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| author | Helge Deller <deller@gmx.de> | 2019-05-07 20:19:05 +0200 |
|---|---|---|
| committer | Helge Deller <deller@gmx.de> | 2019-05-10 21:00:24 +0200 |
| commit | e6eb5fe9123f05dcbf339ae5c0b6d32fcc0685d5 (patch) | |
| tree | af8322072981c930ac0ac33e62ee5b6d0732fc95 /arch/parisc | |
| parent | 62217beb394e654bbd2bb87c533dadd2d8bf62c6 (diff) | |
| download | lwn-e6eb5fe9123f05dcbf339ae5c0b6d32fcc0685d5.tar.gz lwn-e6eb5fe9123f05dcbf339ae5c0b6d32fcc0685d5.zip | |
parisc: Drop LDCW barrier in CAS code when running UP
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>
Diffstat (limited to 'arch/parisc')
| -rw-r--r-- | arch/parisc/kernel/syscall.S | 12 |
1 files changed, 8 insertions, 4 deletions
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 |