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spf=none smtp.mailfrom=saiprakash.ranjan@codeaurora.org From: Sai Prakash Ranjan To: Mathieu Poirier , Suzuki K Poulose , Mike Leach Subject: [PATCHv2] coresight: etm4x: Fix etm4_count race by moving cpuhp callbacks to init Date: Tue, 28 Jul 2020 13:21:02 +0530 Message-Id: <20200728075102.30807-1-saiprakash.ranjan@codeaurora.org> X-Mailer: git-send-email 2.27.0 MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200728_035116_069549_552F1692 X-CRM114-Status: GOOD ( 24.22 ) X-Spam-Score: -0.0 (/) X-Spam-Report: SpamAssassin version 3.4.4 on merlin.infradead.org summary: Content analysis details: (-0.0 points) pts rule name description ---- ---------------------- -------------------------------------------------- -0.0 RCVD_IN_DNSWL_NONE RBL: Sender listed at https://www.dnswl.org/, no trust [104.130.122.29 listed in list.dnswl.org] -0.0 RCVD_IN_MSPIKE_H2 RBL: Average reputation (+2) [104.130.122.29 listed in wl.mailspike.net] -0.0 SPF_PASS SPF: sender matches SPF record 0.0 SPF_HELO_NONE SPF: HELO does not publish an SPF Record -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid 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 , linux-arm-msm@vger.kernel.org, coresight@lists.linaro.org, linux-kernel@vger.kernel.org, Stephen Boyd , linux-arm-kernel@lists.infradead.org Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+patchwork-linux-arm=patchwork.kernel.org@lists.infradead.org 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. 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 v2: * Rearrange cpuhp callbacks and move them to driver init (Suzuki K Poulose) --- drivers/hwtracing/coresight/coresight-etm4x.c | 51 ++++++++++--------- 1 file changed, 27 insertions(+), 24 deletions(-) diff --git a/drivers/hwtracing/coresight/coresight-etm4x.c b/drivers/hwtracing/coresight/coresight-etm4x.c index 6d7d2169bfb2..adb71987a1e3 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, @@ -1403,12 +1401,9 @@ static int etm4_pm_setup_cpuslocked(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", @@ -1432,17 +1427,11 @@ static int etm4_pm_setup_cpuslocked(void) unregister_notifier: cpu_pm_unregister_notifier(&etm4_cpu_pm_nb); - -reduce_count: - --etm4_count; return ret; } static void 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 +1576,29 @@ 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; + + cpus_read_lock(); + ret = etm4_pm_setup_cpuslocked(); + cpus_read_unlock(); + + /* etm4_pm_setup_cpuslocked() does its own cleanup - exit on error */ + if (ret) + return ret; + + ret = amba_driver_register(&etm4x_driver); + if (ret) { + pr_info("Error registering etm4x driver\n"); + goto err_init; + } + + return ret; + +err_init: + etm4_pm_clear(); + return ret; +} +module_init(etm4x_init);