From mboxrd@z Thu Jan 1 00:00:00 1970 From: bobby.prani@gmail.com (Pranith Kumar) Date: Wed, 25 Feb 2015 10:36:20 -0500 Subject: [RFC PATCH] arm: asm/cmpxchg.h: Add support half-word xchg() Message-ID: <1424878581-11701-1-git-send-email-bobby.prani@gmail.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org This patch adds support for a half-word xchg() for ARM using ldrexh/strexh instructions. It also fixes an asm comment for __cmpxchg2. Currently using a half-word xchg() results in the following splat on an ARMv7 machine. [ 45.833303] xchg: bad data size: pc 0xbe806020, ptr 0xeb18deee, size 2 [ 45.833324] ------------[ cut here ]------------ [ 45.837939] kernel BUG at /dvs/git/dirty/git-master_linux/kernel/arch/arm/kernel/traps.c:727! Signed-off-by: Pranith Kumar --- arch/arm/include/asm/cmpxchg.h | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-) diff --git a/arch/arm/include/asm/cmpxchg.h b/arch/arm/include/asm/cmpxchg.h index abb2c37..9505cca 100644 --- a/arch/arm/include/asm/cmpxchg.h +++ b/arch/arm/include/asm/cmpxchg.h @@ -50,6 +50,16 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size : "r" (x), "r" (ptr) : "memory", "cc"); break; + case 2: + asm volatile("@ __xchg2\n" + "1: ldrexh %0, [%3]\n" + " strexh %1, %2, [%3]\n" + " teq %1, #0\n" + " bne 1b" + : "=&r" (ret), "=&r" (tmp) + : "r" (x), "r" (ptr) + : "memory", "cc"); + break; case 4: asm volatile("@ __xchg4\n" "1: ldrex %0, [%3]\n" @@ -93,6 +103,12 @@ static inline unsigned long __xchg(unsigned long x, volatile void *ptr, int size : "memory", "cc"); break; #endif + case 2: + raw_local_irq_save(flags); + ret = *(volatile uint16_t *)ptr; + *(volatile uint16_t *)ptr = x; + raw_local_irq_restore(flags); + break; default: __bad_xchg(ptr, size), ret = 0; break; @@ -158,7 +174,7 @@ static inline unsigned long __cmpxchg(volatile void *ptr, unsigned long old, break; case 2: do { - asm volatile("@ __cmpxchg1\n" + asm volatile("@ __cmpxchg2\n" " ldrexh %1, [%2]\n" " mov %0, #0\n" " teq %1, %3\n" -- 1.9.1