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 01E09F8FA7B for ; Tue, 21 Apr 2026 14:02:32 +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=HVskjFQn8LGLg0wyQDRTc2q4IyQ/3vmBYkuiI0CLoK0=; b=d5DvAzYK8MyepTC+CMJcK7b29S s9UhDKLl87ravLtOHLSH1rv1ZFe4sSFnq9hLOb33uSMXtPbzObz4A4DPC/pWgc/uv2va8uDp2eNFT QwI5mhIWG61g7i2DEA4BDAhX6Z4xfxudkumBwu8OFheJ3KORhc5+8nUs8Z7mi3HGOdsKKIeu0PkqJ aMu2Z0MKkcmhHmXeLqxplFbEGa9DSrV8B1g+y8/gdMYlhKCAT6JjtKuDvMkimogoOvTily1EV/cXu MSWz+GmmGSrnuKRvnx0SN/Nk/RCrY0N0nTMNncy6hiT54O0p4W37nHAGeMCugBl0GWMa3WG46yhL5 wjuuK6uw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wFBgH-00000008hyg-2Co3; Tue, 21 Apr 2026 14:02:25 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1wFBgD-00000008hyK-1w7Z for linux-arm-kernel@lists.infradead.org; Tue, 21 Apr 2026 14:02:24 +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 0E4A22573; Tue, 21 Apr 2026 07:02:12 -0700 (PDT) Received: from e129823.arm.com (e129823.arm.com [10.1.197.6]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 758C73F7B4; Tue, 21 Apr 2026 07:02:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1776780137; bh=UxOuyvqjssBcp1emTpPrTkHhq/tnIYeB21ckVfqA9hY=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=gv7m+V87Vw0axaDcNsT9EZElZp2PBUxga27N8/nnNqzlCNW4IZK9QEz2a29vFu7ou xsZQMCUxflZ0lvKvNzncI1yPY7NWujZL8/rB4pZsLnQbHwhSB/E40KsBZRoYaDAVlu 0JCwe9MNpUyz0IIl07CzuHfVM+Zdkw+sekHM6a9A= Date: Tue, 21 Apr 2026 15:02:14 +0100 From: Yeoreum Yun To: Leo Yan 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 v5 07/12] coresight: etm4x: fix inconsistencies with sysfs configuration Message-ID: References: <20260415165528.3369607-1-yeoreum.yun@arm.com> <20260415165528.3369607-8-yeoreum.yun@arm.com> <20260421104601.GB929984@e132581.arm.com> <20260421132842.GC929984@e132581.arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260421132842.GC929984@e132581.arm.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260421_070221_637111_2C8F9EA7 X-CRM114-Status: GOOD ( 24.54 ) 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 Hi Leo, > On Tue, Apr 21, 2026 at 12:14:20PM +0100, Yeoreum Yun wrote: > > [...] > > > > > - There is a risk of corrupting drvdata->config if a perf session enables > > > > tracing while cscfg_csdev_disable_active_config() is being handled in > > > > etm4_disable_sysfs(). > > > > > > Similiar to above, cscfg_csdev_disable_active_config() is not > > > protected in etm4_disable_sysfs(). > > > > This is not true. > > at the time of etm4_disable_sysfs() "mode" is already taken > > (whether sysfs or perf). In this situation, it's enough to > > call cscfg_csdev_disable_active_config() before chaning > > mode to DISABLED. > > To be clear, I am trying to understand issue _before_ your patch. > Without this patch, cscfg_csdev_disable_active_config() is not > protected by the mode. Right. [...] > > > > @@ -1386,6 +1401,7 @@ static void etm4_init_arch_data(void *info) > > > > drvdata = dev_get_drvdata(init_arg->dev); > > > > caps = &drvdata->caps; > > > > csa = init_arg->csa; > > > > + config = &drvdata->active_config; > > > > > > Should we init drvdata->config instead so make it has sane values ? > > > > > > In other words, drvdata->active_config are always set at the runtime, > > > so don't need to init it at all, right? > > > > No. at least when the initialise, I think we should fill the its > > contesnt with the "etm4_set_default()". > > > > That's why the consequence call etm4_set_default() called with > > active_config and config is coped with the default configutation. > > I'm concerned that some config fields may be reused across sessions. > For example, a sysfs session copies drvdata->config into > drvdata->active_config, and later a perf session may reuse stale > values. The same issue can happen in the reverse direction. > > A clean approach would be to treat drvdata->active_config as > per-session state: > > 1) clear drvdata->active_config at session start > 2) apply the session-specific config > 2.1) sysfs: use drvdata->config > 2.2) perf: use event config > 3) then apply configfs configuration This is not true. In case of "perf", it always clear the "active_config" with 0x00 before enable. so it wouldn't. In case of sysfs we don't need to worries about since "config" field saves everything and this is applied into active_config. So, your issue doesn't exist in this case. -- Sincerely, Yeoreum Yun