linux-kernel - Re: [PATCH -v2 14/33] locking,m68k: Implement atomic_fetch

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Date:	Fri, 17 Jun 2016 17:40:24 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Andreas Schwab <schwab@...ux-m68k.org>
Cc:	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Will Deacon <will.deacon@....com>,
	Paul McKenney <paulmck@...ux.vnet.ibm.com>,
	boqun.feng@...il.com, waiman.long@....com,
	Frédéric Weisbecker <fweisbec@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Linux-Arch <linux-arch@...r.kernel.org>,
	Richard Henderson <rth@...ddle.net>,
	Vineet Gupta <vgupta@...opsys.com>,
	Russell King <linux@....linux.org.uk>,
	Hans-Christian Noren Egtvedt <egtvedt@...fundet.no>,
	Miao Steven <realmz6@...il.com>,
	Yoshinori Sato <ysato@...rs.sourceforge.jp>,
	Richard Kuo <rkuo@...eaurora.org>,
	Tony Luck <tony.luck@...el.com>,
	James Hogan <james.hogan@...tec.com>,
	Ralf Baechle <ralf@...ux-mips.org>,
	David Howells <dhowells@...hat.com>,
	"James E.J. Bottomley" <jejb@...isc-linux.org>,
	Michael Ellerman <mpe@...erman.id.au>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Rich Felker <dalias@...c.org>,
	"David S. Miller" <davem@...emloft.net>, cmetcalf@...lanox.com,
	Max Filippov <jcmvbkbc@...il.com>,
	Arnd Bergmann <arnd@...db.de>, dbueso@...e.de,
	Wu Fengguang <fengguang.wu@...el.com>,
	linux-m68k <linux-m68k@...ts.linux-m68k.org>
Subject: Re: [PATCH -v2 14/33] locking,m68k: Implement
 atomic_fetch_{add,sub,and,or,xor}()


Could either of you comment on the below patch?

All atomic functions that return a value should imply full memory
barrier semantics -- this very much includes a compiler barrier / memory
clobber.



---

 arch/m68k/include/asm/atomic.h  | 19 ++++++++++++-------
 arch/m68k/include/asm/cmpxchg.h |  9 ++++++---
 2 files changed, 18 insertions(+), 10 deletions(-)

diff --git a/arch/m68k/include/asm/atomic.h b/arch/m68k/include/asm/atomic.h
index 3e03de7ae33b..062a60417cb9 100644
--- a/arch/m68k/include/asm/atomic.h
+++ b/arch/m68k/include/asm/atomic.h
@@ -56,7 +56,8 @@ static inline int atomic_##op##_return(int i, atomic_t *v)		\
 			"	casl %2,%1,%0\n"			\
 			"	jne 1b"					\
 			: "+m" (*v), "=&d" (t), "=&d" (tmp)		\
-			: "g" (i), "2" (atomic_read(v)));		\
+			: "g" (i), "2" (atomic_read(v))			\
+			: "memory");					\
 	return t;							\
 }
 
@@ -71,7 +72,8 @@ static inline int atomic_fetch_##op(int i, atomic_t *v)			\
 			"	casl %2,%1,%0\n"			\
 			"	jne 1b"					\
 			: "+m" (*v), "=&d" (t), "=&d" (tmp)		\
-			: "g" (i), "2" (atomic_read(v)));		\
+			: "g" (i), "2" (atomic_read(v))			\
+			: "memory");					\
 	return tmp;							\
 }
 
@@ -141,7 +143,7 @@ static inline void atomic_dec(atomic_t *v)
 static inline int atomic_dec_and_test(atomic_t *v)
 {
 	char c;
-	__asm__ __volatile__("subql #1,%1; seq %0" : "=d" (c), "+m" (*v));
+	__asm__ __volatile__("subql #1,%1; seq %0" : "=d" (c), "+m" (*v) : : "memory");
 	return c != 0;
 }
 
@@ -151,14 +153,15 @@ static inline int atomic_dec_and_test_lt(atomic_t *v)
 	__asm__ __volatile__(
 		"subql #1,%1; slt %0"
 		: "=d" (c), "=m" (*v)
-		: "m" (*v));
+		: "m" (*v)
+		: "memory");
 	return c != 0;
 }
 
 static inline int atomic_inc_and_test(atomic_t *v)
 {
 	char c;
-	__asm__ __volatile__("addql #1,%1; seq %0" : "=d" (c), "+m" (*v));
+	__asm__ __volatile__("addql #1,%1; seq %0" : "=d" (c), "+m" (*v) : : "memory");
 	return c != 0;
 }
 
@@ -204,7 +207,8 @@ static inline int atomic_sub_and_test(int i, atomic_t *v)
 	char c;
 	__asm__ __volatile__("subl %2,%1; seq %0"
 			     : "=d" (c), "+m" (*v)
-			     : ASM_DI (i));
+			     : ASM_DI (i)
+			     : "memory");
 	return c != 0;
 }
 
@@ -213,7 +217,8 @@ static inline int atomic_add_negative(int i, atomic_t *v)
 	char c;
 	__asm__ __volatile__("addl %2,%1; smi %0"
 			     : "=d" (c), "+m" (*v)
-			     : ASM_DI (i));
+			     : ASM_DI (i)
+			     : "memory");
 	return c != 0;
 }
 
diff --git a/arch/m68k/include/asm/cmpxchg.h b/arch/m68k/include/asm/cmpxchg.h
index 83b1df80f0ac..d8b3d2b48785 100644
--- a/arch/m68k/include/asm/cmpxchg.h
+++ b/arch/m68k/include/asm/cmpxchg.h
@@ -98,17 +98,20 @@ static inline unsigned long __cmpxchg(volatile void *p, unsigned long old,
 	case 1:
 		__asm__ __volatile__ ("casb %0,%2,%1"
 				      : "=d" (old), "=m" (*(char *)p)
-				      : "d" (new), "0" (old), "m" (*(char *)p));
+				      : "d" (new), "0" (old), "m" (*(char *)p)
+				      : "memory");
 		break;
 	case 2:
 		__asm__ __volatile__ ("casw %0,%2,%1"
 				      : "=d" (old), "=m" (*(short *)p)
-				      : "d" (new), "0" (old), "m" (*(short *)p));
+				      : "d" (new), "0" (old), "m" (*(short *)p)
+				      : "memory");
 		break;
 	case 4:
 		__asm__ __volatile__ ("casl %0,%2,%1"
 				      : "=d" (old), "=m" (*(int *)p)
-				      : "d" (new), "0" (old), "m" (*(int *)p));
+				      : "d" (new), "0" (old), "m" (*(int *)p)
+				      : "memory");
 		break;
 	default:
 		old = __invalid_cmpxchg_size(p, old, new, size);