %g7
bne,pn %icc, 1b
cmp %g7, 0
bne,pn %icc, 3f
nop
2: retl
nop
3:
save %sp, -192, %sp
call rwsem_down_write_failed
mov %i0, %o0
ret
restore
.size __down_write, .-__down_write
.globl __down_write_trylock
__down_write_trylock:
sethi %hi(RWSEM_ACTIVE_WRITE_BIAS), %g1
or %g1, %lo(RWSEM_ACTIVE_WRITE_BIAS), %g1
1:
lduw [%o0], %g3
cmp %g3, 0
bne,pn %icc, 2f
mov 0, %o1
add %g3, %g1, %g7
cas [%o0], %g3, %g7
cmp %g3, %g7
bne,pn %icc, 1b
mov 1, %o1
2: retl
mov %o1, %o0
.size __down_write_trylock, .-__down_write_trylock
.globl __up_read
__up_read:
1:
lduw [%o0], %g1
sub %g1, 1, %g7
cas [%o0], %g1, %g7
cmp %g1, %g7
bne,pn %icc, 1b
cmp %g7, 0
bl,pn %icc, 3f
nop
2: retl
nop
3: sethi %hi(RWSEM_ACTIVE_MASK), %g1
sub %g7, 1, %g7
or %g1, %lo(RWSEM_ACTIVE_MASK), %g1
andcc %g7, %g1, %g0
bne,pn %icc, 2b
nop
save %sp, -192, %sp
call rwsem_wake
mov %i0, %o0
ret
restore
.size __up_read, .-__up_read
.globl __up_write
__up_write:
sethi %hi(RWSEM_ACTIVE_WRITE_BIAS), %g1
or %g1, %lo(RWSEM_ACTIVE_WRITE_BIAS), %g1
1:
lduw [%o0], %g3
sub %g3, %g1, %g7
cas [%o0], %g3, %g7
cmp %g3, %g7
bne,pn %icc, 1b
sub %g7, %g1, %g7
cmp %g7, 0
bl,pn %icc, 3f
nop
2:
retl
nop
3:
save %sp, -192, %sp
call rwsem_wake
mov %i0, %o0
ret
restore
.size __up_write, .-__up_write
.globl __downgrade_write
__downgrade_write:
sethi %hi(RWSEM_WAITING_BIAS), %g1
or %g1, %lo(RWSEM_WAITING_BIAS), %g1
1:
lduw [%o0], %g3
sub %g3, %g1, %g7
cas [%o0], %g3, %g7
cmp %g3, %g7
bne,pn %icc, 1b
sub %g7, %g1, %g7
cmp %g7, 0
bl,pn %icc, 3f
nop
2:
retl
nop
3:
save %sp, -192, %sp
call rwsem_downgrade_wake
mov %i0, %o0
ret
restore
.size __downgrade_write, .-__downgrade_write