When the devfreq driver and the governor driver are built as modules,
the call to devfreq_add_device() or governor_store() fails because the
governor driver is not loaded at the time the devfreq driver loads. The
devfreq driver has a build dependency on the governor but also should
have a runtime dependency. We need to make sure that the governor driver
is loaded before the devfreq driver.
This patch fixes this bug by adding a try_then_request_governor()
function. First tries to find the governor, and then, if it is not found,
it requests the module and tries again.
Fixes: 1b5c1be2c88e (PM / devfreq: map devfreq drivers to governor using name)
Signed-off-by: Enric Balletbo i Serra <[email protected]>
---
Changes in v4:
- Kept "locked" devfreq_list from the return of find_devfreq_governor() to
the unlock of governor_store(). Requested by MyungJoo Ham.
Changes in v3:
- Remove unneded change in dev_err message.
- Fix err returned value in case to not find the governor.
Changes in v2:
- Add a new function to request the module and call that function from
devfreq_add_device and governor_store.
drivers/devfreq/devfreq.c | 53 ++++++++++++++++++++++++++++++++++-----
1 file changed, 47 insertions(+), 6 deletions(-)
diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 0b5b3abe054e..4ea6b19879a1 100644
--- a/drivers/devfreq/devfreq.c
+++ b/drivers/devfreq/devfreq.c
@@ -11,6 +11,7 @@
*/
#include <linux/kernel.h>
+#include <linux/kmod.h>
#include <linux/sched.h>
#include <linux/errno.h>
#include <linux/err.h>
@@ -221,6 +222,46 @@ static struct devfreq_governor *find_devfreq_governor(const char *name)
return ERR_PTR(-ENODEV);
}
+/**
+ * try_then_request_governor() - Try to find the governor and request the
+ * module if is not found.
+ * @name: name of the governor
+ *
+ * Search the list of devfreq governors and request the module and try again
+ * if is not found. This can happen when both drivers (the governor driver
+ * and the driver that call devfreq_add_device) are built as modules.
+ * devfreq_list_lock should be held by the caller.
+ *
+ * Return: The matched governor's pointer.
+ */
+static struct devfreq_governor *try_then_request_governor(const char *name)
+{
+ struct devfreq_governor *governor;
+ int err = 0;
+
+ WARN(!mutex_is_locked(&devfreq_list_lock),
+ "devfreq_list_lock must be locked.");
+
+ governor = find_devfreq_governor(name);
+ if (IS_ERR(governor)) {
+ mutex_unlock(&devfreq_list_lock);
+
+ if (!strncmp(name, DEVFREQ_GOV_SIMPLE_ONDEMAND,
+ DEVFREQ_NAME_LEN))
+ err = request_module("governor_%s", "simpleondemand");
+ else
+ err = request_module("governor_%s", name);
+ if (err)
+ return NULL;
+
+ mutex_lock(&devfreq_list_lock);
+
+ governor = find_devfreq_governor(name);
+ }
+
+ return governor;
+}
+
static int devfreq_notify_transition(struct devfreq *devfreq,
struct devfreq_freqs *freqs, unsigned int state)
{
@@ -643,11 +684,9 @@ struct devfreq *devfreq_add_device(struct device *dev,
srcu_init_notifier_head(&devfreq->transition_notifier_list);
mutex_unlock(&devfreq->lock);
-
mutex_lock(&devfreq_list_lock);
- list_add(&devfreq->node, &devfreq_list);
- governor = find_devfreq_governor(devfreq->governor_name);
+ governor = try_then_request_governor(devfreq->governor_name);
if (IS_ERR(governor)) {
dev_err(dev, "%s: Unable to find governor for the device\n",
__func__);
@@ -663,14 +702,15 @@ struct devfreq *devfreq_add_device(struct device *dev,
__func__);
goto err_init;
}
+
+ list_add(&devfreq->node, &devfreq_list);
+
mutex_unlock(&devfreq_list_lock);
return devfreq;
err_init:
- list_del(&devfreq->node);
mutex_unlock(&devfreq_list_lock);
-
device_unregister(&devfreq->dev);
err_dev:
if (devfreq)
@@ -989,7 +1029,8 @@ static ssize_t governor_store(struct device *dev, struct device_attribute *attr,
return -EINVAL;
mutex_lock(&devfreq_list_lock);
- governor = find_devfreq_governor(str_governor);
+
+ governor = try_then_request_governor(str_governor);
if (IS_ERR(governor)) {
ret = PTR_ERR(governor);
goto out;
--
2.18.0
>+ if (!strncmp(name, DEVFREQ_GOV_SIMPLE_ONDEMAND,
>+ DEVFREQ_NAME_LEN))
>+ err = request_module("governor_%s", "simpleondemand");
>+ else
>+ err = request_module("governor_%s", name);
>+ if (err)
>+ return NULL;
You are returning without the lock acquired..
