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 <[email protected]>
Signed-off-by: Sai Prakash Ranjan <[email protected]>
---
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() 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
Quoting Sai Prakash Ranjan (2020-07-28 22:13:10)
> 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 <[email protected]>
> Signed-off-by: Sai Prakash Ranjan <[email protected]>
> ---
Reviewed-by: Stephen Boyd <[email protected]>
Tested-by: Stephen Boyd <[email protected]>
On 07/29/2020 06:13 AM, 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 <[email protected]>
> Signed-off-by: Sai Prakash Ranjan <[email protected]>
Reviewed-by: Suzuki K Poulose <[email protected]>
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 <[email protected]>
> Signed-off-by: Sai Prakash Ranjan <[email protected]>
> ---
>
> 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
> [email protected]
> https://lists.linaro.org/mailman/listinfo/coresight
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 <[email protected]>
>> Signed-off-by: Sai Prakash Ranjan <[email protected]>
>> ---
>>
>> 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
>> [email protected]
>> https://lists.linaro.org/mailman/listinfo/coresight
>
> _______________________________________________
> linux-arm-kernel mailing list
> [email protected]
> http://lists.infradead.org/mailman/listinfo/linux-arm-kernel
On Wed, Jul 29, 2020 at 10:43:10AM +0530, 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 <[email protected]>
> Signed-off-by: Sai Prakash Ranjan <[email protected]>
I have applied this patch to my local tree - it will be published when v5.9-rc1
comes out next week.
Thanks,
Mathieu
> ---
>
> 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() 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
>