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=-11.3 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,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 F05FAC433E1 for ; Fri, 7 Aug 2020 03:52:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id D57992177B for ; Fri, 7 Aug 2020 03:52:41 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=mg.codeaurora.org header.i=@mg.codeaurora.org header.b="f/8WTbV8" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726508AbgHGDwk (ORCPT ); Thu, 6 Aug 2020 23:52:40 -0400 Received: from mail29.static.mailgun.info ([104.130.122.29]:63179 "EHLO mail29.static.mailgun.info" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726489AbgHGDwj (ORCPT ); Thu, 6 Aug 2020 23:52:39 -0400 DKIM-Signature: a=rsa-sha256; v=1; c=relaxed/relaxed; d=mg.codeaurora.org; q=dns/txt; s=smtp; t=1596772358; h=In-Reply-To: Content-Type: MIME-Version: References: Message-ID: Subject: Cc: To: From: Date: Sender; bh=rxjodLc5ZHJWICwMrRD3KM/Ju+RN4mYYoX/Mr1d0e5g=; b=f/8WTbV8sHGsbaZjUrRSP+7jQM3TCsMNRE5Vs274s6IqCOQsktCwT2Nk75DbJ02xjP5Yrkgu CtyAeSNUC8t1lF+YVOuJx4uGwgOE9GbdzU/5tRfCX4v3UJs873f2iXGSUdzdc4kGi64+HNYI inRrhVoQG3aSYI8ESO9z+Fiosk0= X-Mailgun-Sending-Ip: 104.130.122.29 X-Mailgun-Sid: WyI0MWYwYSIsICJsaW51eC1rZXJuZWxAdmdlci5rZXJuZWwub3JnIiwgImJlOWU0YSJd Received: from smtp.codeaurora.org (ec2-35-166-182-171.us-west-2.compute.amazonaws.com [35.166.182.171]) by smtp-out-n01.prod.us-west-2.postgun.com with SMTP id 5f2ccfff2f4952907db53c41 (version=TLS1.2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256); Fri, 07 Aug 2020 03:52:31 GMT Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 4C00FC433A0; Fri, 7 Aug 2020 03:52:31 +0000 (UTC) Received: from codeaurora.org (unknown [180.166.53.21]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) (Authenticated sender: tingwei) by smtp.codeaurora.org (Postfix) with ESMTPSA id E60B5C433C9; Fri, 7 Aug 2020 03:52:27 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 smtp.codeaurora.org E60B5C433C9 Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; dmarc=none (p=none dis=none) header.from=codeaurora.org Authentication-Results: aws-us-west-2-caf-mail-1.web.codeaurora.org; spf=none smtp.mailfrom=tingweiz@codeaurora.org Date: Fri, 7 Aug 2020 11:52:21 +0800 From: Tingwei Zhang To: Sai Prakash Ranjan Cc: Mathieu Poirier , Suzuki K Poulose , Mike Leach , Stephen Boyd , linux-arm-msm@vger.kernel.org, coresight@lists.linaro.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org Subject: Re: [PATCHv3] coresight: etm4x: Fix etm4_count race by moving cpuhp callbacks to init Message-ID: <20200807035221.GA6372@codeaurora.org> References: <20200729051310.18436-1-saiprakash.ranjan@codeaurora.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200729051310.18436-1-saiprakash.ranjan@codeaurora.org> User-Agent: Mutt/1.5.24 (2015-08-30) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 29, 2020 at 01:13:10PM +0800, Sai Prakash Ranjan wrote: > etm4_count keeps track of number of ETMv4 registered and on some systems, > a race is observed on etm4_count variable which can lead to multiple calls > to cpuhp_setup_state_nocalls_cpuslocked(). This function internally calls > cpuhp_store_callbacks() which prevents multiple registrations of callbacks > for a given state and due to this race, it returns -EBUSY leading to ETM > probe failures like below. > > coresight-etm4x: probe of 7040000.etm failed with error -16 > > This race can easily be triggered with async probe by setting probe type > as PROBE_PREFER_ASYNCHRONOUS and with ETM power management property > "arm,coresight-loses-context-with-cpu". > > Prevent this race by moving cpuhp callbacks to etm driver init since the > cpuhp callbacks doesn't have to depend on the etm4_count and can be once > setup during driver init. Similarly we move cpu_pm notifier registration > to driver init and completely remove etm4_count usage. Also now we can > use non cpuslocked version of cpuhp callbacks with this movement. > > Fixes: 9b6a3f3633a5 ("coresight: etmv4: Fix CPU power management setup in > probe() function") > Fixes: 58eb457be028 ("hwtracing/coresight-etm4x: Convert to hotplug state > machine") > Suggested-by: Suzuki K Poulose > Signed-off-by: Sai Prakash Ranjan > --- > > Changes in v3: > * Minor cleanups from v2 and change to device_initcall (Stephen Boyd) > * Move to non cpuslocked cpuhp callbacks and rename to etm_pm_setup() (Mike > Leach) > > Changes in v2: > * Rearrange cpuhp callbacks and move them to driver init (Suzuki K Poulose) > > --- > drivers/hwtracing/coresight/coresight-etm4x.c | 65 +++++++++---------- > 1 file changed, 31 insertions(+), 34 deletions(-) > > diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c > b/drivers/hwtracing/coresight/coresight-etm4x.c > index 6d7d2169bfb2..fddfd93b9a7b 100644 > --- a/drivers/hwtracing/coresight/coresight-etm4x.c > +++ b/drivers/hwtracing/coresight/coresight-etm4x.c > @@ -48,8 +48,6 @@ module_param(pm_save_enable, int, 0444); > MODULE_PARM_DESC(pm_save_enable, > "Save/restore state on power down: 1 = never, 2 = self-hosted"); > > -/* The number of ETMv4 currently registered */ > -static int etm4_count; > static struct etmv4_drvdata *etmdrvdata[NR_CPUS]; > static void etm4_set_default_config(struct etmv4_config *config); > static int etm4_set_event_filters(struct etmv4_drvdata *drvdata, > @@ -1398,28 +1396,25 @@ static struct notifier_block etm4_cpu_pm_nb = { > .notifier_call = etm4_cpu_pm_notify, > }; > > -/* Setup PM. Called with cpus locked. Deals with error conditions and > counts */ > -static int etm4_pm_setup_cpuslocked(void) > +/* Setup PM. Deals with error conditions and counts */ > +static int __init etm4_pm_setup(void) > { > int ret; > > - if (etm4_count++) > - return 0; > - > ret = cpu_pm_register_notifier(&etm4_cpu_pm_nb); > if (ret) > - goto reduce_count; > + return ret; > > - ret = > cpuhp_setup_state_nocalls_cpuslocked(CPUHP_AP_ARM_CORESIGHT_STARTING, > - "arm/coresight4:starting", > - etm4_starting_cpu, etm4_dying_cpu); > + ret = cpuhp_setup_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING, > + "arm/coresight4:starting", > + etm4_starting_cpu, etm4_dying_cpu); > > if (ret) > goto unregister_notifier; > > - ret = cpuhp_setup_state_nocalls_cpuslocked(CPUHP_AP_ONLINE_DYN, > - "arm/coresight4:online", > - etm4_online_cpu, NULL); > + ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN, > + "arm/coresight4:online", > + etm4_online_cpu, NULL); > > /* HP dyn state ID returned in ret on success */ > if (ret > 0) { > @@ -1428,21 +1423,15 @@ static int etm4_pm_setup_cpuslocked(void) > } > > /* failed dyn state - remove others */ > - cpuhp_remove_state_nocalls_cpuslocked(CPUHP_AP_ARM_CORESIGHT_STARTING); > + cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING); > > unregister_notifier: > cpu_pm_unregister_notifier(&etm4_cpu_pm_nb); > - > -reduce_count: > - --etm4_count; > return ret; > } > > -static void etm4_pm_clear(void) > +static void __init etm4_pm_clear(void) > { > - if (--etm4_count != 0) > - return; > - > cpu_pm_unregister_notifier(&etm4_cpu_pm_nb); > cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING); > if (hp_online) { > @@ -1498,22 +1487,12 @@ static int etm4_probe(struct amba_device *adev, > const struct amba_id *id) > if (!desc.name) > return -ENOMEM; > > - cpus_read_lock(); > etmdrvdata[drvdata->cpu] = drvdata; > > if (smp_call_function_single(drvdata->cpu, > etm4_init_arch_data, drvdata, 1)) > dev_err(dev, "ETM arch init failed\n"); > > - ret = etm4_pm_setup_cpuslocked(); > - cpus_read_unlock(); > - > - /* etm4_pm_setup_cpuslocked() does its own cleanup - exit on error */ > - if (ret) { > - etmdrvdata[drvdata->cpu] = NULL; > - return ret; > - } > - > if (etm4_arch_supported(drvdata->arch) == false) { > ret = -EINVAL; > goto err_arch_supported; > @@ -1560,7 +1539,6 @@ static int etm4_probe(struct amba_device *adev, const > struct amba_id *id) > > err_arch_supported: > etmdrvdata[drvdata->cpu] = NULL; > - etm4_pm_clear(); > return ret; > } > > @@ -1598,4 +1576,23 @@ static struct amba_driver etm4x_driver = { > .probe = etm4_probe, > .id_table = etm4_ids, > }; > -builtin_amba_driver(etm4x_driver); > + > +static int __init etm4x_init(void) > +{ > + int ret; > + > + ret = etm4_pm_setup(); etm4_pm_setup() is called in etm4x_init(), but etm4_pm_clear() is called in etm4_remove(). If one ETM4x device is removed, etm4_remove() would be called and we could still have other ETM4x device alive. Should etm4_pm_clear() be called in etm4x_exit()? It should only be called when module exits. Thanks, Tingwei > + > + /* etm4_pm_setup() does its own cleanup - exit on error */ > + if (ret) > + return ret; > + > + ret = amba_driver_register(&etm4x_driver); > + if (ret) { > + pr_err("Error registering etm4x driver\n"); > + etm4_pm_clear(); > + } > + > + return ret; > +} > +device_initcall(etm4x_init); > -- > QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member > of Code Aurora Forum, hosted by The Linux Foundation > > _______________________________________________ > CoreSight mailing list > CoreSight@lists.linaro.org > https://lists.linaro.org/mailman/listinfo/coresight