Path: csiph.com!optima2.xanadu-bbs.net!xanadu-bbs.net!news.glorb.com!diesel.cu.mi.it!bofh.it!news.nic.it!robomod From: Vineet Gupta Newsgroups: linux.kernel Subject: [PATCH 5/4] ARC: ensure futex ops are atomic in !LLSC config Date: Thu, 06 Aug 2015 15:50:01 +0200 Message-ID: References: X-Original-To: David Hildenbrand X-Mailer: git-send-email 1.9.1 MIME-Version: 1.0 Content-Type: text/plain X-Originating-IP: [10.12.197.191] Sender: robomod@news.nic.it List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Approved: robomod@news.nic.it Lines: 64 Organization: linux.* mail to news gateway X-Original-Cc: lkml , Vineet Gupta , "Peter Zijlstra (Intel)" , Thomas Gleixner , Michel Lespinasse X-Original-Date: Thu, 6 Aug 2015 19:16:20 +0530 X-Original-Message-ID: <1438868780-8465-1-git-send-email-vgupta@synopsys.com> X-Original-References: <1438864523-31340-1-git-send-email-vgupta@synopsys.com> X-Original-Sender: linux-kernel-owner@vger.kernel.org Xref: csiph.com linux.kernel:1201734 W/o hardware assisted atomic r-m-w the best we can do is to disable preemption. Cc: David Hildenbrand Cc: Peter Zijlstra (Intel) Cc: Thomas Gleixner Cc: Michel Lespinasse Signed-off-by: Vineet Gupta --- arch/arc/include/asm/futex.h | 12 ++++++++++++ 1 file changed, 12 insertions(+) diff --git a/arch/arc/include/asm/futex.h b/arch/arc/include/asm/futex.h index 0ea8bcc7b846..8f449982523b 100644 --- a/arch/arc/include/asm/futex.h +++ b/arch/arc/include/asm/futex.h @@ -87,6 +87,9 @@ static inline int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr) if (!access_ok(VERIFY_WRITE, uaddr, sizeof(int))) return -EFAULT; +#ifndef CONFIG_ARC_HAS_LLSC + preempt_disable(); /* to guarantee atomic r-m-w of futex op */ +#endif pagefault_disable(); switch (op) { @@ -111,6 +114,9 @@ static inline int futex_atomic_op_inuser(int encoded_op, u32 __user *uaddr) } pagefault_enable(); +#ifndef CONFIG_ARC_HAS_LLSC + preempt_enable(); +#endif if (!ret) { switch (cmp) { @@ -153,6 +159,9 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, u32 expval, if (!access_ok(VERIFY_WRITE, uaddr, sizeof(u32))) return -EFAULT; +#ifndef CONFIG_ARC_HAS_LLSC + preempt_disable(); /* to guarantee atomic r-m-w of futex op */ +#endif smp_mb(); __asm__ __volatile__( @@ -182,6 +191,9 @@ futex_atomic_cmpxchg_inatomic(u32 *uval, u32 __user *uaddr, u32 expval, smp_mb(); +#ifndef CONFIG_ARC_HAS_LLSC + preempt_enable(); +#endif *uval = existval; return ret; } -- 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/