Messages in this thread | | | Subject | Re: [PATCH v3] PM / devfreq: Fix devfreq_add_device() when drivers are built as modules. | From | Ezequiel Garcia <> | Date | Thu, 21 Jun 2018 22:11:36 -0300 |
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Hey Enric,
On Fri, 2018-06-22 at 00:04 +0200, 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 <enric.balletbo@collabora.com> > --- > > 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 | 65 ++++++++++++++++++++++++++++++++----- > -- [snip snip] > - 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__); > err = PTR_ERR(governor); > - goto err_init; > + goto err_unregister; > } > > + mutex_lock(&devfreq_list_lock); > +
I know it's not something we are introducing in this patch, but still... calling a hook with a mutex held looks fishy to me.
This lock should only protect the list, unless I am missing something.
> devfreq->governor = governor; > err = devfreq->governor->event_handler(devfreq, > DEVFREQ_GOV_START, > NULL); > @@ -663,14 +703,16 @@ 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); > - > +err_unregister: > device_unregister(&devfreq->dev); > err_dev: > if (devfreq) > @@ -988,12 +1030,13 @@ static ssize_t governor_store(struct device > *dev, struct device_attribute *attr, > if (ret != 1) > 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; > + return PTR_ERR(governor); > } > + > + mutex_lock(&devfreq_list_lock); > + > if (df->governor == governor) { > ret = 0; > goto out; > -- > 2.17.1 > >
Regards, Eze
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