Hi Enric,
On 2018년 07월 03일 22:29, Enric Balletbo i Serra wrote:
> When the devfreq driver and the governor driver are built as modules,
> the call to devfreq_add_device() or governor_store() fails because the
> governor driver is not loaded at the time the devfreq driver loads. The
> devfreq driver has a build dependency on the governor but also should
> have a runtime dependency. We need to make sure that the governor driver
> is loaded before the devfreq driver.
>
> This patch fixes this bug by adding a try_then_request_governor()
> function. First tries to find the governor, and then, if it is not found,
> it requests the module and tries again.
>
> Fixes: 1b5c1be2c88e (PM / devfreq: map devfreq drivers to governor using name)
> Signed-off-by: Enric Balletbo i Serra <[email protected]>
> ---
>
> Changes in v4:
> - Kept "locked" devfreq_list from the return of find_devfreq_governor() to
> the unlock of governor_store(). Requested by MyungJoo Ham.
>
> Changes in v3:
> - Remove unneded change in dev_err message.
> - Fix err returned value in case to not find the governor.
>
> Changes in v2:
> - Add a new function to request the module and call that function from
> devfreq_add_device and governor_store.
>
> drivers/devfreq/devfreq.c | 53 ++++++++++++++++++++++++++++++++++-----
> 1 file changed, 47 insertions(+), 6 deletions(-)
>
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 0b5b3abe054e..4ea6b19879a1 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
> @@ -11,6 +11,7 @@
> */
>
> #include <linux/kernel.h>
> +#include <linux/kmod.h>
> #include <linux/sched.h>
> #include <linux/errno.h>
> #include <linux/err.h>
> @@ -221,6 +222,46 @@ static struct devfreq_governor *find_devfreq_governor(const char *name)
> return ERR_PTR(-ENODEV);
> }
>
> +/**
> + * try_then_request_governor() - Try to find the governor and request the
> + * module if is not found.
> + * @name: name of the governor
Usually, devfreq used 'governor_name' indicating the name of governor.
you better to use 'governor_name' instead of 'name' for more readability.
> + *
> + * Search the list of devfreq governors and request the module and try again
> + * if is not found. This can happen when both drivers (the governor driver
> + * and the driver that call devfreq_add_device) are built as modules.
> + * devfreq_list_lock should be held by the caller.
> + *
> + * Return: The matched governor's pointer.
Usually, devfreq.c didn;t use the 'Return: ...'. So, you better to explain
what is returned from this function with function description.
> + */
> +static struct devfreq_governor *try_then_request_governor(const char *name)
ditto. (name -> governor_name)
> +{
> + struct devfreq_governor *governor;
> + int err = 0;
You have to check whether governor name is NULL or not.
if (IS_ERR_OR_NULL(name)) {
pr_err("DEVFREQ: %s: Invalid parameters\n", __func__);
return ERR_PTR(-EINVAL);
}
> +
> + WARN(!mutex_is_locked(&devfreq_list_lock),
> + "devfreq_list_lock must be locked.");
> +
> + governor = find_devfreq_governor(name);
> + if (IS_ERR(governor)) {
> + mutex_unlock(&devfreq_list_lock);
> +
> + if (!strncmp(name, DEVFREQ_GOV_SIMPLE_ONDEMAND,
> + DEVFREQ_NAME_LEN))
> + err = request_module("governor_%s", "simpleondemand");
> + else
> + err = request_module("governor_%s", name);
> + if (err)
> + return NULL;
When error happen, you unlock the mutex. If failed to request module,
you should restore the previous state. Please mutex_lock(&devfreq_list_lock)
before return.
> +
> + mutex_lock(&devfreq_list_lock);
> +
> + governor = find_devfreq_governor(name);
> + }
> +
> + return governor;
> +}
> +
> static int devfreq_notify_transition(struct devfreq *devfreq,
> struct devfreq_freqs *freqs, unsigned int state)
> {
> @@ -643,11 +684,9 @@ struct devfreq *devfreq_add_device(struct device *dev,
> srcu_init_notifier_head(&devfreq->transition_notifier_list);
>
> mutex_unlock(&devfreq->lock);
> -
This change is not related to this patch.
> mutex_lock(&devfreq_list_lock);
> - list_add(&devfreq->node, &devfreq_list);
>
> - governor = find_devfreq_governor(devfreq->governor_name);
> + governor = try_then_request_governor(devfreq->governor_name);
> if (IS_ERR(governor)) {
> dev_err(dev, "%s: Unable to find governor for the device\n",
> __func__);
> @@ -663,14 +702,15 @@ struct devfreq *devfreq_add_device(struct device *dev,
> __func__);
> goto err_init;
> }
> +
> + list_add(&devfreq->node, &devfreq_list);
> +
> mutex_unlock(&devfreq_list_lock);
>
> return devfreq;
>
> err_init:
> - list_del(&devfreq->node);
> mutex_unlock(&devfreq_list_lock);
> -
This change is not related to this patch.
> device_unregister(&devfreq->dev);
> err_dev:
> if (devfreq)
> @@ -989,7 +1029,8 @@ static ssize_t governor_store(struct device *dev, struct device_attribute *attr,
> return -EINVAL;
>
> mutex_lock(&devfreq_list_lock);
> - governor = find_devfreq_governor(str_governor);
> +
Don't need to add the blank line. It is enough to change the function
from find_devfreq_governor to try_then_request_governor.
> + governor = try_then_request_governor(str_governor);
> if (IS_ERR(governor)) {
> ret = PTR_ERR(governor);
> goto out;
>
--
Best Regards,
Chanwoo Choi
Samsung Electronics
Hi Chanwoo,
On 04/07/18 03:06, Chanwoo Choi wrote:
> Hi Enric,
>
> On 2018년 07월 03일 22:29, Enric Balletbo i Serra wrote:
>> When the devfreq driver and the governor driver are built as modules,
>> the call to devfreq_add_device() or governor_store() fails because the
>> governor driver is not loaded at the time the devfreq driver loads. The
>> devfreq driver has a build dependency on the governor but also should
>> have a runtime dependency. We need to make sure that the governor driver
>> is loaded before the devfreq driver.
>>
>> This patch fixes this bug by adding a try_then_request_governor()
>> function. First tries to find the governor, and then, if it is not found,
>> it requests the module and tries again.
>>
>> Fixes: 1b5c1be2c88e (PM / devfreq: map devfreq drivers to governor using name)
>> Signed-off-by: Enric Balletbo i Serra <[email protected]>
>> ---
>>
>> Changes in v4:
>> - Kept "locked" devfreq_list from the return of find_devfreq_governor() to
>> the unlock of governor_store(). Requested by MyungJoo Ham.
>>
>> Changes in v3:
>> - Remove unneded change in dev_err message.
>> - Fix err returned value in case to not find the governor.
>>
>> Changes in v2:
>> - Add a new function to request the module and call that function from
>> devfreq_add_device and governor_store.
>>
>> drivers/devfreq/devfreq.c | 53 ++++++++++++++++++++++++++++++++++-----
>> 1 file changed, 47 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>> index 0b5b3abe054e..4ea6b19879a1 100644
>> --- a/drivers/devfreq/devfreq.c
>> +++ b/drivers/devfreq/devfreq.c
>> @@ -11,6 +11,7 @@
>> */
>>
>> #include <linux/kernel.h>
>> +#include <linux/kmod.h>
>> #include <linux/sched.h>
>> #include <linux/errno.h>
>> #include <linux/err.h>
>> @@ -221,6 +222,46 @@ static struct devfreq_governor *find_devfreq_governor(const char *name)
>> return ERR_PTR(-ENODEV);
>> }
>>
>> +/**
>> + * try_then_request_governor() - Try to find the governor and request the
>> + * module if is not found.
>> + * @name: name of the governor
>
> Usually, devfreq used 'governor_name' indicating the name of governor.
> you better to use 'governor_name' instead of 'name' for more readability.
>
I don't mind to change if you want. But let me try to convince you first. I used
name for two reasons:
1. I saw that you are using governor_name sometimes, but find_devfreq_governor
uses name not governor_name. IMHO the function name in these two specific cases
'try_then_request_governor(name)' is enough readable.
2. If we want to use governor_name and then do not have the line exceeding the
80 characters I need to split the function in two lines. For me the readability
is better when you have all in one line.
If I did not convince you, just let me now and I'll change for governor_name :)
>> + *
>> + * Search the list of devfreq governors and request the module and try again
>> + * if is not found. This can happen when both drivers (the governor driver
>> + * and the driver that call devfreq_add_device) are built as modules.
>> + * devfreq_list_lock should be held by the caller.
>> + *
>> + * Return: The matched governor's pointer.
>
> Usually, devfreq.c didn;t use the 'Return: ...'. So, you better to explain
> what is returned from this function with function description.
>
OK.
>> + */
>> +static struct devfreq_governor *try_then_request_governor(const char *name)
>
> ditto. (name -> governor_name)
>
I convinced you? ;)
>> +{
>> + struct devfreq_governor *governor;
>> + int err = 0;
>
> You have to check whether governor name is NULL or not.
>
> if (IS_ERR_OR_NULL(name)) {
> pr_err("DEVFREQ: %s: Invalid parameters\n", __func__);
> return ERR_PTR(-EINVAL);
> }
>
Right.
>> +
>> + WARN(!mutex_is_locked(&devfreq_list_lock),
>> + "devfreq_list_lock must be locked.");
>> +
>> + governor = find_devfreq_governor(name);
>> + if (IS_ERR(governor)) {
>> + mutex_unlock(&devfreq_list_lock);
>> +
>> + if (!strncmp(name, DEVFREQ_GOV_SIMPLE_ONDEMAND,
>> + DEVFREQ_NAME_LEN))
>> + err = request_module("governor_%s", "simpleondemand");
>> + else
>> + err = request_module("governor_%s", name);
>> + if (err)
>> + return NULL;
>
> When error happen, you unlock the mutex. If failed to request module,
> you should restore the previous state. Please mutex_lock(&devfreq_list_lock)
> before return.
>
Oh right, my bad.
>> +
>> + mutex_lock(&devfreq_list_lock);
>> +
>> + governor = find_devfreq_governor(name);
>> + }
>> +
>> + return governor;
>> +}
>> +
>> static int devfreq_notify_transition(struct devfreq *devfreq,
>> struct devfreq_freqs *freqs, unsigned int state)
>> {
>> @@ -643,11 +684,9 @@ struct devfreq *devfreq_add_device(struct device *dev,
>> srcu_init_notifier_head(&devfreq->transition_notifier_list);
>>
>> mutex_unlock(&devfreq->lock);
>> -
>
> This change is not related to this patch.
>
Ack.
>> mutex_lock(&devfreq_list_lock);
>> - list_add(&devfreq->node, &devfreq_list);
>>
>> - governor = find_devfreq_governor(devfreq->governor_name);
>> + governor = try_then_request_governor(devfreq->governor_name);
>> if (IS_ERR(governor)) {
>> dev_err(dev, "%s: Unable to find governor for the device\n",
>> __func__);
>> @@ -663,14 +702,15 @@ struct devfreq *devfreq_add_device(struct device *dev,
>> __func__);
>> goto err_init;
>> }
>> +
>> + list_add(&devfreq->node, &devfreq_list);
>> +
>> mutex_unlock(&devfreq_list_lock);
>>
>> return devfreq;
>>
>> err_init:
>> - list_del(&devfreq->node);
>> mutex_unlock(&devfreq_list_lock);
>> -
>
> This change is not related to this patch.
