From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI, SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C244ECA9EBB for ; Mon, 4 Nov 2019 02:02:27 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 8E66221D7C for ; Mon, 4 Nov 2019 02:02:27 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="kw4lp+iW" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8E66221D7C Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=hisilicon.com Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:Date: Message-ID:From:References:To:Subject:Reply-To:Content-ID:Content-Description :Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=G4E+BbvQ4pH4/yy3FSejz0OOj3rKJF5xxh6VHotd4hY=; b=kw4lp+iWvVc5tA H/FRmsB+YSqUY/Zk3PncRwrwPHo9hZ1pjtDuC+Xg2DwDCLEJMTuQvxp2BNrdFg0OSpjdQLe4qFnFG Roued3rLSMSqeZnUA4TLh2k4Rq48T1vt+uHoeeFWvkuMJ9ceKjO9u8VJ5YCCYwitoA6iSkPj2f9bF fjDVH6PRWYFkX8PUWUxJQEnS2TXUQpiCHzxs3KdJCVaXLpUkb9vCwvlH4gG+vL5qHJJBpnSy3HRAn YgDMfrc4Vbcsct3weIXRSUNx/1xxXjZOodestbq8i2Pzs7Fo521b6mAOKXBzbDKjedh1fLUd8IhNO P3sFfYEFvA8zO/vAdIfA==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iRRhL-0004I1-4z; Mon, 04 Nov 2019 02:02:27 +0000 Received: from szxga06-in.huawei.com ([45.249.212.32] helo=huawei.com) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1iRRhH-0004H1-D1 for linux-arm-kernel@lists.infradead.org; Mon, 04 Nov 2019 02:02:25 +0000 Received: from DGGEMS406-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 6F104AC0AF1BEAE267E5; Mon, 4 Nov 2019 10:02:16 +0800 (CST) Received: from [127.0.0.1] (10.74.221.148) by DGGEMS406-HUB.china.huawei.com (10.3.19.206) with Microsoft SMTP Server id 14.3.439.0; Mon, 4 Nov 2019 10:02:15 +0800 Subject: Re: [PATCH] arm64: perf: Simplify the ARMv8 PMUv3 event attributes To: Robin Murphy , Will Deacon References: <1572407177-48229-1-git-send-email-zhangshaokun@hisilicon.com> <20191031160804.GA28325@willie-the-truck> <20191101085319.GA3508@blommer> <20191101103616.GA2392@willie-the-truck> <20191101105557.GC2392@willie-the-truck> <7b1e730e-9083-75b9-f1bc-7d84c686c97c@arm.com> From: Shaokun Zhang Message-ID: <181d59c8-6252-c01c-79a9-364158be7105@hisilicon.com> Date: Mon, 4 Nov 2019 10:02:15 +0800 User-Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.1.1 MIME-Version: 1.0 In-Reply-To: <7b1e730e-9083-75b9-f1bc-7d84c686c97c@arm.com> X-Originating-IP: [10.74.221.148] X-CFilter-Loop: Reflected X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191103_180223_610029_EB6CB335 X-CRM114-Status: GOOD ( 13.83 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Mark Rutland , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hi Robin, On 2019/11/1 19:11, Robin Murphy wrote: > On 2019-11-01 10:55 am, Will Deacon wrote: >> On Fri, Nov 01, 2019 at 10:54:21AM +0000, Robin Murphy wrote: >>> On 2019-11-01 10:36 am, Will Deacon wrote: >>>> On Fri, Nov 01, 2019 at 08:53:19AM +0000, Mark Rutland wrote: >>>>> On Thu, Oct 31, 2019 at 04:08:04PM +0000, Will Deacon wrote: >>>>>> On Wed, Oct 30, 2019 at 11:46:17AM +0800, Shaokun Zhang wrote: >>>>>>> For each PMU event, there is a ARMV8_EVENT_ATTR(xx, XX) and >>>>>>> &armv8_event_attr_xx.attr.attr. Let's redefine the ARMV8_EVENT_ATTR >>>>>>> to simplify the armv8_pmuv3_event_attrs. >>>>>>> >>>>>>> Cc: Will Deacon >>>>>>> Cc: Mark Rutland >>>>>>> Signed-off-by: Shaokun Zhang >>>>>>> --- >>>>>>> arch/arm64/kernel/perf_event.c | 189 ++++++++++++++--------------------------- >>>>>>> 1 file changed, 65 insertions(+), 124 deletions(-) >>>>>>> >>>>>>> diff --git a/arch/arm64/kernel/perf_event.c b/arch/arm64/kernel/perf_event.c >>>>>>> index a0b4f1bca491..d0f084939bcf 100644 >>>>>>> --- a/arch/arm64/kernel/perf_event.c >>>>>>> +++ b/arch/arm64/kernel/perf_event.c >>>>>>> @@ -159,132 +159,73 @@ armv8pmu_events_sysfs_show(struct device *dev, >>>>>>> } >>>>>> >>>>>> [...] >>>>>> >>>>>>> + (&((struct perf_pmu_events_attr[]) { \ >>>>>>> + { .attr = __ATTR(name, 0444, armv8pmu_events_sysfs_show, NULL), \ >>>>>>> + .id = config, } \ >>>>>>> + })[0].attr.attr) >>>>>> >>>>>> I don't get the need for the array here. Why can't you do: >>>>>> >>>>>> (&((struct perf_pmu_events_attr) { >>>>>> .attr = ..., >>>>>> .id = ..., >>>>>> }).attr.attr) >>>>> >>>>> You need want &(obj.attr.attr) rather than &(obj).attr.attr, i.e. >>>>> >>>>> #define ARMV8_EVENT_ATTR(name, config) \ >>>>> (&((struct perf_pmu_events_attr) { \ >>>>> .attr = __ATTR(name, 0444, armv8pmu_events_sysfs_show, NULL), \ >>>>> .id = config, \ >>>>> }.attr.attr)) >>>>> ... which compiles for me. >>>> >>>> Weird, the following compiles fine for me with both GCC and clang: >>>> >>>> #define ARMV8_EVENT_ATTR(name, config) \ >>>> (&((struct perf_pmu_events_attr) { \ >>>> .attr = __ATTR(name, 0444, armv8pmu_events_sysfs_show, NULL), \ >>>> .id = config, \ >>>> }).attr.attr) >>> >>> You know that the expressions are equivalent because unary "&" has lower >>> precedence than ".", right? ;) >> >> Right, which is why it's weird that Shaokun claims that the version I posted >> doesn't compile. I assume it didn't build for Mark either, hence his extra >> brackets. > > Because different compilers have different ideas of whether "obj" is a valid thing to dereference at all, regardless of where you put parentheses. From what I remember, the array trick was the only way to convince older GCCs to treat the floating struct initialiser as an actual object definition. I guess newer versions are a bit more lenient. > Thanks for your detailed explanations, sounds great! Both GCC 5.4 and 7.3 are unhappy without the array trick. Thanks, Shaokun > Robin. > > . > _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel