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parisc: Drop LDCW barrier in CAS code when running UP

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When running an SMP kernel on a single-CPU machine, we can speed up the
CAS code by replacing the LDCW sync barrier with NOP.

Signed-off-by: Helge Deller <deller@gmx.de>
Esse commit está contido em:
Helge Deller
2019-05-07 20:19:05 +02:00
pai 62217beb39
commit e6eb5fe912
1 arquivos alterados com 8 adições e 4 exclusões
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12
arch/parisc/kernel/syscall.S
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@@ -641,7 +641,8 @@ cas_action:
2: stw %r24, 0(%r26)
/* Free lock */
#ifdef CONFIG_SMP
LDCW 0(%sr2,%r20), %r1 /* Barrier */
98: LDCW 0(%sr2,%r20), %r1 /* Barrier */
99: ALTERNATIVE(98b, 99b, ALT_COND_NO_SMP, INSN_NOP)
#endif
stw %r20, 0(%sr2,%r20)
#if ENABLE_LWS_DEBUG
@@ -658,7 +659,8 @@ cas_action:
/* Error occurred on load or store */
/* Free lock */
#ifdef CONFIG_SMP
LDCW 0(%sr2,%r20), %r1 /* Barrier */
98: LDCW 0(%sr2,%r20), %r1 /* Barrier */
99: ALTERNATIVE(98b, 99b, ALT_COND_NO_SMP, INSN_NOP)
#endif
stw %r20, 0(%sr2,%r20)
#if ENABLE_LWS_DEBUG
@@ -862,7 +864,8 @@ cas2_action:
cas2_end:
/* Free lock */
#ifdef CONFIG_SMP
LDCW 0(%sr2,%r20), %r1 /* Barrier */
98: LDCW 0(%sr2,%r20), %r1 /* Barrier */
99: ALTERNATIVE(98b, 99b, ALT_COND_NO_SMP, INSN_NOP)
#endif
stw %r20, 0(%sr2,%r20)
/* Enable interrupts */
@@ -875,7 +878,8 @@ cas2_end:
/* Error occurred on load or store */
/* Free lock */
#ifdef CONFIG_SMP
LDCW 0(%sr2,%r20), %r1 /* Barrier */
98: LDCW 0(%sr2,%r20), %r1 /* Barrier */
99: ALTERNATIVE(98b, 99b, ALT_COND_NO_SMP, INSN_NOP)
#endif
stw %r20, 0(%sr2,%r20)
ssm PSW_SM_I, %r0