linux-kernel - [PATCH 31/37] MIPS: futex: Emit Loongson3 sync workarounds within asm

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Date:   Mon, 30 Sep 2019 23:08:41 +0000
From:   Paul Burton <paul.burton@...s.com>
To:     "linux-mips@...r.kernel.org" <linux-mips@...r.kernel.org>
CC:     Huacai Chen <chenhc@...ote.com>,
        Jiaxun Yang <jiaxun.yang@...goat.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Paul Burton <pburton@...ecomp.com>
Subject: [PATCH 31/37] MIPS: futex: Emit Loongson3 sync workarounds within asm

Generate the sync instructions required to workaround Loongson3 LL/SC
errata within inline asm blocks, which feels a little safer than doing
it from C where strictly speaking the compiler would be well within its
rights to insert a memory access between the separate asm statements we
previously had, containing sync & ll instructions respectively.

Signed-off-by: Paul Burton <paul.burton@...s.com>
---

 arch/mips/include/asm/futex.h | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/arch/mips/include/asm/futex.h b/arch/mips/include/asm/futex.h
index b83b0397462d..45c3e3652f48 100644
--- a/arch/mips/include/asm/futex.h
+++ b/arch/mips/include/asm/futex.h
@@ -16,6 +16,7 @@
 #include <asm/barrier.h>
 #include <asm/compiler.h>
 #include <asm/errno.h>
+#include <asm/sync.h>
 #include <asm/war.h>
 
 #define __futex_atomic_op(insn, ret, oldval, uaddr, oparg)		\
@@ -50,12 +51,12 @@
 		  "i" (-EFAULT)						\
 		: "memory");						\
 	} else if (cpu_has_llsc) {					\
-		loongson_llsc_mb();					\
 		__asm__ __volatile__(					\
 		"	.set	push				\n"	\
 		"	.set	noat				\n"	\
 		"	.set	push				\n"	\
 		"	.set	"MIPS_ISA_ARCH_LEVEL"		\n"	\
+		"	" __SYNC(full, loongson3_war) "		\n"	\
 		"1:	"user_ll("%1", "%4")" # __futex_atomic_op\n"	\
 		"	.set	pop				\n"	\
 		"	" insn	"				\n"	\
@@ -164,13 +165,13 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
 		  "i" (-EFAULT)
 		: "memory");
 	} else if (cpu_has_llsc) {
-		loongson_llsc_mb();
 		__asm__ __volatile__(
 		"# futex_atomic_cmpxchg_inatomic			\n"
 		"	.set	push					\n"
 		"	.set	noat					\n"
 		"	.set	push					\n"
 		"	.set	"MIPS_ISA_ARCH_LEVEL"			\n"
+		"	" __SYNC(full, loongson3_war) "			\n"
 		"1:	"user_ll("%1", "%3")"				\n"
 		"	bne	%1, %z4, 3f				\n"
 		"	.set	pop					\n"
@@ -178,8 +179,7 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
 		"	.set	"MIPS_ISA_ARCH_LEVEL"			\n"
 		"2:	"user_sc("$1", "%2")"				\n"
 		"	beqz	$1, 1b					\n"
-		__WEAK_LLSC_MB
-		"3:							\n"
+		"3:	" __SYNC_ELSE(full, loongson3_war, __WEAK_LLSC_MB) "\n"
 		"	.insn						\n"
 		"	.set	pop					\n"
 		"	.section .fixup,\"ax\"				\n"
@@ -194,7 +194,6 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr,
 		: GCC_OFF_SMALL_ASM() (*uaddr), "Jr" (oldval), "Jr" (newval),
 		  "i" (-EFAULT)
 		: "memory");
-		loongson_llsc_mb();
 	} else
 		return -ENOSYS;
 
-- 
2.23.0