* [PATCH v5] PM / devfreq: Fix devfreq_add_device() when drivers are built as modules.
@ 2018-07-04 8:45 Enric Balletbo i Serra
2018-07-05 0:13 ` Chanwoo Choi
0 siblings, 1 reply; 3+ messages in thread
From: Enric Balletbo i Serra @ 2018-07-04 8:45 UTC (permalink / raw)
To: linux-kernel, stable
Cc: kernel, Chanwoo Choi, Kyungmin Park, MyungJoo Ham, linux-pm
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 <enric.balletbo@collabora.com>
---
Changes in v5:
- Requested by MyungJoo and Chanwoo.
- Fix returning without the lock acquired after request_module.
- Requested by Chanwoo.
- In request governor function check if governor name is NULL or not.
- Remove some unrelated changes (added/removed some blank lines).
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, 49 insertions(+), 4 deletions(-)
diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
index 0b5b3abe054e..aa92fbf9f0dd 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 +222,49 @@ 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. Returns the matched
+ * governor's pointer.
+ */
+static struct devfreq_governor *try_then_request_governor(const char *name)
+{
+ struct devfreq_governor *governor;
+ int err = 0;
+
+ 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);
+ /* Restore previous state before return */
+ mutex_lock(&devfreq_list_lock);
+ if (err)
+ return NULL;
+
+ governor = find_devfreq_governor(name);
+ }
+
+ return governor;
+}
+
static int devfreq_notify_transition(struct devfreq *devfreq,
struct devfreq_freqs *freqs, unsigned int state)
{
@@ -645,9 +689,8 @@ struct devfreq *devfreq_add_device(struct device *dev,
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__);
@@ -663,12 +706,14 @@ 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);
@@ -989,7 +1034,7 @@ 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
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH v5] PM / devfreq: Fix devfreq_add_device() when drivers are built as modules.
2018-07-04 8:45 [PATCH v5] PM / devfreq: Fix devfreq_add_device() when drivers are built as modules Enric Balletbo i Serra
@ 2018-07-05 0:13 ` Chanwoo Choi
2018-07-18 9:04 ` Enric Balletbo i Serra
0 siblings, 1 reply; 3+ messages in thread
From: Chanwoo Choi @ 2018-07-05 0:13 UTC (permalink / raw)
To: Enric Balletbo i Serra
Cc: linux-kernel, stable, kernel, Chanwoo Choi, Kyungmin Park,
MyungJoo Ham, Linux PM list
Hi Enric,
2018-07-04 17:45 GMT+09:00 Enric Balletbo i Serra
<enric.balletbo@collabora.com>:
> 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 <enric.balletbo@collabora.com>
> ---
>
> Changes in v5:
> - Requested by MyungJoo and Chanwoo.
> - Fix returning without the lock acquired after request_module.
> - Requested by Chanwoo.
> - In request governor function check if governor name is NULL or not.
> - Remove some unrelated changes (added/removed some blank lines).
>
> 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, 49 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> index 0b5b3abe054e..aa92fbf9f0dd 100644
> --- a/drivers/devfreq/devfreq.c
> +++ b/drivers/devfreq/devfreq.c
(snip)
Looks good to me.
Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
Best Regards,
Chanwoo Choi
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH v5] PM / devfreq: Fix devfreq_add_device() when drivers are built as modules.
2018-07-05 0:13 ` Chanwoo Choi
@ 2018-07-18 9:04 ` Enric Balletbo i Serra
0 siblings, 0 replies; 3+ messages in thread
From: Enric Balletbo i Serra @ 2018-07-18 9:04 UTC (permalink / raw)
To: cwchoi00
Cc: linux-kernel, stable, kernel, Chanwoo Choi, Kyungmin Park,
MyungJoo Ham, Linux PM list
Hi MyungJoo,
On 05/07/18 02:13, Chanwoo Choi wrote:
> Hi Enric,
>
> 2018-07-04 17:45 GMT+09:00 Enric Balletbo i Serra
> <enric.balletbo@collabora.com>:
>> 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 <enric.balletbo@collabora.com>
>> ---
>>
>> Changes in v5:
>> - Requested by MyungJoo and Chanwoo.
>> - Fix returning without the lock acquired after request_module.
>> - Requested by Chanwoo.
>> - In request governor function check if governor name is NULL or not.
>> - Remove some unrelated changes (added/removed some blank lines).
>>
>> 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, 49 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
>> index 0b5b3abe054e..aa92fbf9f0dd 100644
>> --- a/drivers/devfreq/devfreq.c
>> +++ b/drivers/devfreq/devfreq.c
>
> (snip)
>
> Looks good to me.
> Reviewed-by: Chanwoo Choi <cw00.choi@samsung.com>
>
I was expecting see also this patch in the pull request you did but I didn't
see. Is because of will be merged as a fix in current cycle? or has been forgotten?
Best regards,
Enric
> Best Regards,
> Chanwoo Choi
>
^ permalink raw reply [flat|nested] 3+ messages in thread
end of thread, other threads:[~2018-07-18 9:04 UTC | newest]
Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2018-07-04 8:45 [PATCH v5] PM / devfreq: Fix devfreq_add_device() when drivers are built as modules Enric Balletbo i Serra
2018-07-05 0:13 ` Chanwoo Choi
2018-07-18 9:04 ` Enric Balletbo i Serra
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).