>
Ack.
>> device_unregister(&devfreq->dev);
>> err_dev:
>> if (devfreq)
>> @@ -989,7 +1029,8 @@ static ssize_t governor_store(struct device *dev, struct device_attribute *attr,
>> return -EINVAL;
>>
>> mutex_lock(&devfreq_list_lock);
>> - governor = find_devfreq_governor(str_governor);
>> +
>
> Don't need to add the blank line. It is enough to change the function
> from find_devfreq_governor to try_then_request_governor.
>
>> + governor = try_then_request_governor(str_governor);
>> if (IS_ERR(governor)) {
>> ret = PTR_ERR(governor);
>> goto out;
>>
>
>
Preparing next version, many thanks for the review.
Enric
Hi Enric,
On 2018년 07월 04일 17:16, Enric Balletbo i Serra wrote:
> Hi Chanwoo,
>
> On 04/07/18 03:06, Chanwoo Choi wrote:
>> Hi Enric,
>>
>> On 2018년 07월 03일 22:29, Enric Balletbo i Serra wrote:
>>> When the devfreq driver and the governor driver are built as modules,
>>> the call to devfreq_add_device() or governor_store() fails because the
>>> governor driver is not loaded at the time the devfreq driver loads. The
>>> devfreq driver has a build dependency on the governor but also should
>>> have a runtime dependency. We need to make sure that the governor driver
>>> is loaded before the devfreq driver.
>>>
>>> This patch fixes this bug by adding a try_then_request_governor()
>>> function. First tries to find the governor, and then, if it is not found,
>>> it requests the module and tries again.
>>>
>>> Fixes: 1b5c1be2c88e (PM / devfreq: map devfreq drivers to governor using name)
>>> Signed-off-by: Enric Balletbo i Serra <[email protected]>
>>> ---
>>>
>>> Changes in v4:
>>> - Kept "locked" devfreq_list from the return of find_devfreq_governor() to
>>> the unlock of governor_store(). Requested by MyungJoo Ham.
>>>
>>> Changes in v3:
>>> - Remove unneded change in dev_err message.
>>> - Fix err returned value in case to not find the governor.
>>>
>>> Changes in v2:
>>> - Add a new function to request the module and call that function from
>>> devfreq_add_device and governor_store.
>>>
>>> drivers/devfreq/devfreq.c | 53 ++++++++++++++++++++++++++++++++++-----
>>> 1 file changed, 47 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>>> index 0b5b3abe054e..4ea6b19879a1 100644
>>> --- a/drivers/devfreq/devfreq.c
>>> +++ b/drivers/devfreq/devfreq.c
>>> @@ -11,6 +11,7 @@
>>> */
>>>
>>> #include <linux/kernel.h>
>>> +#include <linux/kmod.h>
>>> #include <linux/sched.h>
>>> #include <linux/errno.h>
>>> #include <linux/err.h>
>>> @@ -221,6 +222,46 @@ static struct devfreq_governor *find_devfreq_governor(const char *name)
>>> return ERR_PTR(-ENODEV);
>>> }
>>>
>>> +/**
>>> + * try_then_request_governor() - Try to find the governor and request the
>>> + * module if is not found.
>>> + * @name: name of the governor
>>
>> Usually, devfreq used 'governor_name' indicating the name of governor.
>> you better to use 'governor_name' instead of 'name' for more readability.
>>
>
> I don't mind to change if you want. But let me try to convince you first. I used
> name for two reasons:
> 1. I saw that you are using governor_name sometimes, but find_devfreq_governor
> uses name not governor_name. IMHO the function name in these two specific cases
> 'try_then_request_governor(name)' is enough readable.
