From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933195AbdCUVVq (ORCPT ); Tue, 21 Mar 2017 17:21:46 -0400 Received: from mail-ot0-f194.google.com ([74.125.82.194]:34611 "EHLO mail-ot0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1758188AbdCUVVl (ORCPT ); Tue, 21 Mar 2017 17:21:41 -0400 MIME-Version: 1.0 In-Reply-To: References: <6bb1c71b87b300d04977c34f0cd8586363bc6170.1489519233.git.dvyukov@google.com> <20170320171718.GL31213@leverpostej> <956a8e10-e03f-a21c-99d9-8a75c2616e0a@virtuozzo.com> <20170321104139.GA22188@leverpostej> From: Arnd Bergmann Date: Tue, 21 Mar 2017 22:20:41 +0100 X-Google-Sender-Auth: k3FkMJwNSfazbzYH-MyjCutRk48 Message-ID: Subject: Re: [PATCH 2/3] asm-generic, x86: wrap atomic operations To: Dmitry Vyukov Cc: Mark Rutland , Andrey Ryabinin , Peter Zijlstra , Ingo Molnar , Will Deacon , Andrew Morton , kasan-dev , "linux-mm@kvack.org" , "x86@kernel.org" , LKML Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 21, 2017 at 7:06 PM, Dmitry Vyukov wrote: > On Tue, Mar 21, 2017 at 11:41 AM, Mark Rutland wrote: >> On Tue, Mar 21, 2017 at 12:25:06PM +0300, Andrey Ryabinin wrote: > > I don't mind changing READ_ONCE_NOCHECK to READ_ONCE. But I don't have > strong preference either way. > > We could do: > #define arch_atomic_read_is_already_instrumented 1 > and then skip instrumentation in asm-generic if it's defined. But I > don't think it's worth it. > > There is no functional difference, it's only an optimization (now > somewhat questionable). As Andrey said, one can get a splash of > reports anyway, and it's the first one that is important. We use KASAN > with panic_on_warn=1 so we don't even see the rest. I'm getting couple of new stack size warnings that are all the result of the _NOCHECK. /git/arm-soc/mm/page_alloc.c: In function 'show_free_areas': /git/arm-soc/mm/page_alloc.c:4685:1: error: the frame size of 3368 bytes is larger than 3072 bytes [-Werror=frame-larger-than=] } /git/arm-soc/lib/atomic64_test.c: In function 'test_atomic': /git/arm-soc/lib/atomic64_test.c:148:1: error: the frame size of 6528 bytes is larger than 3072 bytes [-Werror=frame-larger-than=] } ^ /git/arm-soc/lib/atomic64_test.c: In function 'test_atomic64': /git/arm-soc/lib/atomic64_test.c:243:1: error: the frame size of 7112 bytes is larger than 3072 bytes [-Werror=frame-larger-than=] This is with my previous set of patches already applied, so READ_ONCE should not cause problems. Reverting the READ_ONCE_NOCHECK() in atomic_read() and atomic64_read() back to READ_ONCE() I also get a build failure as a result of your patch, but this one is not addressed by using READ_ONCE(): In file included from /git/arm-soc/arch/x86/include/asm/atomic.h:7:0, from /git/arm-soc/include/linux/atomic.h:4, from /git/arm-soc/arch/x86/include/asm/thread_info.h:53, from /git/arm-soc/include/linux/thread_info.h:25, from /git/arm-soc/arch/x86/include/asm/preempt.h:6, from /git/arm-soc/include/linux/preempt.h:80, from /git/arm-soc/include/linux/spinlock.h:50, from /git/arm-soc/include/linux/mmzone.h:7, from /git/arm-soc/include/linux/gfp.h:5, from /git/arm-soc/include/linux/mm.h:9, from /git/arm-soc/mm/slub.c:12: /git/arm-soc/mm/slub.c: In function '__slab_free': /git/arm-soc/arch/x86/include/asm/cmpxchg.h:174:2: error: 'asm' operand has impossible constraints asm volatile(pfx "cmpxchg%c4b %2; sete %0" \ ^ /git/arm-soc/arch/x86/include/asm/cmpxchg.h:183:2: note: in expansion of macro '__cmpxchg_double' __cmpxchg_double(LOCK_PREFIX, p1, p2, o1, o2, n1, n2) ^~~~~~~~~~~~~~~~ /git/arm-soc/include/asm-generic/atomic-instrumented.h:236:2: note: in expansion of macro 'arch_cmpxchg_double' arch_cmpxchg_double(____p1, (p2), (o1), (o2), (n1), (n2)); \ ^~~~~~~~~~~~~~~~~~~ /git/arm-soc/mm/slub.c:385:7: note: in expansion of macro 'cmpxchg_double' if (cmpxchg_double(&page->freelist, &page->counters, ^~~~~~~~~~~~~~ /git/arm-soc/scripts/Makefile.build:308: recipe for target 'mm/slub.o' failed http://pastebin.com/raw/qXVpi9Ev has the defconfig file I used, and I get the error with any gcc version I tried (4.9 through 7.0.1). Arnd