02.04.2020 16:24, Dmitry Osipenko пишет:
> 02.04.2020 14:50, Wang, Jiada пишет:
>> Hi Dmitry
>>
>> On 2020/04/02 1:04, Dmitry Osipenko wrote:
>>> 31.03.2020 13:50, Jiada Wang пишет:
>>>> From: Sanjeev Chugh <sanjeev_chugh@xxxxxxxxxx>
>>>>
>>>> There could be scope of race conditions when sysfs is being handled
>>>> and at the same time, device removal is occurring. For example,
>>>> we don't want the device removal to begin if the Atmel device
>>>> cfg update is going on or firmware update is going on. In such
>>>> cases, wait for device update to be completed before the removal
>>>> continues.
>>>>
>>>> Thread Thread 2:
>>>> =========================
>>>> =========================
>>>> mxt_update_fw_store() mxt_remove()
>>>> mutex_lock(&data->lock) ...
>>>> mxt_initialize() //Tries to acquire lock
>>>> request_firmware_nowait() mutex_lock(&data->lock)
>>>> ... ==>waits for lock()
>>>> ... .
>>>> ... .
>>>> mutex_unlock(&data->lock) .
>>>> //Gets lock and
>>>> proceeds
>>>>
>>>> mxt_free_input_device();
>>>> ...
>>>>
>>>> mutex_unlock(&data->lock)
>>>> //Frees atmel driver
>>>> data
>>>> kfree(data)
>>>>
>>>> If the request_firmware_nowait() completes after the driver removal,
>>>> and callback is triggered. But kernel crashes since the module is
>>>> already removed.
>>>>
>>>> This commit adds state machine to serialize such scenarios.
>>>
>>> Won't it be easier to bump driver's module use-count by __module_get()
>>> while firmware is updating? Or remove sysfs during of mxt_remove()? >
>>
>> thanks for your inspiration, I will replace state machine with module
>> use-count.
>
> I'm actually now thinking that the suggestion about the module-count
> wasn't very correct because this won't really help in regards to
> mxt_update_fw_store() / mxt_remove() racing.
>
> I see that mxt_remove() already invokes the mxt_sysfs_remove(), which
> should block until mxt_update_fw_store() is completed, shouldn't it?
>
> I guess the kfree(data) isn't the real cause of the problem and
> something like this should help:
>
> diff --git a/drivers/input/touchscreen/atmel_mxt_ts.c
> b/drivers/input/touchscreen/atmel_mxt_ts.c
> index b2edf51e1595..4e66106feeb9 100644
> --- a/drivers/input/touchscreen/atmel_mxt_ts.c
> +++ b/drivers/input/touchscreen/atmel_mxt_ts.c
> @@ -4254,6 +4254,7 @@ static void mxt_sysfs_remove(struct mxt_data *data)
> struct i2c_client *client = data->client;
>
> sysfs_remove_group(&client->dev.kobj, &mxt_attr_group);
> + sysfs_remove_group(&client->dev.kobj, &mxt_fw_attr_group);
> }
>
> static void mxt_reset_slots(struct mxt_data *data)
> @@ -4649,31 +4650,19 @@ static int mxt_remove(struct i2c_client *client)
> {
> struct mxt_data *data = i2c_get_clientdata(client);
>
> - mutex_lock(&data->lock);
> - if (data->e_state == MXT_STATE_UPDATING_CONFIG_ASYNC ||
> - data->e_state == MXT_STATE_UPDATING_CONFIG) {
> - data->e_state = MXT_STATE_GOING_AWAY;
> - mutex_unlock(&data->lock);
> - mxt_wait_for_completion(data, &data->update_cfg_completion,
> - MXT_CONFIG_TIMEOUT);
> - } else {
> - data->e_state = MXT_STATE_GOING_AWAY;
> - mutex_unlock(&data->lock);
> - }
> + mxt_sysfs_remove(data);
>
> - disable_irq(data->irq);
> - sysfs_remove_group(&client->dev.kobj, &mxt_fw_attr_group);
> if (data->reset_gpio) {
> sysfs_remove_link(&client->dev.kobj, "reset");
> gpiod_unexport(data->reset_gpio);
> }
> +
> mxt_debug_msg_remove(data);
> - mxt_sysfs_remove(data);
> mxt_free_input_device(data);
> mxt_free_object_table(data);
>
> if (debug_state)
> cancel_delayed_work_sync(&data->watchdog_work);
> + disable_irq(data->irq);
>
> return 0;
> }
>
I'm also wondering why dev_attr_update_fw needs a separate
attribute_group, couldn't it be moved into mxt_attrs[]?