OK. skip the my comment of changing the variable name. Thanks.
> 2. If we want to use governor_name and then do not have the line exceeding the
> 80 characters I need to split the function in two lines. For me the readability
> is better when you have all in one line.
>
> If I did not convince you, just let me now and I'll change for governor_name :)
>
(snip)
--
Best Regards,
Chanwoo Choi
Samsung Electronics
Hi Enric,
Please send this patch to stable-kernel mailing list.
Regards,
Chanwoo Choi
On 2018년 07월 04일 17:26, Chanwoo Choi wrote:
> Hi Enric,
>
> On 2018년 07월 04일 17:16, Enric Balletbo i Serra wrote:
>> Hi Chanwoo,
>>
>> On 04/07/18 03:06, Chanwoo Choi wrote:
>>> Hi Enric,
>>>
>>> On 2018년 07월 03일 22:29, Enric Balletbo i Serra wrote:
>>>> When the devfreq driver and the governor driver are built as modules,
>>>> the call to devfreq_add_device() or governor_store() fails because the
>>>> governor driver is not loaded at the time the devfreq driver loads. The
>>>> devfreq driver has a build dependency on the governor but also should
>>>> have a runtime dependency. We need to make sure that the governor driver
>>>> is loaded before the devfreq driver.
>>>>
>>>> This patch fixes this bug by adding a try_then_request_governor()
>>>> function. First tries to find the governor, and then, if it is not found,
>>>> it requests the module and tries again.
>>>>
>>>> Fixes: 1b5c1be2c88e (PM / devfreq: map devfreq drivers to governor using name)
>>>> Signed-off-by: Enric Balletbo i Serra <[email protected]>
>>>> ---
>>>>
>>>> Changes in v4:
>>>> - Kept "locked" devfreq_list from the return of find_devfreq_governor() to
>>>> the unlock of governor_store(). Requested by MyungJoo Ham.
>>>>
>>>> Changes in v3:
>>>> - Remove unneded change in dev_err message.
>>>> - Fix err returned value in case to not find the governor.
>>>>
>>>> Changes in v2:
>>>> - Add a new function to request the module and call that function from
>>>> devfreq_add_device and governor_store.
>>>>
>>>> drivers/devfreq/devfreq.c | 53 ++++++++++++++++++++++++++++++++++-----
>>>> 1 file changed, 47 insertions(+), 6 deletions(-)
>>>>
>>>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>>>> index 0b5b3abe054e..4ea6b19879a1 100644
>>>> --- a/drivers/devfreq/devfreq.c
>>>> +++ b/drivers/devfreq/devfreq.c
>>>> @@ -11,6 +11,7 @@
>>>> */
>>>>
>>>> #include <linux/kernel.h>
>>>> +#include <linux/kmod.h>
>>>> #include <linux/sched.h>
>>>> #include <linux/errno.h>
>>>> #include <linux/err.h>
>>>> @@ -221,6 +222,46 @@ static struct devfreq_governor *find_devfreq_governor(const char *name)
>>>> return ERR_PTR(-ENODEV);
>>>> }
>>>>
>>>> +/**
>>>> + * try_then_request_governor() - Try to find the governor and request the
>>>> + * module if is not found.
>>>> + * @name: name of the governor
>>>
>>> Usually, devfreq used 'governor_name' indicating the name of governor.
>>> you better to use 'governor_name' instead of 'name' for more readability.
>>>
>>
>> I don't mind to change if you want. But let me try to convince you first. I used
>> name for two reasons:
>> 1. I saw that you are using governor_name sometimes, but find_devfreq_governor
>> uses name not governor_name. IMHO the function name in these two specific cases
>> 'try_then_request_governor(name)' is enough readable.
>
> OK. skip the my comment of changing the variable name. Thanks.
>
>> 2. If we want to use governor_name and then do not have the line exceeding the
>> 80 characters I need to split the function in two lines. For me the readability
>> is better when you have all in one line.
>>
>> If I did not convince you, just let me now and I'll change for governor_name :)
>>
>
> (snip)
>