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 1F8BFC44500 for ; Tue, 7 Jul 2026 08:25:24 +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:In-Reply-To:Content-Type: MIME-Version:References:Message-ID:Subject:Cc:To:From:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=o8FefcA8h7Zyv8aMG34ldXOa0VD/UGWxIDa1MLM6Xlg=; b=PVyDRGI6faFZ59j3eLz9KLBvOf wBhA1JU2eXhsP7QbZOYn5PWGG3SONqlfn3e9Es6keZAIjBRpzALJTB6mFgmGSySsBlmalX/zNcru/ 6gy4yL4SOXsM0VBWn+stkw5cfmaxAGDsMrXdl8JhhSMVGvbXtgcd6hnN/Ad9Q9hUgtYA4qdCqoNnY Ja9ZmgmAX3ri9BGKc46ZjfiGtt4YEFslq4oCfvPRtq8mywbNTleCTUzCKzLZOPRAjL17AuK/daKgu LKsFKCZaOMxn8yWf4aHqIYnXDSxw1k0TsxJrM107aBx3WrrN09U5FasToroTI48EvGZq7BKAI06h4 2ypScfvQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wh17E-0000000ET2x-3JO1; Tue, 07 Jul 2026 08:25:16 +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 1wh17C-0000000ET1z-06LI for linux-arm-kernel@lists.infradead.org; Tue, 07 Jul 2026 08:25:15 +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 572771BCA; Tue, 7 Jul 2026 01:25:08 -0700 (PDT) Received: from localhost (unknown [10.2.196.114]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2CAEB3F85F; Tue, 7 Jul 2026 01:25:12 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1783412712; bh=jTlDX4SJ8ICjOTtRkPF6dVggVhq5GVFKrlcBmkhYrSg=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=qRhJHQeJFTMPutQU9UP102WwIdjd8bs6xrqbqyS51byqrh8GhrN0VUPIh5/l49eSz YtMR2EKg1Sz4YjRrXf0Th4/p7GI35GfHVx//uL4l42681FCqNceeoto7EsGpTIvOZZ JydQf8KR3jouazYOzmI1DC/UPKJiMZEyhVflnjds= Date: Tue, 7 Jul 2026 09:25:10 +0100 From: Leo Yan To: Yeoreum Yun Cc: coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, suzuki.poulose@arm.com, mike.leach@arm.com, james.clark@linaro.org, alexander.shishkin@linux.intel.com, jie.gan@oss.qualcomm.com Subject: Re: [PATCH v8 08/13] coresight: etm4x: fix inconsistencies with sysfs configuration Message-ID: <20260707082510.GD1024232@e132581.arm.com> References: <20260629090007.1718746-1-yeoreum.yun@arm.com> <20260629090007.1718746-9-yeoreum.yun@arm.com> <20260706172159.GA1024232@e132581.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260707_012514_110079_4D3F548B X-CRM114-Status: GOOD ( 21.00 ) 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 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. > 2. sysfs with _irqsave? > > However, this make a latency for the sysfs. > > I think the (1) seems good. > > Any comments? @Suzuki and @Leo? Yeah, it is good to wait a bit for Suzuki if any ideas. Thanks, Leo