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=-8.3 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 A1A07CA9ECF for ; Fri, 1 Nov 2019 14:36:21 +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 6CCC921734 for ; Fri, 1 Nov 2019 14:36:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="QOqytGKN" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 6CCC921734 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=arm.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:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=75g8efrRGzylNtqNUwrk2J6+Y9tRpzLZykO3+b3FvDo=; b=QOqytGKNZjDnHu EiHm1NK210USnJH5rscIGc+R2UBEG7FgKdasxOTYM4V0tkNGPLSGBPmL5ln1y5A0VCto01Tu49BzD 4abdZcofA7b5ft4erCtyhDCOoTd5afK5r/YM71fKWRuBBVEzpDrF6ZKP24uPri6m7PVy14BTE+5Y0 eY5ZJV7N0dJD2q59z1ho8mzd6rwgqGW0uKgyUfXvLe+oIv2OGLyeDjO8vJbscDvIpzSKXPjqq+Wln JQxZcDpCUzNaLSjLqHM4neuZUs0LfPjlYqfOkF8aV2SGbvy/+ZNzQKP3c94DXxw2QdcH82LmZtzbI MOGrRQBJEy1fhqtdw39A==; 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 1iQY29-000077-3S; Fri, 01 Nov 2019 14:36:13 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92.3 #3 (Red Hat Linux)) id 1iQY25-00006W-9B for linux-arm-kernel@lists.infradead.org; Fri, 01 Nov 2019 14:36:10 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id B20AE31F; Fri, 1 Nov 2019 07:36:07 -0700 (PDT) Received: from blommer (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 6FC6F3F718; Fri, 1 Nov 2019 07:36:06 -0700 (PDT) Date: Fri, 1 Nov 2019 14:36:03 +0000 From: Mark Rutland To: Robin Murphy Subject: Re: [PATCH] arm64: perf: Simplify the ARMv8 PMUv3 event attributes Message-ID: <20191101143602.GB13020@blommer> 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> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <7b1e730e-9083-75b9-f1bc-7d84c686c97c@arm.com> User-Agent: Mutt/1.11.1+11 (2f07cb52) (2018-12-01) X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20191101_073609_413868_86C2766A X-CRM114-Status: GOOD ( 22.71 ) 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: Shaokun Zhang , Will Deacon , 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 On Fri, Nov 01, 2019 at 11:11:49AM +0000, 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. I must've meessed up locally -- sorry for the noise. > 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. I strongly suspect Will's (much cleaner) version would work with those older compilers too, and I just didn't know what I was doing ~8 years ago when I came up with the trick. I can have a go with my toolchain museum on Monday; if old GCCs are happy we can clean up the other instances of the trick to be much more legible. Thanks, Mark. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel