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=-5.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,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 79C5AC433FF for ; Fri, 2 Aug 2019 14:36:24 +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 3E4962054F for ; Fri, 2 Aug 2019 14:36:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="F1OCuYub" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3E4962054F 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: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=UbHAV9MJgNpqdNmEwVFDVUgxf7JGH1r16lgiN9UKXDk=; b=F1OCuYuboasTm2 ltsF2Bkcy3btv8JSAqlOMTqhL26aMyNqCI30CJ/Nk2eVbPDAduT0WVkuVNQqL/5VVSij8lrc3Ml6e U0acPcDfTZMQPQEZTjdOVy6UHfdAf5ZJwRTpYhWXc+DlCHjWiL6lCH7Db2HP7uF954j6vX5ZIDB3p BzNqOjgHinIpvNF8tWt2OIG0vr8GOLjWASFrWDwP850Yug7TXVndi8aHf87SCfNUEyQP0jUtxZGFV CpHGTRY3JEkg+4LZOZb06bbgA3dGOC1n8AmfO3cAUrOLHiaX2xyJVynLBOIpoF9E5svNGUp+xMzXz 9tDS79dZG0j8K97PnlgQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1htYfP-0004qH-QI; Fri, 02 Aug 2019 14:36:23 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1htYfN-0004px-KG for linux-arm-kernel@lists.infradead.org; Fri, 02 Aug 2019 14:36:22 +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 CA4B21596; Fri, 2 Aug 2019 07:36:20 -0700 (PDT) Received: from [10.1.197.45] (e112298-lin.cambridge.arm.com [10.1.197.45]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id EAD923F575; Fri, 2 Aug 2019 07:36:18 -0700 (PDT) Subject: Re: [PATCH v4 4/9] arm: perf: Remove Remove PMU locking To: Will Deacon References: <1563351432-55652-1-git-send-email-julien.thierry@arm.com> <1563351432-55652-5-git-send-email-julien.thierry@arm.com> <20190801130640.4ed5bcy2rdgdtztq@willie-the-truck> From: Julien Thierry Message-ID: <613ebf21-2761-c045-f30d-c1893c3e235e@arm.com> Date: Fri, 2 Aug 2019 15:36:17 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20190801130640.4ed5bcy2rdgdtztq@willie-the-truck> Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190802_073621_712196_AFD7F3C8 X-CRM114-Status: GOOD ( 17.09 ) 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@arm.com, peterz@infradead.org, liwei391@huawei.com, will.deacon@arm.com, Russell King , acme@kernel.org, alexander.shishkin@linux.intel.com, mingo@redhat.com, namhyung@kernel.org, sthotton@marvell.com, jolsa@redhat.com, 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 01/08/2019 14:06, Will Deacon wrote: > [extra 'Remove' in subject] > > On Wed, Jul 17, 2019 at 09:17:07AM +0100, Julien Thierry wrote: >> Since the PMU interrupt saves and restores the value of the selector >> register, there is no need to serialize register accesses against the >> interrupt contexts. >> >> For operations that can be called with interrupts enabled, preemption >> still needs to be disabled to ensure the programming of the PMU is >> done on the expected CPU and not migrated mid-programming. >> >> Signed-off-by: Julien Thierry >> Cc: Will Deacon >> Cc: Mark Rutland >> Cc: Peter Zijlstra >> Cc: Ingo Molnar >> Cc: Arnaldo Carvalho de Melo >> Cc: Alexander Shishkin >> Cc: Jiri Olsa >> Cc: Namhyung Kim >> Cc: Russell King >> --- >> arch/arm/kernel/perf_event_v7.c | 54 ++--------------------------------------- >> 1 file changed, 2 insertions(+), 52 deletions(-) > > I'm struggling to see why this patch is needed or, if it is, why we're not > doing something similar for v6 and xscale. We can't do a similar things for v6 because it doesn't have set/clear registers for event enabling/disabling. To do that on v6 we must do read-modify-write, so we need to keep a spinlock. For v7 we can do without it. Thanks, -- Julien Thierry _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel