Re: [PATCHv2] coresight: etm4x: Fix etm4_count race by moving cpuhp callbacks to init
Hi Mike,
On 2020-07-29 01:46, Mike Leach wrote:
Hi Sai,
On Tue, 28 Jul 2020 at 08:51, 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 704.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)
{
consider renaming this to etm4_pm_setup() and handing any cpu locking
inside the function.
In the circumstances - as part of the driver init rather than probe it
may be sufficient to call the cpuhp_setup functions without the
_cpuslocked suffix and allow the calls to lock the cpus as they are
made.
i.e. cpuhp_setup_state_nocalls_cpuslocked() =>
cpuhp_setup_state_nocalls()
Sure, will make this change.
int ret;
- if (etm4_count++)
- return 0;
-
ret = cpu_pm_register_notifier(_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(_cpu_pm_nb);
-
-reduce_count:
- --etm4_count;
return ret;
}
static void etm4_pm_clear(void)
{
- if (--etm4_count != 0)
- return;
-
cpu_pm_unregister_notifier(_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();
See my comment above about rename and use of cpus_read_lock
Yes, thanks for the review Mike.
Thanks,
Sai
--
QUALCOMM INDIA, on behalf of Qualcomm Innovation
Re: [PATCHv2] coresight: etm4x: Fix etm4_count race by moving cpuhp callbacks to init
Hi Sai,
On Tue, 28 Jul 2020 at 08:51, 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 704.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)
> {
consider renaming this to etm4_pm_setup() and handing any cpu locking
inside the function.
In the circumstances - as part of the driver init rather than probe it
may be sufficient to call the cpuhp_setup functions without the
_cpuslocked suffix and allow the calls to lock the cpus as they are
made.
i.e. cpuhp_setup_state_nocalls_cpuslocked() => cpuhp_setup_state_nocalls()
> int ret;
>
> - if (etm4_count++)
> - return 0;
> -
> ret = cpu_pm_register_notifier(_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(_cpu_pm_nb);
> -
> -reduce_count:
> - --etm4_count;
> return ret;
> }
>
> static void etm4_pm_clear(void)
> {
> - if (--etm4_count != 0)
> - return;
> -
> cpu_pm_unregister_notifier(_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();
See my comment above about rename and use of
Re: [PATCHv2] coresight: etm4x: Fix etm4_count race by moving cpuhp callbacks to init
On 2020-07-28 13:59, Stephen Boyd wrote:
Quoting Sai Prakash Ranjan (2020-07-28 00:51:02)
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)
Is this only called from __init now? If so please mark it as __init
then.
Yes, will change it.
{
int ret;
- if (etm4_count++)
- return 0;
-
ret = cpu_pm_register_notifier(_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(_cpu_pm_nb);
-
-reduce_count:
- --etm4_count;
return ret;
}
static void etm4_pm_clear(void)
This is __init too?
Will change.
{
- if (--etm4_count != 0)
- return;
-
cpu_pm_unregister_notifier(_cpu_pm_nb);
cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING);
if (hp_online) {
@@ -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(_driver);
+ if (ret) {
+ pr_info("Error registering etm4x driver\n");
Use pr_err() please.
Yes indeed, will change.
+ goto err_init;
+ }
+
+ return ret;
+
+err_init:
Why is this a goto?
+ etm4_pm_clear();
+ return ret;
Instead of just putting this in the if (ret) arm?
Will change.
+}
+module_init(etm4x_init);
It was device_initcall before with builtin_amba_driver(), best to not
change that.
Sure.
I will wait to see if there are any more comments on this patch and then
post a v3.
Thanks for the review Stephen.
Thanks,
Sai
--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a
member
of Code Aurora Forum, hosted by The Linux Foundation
Re: [PATCHv2] coresight: etm4x: Fix etm4_count race by moving cpuhp callbacks to init
Quoting Sai Prakash Ranjan (2020-07-28 00:51:02)
> 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)
Is this only called from __init now? If so please mark it as __init
then.
> {
> int ret;
>
> - if (etm4_count++)
> - return 0;
> -
> ret = cpu_pm_register_notifier(_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(_cpu_pm_nb);
> -
> -reduce_count:
> - --etm4_count;
> return ret;
> }
>
> static void etm4_pm_clear(void)
This is __init too?
> {
> - if (--etm4_count != 0)
> - return;
> -
> cpu_pm_unregister_notifier(_cpu_pm_nb);
> cpuhp_remove_state_nocalls(CPUHP_AP_ARM_CORESIGHT_STARTING);
> if (hp_online) {
> @@ -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(_driver);
> + if (ret) {
> + pr_info("Error registering etm4x driver\n");
Use pr_err() please.
> + goto err_init;
> + }
> +
> + return ret;
> +
> +err_init:
Why is this a goto?
> + etm4_pm_clear();
> + return ret;
Instead of just putting this in the if (ret) arm?
> +}
> +module_init(etm4x_init);
It was device_initcall before with builtin_amba_driver(), best to not
change that.
[PATCHv2] 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 704.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(_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(_cpu_pm_nb);
-
-reduce_count:
- --etm4_count;
return ret;
}
static void etm4_pm_clear(void)
{
- if (--etm4_count != 0)
- return;
-
cpu_pm_unregister_notifier(_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(_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);
--
QUALCOMM INDIA, on behalf of Qualcomm Innovation Center, Inc. is a member
of Code Aurora Forum, hosted by The Linux Foundation
