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Fri, 07 Aug 2020 03:58:51 GMT Received: by smtp.codeaurora.org (Postfix, from userid 1001) id 3766EC433CA; Fri, 7 Aug 2020 03:58:51 +0000 (UTC) Received: from mail.codeaurora.org (localhost.localdomain [127.0.0.1]) (using TLSv1 with cipher ECDHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) (Authenticated sender: tingwei) by smtp.codeaurora.org (Postfix) with ESMTPSA id C83F3C433C6; Fri, 7 Aug 2020 03:58:49 +0000 (UTC) MIME-Version: 1.0 Date: Fri, 07 Aug 2020 11:58:49 +0800 From: tingwei@codeaurora.org To: Tingwei Zhang Subject: Re: [PATCHv3] coresight: etm4x: Fix etm4_count race by moving cpuhp callbacks to init In-Reply-To: <20200807035221.GA6372@codeaurora.org> References: <20200729051310.18436-1-saiprakash.ranjan@codeaurora.org> <20200807035221.GA6372@codeaurora.org> Message-ID: <5e6f1de80532ef401d76890969d5a0c6@codeaurora.org> X-Sender: tingwei@codeaurora.org User-Agent: Roundcube Webmail/1.3.9 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200806_235900_962782_5D525A7B X-CRM114-Status: GOOD ( 30.13 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Sai Prakash Ranjan , Mathieu Poirier , Suzuki K Poulose , linux-arm-msm@vger.kernel.org, coresight@lists.linaro.org, linux-kernel@vger.kernel.org, Stephen Boyd , linux-arm-kernel@lists.infradead.org, Mike Leach Content-Transfer-Encoding: 7bit Content-Type: text/plain; charset="us-ascii"; Format="flowed" Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Sorry for the noise. Please ignore previous comment. The change is in old patch set of my series. This change is good to go. On 2020-08-07 11:52, Tingwei Zhang wrote: > 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 > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@lists.infradead.org > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel