Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755881AbbHFMgN (ORCPT ); Thu, 6 Aug 2015 08:36:13 -0400 Received: from us01smtprelay-2.synopsys.com ([198.182.47.9]:53356 "EHLO smtprelay.synopsys.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1755799AbbHFMgJ (ORCPT ); Thu, 6 Aug 2015 08:36:09 -0400 From: Vineet Gupta To: "Peter Zijlstra (Intel)" , Thomas Gleixner CC: Michel Lespinasse , , lkml , Vineet Gupta Subject: [PATCH 3/4] ARC: make futex_atomic_cmpxchg_inatomic() return bimodal Date: Thu, 6 Aug 2015 18:05:22 +0530 Message-ID: <1438864523-31340-4-git-send-email-vgupta@synopsys.com> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1438864523-31340-1-git-send-email-vgupta@synopsys.com> References: <1438864523-31340-1-git-send-email-vgupta@synopsys.com> MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.12.197.191] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2373 Lines: 85 Callers of cmpxchg_futex_value_locked() in futex code expect bimodal return value: !0 (essentially -EFAULT as failure) 0 (success) Before this patch, the success return value was old value of futex, which could very well be non zero, causing caller to possibly take the failure path erroneously. Fix that by returning 0 for success (This fix was done back in 2011 for all upstream arches, which ARC obviously missed) Cc: Peter Zijlstra (Intel) Cc: Thomas Gleixner Cc: Michel Lespinasse Signed-off-by: Vineet Gupta --- arch/arc/include/asm/futex.h | 19 ++++++++++--------- 1 file changed, 10 insertions(+), 9 deletions(-) diff --git a/arch/arc/include/asm/futex.h b/arch/arc/include/asm/futex.h index 82902ff0517f..6c8f207a5f02 100644 --- a/arch/arc/include/asm/futex.h +++ b/arch/arc/include/asm/futex.h @@ -151,6 +151,7 @@ static inline int futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, u32 expval, u32 newval) { + int ret = 0; u32 existval; if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32))) @@ -160,18 +161,18 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, u32 expval, __asm__ __volatile__( #ifdef CONFIG_ARC_HAS_LLSC - "1: llock %0, [%3] \n" - " brne %0, %1, 3f \n" - "2: scond %2, [%3] \n" + "1: llock %1, [%4] \n" + " brne %1, %2, 3f \n" + "2: scond %3, [%4] \n" " bnz 1b \n" #else - "1: ld %0, [%3] \n" - " brne %0, %1, 3f \n" - "2: st %2, [%3] \n" + "1: ld %1, [%4] \n" + " brne %1, %2, 3f \n" + "2: st %3, [%4] \n" #endif "3: \n" " .section .fixup,\"ax\" \n" - "4: mov %0, %4 \n" + "4: mov %0, %5 \n" " b 3b \n" " .previous \n" " .section __ex_table,\"a\" \n" @@ -179,14 +180,14 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, u32 expval, " .word 1b, 4b \n" " .word 2b, 4b \n" " .previous\n" - : "=&r"(existval) + : "+&r"(ret), "=&r"(existval) : "r"(expval), "r"(newval), "r"(uaddr), "ir"(-EFAULT) : "cc", "memory"); smp_mb(); *uval = existval; - return existval; + return ret; } #endif -- 1.9.1 -- 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/