[v3,07/11] x86/percpu: Clean up percpu_xchg_op()
diff mbox series

Message ID 20200720204925.3654302-8-ndesaulniers@google.com
State In Next
Commit cbed196e1434b9669da8be26f486fd9aa4af84aa
Headers show
Series
  • i386 Clang support
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Commit Message

Nick Desaulniers July 20, 2020, 8:49 p.m. UTC
From: Brian Gerst <brgerst@gmail.com>

The core percpu macros already have a switch on the data size, so the switch
in the x86 code is redundant and produces more dead code.

Also use appropriate types for the width of the instructions.  This avoids
errors when compiling with Clang.

Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
---
 arch/x86/include/asm/percpu.h | 61 +++++++++++------------------------
 1 file changed, 18 insertions(+), 43 deletions(-)

Patch
diff mbox series

diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index 0776a11e7e11..ac6d7e76c0d4 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -215,46 +215,21 @@  do {									\
  * expensive due to the implied lock prefix.  The processor cannot prefetch
  * cachelines if xchg is used.
  */
-#define percpu_xchg_op(qual, var, nval)					\
+#define percpu_xchg_op(size, qual, _var, _nval)				\
 ({									\
-	typeof(var) pxo_ret__;						\
-	typeof(var) pxo_new__ = (nval);					\
-	switch (sizeof(var)) {						\
-	case 1:								\
-		asm qual ("\n\tmov "__percpu_arg(1)",%%al"		\
-		    "\n1:\tcmpxchgb %2, "__percpu_arg(1)		\
-		    "\n\tjnz 1b"					\
-			    : "=&a" (pxo_ret__), "+m" (var)		\
-			    : "q" (pxo_new__)				\
-			    : "memory");				\
-		break;							\
-	case 2:								\
-		asm qual ("\n\tmov "__percpu_arg(1)",%%ax"		\
-		    "\n1:\tcmpxchgw %2, "__percpu_arg(1)		\
-		    "\n\tjnz 1b"					\
-			    : "=&a" (pxo_ret__), "+m" (var)		\
-			    : "r" (pxo_new__)				\
-			    : "memory");				\
-		break;							\
-	case 4:								\
-		asm qual ("\n\tmov "__percpu_arg(1)",%%eax"		\
-		    "\n1:\tcmpxchgl %2, "__percpu_arg(1)		\
-		    "\n\tjnz 1b"					\
-			    : "=&a" (pxo_ret__), "+m" (var)		\
-			    : "r" (pxo_new__)				\
-			    : "memory");				\
-		break;							\
-	case 8:								\
-		asm qual ("\n\tmov "__percpu_arg(1)",%%rax"		\
-		    "\n1:\tcmpxchgq %2, "__percpu_arg(1)		\
-		    "\n\tjnz 1b"					\
-			    : "=&a" (pxo_ret__), "+m" (var)		\
-			    : "r" (pxo_new__)				\
-			    : "memory");				\
-		break;							\
-	default: __bad_percpu_size();					\
-	}								\
-	pxo_ret__;							\
+	__pcpu_type_##size pxo_old__;					\
+	__pcpu_type_##size pxo_new__ = __pcpu_cast_##size(_nval);	\
+	asm qual (__pcpu_op2_##size("mov", __percpu_arg([var]),		\
+				    "%[oval]")				\
+		  "\n1:\t"						\
+		  __pcpu_op2_##size("cmpxchg", "%[nval]",		\
+				    __percpu_arg([var]))		\
+		  "\n\tjnz 1b"						\
+		  : [oval] "=&a" (pxo_old__),				\
+		    [var] "+m" (_var)					\
+		  : [nval] __pcpu_reg_##size(, pxo_new__)		\
+		  : "memory");						\
+	(typeof(_var))(unsigned long) pxo_old__;			\
 })
 
 /*
@@ -354,9 +329,9 @@  do {									\
 #define this_cpu_or_1(pcp, val)		percpu_to_op(1, volatile, "or", (pcp), val)
 #define this_cpu_or_2(pcp, val)		percpu_to_op(2, volatile, "or", (pcp), val)
 #define this_cpu_or_4(pcp, val)		percpu_to_op(4, volatile, "or", (pcp), val)
-#define this_cpu_xchg_1(pcp, nval)	percpu_xchg_op(volatile, pcp, nval)
-#define this_cpu_xchg_2(pcp, nval)	percpu_xchg_op(volatile, pcp, nval)
-#define this_cpu_xchg_4(pcp, nval)	percpu_xchg_op(volatile, pcp, nval)
+#define this_cpu_xchg_1(pcp, nval)	percpu_xchg_op(1, volatile, pcp, nval)
+#define this_cpu_xchg_2(pcp, nval)	percpu_xchg_op(2, volatile, pcp, nval)
+#define this_cpu_xchg_4(pcp, nval)	percpu_xchg_op(4, volatile, pcp, nval)
 
 #define raw_cpu_add_return_1(pcp, val)		percpu_add_return_op(1, , pcp, val)
 #define raw_cpu_add_return_2(pcp, val)		percpu_add_return_op(2, , pcp, val)
@@ -409,7 +384,7 @@  do {									\
 #define this_cpu_and_8(pcp, val)		percpu_to_op(8, volatile, "and", (pcp), val)
 #define this_cpu_or_8(pcp, val)			percpu_to_op(8, volatile, "or", (pcp), val)
 #define this_cpu_add_return_8(pcp, val)		percpu_add_return_op(8, volatile, pcp, val)
-#define this_cpu_xchg_8(pcp, nval)		percpu_xchg_op(volatile, pcp, nval)
+#define this_cpu_xchg_8(pcp, nval)		percpu_xchg_op(8, volatile, pcp, nval)
 #define this_cpu_cmpxchg_8(pcp, oval, nval)	percpu_cmpxchg_op(volatile, pcp, oval, nval)
 
 /*