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Date:   Thu, 23 Jul 2020 10:43:41 -0000
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Subject: [tip: x86/asm] x86/percpu: Clean up percpu_xchg_op()
Cc:     Brian Gerst <brgerst@gmail.com>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Sedat Dilek <sedat.dilek@gmail.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        "Peter Zijlstra (Intel)" <peterz@infradead.org>,
        Dennis Zhou <dennis@kernel.org>, x86 <x86@kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
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The following commit has been merged into the x86/asm branch of tip:

Commit-ID:     73ca542fbabb68deaa90130a8153cab1fa8288fe
Gitweb:        https://git.kernel.org/tip/73ca542fbabb68deaa90130a8153cab1fa8288fe
Author:        Brian Gerst <brgerst@gmail.com>
AuthorDate:    Mon, 20 Jul 2020 13:49:21 -07:00
Committer:     Thomas Gleixner <tglx@linutronix.de>
CommitterDate: Thu, 23 Jul 2020 11:46:41 +02:00

x86/percpu: Clean up percpu_xchg_op()

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.

Signed-off-by: Brian Gerst <brgerst@gmail.com>
Signed-off-by: Nick Desaulniers <ndesaulniers@google.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Tested-by: Nick Desaulniers <ndesaulniers@google.com>
Tested-by: Sedat Dilek <sedat.dilek@gmail.com>
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Dennis Zhou <dennis@kernel.org>
Link: https://lkml.kernel.org/r/20200720204925.3654302-8-ndesaulniers@google.com

---
 arch/x86/include/asm/percpu.h | 61 ++++++++++------------------------
 1 file changed, 18 insertions(+), 43 deletions(-)

diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index 0776a11..ac6d7e7 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)
 
 /*