From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753303AbcEaKh0 (ORCPT ); Tue, 31 May 2016 06:37:26 -0400 Received: from merlin.infradead.org ([205.233.59.134]:48583 "EHLO merlin.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751249AbcEaK3v (ORCPT ); Tue, 31 May 2016 06:29:51 -0400 Message-Id: <20160531102642.333689893@infradead.org> User-Agent: quilt/0.61-1 Date: Tue, 31 May 2016 12:19:39 +0200 From: Peter Zijlstra To: torvalds@linux-foundation.org, mingo@kernel.org, tglx@linutronix.de, will.deacon@arm.com, paulmck@linux.vnet.ibm.com, boqun.feng@gmail.com, waiman.long@hpe.com, fweisbec@gmail.com Cc: linux-kernel@vger.kernel.org, linux-arch@vger.kernel.org, rth@twiddle.net, vgupta@synopsys.com, linux@arm.linux.org.uk, egtvedt@samfundet.no, realmz6@gmail.com, ysato@users.sourceforge.jp, rkuo@codeaurora.org, tony.luck@intel.com, geert@linux-m68k.org, james.hogan@imgtec.com, ralf@linux-mips.org, dhowells@redhat.com, jejb@parisc-linux.org, mpe@ellerman.id.au, schwidefsky@de.ibm.com, dalias@libc.org, davem@davemloft.net, cmetcalf@mellanox.com, jcmvbkbc@gmail.com, arnd@arndb.de, peterz@infradead.org, dbueso@suse.de, fengguang.wu@intel.com Subject: [PATCH -v2 14/33] locking,m68k: Implement atomic_fetch_{add,sub,and,or,xor}() References: <20160531101925.702692792@infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline; filename=peterz-atomic-fetch-m68k.patch Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Implement FETCH-OP atomic primitives, these are very similar to the existing OP-RETURN primitives we already have, except they return the value of the atomic variable _before_ modification. This is especially useful for irreversible operations -- such as bitops (because it becomes impossible to reconstruct the state prior to modification). Signed-off-by: Peter Zijlstra (Intel) --- arch/m68k/include/asm/atomic.h | 53 +++++++++++++++++++++++++++++++++++++---- 1 file changed, 49 insertions(+), 4 deletions(-) --- a/arch/m68k/include/asm/atomic.h +++ b/arch/m68k/include/asm/atomic.h @@ -38,6 +38,13 @@ static inline void atomic_##op(int i, at #ifdef CONFIG_RMW_INSNS +/* + * Am I reading these CAS loops right in that %2 is the old value and the first + * iteration uses an uninitialized value? + * + * Would it not make sense to add: tmp = atomic_read(v); to avoid this? + */ + #define ATOMIC_OP_RETURN(op, c_op, asm_op) \ static inline int atomic_##op##_return(int i, atomic_t *v) \ { \ @@ -53,6 +60,21 @@ static inline int atomic_##op##_return(i return t; \ } +#define ATOMIC_FETCH_OP(op, c_op, asm_op) \ +static inline int atomic_fetch_##op(int i, atomic_t *v) \ +{ \ + int t, tmp; \ + \ + __asm__ __volatile__( \ + "1: movel %2,%1\n" \ + " " #asm_op "l %3,%1\n" \ + " casl %2,%1,%0\n" \ + " jne 1b" \ + : "+m" (*v), "=&d" (t), "=&d" (tmp) \ + : "g" (i), "2" (atomic_read(v))); \ + return tmp; \ +} + #else #define ATOMIC_OP_RETURN(op, c_op, asm_op) \ @@ -68,20 +90,43 @@ static inline int atomic_##op##_return(i return t; \ } +#define ATOMIC_FETCH_OP(op, c_op, asm_op) \ +static inline int atomic_fetch_##op(int i, atomic_t * v) \ +{ \ + unsigned long flags; \ + int t; \ + \ + local_irq_save(flags); \ + t = v->counter; \ + v->counter c_op i; \ + local_irq_restore(flags); \ + \ + return t; \ +} + #endif /* CONFIG_RMW_INSNS */ #define ATOMIC_OPS(op, c_op, asm_op) \ ATOMIC_OP(op, c_op, asm_op) \ - ATOMIC_OP_RETURN(op, c_op, asm_op) + ATOMIC_OP_RETURN(op, c_op, asm_op) \ + ATOMIC_FETCH_OP(op, c_op, asm_op) ATOMIC_OPS(add, +=, add) ATOMIC_OPS(sub, -=, sub) -ATOMIC_OP(and, &=, and) -ATOMIC_OP(or, |=, or) -ATOMIC_OP(xor, ^=, eor) +#undef ATOMIC_OPS +#define ATOMIC_OPS(op, c_op, asm_op) \ + ATOMIC_OP(op, c_op, asm_op) \ + ATOMIC_FETCH_OP(op, c_op, asm_op) + +#define atomic_fetch_or atomic_fetch_or + +ATOMIC_OPS(and, &=, and) +ATOMIC_OPS(or, |=, or) +ATOMIC_OPS(xor, ^=, eor) #undef ATOMIC_OPS +#undef ATOMIC_FETCH_OP #undef ATOMIC_OP_RETURN #undef ATOMIC_OP