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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id 743EAC44501 for ; Thu, 16 Jul 2026 12:42:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Transfer-Encoding: Content-Type:In-Reply-To:From:References:Cc:To:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=SEtfcM+KW7L5CPl0b/+m1XcLdqGH3Lnf0/OmVJPKHLg=; b=2e2l4bc8ScxRXD0XRK50jfYHJO kJ7uLIPEUqYsaXSq+TMs221EhAkYvFvXZrVdhmH93zNDSQChM8q03NDI2dMge9f/xJt4wHM6d3Adw +6PdDDFXrqKGJTY1gLUFVMbDxZJrJnHb0q7ta9k3e5/gq2+wbsZmBnmAvPXkxhCvoOm4e/AcvlQsA Cbjo/5LnkUBGTT+Hl17LDh5yqMJhnZZNAoTUO2/8wR5wUBxRIMVub8UNuuNigS7X/ANG0uGsrcWAI 8v2FK3eH5LbBBSslPvBwDBCTuWhkqTUuV1a3CfFbeuQU8nZdN1mHL3ym4tqgE+YUehidjU6WGkqA8 8cmx1mqA==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wkLQ9-0000000HHkC-47ml; Thu, 16 Jul 2026 12:42:34 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wkLQ6-0000000HHjp-45US for linux-arm-kernel@lists.infradead.org; Thu, 16 Jul 2026 12:42:32 +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 EF3F11476; Thu, 16 Jul 2026 05:42:25 -0700 (PDT) Received: from [10.2.197.99] (ewhatever.cambridge.arm.com [10.2.197.99]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id AB1D33F7B4; Thu, 16 Jul 2026 05:42:28 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1784205750; bh=Bu3u6wPSdJa2kf7X/oaorEhXjHXCtj79kYQ35nA1rTs=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=Y7JV1bySJv8kadfk00E+z5GQ/401Y+MIhxN7sxJjscQd4rCtCSNvrNN4ZAuK8iUUI RFmjRwBEtiJbXkoWnWDxr2Hcr/U767395SwiY0pU2h3i208J3xW7u/8Nwq6FrFj2HH MKEAwrxR3Q8tmKXM4vCsRX765WJYiP5f9AGyDF0E= Message-ID: Date: Thu, 16 Jul 2026 13:42:26 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v8 08/13] coresight: etm4x: fix inconsistencies with sysfs configuration To: Yeoreum Yun , Leo Yan Cc: coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, mike.leach@arm.com, james.clark@linaro.org, alexander.shishkin@linux.intel.com, jie.gan@oss.qualcomm.com References: <20260629090007.1718746-1-yeoreum.yun@arm.com> <20260629090007.1718746-9-yeoreum.yun@arm.com> <20260706172159.GA1024232@e132581.arm.com> <20260707082510.GD1024232@e132581.arm.com> Content-Language: en-US From: Suzuki K Poulose In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260716_054231_114693_0B53C9BD X-CRM114-Status: GOOD ( 13.77 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org On 07/07/2026 10:54, Yeoreum Yun wrote: > On Tue, Jul 07, 2026 at 09:59:36AM +0100, Yeoreum Yun wrote: >> On Tue, Jul 07, 2026 at 09:25:10AM +0100, Leo Yan wrote: >>> On Mon, Jul 06, 2026 at 07:16:42PM +0100, Yeoreum Yun wrote: >>> >>> [...] >>> >>>>> I try best to not paste any non-sense AI reviews, record one from >>>>> Sashiko [1]: >>>>> >>>>> | If a user writes to a sysfs attribute like pe_sel_store(), it acquires >>>>> | drvdata->spinlock without disabling interrupts. If an IPI is then handled >>>>> | on the same CPU, etm4_enable_sysfs_smp_call() will call >>>>> | cscfg_csdev_enable_active_config() which attempts to acquire the exact >>>>> | same spinlock, hanging the CPU." >>>>> >>>>> The flow for acquiring drvdata->spinlock in SMP call is: >>>>> >>>>> etm4_enable_sysfs_smp_call() >>>>> `> cscfg_csdev_enable_active_config() >>>>> `> cscfg_csdev_enable_config() >>>>> `> cscfg_prog_config() >>>>> `> cscfg_set_on_enable() >>>>> `> raw_spin_lock_irqsave(feat_csdev->drv_spinlock, flags); >>>>> >>>>> We might expect the complaint from LOCKDEP with this patch. >>>> >>>> Hmm. I miss the this point and there is two solution: >>>> >>>> 1. Remove "feat_csdev->drv_spinlock" >>>> >>>> Before this patch, the "feat_csdev->drv_spinlock" is for >>>> synchronizing with the "drvdata->config". However, >>>> After this patch, the the configfs only show the "active" config >>>> and the active config can be used only after taking the "mode". >>>> >>>> Furthermore, the sysfs only uses the "config" not "active config", >>>> there is no race between the sysfs and the configfs. >>>> >>>> When I check the, "feat_csdev->drv_spinlock" is for the >>>> active/deactive the configfs config, so I seems safe to remove. >>> >>> My interpretation is: >>> >>> After this series, we updates active_config on local CPU within atomic >>> context, it is nature to be protected. So we don't need to use >>> feat_csdev->drv_spinlock when updating active_config. >>> >>> If so, it is fine for me to remove feat_csdev->drv_spinlock. >> >> Yes. but if I add a little bit more comment. the "active_config" >> is accessed after "mode changed (perf of sysfs)" it accesses atomically >> and the "active_config" is refered from the configfs not "config" >> after this patch. So we can remove the "feat_csdev->drv_spinlock". Ack Suzuki