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@xxxxxx> diff --git a/arch/parisc/kernel/syscall.S b/arch/parisc/kernel/syscall.S index e54d5e4d3489..97ac707c6bff 100644 --- a/arch/parisc/kernel/syscall.S +++ b/arch/parisc/kernel/syscall.S @@ -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
