MIPS: syscall: 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@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

arch/mips/kernel/syscall.c

@@ -37,6 +37,7 @@
 #include <asm/signal.h>
 #include <asm/sim.h>
 #include <asm/shmparam.h>
+#include <asm/sync.h>
 #include <asm/sysmips.h>
 #include <asm/switch_to.h>
 
@@ -133,12 +134,12 @@ static inline int mips_atomic_set(unsigned long addr, unsigned long new)
 		  [efault] "i" (-EFAULT)
 		: "memory");
 	} else if (cpu_has_llsc) {
-		loongson_llsc_mb();
 		__asm__ __volatile__ (
 		"	.set	push					\n"
 		"	.set	"MIPS_ISA_ARCH_LEVEL"			\n"
 		"	li	%[err], 0				\n"
 		"1:							\n"
+		"	" __SYNC(full, loongson3_war) "			\n"
 		user_ll("%[old]", "(%[addr])")
 		"	move	%[tmp], %[new]				\n"
 		"2:							\n"