Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755316AbaKEOxk (ORCPT ); Wed, 5 Nov 2014 09:53:40 -0500 Received: from vsp-authed02.binero.net ([195.74.38.226]:47843 "EHLO vsp-authed-04-02.binero.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755006AbaKEOxh (ORCPT ); Wed, 5 Nov 2014 09:53:37 -0500 From: Andreas Larsson To: davem@davemloft.net Cc: sparclinux@vger.kernel.org, sam@ravnborg.org, linux-kernel@vger.kernel.org, software@gaisler.com Subject: [PATCH] sparc32: Implement xchg and atomic_xchg using ATOMIC_HASH locks Date: Wed, 5 Nov 2014 15:52:08 +0100 Message-Id: <1415199128-22339-1-git-send-email-andreas@gaisler.com> X-Mailer: git-send-email 1.7.10.4 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Atomicity between xchg and cmpxchg cannot be guaranteed when xchg is implemented with a swap and cmpxchg is implemented with locks. Without this, e.g. mcs_spin_lock and mcs_spin_unlock are broken. Signed-off-by: Andreas Larsson --- arch/sparc/include/asm/atomic_32.h | 2 +- arch/sparc/include/asm/cmpxchg_32.h | 12 ++---------- arch/sparc/lib/atomic32.c | 27 +++++++++++++++++++++++++++ 3 files changed, 30 insertions(+), 11 deletions(-) diff --git a/arch/sparc/include/asm/atomic_32.h b/arch/sparc/include/asm/atomic_32.h index 765c177..0e69b7e 100644 --- a/arch/sparc/include/asm/atomic_32.h +++ b/arch/sparc/include/asm/atomic_32.h @@ -22,7 +22,7 @@ int atomic_add_return(int, atomic_t *); int atomic_cmpxchg(atomic_t *, int, int); -#define atomic_xchg(v, new) (xchg(&((v)->counter), new)) +int atomic_xchg(atomic_t *, int); int __atomic_add_unless(atomic_t *, int, int); void atomic_set(atomic_t *, int); diff --git a/arch/sparc/include/asm/cmpxchg_32.h b/arch/sparc/include/asm/cmpxchg_32.h index 32c29a1..d38b52d 100644 --- a/arch/sparc/include/asm/cmpxchg_32.h +++ b/arch/sparc/include/asm/cmpxchg_32.h @@ -11,22 +11,14 @@ #ifndef __ARCH_SPARC_CMPXCHG__ #define __ARCH_SPARC_CMPXCHG__ -static inline unsigned long xchg_u32(__volatile__ unsigned long *m, unsigned long val) -{ - __asm__ __volatile__("swap [%2], %0" - : "=&r" (val) - : "0" (val), "r" (m) - : "memory"); - return val; -} - +unsigned long __xchg_u32(volatile u32 *m, u32 new); void __xchg_called_with_bad_pointer(void); static inline unsigned long __xchg(unsigned long x, __volatile__ void * ptr, int size) { switch (size) { case 4: - return xchg_u32(ptr, x); + return __xchg_u32(ptr, x); } __xchg_called_with_bad_pointer(); return x; diff --git a/arch/sparc/lib/atomic32.c b/arch/sparc/lib/atomic32.c index a7c418a..71cd65a 100644 --- a/arch/sparc/lib/atomic32.c +++ b/arch/sparc/lib/atomic32.c @@ -45,6 +45,19 @@ ATOMIC_OP(add, +=) #undef ATOMIC_OP +int atomic_xchg(atomic_t *v, int new) +{ + int ret; + unsigned long flags; + + spin_lock_irqsave(ATOMIC_HASH(v), flags); + ret = v->counter; + v->counter = new; + spin_unlock_irqrestore(ATOMIC_HASH(v), flags); + return ret; +} +EXPORT_SYMBOL(atomic_xchg); + int atomic_cmpxchg(atomic_t *v, int old, int new) { int ret; @@ -137,3 +150,17 @@ unsigned long __cmpxchg_u32(volatile u32 *ptr, u32 old, u32 new) return (unsigned long)prev; } EXPORT_SYMBOL(__cmpxchg_u32); + +unsigned long __xchg_u32(volatile u32 *ptr, u32 new) +{ + unsigned long flags; + u32 prev; + + spin_lock_irqsave(ATOMIC_HASH(ptr), flags); + prev = *ptr; + *ptr = new; + spin_unlock_irqrestore(ATOMIC_HASH(ptr), flags); + + return (unsigned long)prev; +} +EXPORT_SYMBOL(__xchg_u32); -- 1.7.10.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/