linux/arch/sparc64/lib/bitops.S
David S. Miller 24f287e412 [SPARC64]: Implement atomic backoff.
When the cpu count is high and contention hits an atomic object, the
processors can synchronize such that some cpus continually get knocked
out and cannot complete the atomic update.

So implement an exponential backoff when SMP.

Signed-off-by: David S. Miller <davem@davemloft.net>
2007-10-17 16:24:55 -07:00

166 lines
3.1 KiB
ArmAsm

/* bitops.S: Sparc64 atomic bit operations.
*
* Copyright (C) 2000, 2007 David S. Miller (davem@davemloft.net)
*/
#include <asm/asi.h>
#include <asm/backoff.h>
.text
/* On SMP we need to use memory barriers to ensure
* correct memory operation ordering, nop these out
* for uniprocessor.
*/
#ifdef CONFIG_SMP
#define BITOP_PRE_BARRIER membar #StoreLoad | #LoadLoad
#define BITOP_POST_BARRIER \
ba,pt %xcc, 80b; \
membar #StoreLoad | #StoreStore
80: retl
nop
#else
#define BITOP_PRE_BARRIER
#define BITOP_POST_BARRIER
#endif
.globl test_and_set_bit
.type test_and_set_bit,#function
test_and_set_bit: /* %o0=nr, %o1=addr */
BACKOFF_SETUP(%o3)
BITOP_PRE_BARRIER
srlx %o0, 6, %g1
mov 1, %o2
sllx %g1, 3, %g3
and %o0, 63, %g2
sllx %o2, %g2, %o2
add %o1, %g3, %o1
1: ldx [%o1], %g7
or %g7, %o2, %g1
casx [%o1], %g7, %g1
cmp %g7, %g1
bne,pn %xcc, 2f
and %g7, %o2, %g2
clr %o0
movrne %g2, 1, %o0
BITOP_POST_BARRIER
retl
nop
2: BACKOFF_SPIN(%o3, %o4, 1b)
.size test_and_set_bit, .-test_and_set_bit
.globl test_and_clear_bit
.type test_and_clear_bit,#function
test_and_clear_bit: /* %o0=nr, %o1=addr */
BACKOFF_SETUP(%o3)
BITOP_PRE_BARRIER
srlx %o0, 6, %g1
mov 1, %o2
sllx %g1, 3, %g3
and %o0, 63, %g2
sllx %o2, %g2, %o2
add %o1, %g3, %o1
1: ldx [%o1], %g7
andn %g7, %o2, %g1
casx [%o1], %g7, %g1
cmp %g7, %g1
bne,pn %xcc, 2f
and %g7, %o2, %g2
clr %o0
movrne %g2, 1, %o0
BITOP_POST_BARRIER
retl
nop
2: BACKOFF_SPIN(%o3, %o4, 1b)
.size test_and_clear_bit, .-test_and_clear_bit
.globl test_and_change_bit
.type test_and_change_bit,#function
test_and_change_bit: /* %o0=nr, %o1=addr */
BACKOFF_SETUP(%o3)
BITOP_PRE_BARRIER
srlx %o0, 6, %g1
mov 1, %o2
sllx %g1, 3, %g3
and %o0, 63, %g2
sllx %o2, %g2, %o2
add %o1, %g3, %o1
1: ldx [%o1], %g7
xor %g7, %o2, %g1
casx [%o1], %g7, %g1
cmp %g7, %g1
bne,pn %xcc, 2f
and %g7, %o2, %g2
clr %o0
movrne %g2, 1, %o0
BITOP_POST_BARRIER
retl
nop
2: BACKOFF_SPIN(%o3, %o4, 1b)
.size test_and_change_bit, .-test_and_change_bit
.globl set_bit
.type set_bit,#function
set_bit: /* %o0=nr, %o1=addr */
BACKOFF_SETUP(%o3)
srlx %o0, 6, %g1
mov 1, %o2
sllx %g1, 3, %g3
and %o0, 63, %g2
sllx %o2, %g2, %o2
add %o1, %g3, %o1
1: ldx [%o1], %g7
or %g7, %o2, %g1
casx [%o1], %g7, %g1
cmp %g7, %g1
bne,pn %xcc, 2f
nop
retl
nop
2: BACKOFF_SPIN(%o3, %o4, 1b)
.size set_bit, .-set_bit
.globl clear_bit
.type clear_bit,#function
clear_bit: /* %o0=nr, %o1=addr */
BACKOFF_SETUP(%o3)
srlx %o0, 6, %g1
mov 1, %o2
sllx %g1, 3, %g3
and %o0, 63, %g2
sllx %o2, %g2, %o2
add %o1, %g3, %o1
1: ldx [%o1], %g7
andn %g7, %o2, %g1
casx [%o1], %g7, %g1
cmp %g7, %g1
bne,pn %xcc, 2f
nop
retl
nop
2: BACKOFF_SPIN(%o3, %o4, 1b)
.size clear_bit, .-clear_bit
.globl change_bit
.type change_bit,#function
change_bit: /* %o0=nr, %o1=addr */
BACKOFF_SETUP(%o3)
srlx %o0, 6, %g1
mov 1, %o2
sllx %g1, 3, %g3
and %o0, 63, %g2
sllx %o2, %g2, %o2
add %o1, %g3, %o1
1: ldx [%o1], %g7
xor %g7, %o2, %g1
casx [%o1], %g7, %g1
cmp %g7, %g1
bne,pn %xcc, 2f
nop
retl
nop
2: BACKOFF_SPIN(%o3, %o4, 1b)
.size change_bit, .-change_bit