Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

Commit 9d0a5c16 authored by Sai Prakash Ranjan's avatar Sai Prakash Ranjan Committed by Lee Jones
Browse files

UPSTREAM: coresight: etm4x: Fix etm4_count race by moving cpuhp callbacks to init 



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.

Bug: 254441685
Fixes: 9b6a3f3633a5 ("coresight: etmv4: Fix CPU power management setup in probe() function")
Fixes: 58eb457b ("hwtracing/coresight-etm4x: Convert to hotplug state machine")
Suggested-by: default avatarSuzuki K Poulose <suzuki.poulose@arm.com>
Tested-by: default avatarStephen Boyd <swboyd@chromium.org>
Reviewed-by: default avatarStephen Boyd <swboyd@chromium.org>
Reviewed-by: default avatarSuzuki K Poulose <suzuki.poulose@arm.com>
Signed-off-by: default avatarSai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
Signed-off-by: default avatarMathieu Poirier <mathieu.poirier@linaro.org>
Link: https://lore.kernel.org/r/20200916191737.4001561-2-mathieu.poirier@linaro.org


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
(cherry picked from commit 2d1a8bfb61ec0177343e99ebd745e3e4ceb0d0d5)
Signed-off-by: default avatarLee Jones <joneslee@google.com>
Change-Id: I6d4eea8bb57893603d04d27dc301b2736ddd3d6c
parent 16187c3b

drivers/hwtracing/coresight/coresight-etm4x.c

+31 −34
Original line number Diff line number Diff line
@@ -47,8 +47,6 @@ 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,
@@ -1369,26 +1367,23 @@ 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,

	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,

	ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,

					"arm/coresight4:online",

					etm4_online_cpu, NULL);
@@ -1399,21 +1394,15 @@ 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) {
@@ -1469,22 +1458,12 @@ static int etm4_probe(struct amba_device *adev, const struct amba_id *id) 


	drvdata->cpu = pdata ? pdata->cpu : 0;



	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;
@@ -1524,7 +1503,6 @@ 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;

}
@@ -1551,4 +1529,23 @@ 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() 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);