diff options
| author | Paul Burton <paul.burton@mips.com> | 2019-10-01 21:53:38 +0000 |
|---|---|---|
| committer | Paul Burton <paul.burton@mips.com> | 2019-10-07 09:43:01 -0700 |
| commit | a91f2a1dba44c29cd0d75edd8787f4469092ae8f (patch) | |
| tree | 4cda928500a1d8ca12e75a80370ec33d03112291 /arch/mips/include/asm/cmpxchg.h | |
| parent | 6a57d2d1e7c3ac7f47d8c51bddd9082fe2fb485b (diff) | |
MIPS: cmpxchg: Omit redundant barriers for Loongson3
When building a kernel configured to support Loongson3 LL/SC workarounds
(ie. CONFIG_CPU_LOONGSON3_WORKAROUNDS=y) the inline assembly in
__xchg_asm() & __cmpxchg_asm() already emits completion barriers, and as
such we don't need to emit extra barriers from the xchg() or cmpxchg()
macros. Add compile-time constant checks causing us to omit the
redundant memory barriers.
Signed-off-by: Paul Burton <paul.burton@mips.com>
Cc: linux-mips@vger.kernel.org
Cc: Huacai Chen <chenhc@lemote.com>
Cc: Jiaxun Yang <jiaxun.yang@flygoat.com>
Cc: linux-kernel@vger.kernel.org
Diffstat (limited to 'arch/mips/include/asm/cmpxchg.h')
| -rw-r--r-- | arch/mips/include/asm/cmpxchg.h | 26 |
1 files changed, 23 insertions, 3 deletions
diff --git a/arch/mips/include/asm/cmpxchg.h b/arch/mips/include/asm/cmpxchg.h index fc121d20a980..820df68e32e1 100644 --- a/arch/mips/include/asm/cmpxchg.h +++ b/arch/mips/include/asm/cmpxchg.h @@ -94,7 +94,13 @@ static inline unsigned long __xchg(volatile void *ptr, unsigned long x, ({ \ __typeof__(*(ptr)) __res; \ \ - smp_mb__before_llsc(); \ + /* \ + * In the Loongson3 workaround case __xchg_asm() already \ + * contains a completion barrier prior to the LL, so we don't \ + * need to emit an extra one here. \ + */ \ + if (!__SYNC_loongson3_war) \ + smp_mb__before_llsc(); \ \ __res = (__typeof__(*(ptr))) \ __xchg((ptr), (unsigned long)(x), sizeof(*(ptr))); \ @@ -179,9 +185,23 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old, ({ \ __typeof__(*(ptr)) __res; \ \ - smp_mb__before_llsc(); \ + /* \ + * In the Loongson3 workaround case __cmpxchg_asm() already \ + * contains a completion barrier prior to the LL, so we don't \ + * need to emit an extra one here. \ + */ \ + if (!__SYNC_loongson3_war) \ + smp_mb__before_llsc(); \ + \ __res = cmpxchg_local((ptr), (old), (new)); \ - smp_llsc_mb(); \ + \ + /* \ + * In the Loongson3 workaround case __cmpxchg_asm() already \ + * contains a completion barrier after the SC, so we don't \ + * need to emit an extra one here. \ + */ \ + if (!__SYNC_loongson3_war) \ + smp_llsc_mb(); \ \ __res; \ }) |