From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 97A3141B36D for ; Fri, 15 May 2026 08:53:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778835240; cv=none; b=F78CG/wB7Zn4ZpSV7VAGGQdKz4TDCTw3cKpnI+ZAQMnoEkeakIdpTszFM6HTlKVBC6OeXu/BIt49RyEB9korZcUsdV9lUpx3VTaKHV1vFnGELOamP/Q1C1yoN5wO7GdH8s7wygPsM5TB454uhq9VDJxTr3acUkuv3qPEFwgj+KA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1778835240; c=relaxed/simple; bh=J8r6ADKH+Z5jHPKFi221LwI804qFaj/OEXhMifsRm1M=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=IeNuI8x7f2/uBsykOsuD9ZhTtsFZWJBNUqKIYC+T6VtVbzj9f4MQXERap2vT3hXYO6eoOjtJD9W2twRPD47iho3NRwiKbvI6+9kqjcs2nA1Z28k5Xc8hlVhaxPhUSjLhHQqJiPLkJ/8PlCmKOFjO4tdqCZvgoPDXi31QVNn562M= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=eYwqtNHR; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="eYwqtNHR" 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 B913A3597; Fri, 15 May 2026 01:53:52 -0700 (PDT) Received: from localhost (e132581.arm.com [10.1.196.87]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 74DF93F7B4; Fri, 15 May 2026 01:53:57 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1778835238; bh=J8r6ADKH+Z5jHPKFi221LwI804qFaj/OEXhMifsRm1M=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=eYwqtNHRgV7X0NnglSahkmOSmX4kBAm5TsswoqpLf9Oc93QrO5CgE2VLEomxTv7v0 fA4cmIjcQFypMNutkhynOOZyD8dXTqlT63ac/9/zAlv4aCCasnchDLvr7HKOsDkO5Y zkipzpiAom0xRW6mz4URZDkWmNyHjzfCFB+Pzp9o= Date: Fri, 15 May 2026 09:53:54 +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 v6 07/13] coresight: etm4x: fix inconsistencies with sysfs configuration Message-ID: <20260515085354.GH34802@e132581.arm.com> References: <20260422132203.977549-1-yeoreum.yun@arm.com> <20260422132203.977549-8-yeoreum.yun@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260422132203.977549-8-yeoreum.yun@arm.com> On Wed, Apr 22, 2026 at 02:21:57PM +0100, Yeoreum Yun wrote: [...] > - Since active_config and related fields are accessed only by the local CPU > in etm4_enable/disable_sysfs_smp_call() (similar to perf enable/disable), > remove the lock/unlock from the sysfs enable/disable path and > startup/dying_cpu except when to access config fields. Thanks for writing this up, which is helpful for understanding. [...] > @@ -918,40 +948,29 @@ static int etm4_enable_sysfs(struct coresight_device *csdev, struct coresight_pa > > /* enable any config activated by configfs */ > cscfg_config_sysfs_get_active_cfg(&cfg_hash, &preset); With the patch [1], we can move cscfg_config_sysfs_get_active_cfg() to smp call. As a result, all things for enabling cscfg can be in the same place. [1] https://lore.kernel.org/linux-arm-kernel/20260511-arm_coresight_path_power_management_improvement-v12-14-1c9dcb1de8c9@arm.com/ > - if (cfg_hash) { > - ret = cscfg_csdev_enable_active_config(csdev, cfg_hash, preset); > - if (ret) { > - etm4_release_trace_id(drvdata); > - return ret; > - } > - } > - > - raw_spin_lock(&drvdata->spinlock); > - > - drvdata->trcid = path->trace_id; > - > - /* Tracer will never be paused in sysfs mode */ > - drvdata->paused = false; > > /* > * Executing etm4_enable_hw on the cpu whose ETM is being enabled > * ensures that register writes occur when cpu is powered. > */ > arg.drvdata = drvdata; > + arg.path = path; > + arg.cfg_hash = cfg_hash; > + arg.preset = preset; Connect with the comment above , don't need to pass cfg_hash/preset anymore. > + raw_spin_lock(&drvdata->spinlock); > + arg.config = drvdata->config; > + raw_spin_unlock(&drvdata->spinlock); Seems to me, this is right way for locking - here we simply use spinlock for exclusive access config from sysfs knobs. However, we avoid the config copy and directly access in SMP call? we still can use the raw spinlock in SMP call. My suggestion is: - First use a patch to move the drvdata assignment to SMP call and remove spinlock; - Then, rebase this patch for moving cscfg into SMP call. If so, we only need add a new field "arg->path", right? > @@ -1857,13 +1875,11 @@ static int etm4_starting_cpu(unsigned int cpu) > if (!etmdrvdata[cpu]) > return 0; > > - raw_spin_lock(&etmdrvdata[cpu]->spinlock); With the change [2], the starting and dying functions have been removed. If you rebase patches on the top PM series, then you will not bother this. Anyway, this is right to remove spinlock for hotplug notifiers. [2] https://lore.kernel.org/linux-arm-kernel/20260511-arm_coresight_path_power_management_improvement-v12-27-1c9dcb1de8c9@arm.com/